add questions benches

apps: handle err's
+ ord fn's
2023-08-26 13:42:50 +03:00 · 2023-08-25 15:28:19 +03:00 · 2023-08-25 14:41:53 +03:00 · 2023-08-23 13:30:51 +03:00 · 2023-08-18 10:05:22 +03:00 · 2023-08-18 10:03:50 +03:00
22 changed files with 4143 additions and 1087 deletions
--- a/.drone.yml
+++ b/.drone.yml
@ -1,4 +1,5 @@
 kind: pipeline
+type: docker
 name: default

 steps:
@ -6,6 +7,33 @@ steps:
  image: rust:1-alpine
  commands:
  - apk add --no-cache musl-dev
-  - cargo build --verbose --all
-  - cargo test --verbose --all
+  - cargo build --verbose --all-features --all
+  - cargo test --verbose --all-features --all
+  environment:
+    CARGO_REGISTRIES_CRATES_IO_PROTOCOL: sparse

+trigger:
+  event:
+  - push
+
+---
+kind: pipeline
+type: docker
+name: publish
+
+steps:
+- name: push
+  image: rust:1-alpine
+  commands:
+  - apk add --no-cache musl-dev
+  - cargo build -p chgk_ledb_lib --all-features
+  - cargo publish --registry gitea -p chgk_ledb_lib --all-features
+  environment:
+    CARGO_REGISTRIES_CRATES_IO_PROTOCOL: sparse
+    CARGO_REGISTRIES_GITEA_INDEX: https://gitea.b4tman.ru/b4tman/_cargo-index.git
+    CARGO_REGISTRIES_GITEA_TOKEN:
+      from_secret: cargo_gitea_token
+
+trigger:
+  event:
+  - tag
--- a/.gitignore
+++ b/.gitignore
@ -6,3 +6,5 @@ json.zip
 /exp
 /.vscode
 test*.bin
+db.dat
+*.pending-snap
--- a/Cargo.lock
+++ b/Cargo.lock
--- a/Cargo.toml
+++ b/Cargo.toml
@ -1,32 +1,10 @@
-[package]
-name = "chgk_ledb"
-version = "0.1.0"
-authors = ["Dmitry <b4tm4n@mail.ru>"]
-edition = "2021"
-
-# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
-
-[[bench]]
-name = "db_bench"
-harness = false
-
-[dependencies]
-serde="1.0"
-serde_derive="1.0"
-serde_json="1.0"
-ledb = {git = "https://github.com/b4tman/ledb.git", rev="a646b90e", package="ledb"}
-ledb-derive = {git = "https://github.com/b4tman/ledb.git", rev="a646b90e", package="ledb-derive"}
-ledb-types = {git = "https://github.com/b4tman/ledb.git", rev="a646b90e", package="ledb-types"}
-zip="0.6"
-rand="0.8"
-clap = { version = "3.2.22", features = ["derive"] }
-bincode = "^2.0.0-rc.2"
-zstd = "^0.10"
-memmap = "0.7.0"
-
-[dev-dependencies]
-criterion = "0.4.0"
-tempfile = "3.3"
+[workspace]
+resolver = "2"
+members = [
+  "app",
+  "app_async",
+  "lib"
+]

 [profile.release]
 opt-level = 3
--- a/app/Cargo.toml
+++ b/app/Cargo.toml
@ -0,0 +1,32 @@
+[package]
+name = "chgk_ledb"
+version = "1.1.0"
+authors = ["Dmitry <b4tm4n@mail.ru>"]
+edition = "2021"
+repository = "https://gitea.b4tman.ru/b4tman/chgk_ledb"
+license = "MIT"
+description = "Утилита загружающая базу данных ЧГК вопросов из ZIP файла в JSON формате в базу данных."
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[[bench]]
+name = "db_bench"
+harness = false
+
+[[bench]]
+name = "questions_bench"
+harness = false
+
+[dependencies]
+chgk_ledb_lib = {path = "../lib", features = ["sync", "source", "convert"]}
+serde_json="1.0"
+zip="0.6"
+rand="0.8"
+clap = { version = "4.2.7", features = ["derive"] }
+
+[dev-dependencies]
+criterion = "0.4.0"
+tempfile = "3.3"
+bincode = "^2.0.0-rc.2"
+serde="1.0"
+serde_derive="1.0"
--- a/app/benches/db_bench.rs
+++ b/app/benches/db_bench.rs
@ -1,34 +1,50 @@
 #[macro_use]
 extern crate criterion;
+extern crate bincode;
+extern crate serde;
+extern crate serde_derive;
+extern crate serde_json;
+extern crate tempfile;

-#[path = "../src/db.rs"]
-mod db;
-use std::path::PathBuf;
+use chgk_ledb_lib::db;
+use std::path::Path;

 use db::{Reader, Writer, WriterOpts};

 use criterion::{BatchSize, Criterion};
-use tempfile::tempdir;
+use tempfile::{tempdir, NamedTempFile};

-#[derive(bincode::Encode, bincode::Decode, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
+use serde_derive::{Deserialize, Serialize};
+
+#[derive(
+    bincode::Encode,
+    bincode::Decode,
+    Clone,
+    Debug,
+    PartialEq,
+    Eq,
+    PartialOrd,
+    Ord,
+    Serialize,
+    Deserialize,
+)]
 struct TestData {
-    num: u128,
+    num1: u64,
+    num2: u64,
    test: String,
 }

 const N: usize = 4096;

 fn gen_data(count: usize) -> impl Iterator<Item = TestData> {
-    (0..count)
-        .into_iter()
-        .map(|i| 143 + i as u128)
-        .map(|i| TestData {
-            num: i,
-            test: "test ---- Test ____".repeat(123 + i as usize % 15),
-        })
+    (0..count).map(|i| 143 + i as u64).map(|i| TestData {
+        num1: i,
+        num2: (i * 100) ^ 0xDF0E441122334455,
+        test: "test ---- Test ____".repeat(123 + i as usize % 15),
+    })
 }

-fn prepare_db_writer(path: &PathBuf) -> Writer<TestData> {
+fn prepare_db_writer<P: AsRef<Path>>(path: P) -> Writer<TestData> {
    let opts = WriterOpts {
        compress_lvl: 1,
        data_buf_size: 100 * 1024 * 1024,
@ -41,7 +57,9 @@ fn prepare_db_writer(path: &PathBuf) -> Writer<TestData> {

 fn db_read(c: &mut Criterion) {
    let dir = tempdir().expect("tempdir");
-    let tmpfile = dir.path().join("test.tmp");
+    let tmpfile = NamedTempFile::new_in(dir.path())
+        .expect("new tempfile")
+        .into_temp_path();
    let mut writer = prepare_db_writer(&tmpfile);

    let mut items_iter = gen_data(N).collect::<Vec<TestData>>().into_iter();
@ -54,9 +72,8 @@ fn db_read(c: &mut Criterion) {
                let reader: Reader<TestData> = Reader::new(&tmpfile, 2048).expect("new reader");
                reader
            },
-            |mut reader| {
-                let mut reader_iter = reader.iter();
-                while let Some(item) = reader_iter.next() {
+            |reader| {
+                for item in reader {
                    drop(item);
                }
            },
@ -67,10 +84,13 @@ fn db_read(c: &mut Criterion) {

 fn db_write(c: &mut Criterion) {
    let dir = tempdir().expect("tempdir");
-    let tmpfile = dir.path().join("test.tmp");
+
    c.bench_function("write", |b| {
        b.iter_batched(
            || {
+                let tmpfile = NamedTempFile::new_in(dir.path())
+                    .expect("new tempfile")
+                    .into_temp_path();
                let src = gen_data(N).collect::<Vec<TestData>>().into_iter();
                let writer = prepare_db_writer(&tmpfile);
                (src, writer)
--- a/app/benches/questions_bench.rs
+++ b/app/benches/questions_bench.rs
@ -0,0 +1,101 @@
+#[macro_use]
+extern crate criterion;
+extern crate bincode;
+extern crate serde;
+extern crate serde_derive;
+extern crate serde_json;
+extern crate tempfile;
+
+use chgk_ledb_lib::db::{Reader, Writer, WriterOpts};
+use chgk_ledb_lib::questions::{Question, QuestionsConverter};
+use chgk_ledb_lib::source::ReadSourceQuestionsBatches;
+
+use std::path::Path;
+use std::time::Duration;
+use std::{fs, io};
+
+use criterion::{BatchSize, Criterion};
+use tempfile::{tempdir, NamedTempFile};
+
+const ZIP_FILENAME: &str = "../json.zip";
+const NEW_DB_FILENAME: &str = "../db.dat";
+
+const N: usize = 4096;
+
+fn read_sample() -> Vec<Question> {
+    let zip_file = fs::File::open(ZIP_FILENAME).unwrap();
+    let zip_reader = io::BufReader::new(zip_file);
+    let archive = zip::ZipArchive::new(zip_reader).unwrap();
+    let mut source_questions = archive.source_questions();
+
+    source_questions
+        .convert()
+        .take(N)
+        .enumerate()
+        .map(|(num, mut question)| {
+            question.num = 1 + num as u32;
+            question
+        })
+        .collect()
+}
+
+fn prepare_db_writer<P: AsRef<Path>>(path: P) -> Writer<Question> {
+    let opts = WriterOpts {
+        compress_lvl: 1,
+        data_buf_size: 100 * 1024 * 1024,
+        out_buf_size: 100 * 1024 * 1024,
+        current_buf_size: 10240,
+    };
+
+    Writer::new(path, opts).expect("new writer")
+}
+
+fn questions_read(c: &mut Criterion) {
+    c.bench_function("questions_read", |b| {
+        b.iter_batched(
+            || {
+                let reader: Reader<Question> =
+                    Reader::new(NEW_DB_FILENAME, 4096).expect("new reader");
+                reader.into_iter().take(N)
+            },
+            |reader| {
+                for item in reader {
+                    drop(item);
+                }
+            },
+            BatchSize::SmallInput,
+        )
+    });
+}
+
+fn questions_write(c: &mut Criterion) {
+    let dir = tempdir().expect("tempdir");
+
+    c.bench_function("questions_write", |b| {
+        b.iter_batched(
+            || {
+                let tmpfile = NamedTempFile::new_in(dir.path())
+                    .expect("new tempfile")
+                    .into_temp_path();
+                let src = read_sample().into_iter();
+                let writer = prepare_db_writer(&tmpfile);
+                (src, writer)
+            },
+            |(mut src, mut writer)| {
+                writer.load(&mut src).unwrap();
+                writer.finish().unwrap();
+            },
+            BatchSize::SmallInput,
+        )
+    });
+}
+
+fn config() -> Criterion {
+    Criterion::default()
+        .sample_size(40)
+        .warm_up_time(Duration::from_secs(7))
+        .measurement_time(Duration::from_secs(20))
+}
+
+criterion_group! {name=benches; config = config(); targets = questions_read, questions_write}
+criterion_main!(benches);
--- a/app/src/main.rs
+++ b/app/src/main.rs
@ -0,0 +1,181 @@
+extern crate serde_json;
+use clap::{Parser, Subcommand};
+use rand::seq::IteratorRandom;
+
+use std::io;
+use std::time::Instant;
+use std::{fs, sync::mpsc, thread};
+
+use chgk_ledb_lib::db;
+use chgk_ledb_lib::questions;
+use chgk_ledb_lib::source;
+
+use crate::questions::{Question, QuestionsConverter};
+use crate::source::ReadSourceQuestionsBatches;
+use chgk_ledb_lib::util::ErrorToString;
+
+const ZIP_FILENAME: &str = "json.zip";
+const NEW_DB_FILENAME: &str = "db.dat";
+
+#[derive(Subcommand, Debug)]
+enum Command {
+    Write,
+    Print {
+        #[clap(value_parser, default_value = "0")]
+        id: u32,
+    },
+    ZipPrint {
+        #[clap(value_parser, default_value = "0")]
+        file_num: usize,
+        #[clap(value_parser, default_value = "0")]
+        num: usize,
+    },
+}
+
+#[derive(Parser, Debug)]
+#[clap(author, version, about, long_about = None)]
+#[clap(propagate_version = true)]
+struct Cli {
+    #[clap(subcommand)]
+    command: Command,
+    #[clap(short, long, action)]
+    measure: bool,
+}
+
+fn main() {
+    let args = Cli::parse();
+
+    let mut action: Box<dyn FnOnce()> = match &args.command {
+        Command::Write => Box::new(write_db),
+        Command::Print { id } => {
+            let get_question = Box::new(|| read_from_db(*id));
+            Box::new(|| print_question_from(get_question))
+        }
+        Command::ZipPrint { file_num, num } => {
+            let get_question = Box::new(|| read_from_zip(*file_num, *num));
+            Box::new(|| print_question_from(get_question))
+        }
+    };
+
+    if args.measure {
+        action = Box::new(|| measure_and_print(action));
+    }
+
+    action();
+}
+
+// measure and return time elapsed in `func` in seconds
+pub fn measure<F: FnOnce()>(func: F) -> f64 {
+    let start = Instant::now();
+    func();
+    let elapsed = start.elapsed();
+    (elapsed.as_secs() as f64) + (elapsed.subsec_nanos() as f64 / 1_000_000_000.0)
+}
+
+pub fn measure_and_print<F: FnOnce()>(func: F) {
+    let m = measure(func);
+    eprintln!("{}", m);
+}
+
+fn print_question_from<F>(get_q: F)
+where
+    F: FnOnce() -> Result<Question, String>,
+{
+    let q = get_q().expect("question not found");
+    println!("{:#?}", q)
+}
+
+fn read_from_zip(file_num: usize, mut num: usize) -> Result<Question, String> {
+    let mut rng = rand::thread_rng();
+    let zip_file = fs::File::open(ZIP_FILENAME).str_err()?;
+    let zip_reader = io::BufReader::new(zip_file);
+    let archive = zip::ZipArchive::new(zip_reader).str_err()?;
+
+    let mut source_questions = archive.source_questions();
+    let (filename, batch) = if file_num == 0 {
+        source_questions
+            .choose(&mut rng)
+            .ok_or("rand choose".to_string())?
+    } else {
+        source_questions
+            .nth(file_num - 1)
+            .ok_or(format!("file nth #{file_num} => None"))?
+    };
+    let mut batch = batch.map_err(|e| format!("get batch from file #{file_num} => {e}"))?;
+    batch.filename = filename;
+    let questions: Vec<Question> = batch.into();
+    if num == 0 {
+        num = (1..=questions.len())
+            .choose(&mut rng)
+            .ok_or("rand choose".to_string())?;
+    }
+    Ok(questions[num - 1].clone())
+}
+
+fn read_from_db(id: u32) -> Result<Question, String> {
+    let reader: db::Reader<Question> = db::Reader::new(NEW_DB_FILENAME, 2048)?;
+
+    let len = reader.len();
+    let mut questions = reader.into_iter();
+
+    let question = match id {
+        0 => {
+            let mut rng = rand::thread_rng();
+            questions
+                .choose(&mut rng)
+                .ok_or(format!("rand choose, len = {len}"))?
+        }
+        _ => questions
+            .nth((id - 1) as usize)
+            .ok_or(format!("get nth #{id} => None"))?,
+    };
+
+    Ok(question)
+}
+
+fn write_db() {
+    let (tx, rx) = mpsc::channel::<Question>();
+    [
+        thread::spawn(move || zip_reader_task(tx)),
+        thread::spawn(move || db_writer_task(rx)),
+    ]
+    .into_iter()
+    .for_each(|handle| handle.join().expect("thread panic"));
+    println!("all done");
+}
+
+fn zip_reader_task(tx: mpsc::Sender<Question>) {
+    let zip_file = fs::File::open(ZIP_FILENAME).unwrap();
+    let zip_reader = io::BufReader::new(zip_file);
+    let archive = zip::ZipArchive::new(zip_reader).unwrap();
+    let mut source_questions = archive.source_questions();
+
+    let questions = source_questions
+        .convert()
+        .enumerate()
+        .map(|(num, mut question)| {
+            question.num = 1 + num as u32;
+            question
+        });
+    for question in questions {
+        let res = tx.send(question);
+        if res.is_err() {
+            break;
+        }
+    }
+    println!("read done");
+}
+
+fn db_writer_task(rx: mpsc::Receiver<Question>) {
+    let writer_opts = db::WriterOpts::default();
+    let mut writer: db::Writer<Question> =
+        db::Writer::new(NEW_DB_FILENAME, writer_opts).expect("new db writer");
+
+    writer
+        .load(&mut rx.iter())
+        .unwrap_or_else(|e| panic!("db writer load, {e:#?}"));
+
+    writer.finish().expect("db writer finish");
+
+    println!("write done");
+}
--- a/app_async/Cargo.toml
+++ b/app_async/Cargo.toml
@ -0,0 +1,45 @@
+[package]
+name = "chgk_ledb_async"
+version = "1.1.0"
+authors = ["Dmitry <b4tm4n@mail.ru>"]
+edition = "2021"
+repository = "https://gitea.b4tman.ru/b4tman/chgk_ledb"
+license = "MIT"
+description = "Утилита загружающая базу данных ЧГК вопросов из ZIP файла в JSON формате в базу данных."
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[[bench]]
+name = "async_bench"
+harness = false
+
+[[bench]]
+name = "questions_async_bench"
+harness = false
+
+[dependencies]
+chgk_ledb_lib = {path = "../lib", features = ["async", "convert_async"]}
+serde_json="1.0"
+async_zip = { version = "0.0.15", features = [
+    "zstd",
+    "tokio",
+    "tokio-fs"] }
+tokio = { version = "1", features = [
+    "io-util",
+    "fs",
+    "rt-multi-thread"
+] }
+tokio-stream = "0.1"
+rand="0.8"
+clap = { version = "4.2.7", features = ["derive"] }
+futures = "0.3"
+
+[dev-dependencies]
+criterion = { version = "0.5.1", features = ["async_tokio"]}
+tempfile = "3.3"
+bincode = "^2.0.0-rc.2"
+serde="1.0"
+serde_derive="1.0"
+futures = "0.3"
+async-compression = { version = "0.4.1", default-features = false }
+lazy_static = "1.4.0"
--- a/app_async/benches/async_bench.rs
+++ b/app_async/benches/async_bench.rs
@ -0,0 +1,153 @@
+#[macro_use]
+extern crate criterion;
+extern crate bincode;
+extern crate serde;
+extern crate serde_derive;
+extern crate tempfile;
+
+use async_compression::Level;
+use chgk_ledb_lib::async_db::{Reader, Writer, WriterOpts};
+use futures::StreamExt;
+use std::{ops::Deref, path::Path};
+
+use criterion::{BatchSize, Criterion};
+use lazy_static::lazy_static;
+use tempfile::{tempdir, NamedTempFile};
+
+use serde_derive::{Deserialize, Serialize};
+
+#[derive(
+    bincode::Encode,
+    bincode::Decode,
+    Clone,
+    Debug,
+    PartialEq,
+    Eq,
+    PartialOrd,
+    Ord,
+    Serialize,
+    Deserialize,
+)]
+struct TestData {
+    num1: u64,
+    num2: u64,
+    test: String,
+}
+
+use tokio::runtime;
+
+lazy_static! {
+    static ref RUNTIME: tokio::runtime::Runtime =
+        runtime::Builder::new_current_thread().build().unwrap();
+}
+
+const N: usize = 4096;
+
+fn gen_data(count: usize) -> impl Iterator<Item = TestData> {
+    (0..count).map(|i| 143 + i as u64).map(|i| TestData {
+        num1: i,
+        num2: (i * 100) ^ 0xDF0E441122334455,
+        test: "test ---- Test ____".repeat(123 + i as usize % 15),
+    })
+}
+
+async fn prepare_db_writer<P: AsRef<Path>>(path: P) -> Writer<TestData> {
+    let opts = WriterOpts {
+        compress_lvl: Level::Fastest,
+        data_buf_size: 100 * 1024 * 1024,
+        out_buf_size: 100 * 1024 * 1024,
+        current_buf_size: 10240,
+    };
+
+    Writer::new(path, opts).await.expect("new writer")
+}
+
+fn write_sample<P: AsRef<Path>>(path: P) {
+    let rp = path.as_ref().to_str().unwrap().to_string();
+    std::thread::spawn(|| {
+        runtime::Builder::new_current_thread()
+            .build()
+            .unwrap()
+            .block_on(async move {
+                let mut writer = prepare_db_writer(rp).await;
+
+                let items_iter = gen_data(N).collect::<Vec<TestData>>().into_iter();
+                let mut samples_stream = futures::stream::iter(items_iter);
+                writer.load(&mut samples_stream).await.unwrap();
+                writer.finish().await.unwrap();
+            })
+    })
+    .join()
+    .expect("spawn thread");
+}
+
+fn setup_writer<P: AsRef<Path>>(path: P) -> Writer<TestData> {
+    let rp = path.as_ref().to_str().unwrap().to_string();
+
+    std::thread::spawn(|| {
+        runtime::Builder::new_current_thread()
+            .build()
+            .unwrap()
+            .block_on(prepare_db_writer(rp))
+    })
+    .join()
+    .expect("spawn thread")
+}
+
+fn setup_reader<P: AsRef<Path>>(path: P) -> Reader<TestData> {
+    let rp = path.as_ref().to_str().unwrap().to_string();
+    std::thread::spawn(|| {
+        runtime::Builder::new_current_thread()
+            .build()
+            .unwrap()
+            .block_on(async move { Reader::new(rp).await.expect("new reader") })
+    })
+    .join()
+    .expect("spawn thread")
+}
+
+fn async_read(c: &mut Criterion) {
+    let dir = tempdir().expect("tempdir");
+    let tmpfile = NamedTempFile::new_in(dir.path())
+        .expect("new tempfile")
+        .into_temp_path();
+    write_sample(&tmpfile);
+
+    c.bench_function("async_read", |b| {
+        b.to_async(RUNTIME.deref()).iter_batched(
+            || setup_reader(&tmpfile),
+            |reader| async move { reader.stream().for_each(|item| async { drop(item) }).await },
+            BatchSize::SmallInput,
+        )
+    });
+}
+
+fn async_write(c: &mut Criterion) {
+    let dir = tempdir().expect("tempdir");
+
+    c.bench_function("async_write", |b| {
+        b.to_async(RUNTIME.deref()).iter_batched(
+            || {
+                let tmpfile = NamedTempFile::new_in(dir.path())
+                    .expect("new tempfile")
+                    .into_temp_path();
+                let src = gen_data(N).collect::<Vec<TestData>>().into_iter();
+                let src = futures::stream::iter(src);
+                let writer = setup_writer(&tmpfile);
+                (src, writer)
+            },
+            |(mut src, mut writer)| async move {
+                writer.load(&mut src).await.unwrap();
+                writer.finish().await.unwrap();
+            },
+            BatchSize::SmallInput,
+        )
+    });
+}
+
+fn config() -> Criterion {
+    Criterion::default().sample_size(20)
+}
+
+criterion_group! {name=benches; config = config(); targets = async_read, async_write}
+criterion_main!(benches);
--- a/app_async/benches/questions_async_bench.rs
+++ b/app_async/benches/questions_async_bench.rs
@ -0,0 +1,152 @@
+#[macro_use]
+extern crate criterion;
+extern crate bincode;
+extern crate serde;
+extern crate serde_derive;
+extern crate tempfile;
+
+use async_compression::Level;
+use chgk_ledb_lib::async_db::{Reader, Writer, WriterOpts};
+use chgk_ledb_lib::questions::{Question, QuestionsConverterAsyncForStream};
+use chgk_ledb_lib::source::ReadSourceQuestionsBatchesAsync;
+use futures::pin_mut;
+use futures::StreamExt;
+use std::time::Duration;
+use std::{ops::Deref, path::Path};
+
+use async_zip::tokio::read::seek::ZipFileReader;
+
+use criterion::{BatchSize, Criterion};
+use lazy_static::lazy_static;
+use tempfile::{tempdir, NamedTempFile};
+use tokio::{fs, runtime};
+
+const ZIP_FILENAME: &str = "../json.zip";
+const NEW_DB_FILENAME: &str = "../db.dat";
+
+lazy_static! {
+    static ref RUNTIME: tokio::runtime::Runtime =
+        runtime::Builder::new_current_thread().build().unwrap();
+}
+
+const N: usize = 4096;
+
+async fn read_sample() -> Vec<Question> {
+    let mut file = fs::File::open(ZIP_FILENAME).await.expect("open zip");
+    let archive = ZipFileReader::with_tokio(&mut file)
+        .await
+        .expect("open zip file reader");
+    let mut source_questions = archive.source_questions();
+    let source_questions = source_questions.stream();
+    pin_mut!(source_questions);
+
+    source_questions
+        .converter()
+        .convert()
+        .take(N)
+        .enumerate()
+        .map(|(num, mut question)| {
+            question.num = 1 + num as u32;
+            question
+        })
+        .collect()
+        .await
+}
+
+fn read_sample_sync() -> Vec<Question> {
+    std::thread::spawn(|| {
+        runtime::Builder::new_current_thread()
+            .build()
+            .unwrap()
+            .block_on(read_sample())
+    })
+    .join()
+    .expect("spawn thread")
+}
+
+async fn prepare_db_writer<P: AsRef<Path>>(path: P) -> Writer<Question> {
+    let opts = WriterOpts {
+        compress_lvl: Level::Fastest,
+        data_buf_size: 100 * 1024 * 1024,
+        out_buf_size: 100 * 1024 * 1024,
+        current_buf_size: 10240,
+    };
+
+    Writer::<Question>::new(path, opts)
+        .await
+        .expect("new writer")
+}
+
+fn setup_writer<P: AsRef<Path>>(path: P) -> Writer<Question> {
+    let rp = path.as_ref().to_str().unwrap().to_string();
+
+    std::thread::spawn(|| {
+        runtime::Builder::new_current_thread()
+            .build()
+            .unwrap()
+            .block_on(prepare_db_writer(rp))
+    })
+    .join()
+    .expect("spawn thread")
+}
+
+fn setup_reader<P: AsRef<Path>>(path: P) -> Reader<Question> {
+    let rp = path.as_ref().to_str().unwrap().to_string();
+    std::thread::spawn(|| {
+        runtime::Builder::new_current_thread()
+            .build()
+            .unwrap()
+            .block_on(async move { Reader::new(rp).await.expect("new reader") })
+    })
+    .join()
+    .expect("spawn thread")
+}
+
+fn questions_async_read(c: &mut Criterion) {
+    c.bench_function("questions_async_read", |b| {
+        b.to_async(RUNTIME.deref()).iter_batched(
+            || setup_reader(NEW_DB_FILENAME),
+            |reader| async move {
+                reader
+                    .stream()
+                    .take(N)
+                    .for_each(|item| async { drop(item) })
+                    .await
+            },
+            BatchSize::SmallInput,
+        )
+    });
+}
+
+fn questions_async_write(c: &mut Criterion) {
+    let dir = tempdir().expect("tempdir");
+
+    c.bench_function("questions_async_write", |b| {
+        b.to_async(RUNTIME.deref()).iter_batched(
+            || {
+                let tmpfile = NamedTempFile::new_in(dir.path())
+                    .expect("new tempfile")
+                    .into_temp_path();
+                let src = read_sample_sync().into_iter();
+                let src = futures::stream::iter(src);
+                let writer = setup_writer(&tmpfile);
+                (src, writer)
+            },
+            |(mut src, mut writer)| async move {
+                writer.load(&mut src).await.unwrap();
+                writer.finish().await.unwrap();
+            },
+            BatchSize::SmallInput,
+        )
+    });
+}
+
+fn config() -> Criterion {
+    Criterion::default()
+        .sample_size(40)
+        .warm_up_time(Duration::from_secs(7))
+        .measurement_time(Duration::from_secs(20))
+}
+
+criterion_group! {name=benches; config = config(); targets = questions_async_read, questions_async_write}
+criterion_main!(benches);
--- a/app_async/src/main.rs
+++ b/app_async/src/main.rs
@ -0,0 +1,197 @@
+extern crate serde_json;
+use clap::{Parser, Subcommand};
+use futures::{pin_mut, Future};
+use rand::distributions::Uniform;
+use rand::seq::IteratorRandom;
+use rand::{thread_rng, Rng};
+
+use async_zip::tokio::read::seek::ZipFileReader;
+use futures::stream::{self, StreamExt};
+use std::time::Instant;
+use tokio::sync::mpsc::{self, UnboundedReceiver, UnboundedSender};
+
+use async_db::WriterOpts;
+
+use tokio::{fs, io};
+use tokio_stream::wrappers::UnboundedReceiverStream;
+
+use chgk_ledb_lib::async_db;
+use chgk_ledb_lib::questions::Question;
+use chgk_ledb_lib::questions::QuestionsConverterAsyncForStream;
+use chgk_ledb_lib::source::ReadSourceQuestionsBatchesAsync;
+use chgk_ledb_lib::util::ErrorToString;
+
+const ZIP_FILENAME: &str = "json.zip";
+const NEW_DB_FILENAME: &str = "db.dat";
+
+#[derive(Subcommand, Debug)]
+enum Command {
+    Write,
+    Print {
+        #[clap(value_parser, default_value = "0")]
+        id: u32,
+    },
+    ZipPrint {
+        #[clap(value_parser, default_value = "0")]
+        file_num: usize,
+        #[clap(value_parser, default_value = "0")]
+        num: usize,
+    },
+}
+
+#[derive(Parser, Debug)]
+#[clap(author, version, about, long_about = None)]
+#[clap(propagate_version = true)]
+struct Cli {
+    #[clap(subcommand)]
+    command: Command,
+    #[clap(short, long, action)]
+    measure: bool,
+}
+
+#[tokio::main]
+async fn main() {
+    let args = Cli::parse();
+
+    let mut action: Box<dyn Future<Output = _>> = match &args.command {
+        Command::Write => Box::new(write_db()),
+        Command::Print { id } => {
+            let get_question = read_from_db(*id);
+            Box::new(print_question_from(get_question))
+        }
+        Command::ZipPrint { file_num, num } => {
+            let get_question = read_from_zip(*file_num, *num);
+            Box::new(print_question_from(get_question))
+        }
+    };
+
+    if args.measure {
+        action = Box::new(measure_and_print(Box::into_pin(action)));
+    }
+
+    Box::into_pin(action).await;
+}
+
+// measure and return time elapsed in `fut` in seconds
+pub async fn measure<F: Future>(fut: F) -> f64 {
+    let start = Instant::now();
+    fut.await;
+    let elapsed = start.elapsed();
+    (elapsed.as_secs() as f64) + (elapsed.subsec_nanos() as f64 / 1_000_000_000.0)
+}
+
+pub async fn measure_and_print<F: Future>(fut: F) {
+    let m = measure(fut).await;
+    eprintln!("{}", m);
+}
+
+async fn print_question_from<F>(get_q: F)
+where
+    F: Future<Output = Result<Question, String>>,
+{
+    let q = get_q.await.expect("question not found");
+    println!("{:#?}", q)
+}
+
+async fn read_from_zip(file_num: usize, mut num: usize) -> Result<Question, String> {
+    let mut rng = thread_rng();
+    let zip_file = fs::File::open(ZIP_FILENAME).await.str_err()?;
+    let mut zip_reader = io::BufReader::new(zip_file);
+    let archive = ZipFileReader::with_tokio(&mut zip_reader).await.str_err()?;
+
+    let mut source = archive.source_questions();
+    let files_count = source.len();
+    let file_index = if file_num == 0 {
+        let files = Uniform::new(0, files_count);
+        rng.sample(files)
+    } else {
+        file_num - 1
+    };
+
+    let src = source
+        .get(file_index)
+        .await
+        .map_err(|e| format!("get file {file_num} => {e}"))?;
+    let src = stream::once(async { src });
+    pin_mut!(src);
+    let converter = src.converter();
+    let questions: Vec<_> = converter.convert().collect().await;
+    if num == 0 {
+        num = (1..=questions.len()).choose(&mut rng).unwrap();
+    }
+    let mut question = questions
+        .get(num - 1)
+        .ok_or(format!("get question #{num} => None"))?
+        .clone();
+    question.num = num as u32;
+    Ok(question)
+}
+
+async fn read_from_db(id: u32) -> Result<Question, String> {
+    let reader: async_db::Reader<Question> = async_db::Reader::new(NEW_DB_FILENAME).await?;
+
+    let len = reader.len();
+
+    let index = if id == 0 {
+        let mut rng = thread_rng();
+        let questions = Uniform::new(0, len);
+        rng.sample(questions)
+    } else {
+        id as usize - 1
+    };
+
+    reader
+        .get(index)
+        .await
+        .map_err(|e| format!("get #{index} => {e}"))
+}
+
+async fn write_db() {
+    let (tx, rx) = mpsc::unbounded_channel::<Question>();
+    tokio::try_join!(
+        tokio::spawn(zip_reader_task(tx)),
+        tokio::spawn(db_writer_task(rx))
+    )
+    .expect("tokio join");
+    println!("all done");
+}
+
+async fn zip_reader_task(tx: UnboundedSender<Question>) {
+    let mut file = fs::File::open(ZIP_FILENAME).await.expect("open zip");
+    let archive = ZipFileReader::with_tokio(&mut file)
+        .await
+        .expect("open zip file reader");
+    let mut source_questions = archive.source_questions();
+    let source_questions = source_questions.stream();
+    pin_mut!(source_questions);
+
+    source_questions
+        .converter()
+        .convert()
+        .enumerate()
+        .map(|(num, mut question)| {
+            question.num = 1 + (num as u32);
+            question
+        })
+        .for_each_concurrent(None, |question| async {
+            tx.send(question).expect("send");
+        })
+        .await;
+
+    println!("read done");
+}
+
+async fn db_writer_task(rx: UnboundedReceiver<Question>) {
+    let writer_opts = WriterOpts::default();
+    let mut writer: async_db::Writer<Question> =
+        async_db::Writer::new(NEW_DB_FILENAME, writer_opts)
+            .await
+            .unwrap_or_else(|e| panic!("db writer load, {e:#?}"));
+
+    let stream: UnboundedReceiverStream<_> = rx.into();
+    let stream = stream;
+    writer.load(stream).await.expect("load");
+    writer.finish().await.expect("db writer finish");
+
+    println!("write done");
+}
--- a/lib/Cargo.toml
+++ b/lib/Cargo.toml
@ -0,0 +1,76 @@
+[package]
+name = "chgk_ledb_lib"
+version = "1.2.0"
+authors = ["Dmitry <b4tm4n@mail.ru>"]
+edition = "2021"
+repository = "https://gitea.b4tman.ru/b4tman/chgk_ledb"
+license = "MIT"
+description = "Библиотека для доступа к файлу базы данных вопросов ЧГК"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[features]
+default = []
+sync = ["zstd", "memmap"]
+async = [
+    "futures",
+    "futures-core",
+    "futures-util",
+    "fmmap",
+    "tokio",
+    "async-compression",
+    "async-stream",
+    "pin-project",
+]
+source = ["zip"]
+source_async = [
+    "async_zip",
+    "tokio",
+    "futures",
+    "futures-core",
+    "futures-util",
+    "async-stream",
+]
+convert = ["zip"]
+convert_async = [
+    "futures",
+    "futures-core",
+    "futures-util",
+    "async-stream",
+    "async_zip",
+    "tokio",
+]
+
+[dependencies]
+serde = "1.0"
+serde_derive = "1.0"
+serde_json = "1.0"
+bincode = "^2.0.0-rc.2"
+zip = { version = "0.6", optional = true }
+async_zip = { version = "0.0.15" , features = [
+    "zstd",
+    "tokio",
+    "tokio-fs",
+], optional = true }
+fmmap = { version = "0.3", features = ["tokio-async"], optional = true }
+tokio = { version = "1", features = [
+    "fs",
+    "io-util",
+    "rt",
+    "macros",
+], optional = true }
+futures-core = { version = "0.3", optional = true }
+futures = { version = "0.3", optional = true }
+futures-util = { version = "0.3", optional = true }
+async-compression = { version = "0.4.1", default-features = false, features = [
+    "zstd",
+    "tokio",
+], optional = true }
+async-stream = { version = "0.3", optional = true }
+zstd = { version = "^0.12", default-features = false, optional = true }
+memmap = { version = "0.7.0", optional = true }
+pin-project = { version = "1.1.3", optional = true }
+
+[dev-dependencies]
+insta = { version = "1.31.0", features = ["yaml"] }
+tempfile = "3.3"
--- a/lib/src/async_db.rs
+++ b/lib/src/async_db.rs
@ -0,0 +1,787 @@
+use std::marker::PhantomData;
+use std::ops::Deref;
+use std::vec;
+use std::{path::Path, sync::Arc};
+
+use async_compression::tokio::bufread::ZstdDecoder;
+use async_compression::tokio::bufread::ZstdEncoder;
+use async_compression::Level;
+use futures::sink::Sink;
+use futures::stream::StreamExt;
+use futures_core::stream::Stream;
+use futures_core::Future;
+use futures_util::pin_mut;
+
+use std::pin::Pin;
+use std::task::{Context, Poll};
+
+use tokio::{
+    fs,
+    io::{self, AsyncReadExt, AsyncWriteExt},
+};
+
+use fmmap::tokio::{AsyncMmapFile, AsyncMmapFileExt, AsyncOptions};
+
+type LSize = u32;
+const LEN_SIZE: usize = std::mem::size_of::<LSize>();
+const BINCODE_CFG: bincode::config::Configuration = bincode::config::standard();
+
+use crate::util::BincodeVecWriter;
+use crate::util::ErrorToString;
+
+pub struct WriterOpts {
+    pub compress_lvl: Level,
+    pub data_buf_size: usize,
+    pub out_buf_size: usize,
+    pub current_buf_size: usize,
+}
+
+impl Default for WriterOpts {
+    fn default() -> Self {
+        Self {
+            compress_lvl: Level::Default,
+            data_buf_size: 500 * 1024 * 1024,
+            out_buf_size: 200 * 1024 * 1024,
+            current_buf_size: 100 * 1024,
+        }
+    }
+}
+
+pub struct Writer<T>
+where
+    T: bincode::Encode,
+{
+    out: io::BufWriter<fs::File>,
+    data_buf: Vec<u8>,
+    cur_buf_item: BincodeVecWriter,
+    table: Vec<LSize>,
+    compress_lvl: Level,
+    _t: PhantomData<Arc<T>>,
+}
+
+impl<T> Writer<T>
+where
+    T: bincode::Encode,
+{
+    pub async fn new<P: AsRef<Path>>(path: P, opts: WriterOpts) -> Result<Self, String> {
+        let out = fs::File::create(path).await.str_err()?;
+        let out = io::BufWriter::with_capacity(opts.out_buf_size, out);
+        let data_buf: Vec<u8> = Vec::with_capacity(opts.data_buf_size);
+        let cur_buf_item: Vec<u8> = Vec::with_capacity(opts.current_buf_size);
+        let cur_buf_item = BincodeVecWriter::new(cur_buf_item);
+
+        let compress_lvl = opts.compress_lvl;
+
+        let table: Vec<LSize> = vec![];
+
+        Ok(Self {
+            out,
+            data_buf,
+            cur_buf_item,
+            table,
+            compress_lvl,
+            _t: PhantomData,
+        })
+    }
+
+    pub async fn push(&mut self, item: T) -> Result<(), String> {
+        self.push_by_ref(&item).await
+    }
+
+    pub async fn push_by_ref(&mut self, item: &T) -> Result<(), String> {
+        let pos: LSize = self.data_buf.len() as LSize;
+
+        bincode::encode_into_writer(item, &mut self.cur_buf_item, BINCODE_CFG).str_err()?;
+
+        let mut zencoder = ZstdEncoder::with_quality(&self.cur_buf_item[..], self.compress_lvl);
+        io::copy(&mut zencoder, &mut self.data_buf)
+            .await
+            .str_err()?;
+        self.cur_buf_item.clear();
+
+        self.table.push(pos);
+
+        // FIXME
+        // this will break WriterSink::poll_ready (will wait forever), but not Writer::load
+        // tokio::time::sleep(std::time::Duration::from_secs(1)).await;
+
+        Ok(())
+    }
+
+    pub async fn load<S>(&mut self, source: S) -> Result<(), String>
+    where
+        S: Stream<Item = T> + std::marker::Unpin,
+    {
+        let hint = source.size_hint();
+        let hint = std::cmp::max(hint.0, hint.1.unwrap_or(0));
+        if hint > 0 {
+            self.table.reserve(hint);
+        }
+
+        pin_mut!(source);
+        while let Some(item) = source.next().await {
+            self.push(item).await?;
+        }
+
+        Ok(())
+    }
+
+    pub async fn finish(mut self) -> Result<(), String> {
+        // finish tab
+        let pos: LSize = self.data_buf.len() as LSize;
+        self.table.push(pos);
+
+        // write tab
+        let tab_size = (self.table.len() * LEN_SIZE) as LSize;
+        for pos in self.table {
+            let pos_data = (pos + tab_size).to_le_bytes();
+            self.out.write_all(&pos_data).await.str_err()?;
+        }
+        // copy data
+        self.out.write_all(&self.data_buf[..]).await.str_err()?;
+
+        self.out.flush().await.str_err()?;
+        Ok(())
+    }
+
+    pub fn sink(&mut self) -> WriterSink<'_, T> {
+        WriterSink {
+            writer: self,
+            item: None,
+        }
+    }
+}
+
+use pin_project::pin_project;
+
+#[pin_project]
+/// FIXME: not really async
+/// only work when ..push.poll() returns Ready immediately
+pub struct WriterSink<'a, T>
+where
+    T: bincode::Encode,
+{
+    #[pin]
+    writer: &'a mut Writer<T>,
+    item: Option<T>,
+}
+
+impl<'a, T> Sink<T> for WriterSink<'a, T>
+where
+    T: bincode::Encode,
+{
+    type Error = String;
+
+    fn poll_ready(
+        self: std::pin::Pin<&mut Self>,
+        ctx: &mut std::task::Context<'_>,
+    ) -> Poll<Result<(), String>> {
+        let mut this = self.project();
+
+        if this.item.is_none() {
+            return Poll::Ready(Ok(()));
+        }
+
+        let item = this.item.take().unwrap();
+
+        let push_fut = this.writer.push(item); // FIXME:: how to save this future???
+        pin_mut!(push_fut);
+        push_fut.poll(ctx)
+    }
+
+    fn start_send(self: std::pin::Pin<&mut Self>, item: T) -> Result<(), Self::Error> {
+        let this = self.project();
+        *this.item = Some(item);
+        Ok(())
+    }
+
+    fn poll_flush(
+        self: std::pin::Pin<&mut Self>,
+        ctx: &mut std::task::Context<'_>,
+    ) -> Poll<Result<(), Self::Error>> {
+        self.poll_ready(ctx)
+    }
+
+    fn poll_close(
+        mut self: std::pin::Pin<&mut Self>,
+        ctx: &mut std::task::Context<'_>,
+    ) -> Poll<Result<(), Self::Error>> {
+        futures::ready!(self.as_mut().poll_ready(ctx))?;
+        Poll::Ready(Ok(()))
+    }
+}
+
+pub struct Reader<T>
+where
+    T: bincode::Decode,
+{
+    mmap: AsyncMmapFile,
+    count: usize,
+    first_pos: LSize,
+    _t: PhantomData<Arc<T>>,
+}
+
+impl<T> Reader<T>
+where
+    T: bincode::Decode,
+{
+    pub async fn new<P: AsRef<Path>>(path: P) -> Result<Self, String> {
+        let mmap = AsyncOptions::new()
+            .read(true)
+            .open_mmap_file(path)
+            .await
+            .str_err()?;
+        mmap.try_lock_shared().str_err()?;
+
+        // read first pos and records count
+        let first_data: [u8; LEN_SIZE] = mmap.bytes(0, LEN_SIZE).str_err()?.try_into().str_err()?;
+        let first_pos = LSize::from_le_bytes(first_data);
+        let tab_len = (first_pos as usize) / LEN_SIZE;
+        let count = tab_len - 1;
+
+        Ok(Self {
+            mmap,
+            count,
+            first_pos,
+            _t: PhantomData,
+        })
+    }
+
+    pub fn len(&self) -> usize {
+        self.count
+    }
+
+    pub fn is_empty(&self) -> bool {
+        0 == self.len()
+    }
+
+    /// get item at index, reuse data buffer
+    pub async fn get_with_buf(&self, index: usize, data_buf: &mut Vec<u8>) -> Result<T, String> {
+        if index >= self.len() {
+            return Err("index out of range".into());
+        }
+
+        let next_pos: usize = (index + 1) * LEN_SIZE;
+
+        // read item data pos
+        let data_pos = if 0 == index {
+            self.first_pos
+        } else {
+            let tab_pos: usize = index * LEN_SIZE;
+            let pos_curr_data: [u8; LEN_SIZE] = self
+                .mmap
+                .bytes(tab_pos, LEN_SIZE)
+                .str_err()?
+                .try_into()
+                .str_err()?;
+            LSize::from_le_bytes(pos_curr_data)
+        } as usize;
+
+        // read next item pos
+        let pos_next_data: [u8; LEN_SIZE] = self
+            .mmap
+            .bytes(next_pos, LEN_SIZE)
+            .str_err()?
+            .try_into()
+            .str_err()?;
+        let data_pos_next = LSize::from_le_bytes(pos_next_data) as usize;
+        let data_len = data_pos_next - data_pos;
+
+        // read & unpack item data
+        let mut decoder = ZstdDecoder::new(self.mmap.range_reader(data_pos, data_len).str_err()?);
+        decoder.read_to_end(data_buf).await.str_err()?;
+
+        // decode item
+        let item: (T, usize) = bincode::decode_from_slice(data_buf, BINCODE_CFG).str_err()?;
+
+        data_buf.clear();
+        Ok(item.0)
+    }
+
+    /// get item at index
+    pub async fn get(&self, index: usize) -> Result<T, String> {
+        let mut data_buf: Vec<u8> = vec![];
+        self.get_with_buf(index, &mut data_buf).await
+    }
+
+    pub fn stream(&self) -> ReaderStream<'_, T> {
+        ReaderStream::new(self)
+    }
+}
+
+pub struct ReaderStream<'a, T>
+where
+    T: bincode::Decode,
+{
+    reader: &'a Reader<T>,
+    index: Option<usize>,
+}
+
+impl<'a, T> ReaderStream<'a, T>
+where
+    T: bincode::Decode,
+{
+    fn new(reader: &'a Reader<T>) -> Self {
+        ReaderStream {
+            reader,
+            index: None,
+        }
+    }
+}
+
+impl<'a, T> Stream for ReaderStream<'a, T>
+where
+    T: bincode::Decode,
+{
+    type Item = T;
+
+    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<T>> {
+        if self.index.is_none() && !self.reader.is_empty() {
+            self.index = Some(0);
+        }
+
+        if self.index.unwrap() == self.reader.len() {
+            return Poll::Ready(None);
+        }
+
+        // FIXME: mayby work only if reader.get().poll() return Ready immediately
+        let future = self.reader.get(self.index.unwrap());
+        pin_mut!(future);
+        match Pin::new(&mut future).poll(cx) {
+            Poll::Ready(Ok(item)) => {
+                self.index = Some(self.index.unwrap() + 1);
+                Poll::Ready(Some(item))
+            }
+            Poll::Ready(Err(_)) => Poll::Ready(None),
+            Poll::Pending => Poll::Pending,
+        }
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        let len = self.reader.len();
+        if self.index.is_none() {
+            return (len, Some(len));
+        }
+
+        let index = self.index.unwrap();
+        let rem = if len > index + 1 {
+            len - (index + 1)
+        } else {
+            0
+        };
+        (rem, Some(rem))
+    }
+}
+
+pub struct BufReader<T>
+where
+    T: bincode::Decode,
+{
+    inner: Reader<T>,
+    buf: Vec<u8>,
+}
+
+impl<T> BufReader<T>
+where
+    T: bincode::Decode,
+{
+    pub async fn new<P: AsRef<Path>>(path: P, buf_size: usize) -> Result<Self, String> {
+        match Reader::<T>::new(path).await {
+            Ok(inner) => Ok(Self {
+                inner,
+                buf: Vec::with_capacity(buf_size),
+            }),
+            Err(e) => Err(e),
+        }
+    }
+
+    pub async fn get(&mut self, index: usize) -> Result<T, String> {
+        self.inner.get_with_buf(index, &mut self.buf).await
+    }
+
+    pub fn into_inner(self) -> Reader<T> {
+        self.inner
+    }
+
+    pub fn stream(self) -> BufReaderStream<T> {
+        BufReaderStream::new(self)
+    }
+}
+
+impl<T> From<Reader<T>> for BufReader<T>
+where
+    T: bincode::Decode,
+{
+    fn from(inner: Reader<T>) -> Self {
+        Self {
+            inner,
+            buf: Vec::new(),
+        }
+    }
+}
+
+impl<T> From<BufReader<T>> for Reader<T>
+where
+    T: bincode::Decode,
+{
+    fn from(value: BufReader<T>) -> Self {
+        value.into_inner()
+    }
+}
+
+impl<T> Deref for BufReader<T>
+where
+    T: bincode::Decode,
+{
+    type Target = Reader<T>;
+    fn deref(&self) -> &Self::Target {
+        &self.inner
+    }
+}
+
+pub struct BufReaderStream<T>
+where
+    T: bincode::Decode,
+{
+    reader: BufReader<T>,
+    index: Option<usize>,
+}
+
+impl<T> BufReaderStream<T>
+where
+    T: bincode::Decode,
+{
+    fn new(reader: BufReader<T>) -> Self {
+        BufReaderStream {
+            reader,
+            index: None,
+        }
+    }
+
+    async fn get_next(&mut self) -> Result<T, String> {
+        match self.index {
+            None => Err("index is None".into()),
+            Some(index) => {
+                let res = self.reader.get(index).await;
+                self.index = Some(index + 1);
+
+                res
+            }
+        }
+    }
+}
+
+impl<T> Stream for BufReaderStream<T>
+where
+    T: bincode::Decode,
+{
+    type Item = T;
+
+    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<T>> {
+        if self.index.is_none() && !self.reader.is_empty() {
+            self.index = Some(0);
+        }
+
+        if self.index.unwrap() == self.reader.len() {
+            return Poll::Ready(None);
+        }
+
+        // FIXME: mayby work only if reader.get().poll() return Ready immediately
+        let future = self.get_next();
+        pin_mut!(future);
+        match Pin::new(&mut future).poll(cx) {
+            Poll::Ready(Ok(item)) => Poll::Ready(Some(item)),
+            Poll::Ready(Err(_)) => Poll::Ready(None),
+            Poll::Pending => Poll::Pending,
+        }
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        let len = self.reader.len();
+        if self.index.is_none() {
+            return (len, Some(len));
+        }
+
+        let index = self.index.unwrap();
+        let rem = if len > index + 1 {
+            len - (index + 1)
+        } else {
+            0
+        };
+        (rem, Some(rem))
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use core::fmt::Debug;
+    use tempfile::tempdir;
+
+    #[derive(bincode::Encode, bincode::Decode, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
+    struct TestData {
+        num: u64,
+        test: String,
+        vnum: Vec<u64>,
+        vstr: Vec<String>,
+    }
+
+    fn gen_data(count: usize) -> impl Iterator<Item = TestData> {
+        (0..count).map(|i| TestData {
+            num: i as u64,
+            test: "test".repeat(i),
+            vnum: (0..i * 120).map(|x| (x ^ 0x345FE34) as u64).collect(),
+            vstr: (0..i * 111).map(|x| "test".repeat(x)).collect(),
+        })
+    }
+
+    async fn assert_data_eq((x, y): (&TestData, TestData)) {
+        assert_eq!(*x, y);
+    }
+
+    #[tokio::test]
+    async fn test_write() {
+        let dir = tempdir().expect("tempdir");
+        let tmpfile = dir.path().join("test.tmp");
+        let opts = WriterOpts {
+            data_buf_size: 10 * 1024 * 1024,
+            out_buf_size: 10 * 1024 * 1024,
+            ..Default::default()
+        };
+        let mut writer: Writer<TestData> = Writer::new(&tmpfile, opts).await.expect("new writer");
+
+        let items_iter = gen_data(5);
+        let items: Vec<TestData> = items_iter.collect();
+
+        let src = futures::stream::iter(items.clone());
+        pin_mut!(src);
+        writer.load(src).await.expect("load");
+        writer.finish().await.expect("finish write");
+    }
+
+    #[tokio::test]
+    async fn test_write_read() {
+        let dir = tempdir().expect("tempdir");
+        let tmpfile = dir.path().join("test.tmp");
+        let opts = WriterOpts {
+            data_buf_size: 10 * 1024 * 1024,
+            out_buf_size: 10 * 1024 * 1024,
+            ..Default::default()
+        };
+        let mut writer: Writer<TestData> = Writer::new(&tmpfile, opts).await.expect("new writer");
+
+        let items_iter = gen_data(5);
+        let items: Vec<TestData> = items_iter.collect();
+
+        let src = futures::stream::iter(items.clone());
+        pin_mut!(src);
+        writer.load(src).await.expect("load");
+        writer.finish().await.expect("finish write");
+
+        let reader: Reader<TestData> = Reader::new(&tmpfile).await.expect("new reader");
+        assert_eq!(items.len(), reader.len());
+
+        for (idx, item) in items.iter().enumerate() {
+            let ritem = reader.get(idx).await.expect("get");
+            assert_eq!(*item, ritem);
+        }
+    }
+
+    #[tokio::test]
+    async fn test_write_sink_read() {
+        let dir = tempdir().expect("tempdir");
+        let tmpfile = dir.path().join("test.tmp");
+        let opts = WriterOpts {
+            data_buf_size: 10 * 1024 * 1024,
+            out_buf_size: 10 * 1024 * 1024,
+            ..Default::default()
+        };
+        let mut writer: Writer<TestData> = Writer::new(&tmpfile, opts).await.expect("new writer");
+
+        let items_iter = gen_data(5);
+        let items: Vec<TestData> = items_iter.collect();
+
+        let src = futures::stream::iter(items.clone()).map(Ok);
+        pin_mut!(src);
+        src.forward(writer.sink()).await.expect("forward");
+        writer.finish().await.expect("finish write");
+
+        let reader: Reader<TestData> = Reader::new(&tmpfile).await.expect("new reader");
+        assert_eq!(items.len(), reader.len());
+
+        for (idx, item) in items.iter().enumerate() {
+            let ritem = reader.get(idx).await.expect("get");
+            assert_eq!(*item, ritem);
+        }
+    }
+
+    #[tokio::test]
+    async fn test_write_read_get_with_buf() {
+        let dir = tempdir().expect("tempdir");
+        let tmpfile = dir.path().join("test.tmp");
+        let opts = WriterOpts {
+            data_buf_size: 10 * 1024 * 1024,
+            out_buf_size: 10 * 1024 * 1024,
+            ..Default::default()
+        };
+        let mut writer: Writer<TestData> = Writer::new(&tmpfile, opts).await.expect("new writer");
+
+        let items_iter = gen_data(5);
+        let items: Vec<TestData> = items_iter.collect();
+
+        let src = futures::stream::iter(items.clone());
+        pin_mut!(src);
+        writer.load(src).await.expect("load");
+        writer.finish().await.expect("finish write");
+
+        let reader: Reader<TestData> = Reader::new(&tmpfile).await.expect("new reader");
+        assert_eq!(items.len(), reader.len());
+
+        for (idx, item) in items.iter().enumerate() {
+            let mut data_buf: Vec<u8> = vec![];
+            let ritem = reader.get_with_buf(idx, &mut data_buf).await.expect("get");
+            assert_eq!(*item, ritem);
+        }
+    }
+
+    #[tokio::test]
+    async fn test_write_read_stream() {
+        let dir = tempdir().expect("tempdir");
+        let tmpfile = dir.path().join("test.tmp");
+        let opts = WriterOpts {
+            data_buf_size: 10 * 1024 * 1024,
+            out_buf_size: 10 * 1024 * 1024,
+            ..Default::default()
+        };
+        let mut writer: Writer<TestData> = Writer::new(&tmpfile, opts).await.expect("new writer");
+
+        let items_iter = gen_data(5);
+        let items: Vec<TestData> = items_iter.collect();
+
+        let src = futures::stream::iter(items.clone());
+        pin_mut!(src);
+        writer.load(src).await.expect("load");
+        writer.finish().await.expect("finish write");
+
+        let reader: Reader<TestData> = Reader::new(&tmpfile).await.expect("new reader");
+        assert_eq!(items.len(), reader.len());
+
+        let dst_stream = reader.stream();
+        let src_stream = futures::stream::iter(items.iter());
+
+        let mut count = 0;
+        src_stream
+            .zip(dst_stream)
+            .map(|x| {
+                count += 1;
+                x
+            })
+            .for_each(assert_data_eq)
+            .await;
+        assert_eq!(count, items.len())
+    }
+    /// sharing Reader instance between threads
+    #[tokio::test]
+    async fn test_share_reader() {
+        let dir = tempdir().expect("tempdir");
+        let tmpfile = dir.path().join("test.tmp");
+        let opts = WriterOpts {
+            data_buf_size: 10 * 1024 * 1024,
+            out_buf_size: 10 * 1024 * 1024,
+            ..Default::default()
+        };
+        let mut writer: Writer<TestData> = Writer::new(&tmpfile, opts).await.expect("new writer");
+
+        let items_iter = gen_data(5);
+        let items: Vec<TestData> = items_iter.collect();
+
+        let src = futures::stream::iter(items.clone());
+        pin_mut!(src);
+        writer.load(src).await.expect("load");
+        writer.finish().await.expect("finish write");
+
+        let reader: Reader<TestData> = Reader::new(&tmpfile).await.expect("new reader");
+        assert_eq!(items.len(), reader.len());
+
+        let reader = Arc::new(reader);
+        for _ in 0..=3 {
+            let cur_items = items.clone();
+            let cur_reader = Arc::clone(&reader);
+            tokio::spawn(async move {
+                let dst_stream = cur_reader.stream();
+                let src_stream = futures::stream::iter(cur_items.iter());
+
+                src_stream.zip(dst_stream).for_each(assert_data_eq).await;
+            });
+        }
+    }
+
+    #[tokio::test]
+    async fn test_write_bufread() {
+        let dir = tempdir().expect("tempdir");
+        let tmpfile = dir.path().join("test.tmp");
+        let opts = WriterOpts {
+            data_buf_size: 10 * 1024 * 1024,
+            out_buf_size: 10 * 1024 * 1024,
+            ..Default::default()
+        };
+        let mut writer: Writer<TestData> = Writer::new(&tmpfile, opts).await.expect("new writer");
+
+        let items_iter = gen_data(5);
+        let items: Vec<TestData> = items_iter.collect();
+
+        let src = futures::stream::iter(items.clone());
+        pin_mut!(src);
+        writer.load(src).await.expect("load");
+        writer.finish().await.expect("finish write");
+
+        let mut reader = BufReader::<TestData>::new(&tmpfile, 4096)
+            .await
+            .expect("new buf reader");
+        assert_eq!(items.len(), reader.len());
+
+        for (idx, item) in items.iter().enumerate() {
+            let ritem = reader.get(idx).await.expect("get");
+            assert_eq!(*item, ritem);
+        }
+    }
+
+    #[tokio::test]
+    async fn test_write_bufread_stream() {
+        let dir = tempdir().expect("tempdir");
+        let tmpfile = dir.path().join("test.tmp");
+        let opts = WriterOpts {
+            data_buf_size: 10 * 1024 * 1024,
+            out_buf_size: 10 * 1024 * 1024,
+            ..Default::default()
+        };
+        let mut writer: Writer<TestData> = Writer::new(&tmpfile, opts).await.expect("new writer");
+
+        let items_iter = gen_data(5);
+        let items: Vec<TestData> = items_iter.collect();
+
+        let src = futures::stream::iter(items.clone());
+        pin_mut!(src);
+        writer.load(src).await.expect("load");
+        writer.finish().await.expect("finish write");
+
+        let reader = BufReader::<TestData>::new(&tmpfile, 4096)
+            .await
+            .expect("new buf reader");
+        assert_eq!(items.len(), reader.len());
+
+        let dst_stream = reader.stream();
+        let src_stream = futures::stream::iter(items.iter());
+
+        let mut count = 0;
+        src_stream
+            .zip(dst_stream)
+            .map(|x| {
+                count += 1;
+                x
+            })
+            .for_each(assert_data_eq)
+            .await;
+        assert_eq!(count, items.len())
+    }
+}
--- a/lib/src/db.rs
+++ b/lib/src/db.rs
@ -3,6 +3,7 @@ use std::{
    io::{self, Cursor, Read, Write},
    marker::PhantomData,
    path::Path,
+    sync::Arc,
 };

 use memmap::{Mmap, MmapOptions};
@ -11,20 +12,8 @@ type LSize = u32;
 const LEN_SIZE: usize = std::mem::size_of::<LSize>();
 const BINCODE_CFG: bincode::config::Configuration = bincode::config::standard();

-trait ErrorToString {
-    type Output;
-    fn str_err(self) -> std::result::Result<Self::Output, String>;
-}
-
-impl<T, E> ErrorToString for std::result::Result<T, E>
-where
-    E: std::error::Error,
-{
-    type Output = T;
-    fn str_err(self) -> std::result::Result<Self::Output, String> {
-        self.map_err(|e| e.to_string())
-    }
-}
+use crate::util::BincodeVecWriter;
+use crate::util::ErrorToString;

 pub struct WriterOpts {
    pub compress_lvl: i32,
@ -51,9 +40,10 @@ where
    out: io::BufWriter<fs::File>,
    data_buf: Cursor<Vec<u8>>,
    cur_buf_raw: Cursor<Vec<u8>>,
+    cur_buf_item: BincodeVecWriter,
    table: Vec<LSize>,
    compress_lvl: i32,
-    _t: PhantomData<*const T>,
+    _t: PhantomData<Arc<T>>,
 }

 impl<T> Writer<T>
@ -68,6 +58,8 @@ where

        let cur_buf_raw: Vec<u8> = Vec::with_capacity(opts.current_buf_size);
        let cur_buf_raw = Cursor::new(cur_buf_raw);
+        let cur_buf_item: Vec<u8> = Vec::with_capacity(opts.current_buf_size);
+        let cur_buf_item = BincodeVecWriter::new(cur_buf_item);

        let compress_lvl = opts.compress_lvl;

@ -77,6 +69,7 @@ where
            out,
            data_buf,
            cur_buf_raw,
+            cur_buf_item,
            table,
            compress_lvl,
            _t: PhantomData,
@ -84,20 +77,25 @@ where
    }

    pub fn push(&mut self, item: T) -> Result<(), String> {
+        self.push_by_ref(&item)
+    }
+
+    pub fn push_by_ref(&mut self, item: &T) -> Result<(), String> {
        let pos: LSize = self.data_buf.position() as LSize;

-        let item_data = bincode::encode_to_vec(item, BINCODE_CFG).str_err()?;
+        bincode::encode_into_writer(item, &mut self.cur_buf_item, BINCODE_CFG).str_err()?;

        let mut zencoder = zstd::stream::raw::Encoder::new(self.compress_lvl).str_err()?;
        zencoder
-            .set_pledged_src_size(item_data.len() as u64)
+            .set_pledged_src_size(Some(self.cur_buf_item.len() as u64))
            .str_err()?;

        self.cur_buf_raw.set_position(0);
        let mut cur_buf_z = zstd::stream::zio::Writer::new(&mut self.cur_buf_raw, zencoder);
-        cur_buf_z.write_all(&item_data).str_err()?;
+        cur_buf_z.write_all(&self.cur_buf_item).str_err()?;
        cur_buf_z.finish().str_err()?;
        cur_buf_z.flush().str_err()?;
+        self.cur_buf_item.clear();

        self.table.push(pos);
        let (cur_buf_raw, _) = cur_buf_z.into_inner();
@ -157,7 +155,7 @@ where
    mmap: Mmap,
    count: usize,
    first_pos: LSize,
-    _t: PhantomData<*const T>,
+    _t: PhantomData<Arc<T>>,
 }

 impl<T> Reader<T>
@ -186,7 +184,11 @@ where
        self.count
    }

-    pub fn get(&mut self, index: usize) -> Result<T, String> {
+    pub fn is_empty(&self) -> bool {
+        0 == self.len()
+    }
+
+    pub fn get(&self, index: usize) -> Result<T, String> {
        if index >= self.len() {
            return Err("index out of range".into());
        }
@ -218,7 +220,7 @@ where
        Ok(item.0)
    }

-    pub fn iter(&mut self) -> ReaderIter<'_, T> {
+    pub fn iter(&self) -> ReaderIter<'_, T> {
        ReaderIter::new(self)
    }
 }
@ -227,7 +229,7 @@ pub struct ReaderIter<'a, T>
 where
    T: bincode::Decode,
 {
-    reader: &'a mut Reader<T>,
+    reader: &'a Reader<T>,
    index: Option<usize>,
 }

@ -235,7 +237,7 @@ impl<'a, T> ReaderIter<'a, T>
 where
    T: bincode::Decode,
 {
-    fn new(reader: &'a mut Reader<T>) -> Self {
+    fn new(reader: &'a Reader<T>) -> Self {
        ReaderIter {
            reader,
            index: None,
@ -250,7 +252,7 @@ where
    type Item = T;

    fn next(&mut self) -> Option<Self::Item> {
-        if self.index.is_none() && self.reader.len() != 0 {
+        if self.index.is_none() && !self.reader.is_empty() {
            self.index = Some(0);
        }

@ -305,6 +307,100 @@ where
    }
 }

+pub struct ReaderIntoIter<T>
+where
+    T: bincode::Decode,
+{
+    reader: Reader<T>,
+    index: Option<usize>,
+}
+
+impl<T> ReaderIntoIter<T>
+where
+    T: bincode::Decode,
+{
+    fn new(reader: Reader<T>) -> Self {
+        Self {
+            reader,
+            index: None,
+        }
+    }
+}
+
+impl<T> Iterator for ReaderIntoIter<T>
+where
+    T: bincode::Decode,
+{
+    type Item = T;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.index.is_none() && !self.reader.is_empty() {
+            self.index = Some(0);
+        }
+
+        match self.index {
+            Some(i) if i < self.reader.len() => self.nth(i),
+            _ => None,
+        }
+    }
+
+    fn nth(&mut self, n: usize) -> Option<Self::Item> {
+        if self.reader.len() <= n {
+            return None;
+        }
+        self.index = Some(n + 1);
+
+        let item = self.reader.get(n);
+        match item {
+            Ok(item) => Some(item),
+            Err(_) => None,
+        }
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        let len = self.reader.len();
+        if self.index.is_none() {
+            return (len, Some(len));
+        }
+
+        let index = self.index.unwrap();
+        let rem = if len > index + 1 {
+            len - (index + 1)
+        } else {
+            0
+        };
+        (rem, Some(rem))
+    }
+
+    fn count(self) -> usize
+    where
+        Self: Sized,
+    {
+        self.reader.len()
+    }
+}
+
+impl<T> ExactSizeIterator for ReaderIntoIter<T>
+where
+    T: bincode::Decode,
+{
+    fn len(&self) -> usize {
+        self.reader.len()
+    }
+}
+
+impl<T> IntoIterator for Reader<T>
+where
+    T: bincode::Decode,
+{
+    type Item = T;
+    type IntoIter = ReaderIntoIter<Self::Item>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        Self::IntoIter::new(self)
+    }
+}
+
 #[cfg(test)]
 mod test {
    use super::*;
@ -317,7 +413,7 @@ mod test {
    }

    fn gen_data(count: usize) -> impl Iterator<Item = TestData> {
-        (0..count).into_iter().map(|i| TestData {
+        (0..count).map(|i| TestData {
            num: i as u64,
            test: "test".repeat(i),
        })
@ -341,7 +437,7 @@ mod test {
        writer.load(&mut items.clone().into_iter()).expect("load");
        writer.finish().expect("finish write");

-        let mut reader: Reader<TestData> = Reader::new(&tmpfile, 2048).expect("new reader");
+        let reader: Reader<TestData> = Reader::new(&tmpfile, 2048).expect("new reader");
        assert_eq!(items.len(), reader.len());

        for (idx, item) in items.iter().enumerate() {
@ -368,11 +464,76 @@ mod test {
        writer.load(&mut items.clone().into_iter()).expect("load");
        writer.finish().expect("finish write");

-        let mut reader: Reader<TestData> = Reader::new(&tmpfile, 2048).expect("new reader");
+        let reader: Reader<TestData> = Reader::new(&tmpfile, 2048).expect("new reader");
        assert_eq!(items.len(), reader.len());

        items.into_iter().zip(reader.iter()).for_each(|pair| {
            assert_eq!(pair.0, pair.1);
        });
    }
+
+    #[test]
+    fn test_write_read_into_iter() {
+        let dir = tempdir().expect("tempdir");
+        let tmpfile = dir.path().join("test.tmp");
+        let opts = WriterOpts {
+            compress_lvl: 1,
+            data_buf_size: 10 * 1024 * 1024,
+            out_buf_size: 10 * 1024 * 1024,
+            current_buf_size: 4096,
+        };
+        let mut writer: Writer<TestData> = Writer::new(&tmpfile, opts).expect("new writer");
+
+        let items_iter = gen_data(10);
+        let items: Vec<TestData> = items_iter.collect();
+
+        writer.load(&mut items.clone().into_iter()).expect("load");
+        writer.finish().expect("finish write");
+
+        let reader: Reader<TestData> = Reader::new(&tmpfile, 2048).expect("new reader");
+        assert_eq!(items.len(), reader.len());
+
+        items.into_iter().zip(reader).for_each(|pair| {
+            assert_eq!(pair.0, pair.1);
+        });
+    }
+
+    /// sharing Reader instance between threads
+    #[test]
+    fn test_share_reader() {
+        use std::thread;
+
+        let dir = tempdir().expect("tempdir");
+        let tmpfile = dir.path().join("test.tmp");
+        let opts = WriterOpts {
+            compress_lvl: 1,
+            data_buf_size: 10 * 1024 * 1024,
+            out_buf_size: 10 * 1024 * 1024,
+            current_buf_size: 4096,
+        };
+        let mut writer: Writer<TestData> = Writer::new(&tmpfile, opts).expect("new writer");
+
+        let items_iter = gen_data(10);
+        let items: Vec<TestData> = items_iter.collect();
+
+        writer.load(&mut items.clone().into_iter()).expect("load");
+        writer.finish().expect("finish write");
+
+        let reader: Reader<TestData> = Reader::new(&tmpfile, 2048).expect("new reader");
+        assert_eq!(items.len(), reader.len());
+
+        let reader = Arc::new(reader);
+        for _ in 0..=3 {
+            let cur_items = items.clone();
+            let cur_reader = Arc::clone(&reader);
+            thread::spawn(move || {
+                cur_items
+                    .into_iter()
+                    .zip(cur_reader.iter())
+                    .for_each(|pair| {
+                        assert_eq!(pair.0, pair.1);
+                    });
+            });
+        }
+    }
 }
--- a/lib/src/lib.rs
+++ b/lib/src/lib.rs
@ -0,0 +1,13 @@
+#[cfg(feature = "async")]
+pub mod async_db;
+#[cfg(feature = "sync")]
+pub mod db;
+pub mod questions;
+#[cfg(any(
+    feature = "source",
+    feature = "source_async",
+    feature = "convert",
+    feature = "convert_async"
+))]
+pub mod source;
+pub mod util;
--- a/lib/src/questions.rs
+++ b/lib/src/questions.rs
@ -0,0 +1,398 @@
+use serde_derive::{Deserialize, Serialize};
+
+#[derive(
+    Debug, Default, Clone, Serialize, Deserialize, bincode::Decode, bincode::Encode, PartialEq,
+)]
+pub struct BatchInfo {
+    #[serde(default, skip_serializing_if = "String::is_empty")]
+    pub filename: String,
+    #[serde(default, skip_serializing_if = "String::is_empty")]
+    pub description: String,
+    #[serde(default, skip_serializing_if = "String::is_empty")]
+    pub author: String,
+    #[serde(default, skip_serializing_if = "String::is_empty")]
+    pub comment: String,
+    #[serde(default, skip_serializing_if = "String::is_empty")]
+    pub url: String,
+    #[serde(default, skip_serializing_if = "String::is_empty")]
+    pub date: String,
+    #[serde(default, skip_serializing_if = "String::is_empty")]
+    pub processed_by: String,
+    #[serde(default, skip_serializing_if = "String::is_empty")]
+    pub redacted_by: String,
+    #[serde(default, skip_serializing_if = "String::is_empty")]
+    pub copyright: String,
+    #[serde(default, skip_serializing_if = "String::is_empty")]
+    pub theme: String,
+    #[serde(default, skip_serializing_if = "String::is_empty")]
+    pub kind: String,
+    #[serde(default, skip_serializing_if = "String::is_empty")]
+    pub source: String,
+    #[serde(default, skip_serializing_if = "String::is_empty")]
+    pub rating: String,
+}
+
+#[derive(
+    Debug, Default, Clone, Serialize, Deserialize, bincode::Decode, bincode::Encode, PartialEq,
+)]
+pub struct Question {
+    #[serde(default, skip_serializing_if = "u32_is_zero")]
+    pub num: u32,
+    pub id: String,
+
+    pub description: String,
+    pub answer: String,
+
+    #[serde(default, skip_serializing_if = "String::is_empty")]
+    pub author: String,
+    #[serde(default, skip_serializing_if = "String::is_empty")]
+    pub comment: String,
+    #[serde(default, skip_serializing_if = "String::is_empty")]
+    pub comment1: String,
+    #[serde(default, skip_serializing_if = "String::is_empty")]
+    pub tour: String,
+    #[serde(default, skip_serializing_if = "String::is_empty")]
+    pub url: String,
+    #[serde(default, skip_serializing_if = "String::is_empty")]
+    pub date: String,
+    #[serde(default, skip_serializing_if = "String::is_empty")]
+    pub processed_by: String,
+    #[serde(default, skip_serializing_if = "String::is_empty")]
+    pub redacted_by: String,
+    #[serde(default, skip_serializing_if = "String::is_empty")]
+    pub copyright: String,
+    #[serde(default, skip_serializing_if = "String::is_empty")]
+    pub theme: String,
+    #[serde(default, skip_serializing_if = "String::is_empty")]
+    pub kind: String,
+    #[serde(default, skip_serializing_if = "String::is_empty")]
+    pub source: String,
+    #[serde(default, skip_serializing_if = "String::is_empty")]
+    pub rating: String,
+    #[serde(default, skip_serializing_if = "BatchInfo::is_default")]
+    pub batch_info: BatchInfo,
+}
+
+fn u32_is_zero(num: &u32) -> bool {
+    *num == 0
+}
+
+impl BatchInfo {
+    pub fn is_default(&self) -> bool {
+        *self == BatchInfo::default()
+    }
+}
+
+#[cfg(any(feature = "convert", feature = "convert_async"))]
+pub mod convert_common {
+    use super::{BatchInfo, Question};
+    use crate::source::{SourceQuestion, SourceQuestionsBatch};
+
+    macro_rules! make {
+        ($Target:ident; by {$($field:ident),+}; from $src:expr) => {$Target {$(
+            $field: $src.$field
+        ),+}};
+        ($Target:ident; with defaults and by {$($field:ident),+}; from $src:expr) => {$Target {$(
+            $field: $src.$field
+        ),+ ,..$Target::default()}}
+    }
+
+    impl From<SourceQuestion> for Question {
+        fn from(src: SourceQuestion) -> Self {
+            make! {Self; with defaults and by {
+                num, id, description, answer, author, comment, comment1, tour, url,
+                date, processed_by, redacted_by, copyright, theme, kind, source, rating
+            }; from src}
+        }
+    }
+
+    impl From<SourceQuestionsBatch> for BatchInfo {
+        fn from(src: SourceQuestionsBatch) -> Self {
+            make! {Self; by {
+                filename, description, author, comment, url, date,
+                processed_by, redacted_by, copyright, theme, kind, source, rating
+            }; from src}
+        }
+    }
+
+    impl From<SourceQuestionsBatch> for Vec<Question> {
+        fn from(src: SourceQuestionsBatch) -> Self {
+            let mut src = src;
+            let mut questions: Vec<SourceQuestion> = vec![];
+            std::mem::swap(&mut src.questions, &mut questions);
+            let mut result: Vec<Question> = questions.into_iter().map(|item| item.into()).collect();
+            let batch_info = BatchInfo::from(src);
+            result.iter_mut().for_each(|question| {
+                question.batch_info = batch_info.clone();
+            });
+
+            result
+        }
+    }
+}
+
+#[cfg(feature = "convert")]
+pub mod convert {
+    use super::Question;
+    use crate::source::SourceQuestionsBatch;
+
+    pub trait QuestionsConverter {
+        fn convert<'a>(&'a mut self) -> Box<dyn Iterator<Item = Question> + 'a>;
+    }
+
+    impl<T> QuestionsConverter for T
+    where
+        T: Iterator<Item = (String, Result<SourceQuestionsBatch, serde_json::Error>)>,
+    {
+        fn convert<'a>(&'a mut self) -> Box<dyn Iterator<Item = Question> + 'a> {
+            let iter = self
+                .filter(|(_, data)| data.is_ok())
+                .flat_map(|(filename, data)| {
+                    let mut batch = data.unwrap();
+                    batch.filename = filename;
+                    let questions: Vec<Question> = batch.into();
+                    questions
+                });
+            Box::new(iter)
+        }
+    }
+
+    #[cfg(test)]
+    mod test {
+        use crate::questions::test::convert_common::sample_batch;
+
+        use super::*;
+        use insta::assert_yaml_snapshot;
+        use std::iter;
+
+        #[test]
+        fn test_convert() {
+            let mut source = iter::once((
+                String::from("test.json"),
+                Ok::<SourceQuestionsBatch, serde_json::Error>(sample_batch()),
+            ));
+            let converted: Vec<_> = source.convert().collect();
+            assert_yaml_snapshot!(converted, @r#"
+            ---
+            - id: Вопрос 1
+              description: Сколько будет (2 * 2 * 2 + 2) * 2 * 2 + 2
+              answer: "42"
+              batch_info:
+                filename: test.json
+                description: Тестовый
+                date: 00-000-2000
+            - id: Вопрос 2
+              description: Зимой и летом одним цветом
+              answer: ёлка
+              batch_info:
+                filename: test.json
+                description: Тестовый
+                date: 00-000-2000
+              
+            "#);
+        }
+    }
+}
+#[cfg(feature = "convert")]
+pub use convert::QuestionsConverter;
+
+#[cfg(feature = "convert_async")]
+pub mod convert_async {
+    use futures::stream;
+    use futures_core::stream::Stream;
+    use futures_util::StreamExt;
+
+    use super::Question;
+    use crate::source::SourceQuestionsBatch;
+
+    pub struct QuestionsConverterAsync<T>
+    where
+        T: Stream<Item = (String, Result<SourceQuestionsBatch, serde_json::Error>)>
+            + std::marker::Unpin,
+    {
+        inner: T,
+    }
+
+    impl<T> From<T> for QuestionsConverterAsync<T>
+    where
+        T: Stream<Item = (String, Result<SourceQuestionsBatch, serde_json::Error>)>
+            + std::marker::Unpin,
+    {
+        fn from(inner: T) -> Self {
+            Self { inner }
+        }
+    }
+
+    pub trait QuestionsConverterAsyncForStream<T>
+    where
+        T: Stream<Item = (String, Result<SourceQuestionsBatch, serde_json::Error>)>
+            + std::marker::Unpin,
+    {
+        fn converter(&mut self) -> QuestionsConverterAsync<&mut T>;
+    }
+
+    impl<T> QuestionsConverterAsyncForStream<T> for T
+    where
+        T: Stream<Item = (String, Result<SourceQuestionsBatch, serde_json::Error>)>
+            + std::marker::Unpin,
+    {
+        fn converter(&mut self) -> QuestionsConverterAsync<&mut T> {
+            QuestionsConverterAsync::from(self)
+        }
+    }
+
+    impl<T> QuestionsConverterAsync<T>
+    where
+        T: Stream<Item = (String, Result<SourceQuestionsBatch, serde_json::Error>)>
+            + std::marker::Unpin,
+    {
+        pub fn convert(self) -> impl Stream<Item = Question> {
+            self.inner
+                .filter_map(|(name, res)| async move {
+                    if let Ok(item) = res {
+                        Some((name, item))
+                    } else {
+                        None
+                    }
+                })
+                .flat_map(|(filename, batch)| {
+                    stream::iter({
+                        let mut batch = batch;
+                        batch.filename = filename;
+                        let questions: Vec<Question> = batch.into();
+                        questions
+                    })
+                })
+        }
+    }
+
+    #[cfg(test)]
+    mod test {
+        use crate::questions::test::convert_common::sample_batch;
+
+        use super::*;
+        use futures_util::{pin_mut, StreamExt};
+        use insta::assert_yaml_snapshot;
+
+        #[tokio::test]
+        async fn test_convert_stream() {
+            let source = futures::stream::once(async {
+                (
+                    String::from("test.json"),
+                    Ok::<SourceQuestionsBatch, serde_json::Error>(sample_batch()),
+                )
+            });
+
+            pin_mut!(source);
+            let converter = source.converter();
+            let converter = converter.convert();
+            let converted: Vec<_> = converter.collect().await;
+            assert_yaml_snapshot!(converted, @r#"
+            ---
+            - id: Вопрос 1
+              description: Сколько будет (2 * 2 * 2 + 2) * 2 * 2 + 2
+              answer: "42"
+              batch_info:
+                filename: test.json
+                description: Тестовый
+                date: 00-000-2000
+            - id: Вопрос 2
+              description: Зимой и летом одним цветом
+              answer: ёлка
+              batch_info:
+                filename: test.json
+                description: Тестовый
+                date: 00-000-2000
+              
+            "#);
+        }
+    }
+}
+#[cfg(feature = "convert_async")]
+pub use convert_async::{QuestionsConverterAsync, QuestionsConverterAsyncForStream};
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use insta::assert_yaml_snapshot;
+    use serde_json::json;
+
+    #[cfg(any(feature = "convert", feature = "convert_async"))]
+    pub mod convert_common {
+        use crate::source::{SourceQuestion, SourceQuestionsBatch};
+
+        pub fn sample_batch() -> SourceQuestionsBatch {
+            SourceQuestionsBatch {
+                description: "Тестовый".into(),
+                date: "00-000-2000".into(),
+                questions: vec![
+                    SourceQuestion {
+                        id: "Вопрос 1".into(),
+                        description: "Сколько будет (2 * 2 * 2 + 2) * 2 * 2 + 2".into(),
+                        answer: "42".into(),
+                        ..Default::default()
+                    },
+                    SourceQuestion {
+                        id: "Вопрос 2".into(),
+                        description: "Зимой и летом одним цветом".into(),
+                        answer: "ёлка".into(),
+                        ..Default::default()
+                    },
+                ],
+                ..Default::default()
+            }
+        }
+    }
+
+    pub fn sample_question() -> Question {
+        Question {
+            id: "Вопрос 1".into(),
+            description: "Сколько будет (2 * 2 * 2 + 2) * 2 * 2 + 2".into(),
+            answer: "42".into(),
+            batch_info: BatchInfo {
+                description: "Тестовый".into(),
+                date: "00-000-2000".into(),
+                ..Default::default()
+            },
+            ..Default::default()
+        }
+    }
+
+    #[test]
+    fn test_question_ser() {
+        assert_yaml_snapshot!(sample_question(), @r#"
+            ---
+            id: Вопрос 1
+            description: Сколько будет (2 * 2 * 2 + 2) * 2 * 2 + 2
+            answer: "42"
+            batch_info:
+              description: Тестовый
+              date: 00-000-2000
+              
+            "#);
+    }
+    #[test]
+    fn test_question_de() {
+        let question_from_json: Result<Question, _> = serde_json::from_value(json!({
+            "id": "Вопрос 1",
+            "description": "Сколько будет (2 * 2 * 2 + 2) * 2 * 2 + 2",
+            "answer": "42",
+            "batch_info": {
+                "description": "Тестовый",
+                "date": "00-000-2000"
+            }
+        }));
+        assert!(question_from_json.is_ok());
+
+        assert_yaml_snapshot!(question_from_json.unwrap(), @r#"
+        ---
+        id: Вопрос 1
+        description: Сколько будет (2 * 2 * 2 + 2) * 2 * 2 + 2
+        answer: "42"
+        batch_info:
+          description: Тестовый
+          date: 00-000-2000
+          
+        "#);
+    }
+}
--- a/lib/src/source.rs
+++ b/lib/src/source.rs
@ -0,0 +1,579 @@
+use serde_derive::{Deserialize, Serialize};
+
+#[derive(Debug, Default, Clone, Serialize, Deserialize, PartialEq)]
+pub struct SourceQuestion {
+    #[serde(default, skip_serializing_if = "u32_is_zero")]
+    pub num: u32,
+    #[serde(default)]
+    pub id: String,
+
+    #[serde(alias = "Вопрос")]
+    pub description: String,
+    #[serde(alias = "Ответ")]
+    pub answer: String,
+
+    #[serde(alias = "Автор", default, skip_serializing_if = "String::is_empty")]
+    pub author: String,
+    #[serde(
+        default,
+        alias = "Комментарий",
+        skip_serializing_if = "String::is_empty"
+    )]
+    pub comment: String,
+    #[serde(
+        default,
+        alias = "Комментарии",
+        alias = "Инфо",
+        skip_serializing_if = "String::is_empty"
+    )]
+    pub comment1: String,
+    #[serde(default, alias = "Тур", skip_serializing_if = "String::is_empty")]
+    pub tour: String,
+    #[serde(
+        default,
+        alias = "Ссылка",
+        alias = "URL",
+        skip_serializing_if = "String::is_empty"
+    )]
+    pub url: String,
+    #[serde(default, alias = "Дата", skip_serializing_if = "String::is_empty")]
+    pub date: String,
+    #[serde(default, alias = "Обработан", skip_serializing_if = "String::is_empty")]
+    pub processed_by: String,
+    #[serde(default, alias = "Редактор", skip_serializing_if = "String::is_empty")]
+    pub redacted_by: String,
+    #[serde(default, alias = "Копирайт", skip_serializing_if = "String::is_empty")]
+    pub copyright: String,
+    #[serde(default, alias = "Тема", skip_serializing_if = "String::is_empty")]
+    pub theme: String,
+    #[serde(
+        default,
+        alias = "Вид",
+        alias = "Тип",
+        skip_serializing_if = "String::is_empty"
+    )]
+    pub kind: String,
+    #[serde(default, alias = "Источник", skip_serializing_if = "String::is_empty")]
+    pub source: String,
+    #[serde(default, alias = "Рейтинг", skip_serializing_if = "String::is_empty")]
+    pub rating: String,
+}
+
+#[derive(Debug, Default, Clone, Serialize, Deserialize, PartialEq)]
+pub struct SourceQuestionsBatch {
+    #[serde(default, skip_serializing_if = "String::is_empty")]
+    pub filename: String,
+    #[serde(alias = "Пакет", alias = "Чемпионат")]
+    pub description: String,
+    #[serde(default, alias = "Автор", skip_serializing_if = "String::is_empty")]
+    pub author: String,
+    #[serde(
+        default,
+        alias = "Комментарий",
+        alias = "Комментарии",
+        alias = "Инфо",
+        skip_serializing_if = "String::is_empty"
+    )]
+    pub comment: String,
+    #[serde(
+        default,
+        alias = "Ссылка",
+        alias = "URL",
+        skip_serializing_if = "String::is_empty"
+    )]
+    pub url: String,
+    #[serde(default, alias = "Дата", skip_serializing_if = "String::is_empty")]
+    pub date: String,
+    #[serde(default, alias = "Обработан", skip_serializing_if = "String::is_empty")]
+    pub processed_by: String,
+    #[serde(default, alias = "Редактор", skip_serializing_if = "String::is_empty")]
+    pub redacted_by: String,
+    #[serde(default, alias = "Копирайт", skip_serializing_if = "String::is_empty")]
+    pub copyright: String,
+    #[serde(default, alias = "Тема", skip_serializing_if = "String::is_empty")]
+    pub theme: String,
+    #[serde(
+        default,
+        alias = "Вид",
+        alias = "Тип",
+        skip_serializing_if = "String::is_empty"
+    )]
+    pub kind: String,
+    #[serde(default, alias = "Источник", skip_serializing_if = "String::is_empty")]
+    pub source: String,
+    #[serde(default, alias = "Рейтинг", skip_serializing_if = "String::is_empty")]
+    pub rating: String,
+    #[serde(alias = "Вопросы")]
+    pub questions: Vec<SourceQuestion>,
+}
+
+fn u32_is_zero(num: &u32) -> bool {
+    *num == 0
+}
+
+#[cfg(any(feature = "convert", feature = "source"))]
+pub mod reader_sync {
+    use std::io::{Read, Seek};
+    use zip::ZipArchive;
+
+    use super::SourceQuestionsBatch;
+
+    pub struct SourceQuestionsZipReader<R>
+    where
+        R: Read + Seek,
+    {
+        zipfile: ZipArchive<R>,
+        index: Option<usize>,
+    }
+
+    impl<R> SourceQuestionsZipReader<R>
+    where
+        R: Read + Seek,
+    {
+        fn new(zipfile: ZipArchive<R>) -> Self {
+            SourceQuestionsZipReader {
+                zipfile,
+                index: None,
+            }
+        }
+    }
+
+    impl<R> Iterator for SourceQuestionsZipReader<R>
+    where
+        R: Read + Seek,
+    {
+        type Item = (String, Result<SourceQuestionsBatch, serde_json::Error>);
+
+        fn next(&mut self) -> Option<Self::Item> {
+            if self.index.is_none() && !self.zipfile.is_empty() {
+                self.index = Some(0);
+            }
+
+            match self.index {
+                Some(i) if i < self.zipfile.len() => {
+                    self.index = Some(i + 1);
+
+                    self.nth(i)
+                }
+                _ => None,
+            }
+        }
+
+        fn nth(&mut self, n: usize) -> Option<Self::Item> {
+            if self.zipfile.len() <= n {
+                return None;
+            }
+            self.index = Some(n + 1);
+
+            let file = self.zipfile.by_index(n).unwrap();
+            let name = file.mangled_name();
+            let name_str = name.to_str().unwrap();
+
+            let data: Result<SourceQuestionsBatch, _> = serde_json::from_reader(file);
+
+            Some((String::from(name_str), data))
+        }
+
+        fn size_hint(&self) -> (usize, Option<usize>) {
+            let len = self.zipfile.len();
+            let index = self.index.unwrap_or(0);
+            let rem = if len > index + 1 {
+                len - (index + 1)
+            } else {
+                0
+            };
+            (rem, Some(rem))
+        }
+
+        fn count(self) -> usize
+        where
+            Self: Sized,
+        {
+            self.zipfile.len()
+        }
+    }
+
+    impl<R> ExactSizeIterator for SourceQuestionsZipReader<R>
+    where
+        R: Read + Seek,
+    {
+        fn len(&self) -> usize {
+            self.zipfile.len()
+        }
+    }
+
+    pub trait ReadSourceQuestionsBatches<R>
+    where
+        R: Read + Seek,
+    {
+        fn source_questions(self) -> SourceQuestionsZipReader<R>;
+    }
+
+    impl<R> ReadSourceQuestionsBatches<R> for ZipArchive<R>
+    where
+        R: Read + Seek,
+    {
+        fn source_questions(self) -> SourceQuestionsZipReader<R> {
+            SourceQuestionsZipReader::new(self)
+        }
+    }
+    #[cfg(test)]
+    mod test {
+        use super::super::test::sample_batch;
+        use super::*;
+        use std::fs;
+        use std::{io::Write, iter, path::Path};
+        use tempfile::tempdir;
+
+        fn write_sample_zip<P>(path: P)
+        where
+            P: AsRef<Path>,
+        {
+            let batch = sample_batch();
+            let z_file = fs::File::create(path).expect("crerate zip file");
+            let mut zip_file = zip::ZipWriter::new(z_file);
+            let options =
+                zip::write::FileOptions::default().compression_method(zip::CompressionMethod::Zstd);
+            zip_file
+                .start_file("test.json", options)
+                .expect("zip start file");
+            let data = serde_json::to_vec(&batch).unwrap();
+            let amount = zip_file.write(data.as_slice()).expect("write entry");
+            assert_eq!(amount, data.len());
+            zip_file.finish().expect("finish zip file");
+        }
+
+        #[test]
+        fn test_source_questions_get() {
+            let expected_batch = sample_batch();
+            let dir = tempdir().expect("tempdir");
+
+            // write sample
+            let tmpfile_zip = dir.path().join("test.zip");
+            write_sample_zip(&tmpfile_zip);
+
+            let z_file = fs::File::open(tmpfile_zip).expect("open zip file");
+            let zip_file = zip::ZipArchive::new(z_file).expect("open zip file reader");
+
+            let mut source = zip_file.source_questions();
+            assert_eq!(source.len(), 1);
+
+            let actual = source.next().expect("get batch");
+            assert_eq!(actual.0, "test.json");
+            assert_eq!(actual.1.expect("parse batch"), expected_batch);
+        }
+
+        #[test]
+        fn test_source_questions_iter() {
+            let expected_batch = sample_batch();
+            let dir = tempdir().expect("tempdir");
+
+            // write sample
+            let tmpfile_zip = dir.path().join("test.zip");
+            write_sample_zip(&tmpfile_zip);
+
+            let z_file = fs::File::open(tmpfile_zip).expect("open zip file");
+            let zip_file = zip::ZipArchive::new(z_file).expect("open zip file reader");
+
+            let source = zip_file.source_questions();
+            assert_eq!(source.len(), 1);
+
+            let expected_iter = iter::once((String::from("test.json"), Ok(expected_batch)));
+
+            assert!(source
+                .map(|x| (x.0, x.1.map_err(|e| e.to_string())))
+                .eq(expected_iter));
+        }
+    }
+}
+
+#[cfg(any(feature = "convert", feature = "source"))]
+pub use reader_sync::{ReadSourceQuestionsBatches, SourceQuestionsZipReader};
+
+#[cfg(any(feature = "convert_async", feature = "source_async"))]
+pub mod reader_async {
+    use async_stream::stream;
+    use async_zip::tokio::read::seek::ZipFileReader;
+    use futures_core::stream::Stream;
+    use futures_util::AsyncReadExt;
+
+    use tokio::io::{AsyncRead, AsyncSeek};
+
+    use super::SourceQuestionsBatch;
+
+    pub struct SourceQuestionsZipReaderAsync<R>
+    where
+        R: AsyncRead + AsyncSeek + Unpin,
+    {
+        zipfile: ZipFileReader<R>,
+        index: Option<usize>,
+    }
+
+    impl<R> SourceQuestionsZipReaderAsync<R>
+    where
+        R: AsyncRead + AsyncSeek + Unpin,
+    {
+        pub fn new(zipfile: ZipFileReader<R>) -> Self {
+            SourceQuestionsZipReaderAsync {
+                zipfile,
+                index: None,
+            }
+        }
+
+        pub fn len(&self) -> usize {
+            self.zipfile.file().entries().len()
+        }
+
+        pub fn is_empty(&self) -> bool {
+            self.len() == 0
+        }
+
+        pub async fn get(
+            &mut self,
+            index: usize,
+        ) -> Result<(String, Result<SourceQuestionsBatch, serde_json::Error>), String>
+        where
+            R: AsyncRead + AsyncSeek + Unpin,
+        {
+            let len = self.len();
+            if index >= len {
+                return Err(format!("get index={index}, when len={len}"));
+            }
+
+            let reader = self.zipfile.reader_with_entry(index).await;
+            if let Err(error) = reader {
+                return Err(format!("reader_with_entry: {error:?}"));
+            }
+            let mut reader = reader.unwrap();
+
+            let filename = reader.entry().filename().clone().into_string().unwrap();
+            let mut data: Vec<u8> = Vec::new();
+            let readed = reader.read_to_end(&mut data).await;
+            if let Err(error) = readed {
+                return Err(format!("read_to_end: {error:?}"));
+            }
+            let parsed: Result<SourceQuestionsBatch, _> = serde_json::from_slice(&data);
+            Ok((filename, parsed))
+        }
+        pub async fn get_next(
+            &mut self,
+        ) -> Option<Result<(String, Result<SourceQuestionsBatch, serde_json::Error>), String>>
+        where
+            R: AsyncRead + AsyncSeek + Unpin,
+        {
+            if self.index.is_none() && !self.is_empty() {
+                self.index = Some(0);
+            }
+
+            if self.index.unwrap() >= self.len() {
+                return None;
+            }
+
+            let item = self.get(self.index.unwrap()).await;
+            self.index = Some(self.index.unwrap() + 1);
+
+            Some(item)
+        }
+        pub fn stream(
+            &mut self,
+        ) -> impl Stream<Item = (String, Result<SourceQuestionsBatch, serde_json::Error>)> + '_
+        {
+            stream! {
+                while let Some(Ok(item)) = self.get_next().await {
+                    yield item
+                }
+            }
+        }
+    }
+
+    pub trait ReadSourceQuestionsBatchesAsync<R>
+    where
+        R: AsyncRead + AsyncSeek + Unpin,
+    {
+        fn source_questions(self) -> SourceQuestionsZipReaderAsync<R>;
+    }
+
+    impl<R> ReadSourceQuestionsBatchesAsync<R> for ZipFileReader<R>
+    where
+        R: AsyncRead + AsyncSeek + Unpin,
+    {
+        fn source_questions(self) -> SourceQuestionsZipReaderAsync<R> {
+            SourceQuestionsZipReaderAsync::new(self)
+        }
+    }
+
+    #[cfg(test)]
+    mod test {
+        use crate::source::SourceQuestion;
+
+        use super::super::test::sample_batch;
+        use super::*;
+        use async_zip::{base::write::ZipFileWriter, ZipEntryBuilder};
+        use core::fmt::Debug;
+        use futures_util::StreamExt;
+        use std::path::Path;
+        use tempfile::tempdir;
+        use tokio::fs;
+
+        async fn write_sample_zip<P>(path: P)
+        where
+            P: AsRef<Path>,
+        {
+            let batch = sample_batch();
+            let z_file = fs::File::create(path).await.expect("crerate zip file");
+            let mut zip_file = ZipFileWriter::with_tokio(z_file);
+            let entry =
+                ZipEntryBuilder::new("test.json".into(), async_zip::Compression::Zstd).build();
+            zip_file
+                .write_entry_whole(entry, serde_json::to_vec(&batch).unwrap().as_slice())
+                .await
+                .expect("write entry");
+            zip_file.close().await.expect("close zip");
+        }
+
+        async fn assert_data_rref_eq<T>((x, y): (T, &T))
+        where
+            T: PartialEq + Debug,
+        {
+            assert_eq!(x, *y);
+        }
+
+        #[tokio::test]
+        async fn test_source_questions_stream() {
+            let expected_batch = sample_batch();
+            let dir = tempdir().expect("tempdir");
+
+            // write sample
+            let tmpfile_zip = dir.path().join("test.zip");
+            write_sample_zip(&tmpfile_zip).await;
+
+            let mut z_file = fs::File::open(tmpfile_zip).await.expect("open zip file");
+            let zip_file = ZipFileReader::with_tokio(&mut z_file)
+                .await
+                .expect("open zip file reader");
+
+            let expected_count = expected_batch.questions.len();
+            let expected_stream = futures::stream::iter(expected_batch.questions.iter());
+            let mut actual_source = zip_file.source_questions();
+            let actual_stream = actual_source.stream();
+            let mut actual_count: usize = 0;
+
+            actual_stream
+                .flat_map(|x| futures::stream::iter(x.1.expect("parse batch").questions))
+                .zip(expected_stream)
+                .map(|x| {
+                    actual_count += 1;
+                    x
+                })
+                .for_each(assert_data_rref_eq::<SourceQuestion>)
+                .await;
+            assert_eq!(actual_count, expected_count);
+        }
+
+        #[tokio::test]
+        async fn test_source_questions_get() {
+            let expected_batch = sample_batch();
+            let dir = tempdir().expect("tempdir");
+
+            // write sample
+            let tmpfile_zip = dir.path().join("test.zip");
+            write_sample_zip(&tmpfile_zip).await;
+
+            let mut z_file = fs::File::open(tmpfile_zip).await.expect("open zip file");
+            let zip_file = ZipFileReader::with_tokio(&mut z_file)
+                .await
+                .expect("open zip file reader");
+
+            let mut source = zip_file.source_questions();
+            assert_eq!(source.len(), 1);
+
+            let actual = source.get(0).await.expect("get batch");
+            assert_eq!(actual.0, "test.json");
+            assert_eq!(actual.1.expect("parse batch"), expected_batch);
+        }
+    }
+}
+#[cfg(any(feature = "convert_async", feature = "source_async"))]
+pub use reader_async::{ReadSourceQuestionsBatchesAsync, SourceQuestionsZipReaderAsync};
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use insta::assert_yaml_snapshot;
+    use serde_json::json;
+
+    pub fn sample_batch() -> SourceQuestionsBatch {
+        SourceQuestionsBatch {
+            description: "Тестовый".into(),
+            date: "00-000-2000".into(),
+            questions: vec![
+                SourceQuestion {
+                    id: "Вопрос 1".into(),
+                    description: "Сколько будет (2 * 2 * 2 + 2) * 2 * 2 + 2".into(),
+                    answer: "42".into(),
+                    ..Default::default()
+                },
+                SourceQuestion {
+                    id: "Вопрос 2".into(),
+                    description: "Зимой и летом одним цветом".into(),
+                    answer: "ёлка".into(),
+                    ..Default::default()
+                },
+            ],
+            ..Default::default()
+        }
+    }
+
+    #[test]
+    fn test_batch_ser() {
+        let batch = sample_batch();
+
+        assert_yaml_snapshot!(batch, @r#"
+            ---
+            description: Тестовый
+            date: 00-000-2000
+            questions:
+              - id: Вопрос 1
+                description: Сколько будет (2 * 2 * 2 + 2) * 2 * 2 + 2
+                answer: "42"
+              - id: Вопрос 2
+                description: Зимой и летом одним цветом
+                answer: ёлка
+            
+            "#);
+    }
+    #[test]
+    fn test_batch_de() {
+        let batch_from_json: Result<SourceQuestionsBatch, _> = serde_json::from_value(json!({
+            "Чемпионат": "Тестовый",
+            "Дата": "00-000-2000",
+            "Вопросы": [
+                {
+                    "id": "Вопрос 1",
+                    "Вопрос": "Сколько будет (2 * 2 * 2 + 2) * 2 * 2 + 2",
+                    "Ответ": "42",
+                   },
+                   {
+                    "id": "Вопрос 2",
+                    "Вопрос": "Зимой и летом одним цветом",
+                    "Ответ": "ёлка",
+                   },
+            ]
+        }));
+        assert!(batch_from_json.is_ok());
+
+        assert_yaml_snapshot!(batch_from_json.unwrap(), @r#"
+            ---
+            description: Тестовый
+            date: 00-000-2000
+            questions:
+              - id: Вопрос 1
+                description: Сколько будет (2 * 2 * 2 + 2) * 2 * 2 + 2
+                answer: "42"
+              - id: Вопрос 2
+                description: Зимой и летом одним цветом
+                answer: ёлка
+            
+            "#);
+    }
+}
--- a/lib/src/util.rs
+++ b/lib/src/util.rs
@ -0,0 +1,57 @@
+pub trait ErrorToString {
+    type Output;
+    fn str_err(self) -> std::result::Result<Self::Output, String>;
+}
+
+impl<T, E> ErrorToString for std::result::Result<T, E>
+where
+    E: std::error::Error,
+{
+    type Output = T;
+    fn str_err(self) -> std::result::Result<Self::Output, String> {
+        self.map_err(|e| e.to_string())
+    }
+}
+
+#[cfg(any(feature = "sync", feature = "async"))]
+mod bincode_utils {
+    use std::ops::{Deref, DerefMut};
+
+    use bincode::enc::write::Writer;
+    use bincode::error::EncodeError;
+
+    /// struct that allows [`Vec<u8>`] to implement [bincode::enc::write::Writer] trait
+    pub struct BincodeVecWriter {
+        vec: Vec<u8>,
+    }
+
+    impl BincodeVecWriter {
+        pub fn new(vec: Vec<u8>) -> BincodeVecWriter {
+            BincodeVecWriter { vec }
+        }
+    }
+
+    impl Deref for BincodeVecWriter {
+        type Target = Vec<u8>;
+
+        fn deref(&self) -> &Self::Target {
+            &self.vec
+        }
+    }
+
+    impl DerefMut for BincodeVecWriter {
+        fn deref_mut(&mut self) -> &mut Self::Target {
+            &mut self.vec
+        }
+    }
+
+    impl Writer for BincodeVecWriter {
+        fn write(&mut self, bytes: &[u8]) -> Result<(), EncodeError> {
+            self.vec.extend_from_slice(bytes);
+            Ok(())
+        }
+    }
+}
+
+#[cfg(any(feature = "sync", feature = "async"))]
+pub use bincode_utils::BincodeVecWriter;
--- a/src/main.rs
+++ b/src/main.rs
@ -1,276 +0,0 @@
-extern crate serde;
-extern crate serde_derive;
-#[macro_use]
-extern crate serde_json;
-extern crate ledb;
-extern crate ledb_types;
-extern crate zip;
-
-use clap::{Parser, Subcommand};
-use rand::seq::IteratorRandom;
-
-use std::io;
-use std::path::PathBuf;
-use std::time::Instant;
-use std::{fs, sync::mpsc, thread};
-
-use ledb::{Options, Storage};
-
-mod db;
-mod questions;
-mod source;
-
-use crate::questions::{Question, QuestionsConverter};
-use crate::source::ReadSourceQuestionsBatches;
-
-const ZIP_FILENAME: &str = "json.zip";
-const NEW_DB_FILENAME: &str = "test.bin";
-const DB_DIR: &str = "db";
-
-#[derive(Subcommand, Debug)]
-enum Command {
-    Write,
-    Compact,
-    Print {
-        #[clap(value_parser, default_value = "0")]
-        id: u32,
-    },
-    ZipPrint {
-        #[clap(value_parser, default_value = "0")]
-        file_num: usize,
-        #[clap(value_parser, default_value = "0")]
-        num: usize,
-    },
-    Write2,
-    Print2 {
-        #[clap(value_parser, default_value = "0")]
-        id: u32,
-    },
-}
-
-#[derive(Parser, Debug)]
-#[clap(author, version, about, long_about = None)]
-#[clap(propagate_version = true)]
-struct Cli {
-    #[clap(subcommand)]
-    command: Command,
-    #[clap(short, long, action)]
-    measure: bool,
-}
-
-fn zip_reader_task(tx: mpsc::Sender<Question>) {
-    let zip_file = fs::File::open(ZIP_FILENAME).unwrap();
-    let zip_reader = io::BufReader::new(zip_file);
-    let archive = zip::ZipArchive::new(zip_reader).unwrap();
-    let mut source_questions = archive.source_questions();
-
-    let questions = source_questions
-        .convert()
-        .enumerate()
-        .map(|(num, mut question)| {
-            question.num = 1 + num as u32;
-            question
-        });
-    for question in questions {
-        let res = tx.send(question);
-        if res.is_err() {
-            break;
-        }
-    }
-    println!("read done");
-}
-fn db_writer_task(rx: mpsc::Receiver<Question>) {
-    let out_file: PathBuf = [DB_DIR, "data.mdb"].into_iter().collect();
-    match fs::metadata(&out_file) {
-        Ok(x) if x.is_file() => {
-            fs::remove_file(&out_file).unwrap();
-            println!(r#""{}" removed"#, out_file.to_str().unwrap());
-        }
-        _ => {}
-    };
-
-    let options: Options = serde_json::from_value(json!({
-        "map_size": 900 * 1024 * 1024, // 900mb
-        "write_map": true,
-        "map_async": true,
-        "no_lock": true,
-        "no_meta_sync": true,
-        "no_sync": true,
-    }))
-    .unwrap();
-
-    let storage = Storage::new(DB_DIR, options).unwrap();
-    let collection = storage.collection("questions").unwrap();
-
-    let count = collection.load(rx).expect("load");
-
-    println!("loaded {count}");
-
-    println!("syncing to disk...");
-    storage.sync(true).unwrap();
-
-    print!("stats: ");
-    let stats = storage.stat().unwrap();
-    println!("{:?}", stats);
-
-    drop(storage);
-    println!("write done");
-}
-
-fn write_db() {
-    let (tx, rx) = mpsc::channel::<Question>();
-    [
-        thread::spawn(move || zip_reader_task(tx)),
-        thread::spawn(move || db_writer_task(rx)),
-    ]
-    .into_iter()
-    .for_each(|handle| handle.join().expect("thread panic"));
-    println!("all done");
-}
-
-fn print_question_from<F>(get_q: F)
-where
-    F: FnOnce() -> Option<Question>,
-{
-    let q = get_q().unwrap();
-    println!("{:#?}", q)
-}
-
-fn read_from_zip(file_num: usize, mut num: usize) -> Option<Question> {
-    let mut rng = rand::thread_rng();
-    let zip_file = fs::File::open(ZIP_FILENAME).unwrap();
-    let zip_reader = io::BufReader::new(zip_file);
-    let archive = zip::ZipArchive::new(zip_reader).unwrap();
-
-    let mut source_questions = archive.source_questions();
-    let (filename, batch) = if file_num == 0 {
-        source_questions.choose(&mut rng).unwrap()
-    } else {
-        source_questions.nth(file_num - 1).unwrap()
-    };
-    let mut batch = batch.unwrap();
-    batch.filename = filename;
-    let questions: Vec<Question> = batch.into();
-    if num == 0 {
-        num = (1..=questions.len()).choose(&mut rng).unwrap();
-    }
-    Some(questions[num - 1].clone())
-}
-
-fn compact_db() {
-    let options: Options = serde_json::from_value(json!({
-        "write_map": true,
-        "map_async": true,
-        "no_lock": true,
-        "no_meta_sync": true,
-        "no_sync": true,
-        "compact": true,
-    }))
-    .unwrap();
-
-    let storage = Storage::new(DB_DIR, options).unwrap();
-
-    storage.sync(true).unwrap();
-    let stats = storage.stat().unwrap();
-    println!("{:?}", stats);
-    drop(storage);
-}
-
-fn read_from_db(mut id: u32) -> Option<Question> {
-    let options: Options = serde_json::from_value(json!({
-        "read_only": true,
-        "map_async": true,
-        "no_lock": true,
-    }))
-    .unwrap();
-
-    let storage = Storage::new(DB_DIR, options).unwrap();
-    let collection = storage.collection("questions").unwrap();
-    let mut rng = rand::thread_rng();
-
-    if id == 0 {
-        let last_id = collection.last_id().unwrap();
-        id = (1..=last_id).choose(&mut rng).unwrap();
-    }
-
-    collection.get::<Question>(id).unwrap()
-}
-
-// measure and return time elapsed in `func` in seconds
-pub fn measure<F: FnOnce()>(func: F) -> f64 {
-    let start = Instant::now();
-    func();
-    let elapsed = start.elapsed();
-    (elapsed.as_secs() as f64) + (elapsed.subsec_nanos() as f64 / 1_000_000_000.0)
-}
-
-pub fn measure_and_print<F: FnOnce()>(func: F) {
-    let m = measure(func);
-    eprintln!("{}", m);
-}
-
-fn main() {
-    let args = Cli::parse();
-
-    let mut action: Box<dyn FnOnce()> = match &args.command {
-        Command::Write => Box::new(write_db),
-        Command::Compact => Box::new(compact_db),
-        Command::Print { id } => {
-            let get_question = Box::new(|| read_from_db(*id));
-            Box::new(|| print_question_from(get_question))
-        }
-        Command::ZipPrint { file_num, num } => {
-            let get_question = Box::new(|| read_from_zip(*file_num, *num));
-            Box::new(|| print_question_from(get_question))
-        }
-        Command::Write2 => Box::new(write_db2),
-        Command::Print2 { id } => {
-            let get_question = Box::new(|| read_from_db2(*id));
-            Box::new(|| print_question_from(get_question))
-        }
-    };
-
-    if args.measure {
-        action = Box::new(|| measure_and_print(action));
-    }
-
-    action();
-}
-
-fn read_from_db2(id: u32) -> Option<Question> {
-    let mut reader: db::Reader<Question> =
-        db::Reader::new(NEW_DB_FILENAME, 2048).expect("new db reader");
-
-    let mut questions = reader.iter();
-
-    match id {
-        0 => {
-            let mut rng = rand::thread_rng();
-            questions.choose(&mut rng)
-        }
-        _ => questions.nth((id - 1) as usize),
-    }
-}
-fn write_db2() {
-    let (tx, rx) = mpsc::channel::<Question>();
-    [
-        thread::spawn(move || zip_reader_task(tx)),
-        thread::spawn(move || db_writer2_task(rx)),
-    ]
-    .into_iter()
-    .for_each(|handle| handle.join().expect("thread panic"));
-    println!("all done");
-}
-fn db_writer2_task(rx: mpsc::Receiver<Question>) {
-    let writer_opts = db::WriterOpts::default();
-    let mut writer: db::Writer<Question> =
-        db::Writer::new(NEW_DB_FILENAME, writer_opts).expect("new db writer");
-
-    writer
-        .load(&mut rx.iter())
-        .unwrap_or_else(|e| panic!("db writer load, {e:#?}"));
-
-    writer.finish().expect("db writer finish");
-
-    println!("write done");
-}
--- a/src/questions.rs
+++ b/src/questions.rs
@ -1,145 +0,0 @@
-use ledb::Document;
-use serde_derive::{Deserialize, Serialize};
-
-use crate::source::{SourceQuestion, SourceQuestionsBatch};
-
-macro_rules! make {
-    ($Target:ident; by {$($field:ident),+}; from $src:expr) => {$Target {$(
-        $field: $src.$field
-    ),+}};
-    ($Target:ident; with defaults and by {$($field:ident),+}; from $src:expr) => {$Target {$(
-        $field: $src.$field
-    ),+ ,..$Target::default()}}
-}
-
-#[derive(
-    Debug, Default, Clone, Serialize, Deserialize, Document, bincode::Decode, bincode::Encode,
-)]
-pub struct BatchInfo {
-    #[document(primary)]
-    #[serde(default)]
-    pub filename: String,
-    #[serde(default)]
-    pub description: String,
-    #[serde(default)]
-    pub author: String,
-    #[serde(default)]
-    pub comment: String,
-    #[serde(default)]
-    pub url: String,
-    #[serde(default)]
-    pub date: String,
-    #[serde(default)]
-    pub processed_by: String,
-    #[serde(default)]
-    pub redacted_by: String,
-    #[serde(default)]
-    pub copyright: String,
-    #[serde(default)]
-    pub theme: String,
-    #[serde(default)]
-    pub kind: String,
-    #[serde(default)]
-    pub source: String,
-    #[serde(default)]
-    pub rating: String,
-}
-
-#[derive(
-    Debug, Default, Clone, Serialize, Deserialize, Document, bincode::Decode, bincode::Encode,
-)]
-pub struct Question {
-    #[document(primary)]
-    #[serde(default)]
-    pub num: u32,
-    #[document(index)]
-    pub id: String,
-
-    pub description: String,
-    pub answer: String,
-
-    #[serde(default)]
-    pub author: String,
-    #[serde(default)]
-    pub comment: String,
-    #[serde(default)]
-    pub comment1: String,
-    #[serde(default)]
-    pub tour: String,
-    #[serde(default)]
-    pub url: String,
-    #[serde(default)]
-    pub date: String,
-    #[serde(default)]
-    pub processed_by: String,
-    #[serde(default)]
-    pub redacted_by: String,
-    #[serde(default)]
-    pub copyright: String,
-    #[serde(default)]
-    pub theme: String,
-    #[serde(default)]
-    pub kind: String,
-    #[serde(default)]
-    pub source: String,
-    #[serde(default)]
-    pub rating: String,
-    #[document(nested)]
-    #[serde(default)]
-    pub batch_info: BatchInfo,
-}
-
-impl From<SourceQuestion> for Question {
-    fn from(src: SourceQuestion) -> Self {
-        make! {Self; with defaults and by {
-            num, id, description, answer, author, comment, comment1, tour, url,
-            date, processed_by, redacted_by, copyright, theme, kind, source, rating
-        }; from src}
-    }
-}
-
-impl From<SourceQuestionsBatch> for BatchInfo {
-    fn from(src: SourceQuestionsBatch) -> Self {
-        make! {Self; by {
-            filename, description, author, comment, url, date,
-            processed_by, redacted_by, copyright, theme, kind, source, rating
-        }; from src}
-    }
-}
-
-impl From<SourceQuestionsBatch> for Vec<Question> {
-    fn from(src: SourceQuestionsBatch) -> Self {
-        let mut result: Vec<Question> = src
-            .questions
-            .iter()
-            .map(|item| item.clone().into())
-            .collect();
-        let batch_info = BatchInfo::from(src);
-        result.iter_mut().for_each(|mut question| {
-            question.batch_info = batch_info.clone();
-        });
-
-        result
-    }
-}
-
-pub trait QuestionsConverter {
-    fn convert<'a>(&'a mut self) -> Box<dyn Iterator<Item = Question> + 'a>;
-}
-
-impl<T> QuestionsConverter for T
-where
-    T: Iterator<Item = (String, Result<SourceQuestionsBatch, serde_json::Error>)>,
-{
-    fn convert<'a>(&'a mut self) -> Box<dyn Iterator<Item = Question> + 'a> {
-        let iter = self
-            .filter(|(_, data)| data.is_ok())
-            .flat_map(|(filename, data)| {
-                let mut batch = data.unwrap();
-                batch.filename = filename;
-                let questions: Vec<Question> = batch.into();
-                questions
-            });
-        Box::new(iter)
-    }
-}
--- a/src/source.rs
+++ b/src/source.rs
@ -1,206 +0,0 @@
-use serde_derive::{Deserialize, Serialize};
-use std::io::{Read, Seek};
-use zip::ZipArchive;
-
-#[derive(Debug, Default, Clone, Serialize, Deserialize)]
-pub struct SourceQuestion {
-    #[serde(default)]
-    pub num: u32,
-    pub id: String,
-
-    #[serde(alias = "Вопрос")]
-    pub description: String,
-    #[serde(alias = "Ответ")]
-    pub answer: String,
-
-    #[serde(alias = "Автор")]
-    #[serde(default)]
-    pub author: String,
-    #[serde(alias = "Комментарий")]
-    #[serde(default)]
-    pub comment: String,
-    #[serde(alias = "Комментарии")]
-    #[serde(alias = "Инфо")]
-    #[serde(default)]
-    pub comment1: String,
-    #[serde(alias = "Тур")]
-    #[serde(default)]
-    pub tour: String,
-    #[serde(alias = "Ссылка")]
-    #[serde(alias = "URL")]
-    #[serde(default)]
-    pub url: String,
-    #[serde(alias = "Дата")]
-    #[serde(default)]
-    pub date: String,
-    #[serde(alias = "Обработан")]
-    #[serde(default)]
-    pub processed_by: String,
-    #[serde(alias = "Редактор")]
-    #[serde(default)]
-    pub redacted_by: String,
-    #[serde(alias = "Копирайт")]
-    #[serde(default)]
-    pub copyright: String,
-    #[serde(alias = "Тема")]
-    #[serde(default)]
-    pub theme: String,
-    #[serde(alias = "Вид")]
-    #[serde(alias = "Тип")]
-    #[serde(default)]
-    pub kind: String,
-    #[serde(alias = "Источник")]
-    #[serde(default)]
-    pub source: String,
-    #[serde(alias = "Рейтинг")]
-    #[serde(default)]
-    pub rating: String,
-}
-
-#[derive(Debug, Default, Clone, Serialize, Deserialize)]
-pub struct SourceQuestionsBatch {
-    #[serde(default)]
-    pub filename: String,
-    #[serde(alias = "Пакет")]
-    #[serde(alias = "Чемпионат")]
-    pub description: String,
-    #[serde(alias = "Автор")]
-    #[serde(default)]
-    pub author: String,
-    #[serde(alias = "Комментарий")]
-    #[serde(alias = "Комментарии")]
-    #[serde(alias = "Инфо")]
-    #[serde(default)]
-    pub comment: String,
-    #[serde(alias = "Ссылка")]
-    #[serde(alias = "URL")]
-    #[serde(default)]
-    pub url: String,
-    #[serde(alias = "Дата")]
-    #[serde(default)]
-    pub date: String,
-    #[serde(alias = "Обработан")]
-    #[serde(default)]
-    pub processed_by: String,
-    #[serde(alias = "Редактор")]
-    #[serde(default)]
-    pub redacted_by: String,
-    #[serde(alias = "Копирайт")]
-    #[serde(default)]
-    pub copyright: String,
-    #[serde(alias = "Тема")]
-    #[serde(default)]
-    pub theme: String,
-    #[serde(alias = "Вид")]
-    #[serde(alias = "Тип")]
-    #[serde(default)]
-    pub kind: String,
-    #[serde(alias = "Источник")]
-    #[serde(default)]
-    pub source: String,
-    #[serde(alias = "Рейтинг")]
-    #[serde(default)]
-    pub rating: String,
-    #[serde(alias = "Вопросы")]
-    pub questions: Vec<SourceQuestion>,
-}
-
-pub struct SourceQuestionsZipReader<R>
-where
-    R: Read + Seek,
-{
-    zipfile: ZipArchive<R>,
-    index: Option<usize>,
-}
-
-impl<R> SourceQuestionsZipReader<R>
-where
-    R: Read + Seek,
-{
-    fn new(zipfile: ZipArchive<R>) -> Self {
-        SourceQuestionsZipReader {
-            zipfile,
-            index: None,
-        }
-    }
-}
-
-impl<R> Iterator for SourceQuestionsZipReader<R>
-where
-    R: Read + Seek,
-{
-    type Item = (String, Result<SourceQuestionsBatch, serde_json::Error>);
-
-    fn next(&mut self) -> Option<Self::Item> {
-        if self.index.is_none() && !self.zipfile.is_empty() {
-            self.index = Some(0);
-        }
-
-        match self.index {
-            Some(i) if i < self.zipfile.len() => {
-                self.index = Some(i + 1);
-
-                self.nth(i)
-            }
-            _ => None,
-        }
-    }
-
-    fn nth(&mut self, n: usize) -> Option<Self::Item> {
-        if self.zipfile.len() <= n {
-            return None;
-        }
-        self.index = Some(n + 1);
-
-        let file = self.zipfile.by_index(n).unwrap();
-        let name = file.mangled_name();
-        let name_str = name.to_str().unwrap();
-
-        let data: Result<SourceQuestionsBatch, _> = serde_json::from_reader(file);
-
-        Some((String::from(name_str), data))
-    }
-
-    fn size_hint(&self) -> (usize, Option<usize>) {
-        let len = self.zipfile.len();
-        let index = self.index.unwrap_or(0);
-        let rem = if len > index + 1 {
-            len - (index + 1)
-        } else {
-            0
-        };
-        (rem, Some(rem))
-    }
-
-    fn count(self) -> usize
-    where
-        Self: Sized,
-    {
-        self.zipfile.len()
-    }
-}
-
-impl<R> ExactSizeIterator for SourceQuestionsZipReader<R>
-where
-    R: Read + Seek,
-{
-    fn len(&self) -> usize {
-        self.zipfile.len()
-    }
-}
-
-pub trait ReadSourceQuestionsBatches<R>
-where
-    R: Read + Seek,
-{
-    fn source_questions(self) -> SourceQuestionsZipReader<R>;
-}
-
-impl<R> ReadSourceQuestionsBatches<R> for ZipArchive<R>
-where
-    R: Read + Seek,
-{
-    fn source_questions(self) -> SourceQuestionsZipReader<R> {
-        SourceQuestionsZipReader::new(self)
-    }
-}
Author	SHA1	Message	Date
Dmitry	1b88db07be	add questions benches All checks were successful continuous-integration/drone/push Build is passing Details	2023-08-26 13:42:50 +03:00
Dmitry	c4b68cc727	apps: handle err's All checks were successful continuous-integration/drone/push Build is passing Details + ord fn's	2023-08-25 15:28:19 +03:00
Dmitry	9c5f05b6a9	app_async: fix print random question	2023-08-25 14:41:53 +03:00
Dmitry	760f6d9415	add async bench All checks were successful continuous-integration/drone/push Build is passing Details	2023-08-23 13:30:51 +03:00
Dmitry	699478f85e	async_zip, async-compression from crates.io All checks were successful continuous-integration/drone/push Build is passing Details instead of git	2023-08-18 10:05:22 +03:00
Dmitry	23f8537e4e	source: pub fn new in async zip reader	2023-08-18 10:03:50 +03:00
Dmitry	cd93f577be	lib: v1.2.0 All checks were successful continuous-integration/drone/push Build is passing Details	2023-08-18 09:37:27 +03:00
Dmitry	cd7f3674ca	ci: publish lib with all features All checks were successful continuous-integration/drone/push Build is passing Details	2023-08-18 09:33:42 +03:00
Dmitry Belyaev	a0c13ea205	Merge pull request 'add async feature' (#1 ) from async into master All checks were successful continuous-integration/drone/push Build is passing Details Reviewed-on: #1	2023-08-18 06:29:44 +00:00
Dmitry	797f781959	app_async: use for_each_concurrent All checks were successful continuous-integration/drone/push Build is passing Details	2023-08-16 14:48:47 +03:00
Dmitry	6d850be1dc	async_db: add [bufread, bufread_stream] tests All checks were successful continuous-integration/drone/push Build is passing Details	2023-08-16 12:04:57 +03:00
Dmitry	33abc15268	app_async: fix Reader::new	2023-08-16 11:49:08 +03:00
Dmitry	feb2303db9	async_db: add BufReader, BufReaderStream for using as mutable reader	2023-08-16 11:48:45 +03:00
Dmitry	ae96fb3bf8	add FIXME comment All checks were successful continuous-integration/drone/push Build is passing Details	2023-08-15 14:54:40 +03:00
Dmitry	5ed0398203	db(+async) writer: add push_by_ref	2023-08-15 11:03:15 +03:00
Dmitry	9196c61a12	add test for writer.sink()	2023-08-15 10:45:08 +03:00
Dmitry	0adc11cabf	app_async: don't use writer.sink()	2023-08-15 10:44:32 +03:00
Dmitry	07d7ba50cc	async_db "fixme" comments	2023-08-15 10:36:42 +03:00
Dmitry	f1d4cf05c5	async_db: refactor WriterSink::poll_ready All checks were successful continuous-integration/drone/push Build is passing Details	2023-08-14 17:11:53 +03:00
Dmitry	3ea4930105	async_db: add Reader::get_with_buf +test All checks were successful continuous-integration/drone/push Build is passing Details	2023-08-14 16:24:36 +03:00
Dmitry	645b654dac	use BincodeVecWriter in (sync) db All checks were successful continuous-integration/drone/push Build is passing Details for reusing current item buf	2023-08-14 15:54:26 +03:00
Dmitry	e074108560	use BincodeVecWriter in async_db for reusing current item buf	2023-08-14 15:53:17 +03:00
Dmitry	ddd728cd5d	add utils::BincodeVecWriter	2023-08-14 15:50:50 +03:00
Dmitry	c326fc59d3	questions converter: remove src clone	2023-08-14 12:21:14 +03:00
Dmitry	31c02ae8ef	async_db: add WriterSink All checks were successful continuous-integration/drone/push Build is passing Details	2023-08-13 18:16:49 +03:00
Dmitry	3e3572ce12	async deps: add pin-project	2023-08-13 18:14:41 +03:00
Dmitry	908a6d8cae	fix source decode	2023-08-13 18:11:29 +03:00
Dmitry	cd87529ede	questions: add QuestionsConverterAsyncForStream	2023-08-13 16:01:10 +03:00
Dmitry	270af2c373	questions: add async convert_stream test All checks were successful continuous-integration/drone/push Build is passing Details	2023-08-13 13:19:40 +03:00
Dmitry	ff6af8389d	questions: add sync convert test	2023-08-13 12:55:35 +03:00
Dmitry	8e87e5e17b	source tests: reuse fn sample_batch()	2023-08-13 12:34:22 +03:00
Dmitry	ed37fee697	fix clippy warnings in tests	2023-08-13 12:33:19 +03:00
Dmitry	e0326e3b0a	add questions ser/de tests All checks were successful continuous-integration/drone/push Build is passing Details	2023-08-12 23:35:17 +03:00
Dmitry	c061fef267	questions: add `skip_serializing_if` attr's All checks were successful continuous-integration/drone/push Build is passing Details	2023-08-12 22:53:36 +03:00
Dmitry	acf741e721	source tests: check write on `write_sample_zip`	2023-08-12 22:51:39 +03:00
Dmitry	e32316c6aa	source: reformat struct's All checks were successful continuous-integration/drone/push Build is passing Details	2023-08-12 22:34:01 +03:00
Dmitry	ef98b1fea4	add source::reader_async get/stream tests All checks were successful continuous-integration/drone/push Build is passing Details	2023-08-12 22:11:36 +03:00
Dmitry	08acb4e71b	add source::reader_sync get/iter tests	2023-08-12 22:10:48 +03:00
Dmitry	7e633577b1	add source batch ser/de tests	2023-08-12 22:08:25 +03:00
Dmitry	d4913a13f9	deps: add `insta` for tests	2023-08-12 21:42:14 +03:00
Dmitry	21571787f2	source: add `skip_serializing_if` attr's	2023-08-12 21:40:33 +03:00
Dmitry	f874e59a11	fix convert feature without source All checks were successful continuous-integration/drone/push Build is passing Details	2023-08-10 14:20:58 +03:00
Dmitry	9c4882fbbb	Merge branch 'master' into async All checks were successful continuous-integration/drone/push Build is passing Details	2023-08-10 11:50:20 +03:00
Dmitry	b12048c38d	PhantomData<Arc<T>> for Send to Reader/Writer All checks were successful continuous-integration/drone/push Build is passing Details	2023-08-10 11:48:34 +03:00
Dmitry	68b276ce5e	PhantomData<Arc<T>> All checks were successful continuous-integration/drone/push Build is passing Details	2023-08-10 11:20:38 +03:00
Dmitry	48438c1aec	Revert "ci: fix pipeline build" All checks were successful continuous-integration/drone/push Build is passing Details This reverts commit `851058245d`.	2023-08-08 17:10:14 +03:00
Dmitry	f2fc72056b	fmt All checks were successful continuous-integration/drone/push Build is passing Details	2023-08-08 16:55:22 +03:00
Dmitry	4c555df8ca	fix async_db tests using ZstdEncoder from ..:tokio::bufread instead of ..:tokio::write	2023-08-08 16:54:40 +03:00
Dmitry	daf41625ff	remove debug prints	2023-08-08 16:52:30 +03:00
Dmitry	2c3950ccfc	fix write_db tokio join	2023-08-08 16:50:02 +03:00
Dmitry	8306c76a0c	fix app_async Some checks failed continuous-integration/drone/push Build is failing Details	2023-08-08 14:31:08 +03:00
Dmitry	965c021d83	fix async_db tests (to fail) --- failures: async_db::test::test_write_read async_db::test::test_write_read_stream thread 'async_db::test::test_write_read' panicked at 'get: "UnexpectedEnd { additional: 1 }	2023-08-08 14:29:18 +03:00
Dmitry	a1a1d41403	replace PhantomData in async_db::Writer for Send for Writer	2023-08-08 14:25:01 +03:00
Dmitry	b768d27f83	combine convert sync/async features	2023-08-08 14:22:29 +03:00
Dmitry	7cbf5439b7	rewrite SourceQuestionsZipReaderAsync "impl Stream for SourceQuestionsZipReaderAsync" dropped	2023-08-08 14:20:40 +03:00
Dmitry	8c4631e89f	add app_async -- write invalid: "UnexpectedEnd { additional: 385 }"	2023-08-07 22:06:21 +03:00
Dmitry	467ebfcc67	rewrite async converter (poll_next removed // not work)	2023-08-07 22:04:29 +03:00
Dmitry	80dda8d821	rewrite SourceQuestionsZipReaderAsync stream (poll_next not work)	2023-08-07 22:02:41 +03:00
Dmitry	851058245d	ci: fix pipeline build All checks were successful continuous-integration/drone/push Build is passing Details	2023-08-06 17:03:18 +03:00
Dmitry	ecfc34e821	+ async source (reader and converter)	2023-08-06 17:01:22 +03:00
Dmitry	f55b6f681c	move str_err to util.rs	2023-08-06 16:58:43 +03:00
Dmitry	c0193e4f74	ci: add "publish" pipeline type All checks were successful continuous-integration/drone/push Build is passing Details	2023-08-06 01:19:19 +03:00
Dmitry	a496f37ef2	ci: build/test with --all-features All checks were successful continuous-integration/drone/push Build is passing Details	2023-08-06 01:09:57 +03:00
Dmitry	5632c19866	ci: add pipeline type	2023-08-06 01:09:32 +03:00
Dmitry	cad8ff0404	add async test_share_reader	2023-08-06 01:05:36 +03:00
Dmitry	39ce0d8ceb	add async reader stream	2023-08-06 00:56:49 +03:00
Dmitry	1ba645f337	add async reader	2023-08-06 00:12:15 +03:00
Dmitry	150527efeb	move macro to convert mod	2023-08-06 00:11:44 +03:00
Dmitry	0c0a4e31ba	optional feature for source All checks were successful continuous-integration/drone/push Build is passing Details	2023-08-05 23:26:45 +03:00
Dmitry	abcb7d6dc2	add async writer All checks were successful continuous-integration/drone/push Build is passing Details	2023-08-05 23:10:30 +03:00
Dmitry	307790ce49	fix set_pledged_src_size	2023-08-05 23:07:16 +03:00
Dmitry	a6e5931f35	add sync/async features	2023-08-05 23:06:55 +03:00
Dmitry	1e8cd4b461	cargo update All checks were successful continuous-integration/drone/push Build is passing Details	2023-07-19 14:43:22 +03:00
Dmitry	9246d06783	cargo fix	2023-07-19 14:40:56 +03:00
Dmitry	cc5ab52f32	ref bench	2023-07-19 14:40:25 +03:00
Dmitry	e7491f6d3a	upd clap to v4	2023-05-07 18:15:45 +03:00
Dmitry	39d4d6b610	add locks + file alloc in Writer::finish All checks were successful continuous-integration/drone/push Build is passing Details	2023-04-05 16:53:40 +03:00
Dmitry	27260695f7	upd lock All checks were successful continuous-integration/drone/push Build is passing Details	2023-04-03 15:35:58 +03:00
Dmitry	f5bd72b298	fix publish 2 All checks were successful continuous-integration/drone/push Build is passing Details	2023-03-29 13:46:21 +03:00
Dmitry	dda50e7d2b	fix build on publish All checks were successful continuous-integration/drone/push Build is passing Details	2023-03-29 13:31:23 +03:00
Dmitry	693f349ae3	fix license	2023-03-29 13:30:57 +03:00
Dmitry	7a2e58b1b9	remove branch filter for publish All checks were successful continuous-integration/drone/push Build is passing Details	2023-03-29 13:23:03 +03:00
Dmitry	9570b1d6e2	add manifest info	2023-03-29 13:22:37 +03:00
Dmitry	5355d0398d	remove ledb All checks were successful continuous-integration/drone Build is passing Details	2023-03-29 13:00:17 +03:00
Dmitry	b63e9aa45c	add publish pipeline	2023-03-29 12:59:35 +03:00
Dmitry	8120a996a3	add test_share_reader All checks were successful continuous-integration/drone/push Build is passing Details	2023-03-28 15:43:08 +03:00
Dmitry	3a26a4aa7f	upd bench	2023-03-28 15:37:21 +03:00
Dmitry	103b677d21	into_iter() for reader	2023-03-28 15:01:14 +03:00
Dmitry	e18539a982	reader without mut	2023-03-28 14:59:44 +03:00
Dmitry	249ac3a4ef	ci: use sparse protocol for crates.io All checks were successful continuous-integration/drone/push Build is passing Details	2023-03-13 17:10:09 +03:00
Dmitry	e940f1c37c	cargo update All checks were successful continuous-integration/drone/push Build is passing Details	2023-03-02 14:50:06 +03:00
Dmitry	f3dabe7a06	new db file rename	2023-01-03 23:52:50 +03:00
Dmitry	e521e39f5e	add ledb read/write benches All checks were successful continuous-integration/drone/push Build is passing Details	2022-11-10 22:21:55 +03:00
Dmitry	cf591198a0	separate lib All checks were successful continuous-integration/drone/push Build is passing Details	2022-11-10 21:43:15 +03:00