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Add dictionary support to Zstd and Brotli compressor input streams - #821
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Add ZstdCompressorInputStream.Builder.setDict(byte[]) and BrotliCompressorInputStream.Builder.setDict(byte[]) to decompress input compressed with a dictionary, for example Compression Dictionary Transport (RFC 9842) payloads.
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🟡 Changes recommended
The Zstandard path-based builder leaks its internally opened input stream because close propagation is disabled.
Review effort: Balanced
Findings: 1
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What changed in this PR
Adds dictionary-based decompression support to Brotli and Zstandard input streams.
Changes:
- Adds builders with
setDict(byte[]). - Adds dictionary decompression and missing-dictionary tests.
- Adds fixtures, release notes, and binary resource handling.
| File | Description |
|---|---|
.gitattributes |
Marks dictionary fixtures as binary. |
src/changes/changes.xml |
Documents both new APIs. |
BrotliCompressorInputStream.java |
Adds dictionary-aware builder. |
ZstdCompressorInputStream.java |
Adds dictionary-aware builder. |
BrotliCompressorInputStreamTest.java |
Tests Brotli dictionary decoding. |
ZstdCompressorInputStreamTest.java |
Tests Zstandard dictionary decoding. |
brotli.dictionary.dict |
Provides the test dictionary. |
brotli.dictionary.uncompressed |
Provides expected decompressed data. |
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| @SuppressWarnings("resource") // Caller closes | ||
| private ZstdCompressorInputStream(final Builder builder) throws IOException { | ||
| this.decIS = new ZstdInputStream( | ||
| countingStream = BoundedInputStream.builder().setInputStream(builder.getInputStream()).setPropagateClose(false).get()); |
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@arturobernalg |
garydgregory
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Oct 7, 2026
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I added 2 questions about the byte array setters.
| * @return {@code this} instance. | ||
| */ | ||
| public Builder setDict(final byte[] dict) { | ||
| this.dict = dict; |
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Should the builder track a defensive copy?
| * @see <a href="https://facebook.github.io/zstd/zstd_manual.html#Chapter14">Zstd manual Chapter14</a> | ||
| */ | ||
| public Builder setDict(final byte[] dict) { | ||
| this.dict = dict; |
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Should the builder track a defensive copy?
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Add ZstdCompressorInputStream.Builder.setDict(byte[]) and BrotliCompressorInputStream.Builder.setDict(byte[]) to decompress input compressed with a dictionary, for example Compression Dictionary Transport (RFC 9842) payloads.
Motivation: Compression Dictionary Transport (RFC 9842) support in Apache HttpClient, see apache/httpcomponents-client#881
Thanks for your contribution to Apache Commons! Your help is appreciated!
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