[GitHub] [arrow] mqy commented on a change in pull request #9137: ARROW-8676: [Rust] IPC RecordBatch body compression

[GitBox <gi...@apache.org>]

mqy commented on a change in pull request #9137:
URL: https://github.com/apache/arrow/pull/9137#discussion_r554081674



##########
File path: rust/arrow/src/ipc/compression.rs
##########
@@ -0,0 +1,122 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+//! IPC Compression Utilities
+
+use std::io::{Read, Write};
+
+use crate::error::{ArrowError, Result};
+use crate::ipc::gen::Message::CompressionType;
+
+pub trait IpcCompressionCodec {
+    fn compress(&self, input_buf: &[u8], output_buf: &mut Vec<u8>) -> Result<()>;
+    fn decompress(&self, input_buf: &[u8], output_buf: &mut Vec<u8>) -> Result<usize>;
+    fn get_compression_type(&self) -> CompressionType;
+}
+
+pub type Codec = Box<dyn IpcCompressionCodec>;
+
+#[inline]
+pub(crate) fn get_codec(
+    compression_type: Option<CompressionType>,
+) -> Result<Option<Codec>> {
+    match compression_type {
+        Some(CompressionType::LZ4_FRAME) => Ok(Some(Box::new(Lz4CompressionCodec {}))),
+        Some(ctype) => Err(ArrowError::InvalidArgumentError(format!(
+            "IPC CompresstionType {:?} not yet supported",
+            ctype
+        ))),
+        None => Ok(None),
+    }
+}
+
+pub struct Lz4CompressionCodec {}
+const LZ4_BUFFER_SIZE: usize = 4096;
+
+impl IpcCompressionCodec for Lz4CompressionCodec {
+    fn compress(&self, input_buf: &[u8], output_buf: &mut Vec<u8>) -> Result<()> {
+        if input_buf.is_empty() {
+            output_buf.write_all(&8i64.to_le_bytes())?;
+            return Ok(());
+        }
+        // write out the uncompressed length as a LE i64 value
+        output_buf.write_all(&(input_buf.len() as i64).to_le_bytes())?;
+        let mut encoder = lz4::EncoderBuilder::new().build(output_buf)?;
+        let mut from = 0;
+        loop {

Review comment:
       This loop can be omitted.




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