Added compression to Avro write

Cargo.toml

@@ -74,6 +74,7 @@ avro-schema = { version = "0.2", optional = true }
 # compression of avro
 libflate = { version = "1.1.1", optional = true }
 snap = { version = "1", optional = true }
+crc = { version = "1", optional = true }
 # async avro
 async-stream = { version = "0.3.2", optional = true }
 
@@ -142,6 +143,7 @@ io_avro = ["avro-schema", "streaming-iterator", "fallible-streaming-iterator", "
 io_avro_compression = [
     "libflate",
     "snap",
+    "crc",
 ]
 io_avro_async = ["io_avro", "futures", "async-stream"]
 # io_json: its dependencies + error handling

examples/avro_write.rs

@@ -26,12 +26,7 @@ fn write_avro<W: std::io::Write>(
 
     let mut compressed_block = write::CompressedBlock::default();
 
-    if let Some(compression) = compression {
-        write::compress(&block, &mut compressed_block, compression)?;
-    } else {
-        compressed_block.number_of_rows = block.number_of_rows;
-        std::mem::swap(&mut compressed_block.data, &mut block.data);
-    }
+    let _was_compressed = write::compress(&mut block, &mut compressed_block, compression)?;
 
     write::write_metadata(file, avro_fields.clone(), compression)?;
 

src/io/avro/read/decompress.rs

@@ -34,13 +34,23 @@ pub fn decompress_block(
         }
         #[cfg(feature = "io_avro_compression")]
         Some(Compression::Snappy) => {
-            let len = snap::raw::decompress_len(&block[..block.len() - 4])
-                .map_err(|_| ArrowError::ExternalFormat("Failed to decompress snap".to_string()))?;
+            let (crc, block) = block.split_at(block.len() - 4);
+
+            let len = snap::raw::decompress_len(block)
+                .map_err(|e| ArrowError::ExternalFormat(e.to_string()))?;
             decompressed.clear();
             decompressed.resize(len, 0);
             snap::raw::Decoder::new()
-                .decompress(&block[..block.len() - 4], decompressed)
-                .map_err(|_| ArrowError::ExternalFormat("Failed to decompress snap".to_string()))?;
+                .decompress(block, decompressed)
+                .map_err(|e| ArrowError::ExternalFormat(e.to_string()))?;
+
+            let expected_crc = u32::from_be_bytes([crc[0], crc[1], crc[2], crc[3]]);
+            let actual_crc = crc::crc32::checksum_ieee(decompressed);
+            if expected_crc != actual_crc {
+                return Err(ArrowError::ExternalFormat(
+                    "The crc of snap-compressed block does not match".to_string(),
+                ));
+            }
             Ok(false)
         }
         #[cfg(not(feature = "io_avro_compression"))]

src/io/avro/write/block.rs

@@ -1,8 +1,8 @@
 use std::io::Write;
 
-use crate::{error::Result, io::avro::Compression};
+use crate::error::Result;
 
-use super::super::{Block, CompressedBlock};
+use super::super::CompressedBlock;
 use super::{util::zigzag_encode, SYNC_NUMBER};
 
 /// Writes a [`CompressedBlock`] to `writer`
@@ -17,16 +17,3 @@ pub fn write_block<W: Write>(writer: &mut W, compressed_block: &CompressedBlock)
 
     Ok(())
 }
-
-/// Compresses an [`Block`] to a [`CompressedBlock`].
-pub fn compress(
-    block: &Block,
-    compressed_block: &mut CompressedBlock,
-    compression: Compression,
-) -> Result<()> {
-    compressed_block.number_of_rows = block.number_of_rows;
-    match compression {
-        Compression::Deflate => todo!(),
-        Compression::Snappy => todo!(),
-    }
-}

src/io/avro/write/compress.rs

@@ -0,0 +1,60 @@
+//! APIs to read from Avro format to arrow.
+
+use crate::error::Result;
+
+use super::Compression;
+use super::{Block, CompressedBlock};
+
+/// Compresses a [`Block`] to a [`CompressedBlock`].
+pub fn compress(
+    block: &mut Block,
+    compressed: &mut CompressedBlock,
+    compression: Option<Compression>,
+) -> Result<bool> {
+    compressed.number_of_rows = block.number_of_rows;
+    let block = &mut block.data;
+    let compressed = &mut compressed.data;
+
+    match compression {
+        None => {
+            std::mem::swap(block, compressed);
+            Ok(true)
+        }
+        #[cfg(feature = "io_avro_compression")]
+        Some(Compression::Deflate) => {
+            use std::io::Write;
+            compressed.clear();
+            let mut encoder = libflate::deflate::Encoder::new(compressed);
+            encoder.write_all(block)?;
+            encoder.finish();
+            Ok(false)
+        }
+        #[cfg(feature = "io_avro_compression")]
+        Some(Compression::Snappy) => {
+            use snap::raw::{max_compress_len, Encoder};
+
+            compressed.clear();
+
+            let required_len = max_compress_len(block.len());
+            compressed.resize(required_len, 0);
+            let compressed_bytes = Encoder::new()
+                .compress(block, compressed)
+                .map_err(|e| crate::error::ArrowError::ExternalFormat(e.to_string()))?;
+            compressed.truncate(compressed_bytes);
+
+            let crc = crc::crc32::checksum_ieee(block);
+            compressed.extend(crc.to_be_bytes());
+            Ok(false)
+        }
+        #[cfg(not(feature = "io_avro_compression"))]
+        Some(Compression::Deflate) => Err(crate::error::ArrowError::InvalidArgumentError(
+            "Trying to compress Avro with deflate but feature 'io_avro_compression' is not active."
+                .to_string(),
+        )),
+        #[cfg(not(feature = "io_avro_compression"))]
+        Some(Compression::Snappy) => Err(crate::error::ArrowError::InvalidArgumentError(
+            "Trying to compress Avro with snappy but feature 'io_avro_compression' is not active."
+                .to_string(),
+        )),
+    }
+}

src/io/avro/write/mod.rs

@@ -15,7 +15,9 @@ mod serialize;
 pub use serialize::{can_serialize, new_serializer, BoxSerializer};
 mod block;
 pub use block::*;
+mod compress;
 mod util;
+pub use compress::compress;
 
 pub use super::{Block, CompressedBlock};
 

tests/it/io/avro/write.rs

@@ -55,12 +55,7 @@ fn write_avro<R: AsRef<dyn Array>>(
 
     let mut compressed_block = write::CompressedBlock::default();
 
-    if let Some(compression) = compression {
-        write::compress(&block, &mut compressed_block, compression)?;
-    } else {
-        compressed_block.number_of_rows = block.number_of_rows;
-        std::mem::swap(&mut compressed_block.data, &mut block.data);
-    }
+    write::compress(&mut block, &mut compressed_block, compression)?;
 
     let mut file = vec![];
 
@@ -93,3 +88,13 @@ fn roundtrip(compression: Option<write::Compression>) -> Result<()> {
 fn no_compression() -> Result<()> {
     roundtrip(None)
 }
+
+#[test]
+fn snappy() -> Result<()> {
+    roundtrip(Some(write::Compression::Snappy))
+}
+
+#[test]
+fn deflate() -> Result<()> {
+    roundtrip(Some(write::Compression::Deflate))
+}