add async test_share_reader

lib/src/async_db.rs

@@ -402,4 +402,43 @@ mod test {
 
         src_stream.zip(dst_stream).for_each(test_values).await;
     }
+    /// 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 {
+            compress_lvl: Level::Default,
+            data_buf_size: 10 * 1024 * 1024,
+            out_buf_size: 10 * 1024 * 1024,
+        };
+        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 = stream_iter(items.clone().into_iter());
+        pin_mut!(src);
+        writer.load(src).await.expect("load");
+        writer.finish().await.expect("finish write");
+
+        let reader: Reader<TestData> = Reader::new(&tmpfile, 2048).await.expect("new reader");
+        assert_eq!(items.len(), reader.len());
+
+        async fn test_values((x, y): (&TestData, TestData)) {
+            assert_eq!(*x, y);
+        }
+
+        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 = stream_iter(cur_items.iter());
+
+                src_stream.zip(dst_stream).for_each(test_values).await;
+            });
+        }
+    }
 }