app/benches/db_bench.rs

@@ -79,8 +79,9 @@ fn db_read(c: &mut Criterion) {
                 let reader: Reader<TestData> = Reader::new(&tmpfile, 2048).expect("new reader");
                 reader
             },
-            |reader| {
-                for item in reader {
+            |mut reader| {
+                let mut reader_iter = reader.iter();
+                while let Some(item) = reader_iter.next() {
                     drop(item);
                 }
             },

app/src/main.rs

@@ -232,7 +232,7 @@ fn main() {
 }
 
 fn read_from_db2(id: u32) -> Option<Question> {
-    let reader: db::Reader<Question> =
+    let mut reader: db::Reader<Question> =
         db::Reader::new(NEW_DB_FILENAME, 2048).expect("new db reader");
 
     let mut questions = reader.iter();

lib/src/db.rs

@@ -3,7 +3,6 @@ use std::{
     io::{self, Cursor, Read, Write},
     marker::PhantomData,
     path::Path,
-    sync::Arc
 };
 
 use memmap::{Mmap, MmapOptions};
@@ -158,7 +157,7 @@ where
     mmap: Mmap,
     count: usize,
     first_pos: LSize,
-    _t: Option<Arc<T>> // PhantomData replacement
+    _t: PhantomData<*const T>,
 }
 
 impl<T> Reader<T>
@@ -179,7 +178,7 @@ where
             mmap,
             count,
             first_pos,
-            _t: None
+            _t: PhantomData,
         })
     }
 
@@ -191,7 +190,7 @@ where
         0 == self.len()
     }
 
-    pub fn get(&self, index: usize) -> Result<T, String> {
+    pub fn get(&mut self, index: usize) -> Result<T, String> {
         if index >= self.len() {
             return Err("index out of range".into());
         }
@@ -223,20 +222,16 @@ where
         Ok(item.0)
     }
 
-    pub fn iter(&self) -> ReaderIter<'_, T> {
+    pub fn iter(&mut self) -> ReaderIter<'_, T> {
         ReaderIter::new(self)
     }
-
-    pub fn into_iter(self) -> ReaderIntoIter<T> {
-        ReaderIntoIter::new(self)
-    }
 }
 
 pub struct ReaderIter<'a, T>
 where
     T: bincode::Decode,
 {
-    reader: &'a Reader<T>,
+    reader: &'a mut Reader<T>,
     index: Option<usize>,
 }
 
@@ -244,7 +239,7 @@ impl<'a, T> ReaderIter<'a, T>
 where
     T: bincode::Decode,
 {
-    fn new(reader: &'a Reader<T>) -> Self {
+    fn new(reader: &'a mut Reader<T>) -> Self {
         ReaderIter {
             reader,
             index: None,
@@ -314,100 +309,6 @@ 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.into_iter()
-    }
-}
-
 #[cfg(test)]
 mod test {
     use super::*;
@@ -444,7 +345,7 @@ mod test {
         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");
+        let mut reader: Reader<TestData> = Reader::new(&tmpfile, 2048).expect("new reader");
         assert_eq!(items.len(), reader.len());
 
         for (idx, item) in items.iter().enumerate() {
@@ -471,73 +372,11 @@ mod test {
         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");
+        let mut 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);
-                });
-            });
-        }
-    }
 }