Avoid zeroed allocation in reading avro

src/io/avro/read/block.rs

@@ -40,8 +40,8 @@ fn read_block<R: Read>(
     };
 
     block.data.clear();
-    block.data.resize(bytes, 0);
-    reader.read_exact(&mut block.data)?;
+    block.data.try_reserve(bytes)?;
+    reader.take(bytes as u64).read_to_end(&mut block.data)?;
 
     let mut marker = [0u8; 16];
     reader.read_exact(&mut marker)?;

src/io/avro/read/util.rs

@@ -23,8 +23,9 @@ fn decode_variable<R: Read>(reader: &mut R) -> Result<u64> {
 
 fn _read_binary<R: Read>(reader: &mut R) -> Result<Vec<u8>> {
     let len: usize = zigzag_i64(reader)? as usize;
-    let mut buf = vec![0u8; len];
-    reader.read_exact(&mut buf)?;
+    let mut buf = vec![];
+    buf.try_reserve(len)?;
+    reader.take(len as u64).read_to_end(&mut buf)?;
     Ok(buf)
 }
 

src/io/avro/read_async/block.rs

@@ -42,8 +42,11 @@ async fn read_block<R: AsyncRead + Unpin + Send>(
     };
 
     block.data.clear();
-    block.data.resize(bytes, 0);
-    reader.read_exact(&mut block.data).await?;
+    block.data.try_reserve(bytes)?;
+    reader
+        .take(bytes as u64)
+        .read_to_end(&mut block.data)
+        .await?;
 
     let mut marker = [0u8; 16];
     reader.read_exact(&mut marker).await?;

src/io/avro/read_async/metadata.rs

@@ -48,8 +48,9 @@ async fn read_file_marker<R: AsyncRead + Unpin + Send>(reader: &mut R) -> Result
 
 async fn _read_binary<R: AsyncRead + Unpin + Send>(reader: &mut R) -> Result<Vec<u8>> {
     let len: usize = zigzag_i64(reader).await? as usize;
-    let mut buf = vec![0u8; len];
-    reader.read_exact(&mut buf).await?;
+    let mut buf = vec![];
+    buf.try_reserve(len)?;
+    reader.take(len as u64).read_to_end(&mut buf).await?;
     Ok(buf)
 }