Add span-based Deflate, ZLib and GZip encoder/decoder APIs by iremyux · Pull Request #123145 · dotnet/runtime

iremyux · 2026-01-13T18:46:21Z

This PR introduces new span-based, streamless compression and decompression APIs for Deflate, ZLib, and GZip formats, matching the existing BrotliEncoder/BrotliDecoder pattern.

New APIs

DeflateEncoder / DeflateDecoder
ZLibEncoder / ZLibDecoder
GZipEncoder / GZipDecoder

These classes provide:

Instance-based API for streaming/chunked compression with Compress(), Decompress(), and Flush()
Static one-shot API via TryCompress() and TryDecompress() for simple scenarios
GetMaxCompressedLength() to calculate buffer sizes

Closes #62113
Closes #39327
Closes #44793

src/libraries/System.IO.Compression/src/System/IO/Compression/ZlibEncoderOptions.cs

src/libraries/System.IO.Compression/src/System/IO/Compression/ZlibEncoder.cs

src/libraries/System.IO.Compression/ref/System.IO.Compression.cs

src/libraries/System.IO.Compression/src/System/IO/Compression/ZlibDecoder.cs

src/libraries/System.IO.Compression/src/System/IO/Compression/ZlibEncoder.cs

…mpressedLength

AraHaan · 2026-01-22T23:44:38Z

src/libraries/System.IO.Compression/src/System/IO/Compression/DeflateEncoder.cs

+                CompressionLevel.Fastest => ZLibNative.CompressionLevel.BestSpeed,
+                CompressionLevel.NoCompression => ZLibNative.CompressionLevel.NoCompression,
+                CompressionLevel.SmallestSize => ZLibNative.CompressionLevel.BestCompression,
+                _ => throw new ArgumentOutOfRangeException(nameof(compressionLevel)),


This would fail on valid native compression levels not covered by the CompressionLevel enum. Instead I think it should check if the value is is < -1 or > 9 to throw out of range instead.

Also to add on to the above, now those who want compression levels that just happen to == a value in the CompressionLevel enum will now not be able to use those compression levels either. Perhaps a solution to this is to expose a version of the ctor with CompressionLevel and a version with int that gets casted to ZLibNative.CompressionLevel after a range check.

src/libraries/System.IO.Compression/tests/DeflateZLibGZipEncoderDecoderTests.cs

src/libraries/System.IO.Compression/src/System/IO/Compression/GZipEncoder.cs

Copilot

Pull request overview

Copilot reviewed 30 out of 30 changed files in this pull request and generated 3 comments.

src/libraries/System.IO.Compression/src/System/IO/Compression/DeflateEncoder.cs

src/native/libs/System.IO.Compression.Native/pal_zlib.h

alinpahontu2912

Some nitpicks about styling and a few questions, but lgtm, good job 👍

src/libraries/System.IO.Compression/src/Resources/Strings.resx

src/libraries/System.IO.Compression/src/System/IO/Compression/ZLibCompressionOptions.cs

src/libraries/System.IO.Compression/src/System/IO/Compression/ZLibStream.cs

alinpahontu2912 · 2026-03-16T09:28:07Z

src/libraries/System.IO.Compression/tests/CompressionStreamUnitTests.ZLib.cs

+        [InlineData(10)]
+        [InlineData(15)]
+        [InlineData(-1)]
+        public void RoundTrip_WithWindowLog(int windowLog)


this test with the inline data is repeated 3 times, could we maybe avoid duplication ?

moving it to CompressionStreamUnitTestBase so it runs for all three formats without duplication

src/native/libs/System.IO.Compression.Native/pal_zlib.c

src/libraries/Common/tests/System/IO/Compression/EncoderDecoderTestBase.cs

src/libraries/System.IO.Compression/src/System/IO/Compression/DeflateZLib/DeflateStream.cs

src/libraries/System.IO.Compression/tests/ZlibEncoderDecoderTests.cs

Copilot

Pull request overview

Copilot reviewed 33 out of 33 changed files in this pull request and generated 2 comments.

src/native/libs/System.IO.Compression.Native/pal_zlib.c

src/libraries/System.IO.Compression/src/System/IO/Compression/DeflateEncoder.cs

iremyux and others added 3 commits January 12, 2026 20:46

Add Zlib Encoder and Decoder classes

e402958

Add tests

95ac930

Merge branch 'dotnet:main' into 62113-zlib-encoder-decoder

88acc57

iremyux self-assigned this Jan 13, 2026

iremyux added the area-System.IO.Compression label Jan 13, 2026