add test_share_reader

app/benches/db_bench.rs

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

lib/src/db.rs

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