[GitHub] [arrow-rs] pitrou commented on a diff in pull request #1855: support compression for IPC

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

pitrou commented on code in PR #1855:
URL: https://github.com/apache/arrow-rs/pull/1855#discussion_r908515907


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arrow/src/ipc/compression/ipc_compression.rs:
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@@ -0,0 +1,124 @@
+// 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.
+
+use crate::ipc::CompressionType;
+
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub enum CompressionCodecType {
+    NoCompression,
+    Lz4Frame,
+    Zstd,
+}
+
+impl From<CompressionType> for CompressionCodecType {
+    fn from(compression_type: CompressionType) -> Self {
+        match compression_type {
+            CompressionType::ZSTD => CompressionCodecType::Zstd,
+            CompressionType::LZ4_FRAME => CompressionCodecType::Lz4Frame,
+            _ => CompressionCodecType::NoCompression,
+        }
+    }
+}
+
+impl From<CompressionCodecType> for Option<CompressionType> {
+    fn from(codec: CompressionCodecType) -> Self {
+        match codec {
+            CompressionCodecType::NoCompression => None,
+            CompressionCodecType::Lz4Frame => Some(CompressionType::LZ4_FRAME),
+            CompressionCodecType::Zstd => Some(CompressionType::ZSTD),
+        }
+    }
+}
+
+#[cfg(any(feature = "zstd,lz4", test))]
+mod compression_function {
+    use crate::error::Result;
+    use crate::ipc::compression::ipc_compression::CompressionCodecType;
+    use std::io::{Read, Write};
+
+    impl CompressionCodecType {
+        pub fn compress(&self, input: &[u8], output: &mut Vec<u8>) -> Result<()> {
+            match self {
+                CompressionCodecType::Lz4Frame => {
+                    let mut encoder = lz4::EncoderBuilder::new().build(output).unwrap();

Review Comment:
   As [the doc](https://docs.rs/lz4/1.23.3/lz4/) seems to say, "This module provides access to the block mode functions of the lz4 C library".
   LZ4_FRAME compression requires the frame functions of the lz4 C library. Apparently you can use https://docs.rs/lz4_flex/latest/lz4_flex/ instead.



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