news.rst

Version History

1.0.0 (not yet released)

Actions Blocking Release

• Properly handle non-blocking I/O and partial writes for objects implementing io.RawIOBase.
• Consider making reads across frames configurable behavior.
• Overall API design review.
• Use Python allocator where possible.
• Figure out what to do about experimental APIs not implemented by CFFI.
• APIs for auto adjusting compression parameters based on input size. e.g. clamping the window log so it isn't too large for input.
• Consider allowing compressor and decompressor instances to be thread safe, support concurrent operations. Or track when an operation is in progress and refuse to let concurrent operations use the same instance.
• Support for magic-less frames for all decompression operations (decompress() doesn't work due to sniffing the content size and the lack of a ZSTD API to sniff magic-less frames - this should be fixed in 1.3.5.).
• Audit for complete flushing when ending compression streams.
• Deprecate legacy APIs.
• Audit for ability to control read/write sizes on all APIs.
• Detect memory leaks via bench.py.
• Remove low-level compression parameters from ZstdCompressor.__init__ and require use of ZstdCompressionParameters.
• Consider a chunker() API for decompression.
• Consider stats for chunker() API, including finding the last consumed offset of input data.
• Consider controls over resetting compression contexts (session only, parameters, or session and parameters).
• Utilize ZSTD_getDictID_fromCDict()?
• Stop relying on private libzstd headers and symbols (namely pool.h).

Other Actions Not Blocking Release

• Support for block compression APIs.
• API for ensuring max memory ceiling isn't exceeded.
• Move off nose for testing.

0.24.0 (not yet released)

Changes

• We now use a non-rc version of cffi 1.17 on all Python versions. Python <=3.12 have cffi upgraded from cffi 1.16 -> 1.17.

• The pyproject.toml file now defines a [project] section.

0.23.0 (released 2024-07-14)

Changes

• Bundled zstd library upgraded from 1.5.5 to 1.5.6.
• Releases now publish wheels for manylinux2014_ppc64le, manylinux2014_s390x, musllinux_1_2_aarch64, musllinux_1_2_i686, musllinux_1_2_ppc64le, musllinux_1_2_s390x, and musllinux_1_2_x86_64.
• PyO3 Rust crate upgraded from 0.18 to 0.21.
• Semi official support for CPython 3.13. Binary wheels for 3.13 are now published during releases. There were no meaningful code changes to support Python 3.13. Support is semi official since 3.13 is still in beta and 3.13 is currently being built against a pre-release version of cffi 1.17. We also lack a Rust extension for 3.13 since PyO3 lacks a release with 3.13 support.
• pyproject.toml now lists version constraints of [build-system] requirements, not exact versions. This should provide more compatibility with more environments. setuptools is held back before 69.0.0 because that version apparently broke support for using --global-settings=--build-option in editable installs, which our CI relies on.

0.22.0 (released 2023-11-01)

Backwards Compatibility Notes

• ZstdDecompressor.decompressobj() will change read_across_frames to default to True in a future release. If you depend on the current functionality of stopping at frame boundaries, start explicitly passing read_across_frames=False to preserve the current behavior.
• manylinux2010 wheels are no longer published since this wheel format is no longer supported by the pypa/manylinux project.
• Removed CI coverage for PyPy 3.7 and 3.8, which are no longer supported PyPy versions.
• Support for Python 3.7 has been dropped because it reached end of life. Python 3.8 is the minimum supported Python version. The code should still be compatible with Python 3.7 and removing of version checks from setup.py will likely yield a working install. However, this is no officially supported.

Changes

• ZstdDecompressor.decompressobj() now accepts a read_across_frames boolean named argument to control whether to transparently read across multiple zstd frames. It defaults to False to preserve existing behavior.
• Added CI coverage for PyPy 3.10.
• Added CI coverage for newer Anaconda Python versions.
• Packages used in CI have been upgraded to latest versions. This should nominally only impact developers of this project and not end-users.
• pyproject.toml now declares a [build-system] section saying to build with setuptools.
• CI now builds wheels with pip instead of setup.py directly.
• Official support for CPython 3.12. Binary wheels for 3.12 are now published during releases. There were no meaningful code changes to support Python 3.12.
• Binary wheels for musllinux_1_1 x86_64 and aarch64 are now being built and published.

0.21.0 (released 2023-04-16)

Backwards Compatibility Notes

• Support for Python 3.6 has been dropped. Python 3.7 is the minimum supported Python version.

Changes

• Bundled zstd library upgraded from 1.5.4 to 1.5.5.
• PyO3 Rust crate upgraded from 0.15 to 0.18.
• CI environment changed from Ubuntu 20.04 -> 22.04, Windows 2019 -> 2022, macOS 11 -> macOS 12.
• C types now use PyType_Spec and corresponding APIs. (#187) Contributed by Mike Hommey.

0.20.0 (released 2023-02-20)

Backwards Compatibility Notes

• This will likely be the last release officially supporting Python 3.6. Python 3.6 is end of life as of 2021-12-23.

Changes

• Bundled zstd library upgraded from 1.5.2 to 1.5.4.
• Use of the deprecated ZSTD_copyDCtx() was removed from the C and Rust backends.

0.19.0 (released 2022-10-29)

Bug Fixes

• The C backend implementation of ZstdDecompressionObj.decompress() could have raised an assertion in cases where the function was called multiple times on an instance. In non-debug builds, calls to this method could have leaked memory.

Changes

• PyPy 3.6 support dropped; Pypy 3.8 and 3.9 support added.
• Anaconda 3.6 support dropped.
• Official support for Python 3.11. This did not require meaningful code changes and previous release(s) likely worked with 3.11 without any changes.
• CFFI's build system now respects distutils's compiler.preprocessor if it is set. (#179)
• The internal logic of ZstdDecompressionObj.decompress() was refactored. This may have fixed unconfirmed issues where unused_data was set prematurely. The new logic will also avoid an extra call to ZSTD_decompressStream() in some scenarios, possibly improving performance.
• ZstdDecompressor.decompress() how has a read_across_frames keyword argument. It defaults to False. True is not yet implemented and will raise an exception if used. The new argument will default to True in a future release and is provided now so callers can start passing read_across_frames=False to preserve the existing functionality during a future upgrade.
• ZstdDecompressor.decompress() now has an allow_extra_data keyword argument to control whether an exception is raised if input contains extra data. It defaults to True, preserving existing behavior of ignoring extra data. It will likely default to False in a future release. Callers desiring the current behavior are encouraged to explicitly pass allow_extra_data=True so behavior won't change during a future upgrade.

0.18.0 (released 2022-06-20)

Changes

• Bundled zstd library upgraded from 1.5.1 to 1.5.2.
• ZstdDecompressionObj now has an unused_data attribute. It will contain data beyond the fully decoded zstd frame data if said data exists.
• ZstdDecompressionObj now has an unconsumed_tail attribute. This attribute currently always returns the empty bytes value (b"").
• ZstdDecompressionObj now has an eof attribute returning whether the compressed data has been fully read.

0.17.0 (released 2021-01-18)

Backwards Compatibility Notes

• ZstdCompressionWriter and ZstdDecompressionWriter now implement __iter__() and __next__(). The methods always raise io.UnsupportedOperation. The added methods are part of the io.IOBase abstract base class / interface and help ensure instances look like other I/O types. (#167, #168)
• The HASHLOG3_MAX constant has been removed since it is no longer defined in zstd 1.5.1.

Bug Fixes

• The ZstdCompressionReader, ZstdCompressionWriter, ZstdDecompressionReader, and ZstdDecompressionWriter types in the C backend now tracks their closed attribute using the proper C type. Before, due to a mismatch between the C struct type and the type declared to Python, Python could read the wrong bits on platforms like s390x and incorrectly report the value of the closed attribute to Python. (#105, #164)

Changes

• Bundled zstd library upgraded from 1.5.0 to 1.5.1.
• The C backend now exposes the symbols ZstdCompressionReader, ZstdCompressionWriter, ZstdDecompressionReader, and ZstdDecompressionWriter. This should match the behavior of the CFFI backend. (#165)
• ZstdCompressionWriter and ZstdDecompressionWriter now implement __iter__ and __next__, which always raise io.UnsupportedOperation.
• Documentation on thread safety has been updated to note that derived objects like ZstdCompressionWriter have the same thread unsafety as the contexts they were derived from. (#166)

0.16.0 (released 2021-10-16)

Backwards Compatibility Notes

• Support for Python 3.5 has been dropped. Python 3.6 is now the minimum required Python version.

Changes

• Bundled zstd library upgraded from 1.4.8 to 1.5.0.
• manylinux2014_aarch64 wheels are now being produced for CPython 3.6+. (#145).
• Wheels are now being produced for CPython 3.10.
• Arguments to ZstdCompressor() and ZstdDecompressor() are now all optional in the C backend and an explicit None value is accepted. Before, the C backend wouldn't accept an explicit None value (but the CFFI backend would). The new behavior should be consistent between the backends. (#153)

0.15.2 (released 2021-02-27)

Backwards Compatibility Notes

• ZstdCompressor.multi_compress_to_buffer() and ZstdDecompressor.multi_decompress_to_buffer() are no longer available when linking against a system zstd library. These experimental features are only available when building against the bundled single file zstd C source file distribution. (#106)

Changes

• setup.py now recognizes a ZSTD_EXTRA_COMPILER_ARGS environment variable to specify additional compiler arguments to use when compiling the C backend.
• PyPy build and test coverage has been added to CI.
• Added CI jobs for building against external zstd library.
• Wheels supporting macOS ARM/M1 devices are now being produced.
• References to Python 2 have been removed from the in-repo Debian packaging code.
• Significant work has been made on a Rust backend. It is currently feature complete but not yet optimized. We are not yet shipping the backend as part of the distributed wheels until it is more mature.
• The .pyi type annotations file has replaced various default argument values with ....

0.15.1 (released 2020-12-31)

Bug Fixes

• setup.py no longer attempts to build the C backend on PyPy. (#130)
• <sys/types.h> is now included before <sys/sysctl.h>. This was the case in releases prior to 0.15.0 and the include order was reversed as part of running clang-format. The old/working order has been restored. (#128)
• Include some private zstd C headers so we can build the C extension against a system library. The previous behavior of referencing these headers is restored. That behave is rather questionable and undermines the desire to use the system zstd.

0.15.0 (released 2020-12-29)

Backwards Compatibility Notes

• Support for Python 2.7 has been dropped. Python 3.5 is now the minimum required Python version. (#109)
• train_dictionary() now uses the fastcover training mechanism (as opposed to cover). Some parameter values that worked with the old mechanism may not work with the new one. e.g. d must be 6 or 8 if it is defined.
• train_dictionary() now always calls ZDICT_optimizeTrainFromBuffer_fastCover() instead of different APIs depending on which arguments were passed.
• The names of various Python modules have been changed. The C extension is now built as zstandard.backend_c instead of zstd. The CFFI extension module is now built as zstandard._cffi instead of _zstd_cffi. The CFFI backend is now zstandard.backend_cffi instead of zstandard.cffi.
• ZstdDecompressionReader.seekable() now returns False instead of True because not all seek operations are supported and some Python code in the wild keys off this value to determine if seek() can be called for all scenarios.
• ZstdDecompressionReader.seek() now raises OSError instead of ValueError when the seek cannot be fulfilled. (#107)
• ZstdDecompressionReader.readline() and ZstdDecompressionReader.readlines() now accept an integer argument. This makes them conform with the IO interface. The methods still raise io.UnsupportedOperation.
• ZstdCompressionReader.__enter__ and ZstdDecompressionReader.__enter__ now raise ValueError if the instance was already closed.
• The deprecated overlap_size_log attribute on ZstdCompressionParameters instances has been removed. The overlap_log attribute should be used instead.
• The deprecated overlap_size_log argument to ZstdCompressionParameters has been removed. The overlap_log argument should be used instead.
• The deprecated ldm_hash_every_log attribute on ZstdCompressionParameters instances has been removed. The ldm_hash_rate_log attribute should be used instead.
• The deprecated ldm_hash_every_log argument to ZstdCompressionParameters has been removed. The ldm_hash_rate_log argument should be used instead.
• The deprecated CompressionParameters type alias to ZstdCompressionParamaters has been removed. Use ZstdCompressionParameters.
• The deprecated aliases ZstdCompressor.read_from() and ZstdDecompressor.read_from() have been removed. Use the corresponding read_to_iter() methods instead.
• The deprecated aliases ZstdCompressor.write_to() and ZstdDecompressor.write_to() have been removed. Use the corresponding stream_writer() methods instead.
• ZstdCompressor.copy_stream(), ZstdCompressorIterator.__next__(), and ZstdDecompressor.copy_stream() now raise the original exception on error calling the source stream's read() instead of raising ZstdError. This only affects the C backend.
• ZstdDecompressionObj.flush() now returns bytes instead of None. This makes it behave more similarly to flush() methods for similar types in the Python standard library. (#78)
• ZstdCompressionWriter.__exit__() now always calls close(). Previously, close() would not be called if the context manager raised an exception. The old behavior was inconsistent with other stream types in this package and with the behavior of Python's standard library IO types. (#86)
• Distribution metadata no longer lists cffi as an install_requires except when running on PyPy. Instead, cffi is listed as an extras_require.
• ZstdCompressor.stream_reader() and ZstdDecompressor.stream_reader() now default to closing the source stream when the instance is itself closed. To change this behavior, pass closefd=False. (#76)
• The CFFI backend now defines ZstdCompressor.multi_compress_to_buffer() and ZstdDecompressor.multi_decompress_to_buffer(). However, they raise NotImplementedError, as they are not yet implemented.
• The CFFI backend now exposes the types ZstdCompressionChunker, ZstdCompressionObj, ZstdCompressionReader, ZstdCompressionWriter, ZstdDecompressionObj, ZstdDecompressionReader, and ZstdDecompressionWriter as symbols on the zstandard module.
• The CFFI backend now exposes the types BufferSegment, BufferSegments, BufferWithSegments, and BufferWithSegmentsCollection. However, they are not implemented.
• ZstdCompressionWriter.flush() now calls flush() on the inner stream if such a method exists. However, when close() itself calls self.flush(), flush() is not called on the inner stream.
• ZstdDecompressionWriter.close() no longer calls flush() on the inner stream. However, ZstdDecompressionWriter.flush() still calls flush() on the inner stream.
• ZstdCompressor.stream_writer() and ZstdDecompressor.stream_writer() now have their write_return_read argument default to True. This brings the behavior of write() in compliance with the io.RawIOBase interface by default. The argument may be removed in a future release.
• ZstdCompressionParameters no longer exposes a compression_strategy property. Its constructor no longer accepts a compression_strategy argument. Use the strategy property/argument instead.

Bug Fixes

• Fix a memory leak in stream_reader decompressor when reader is closed before reading everything. (Patch by Pierre Fersing.)
• The C backend now properly checks for errors after calling IO methods on inner streams in various methods. ZstdCompressionWriter.write() now catches exceptions when calling the inner stream's write(). ZstdCompressionWriter.flush() on inner stream's write(). ZstdCompressor.copy_stream() on dest stream's write(). ZstdDecompressionWriter.write() on inner stream's write(). ZstdDecompressor.copy_stream() on dest stream's write(). (#102)

Changes

• Bundled zstandard library upgraded from 1.4.5 to 1.4.8.
• The bundled zstandard library is now using the single C source file distribution. The 2 main header files are still present, as these are needed by CFFI to generate the CFFI bindings.
• PyBuffer instances are no longer checked to be C contiguous and have a single dimension. The former was redundant with what PyArg_ParseTuple() already did and the latter is not necessary in practice because very few extension modules create buffers with more than 1 dimension. (#124)
• Added Python typing stub file for the zstandard module. (#120)
• The make_cffi.py script should now respect the CC environment variable for locating the compiler. (#103)
• CI now properly uses the cffi backend when running all tests.
• train_dictionary() has been rewritten to use the fastcover APIs and to consistently call ZDICT_optimizeTrainFromBuffer_fastCover() instead of different C APIs depending on what arguments were passed. The function also now accepts arguments f, split_point, and accel, which are parameters unique to fastcover.
• CI now tests and builds wheels for Python 3.9.
• zstd.c file renamed to c-ext/backend_c.c.
• All built/installed Python modules are now in the zstandard package. Previously, there were modules in other packages. (#115)
• C source code is now automatically formatted with clang-format.
• ZstdCompressor.stream_writer(), ZstdCompressor.stream_reader(), ZstdDecompressor.stream_writer(), and ZstdDecompressor.stream_reader() now accept a closefd argument to control whether the underlying stream should be closed when the ZstdCompressionWriter, ZstdCompressReader, ZstdDecompressionWriter, or ZstdDecompressionReader is closed. (#76)
• There is now a zstandard.open() function for returning a file object with zstd (de)compression. (#64)
• The zstandard module now exposes a backend_features attribute containing a set of strings denoting optional features present in that backend. This can be used to sniff feature support by performing a string lookup instead of sniffing for API presence or behavior.
• Python docstrings have been moved from the C backend to the CFFI backend. Sphinx docs have been updated to generate API documentation via the CFFI backend. Documentation for Python APIs is now fully defined via Python docstrings instead of spread across Sphinx ReST files and source code.
• ZstdCompressionParameters now exposes a strategy property.
• There are now compress() and decompress() convenience functions on the zstandard module. These are simply wrappers around the corresponding APIs on ZstdCompressor and ZstdDecompressor.

0.14.1 (released 2020-12-05)

Changes

• Python 3.9 wheels are now provided.

0.14.0 (released 2020-06-13)

Backwards Compatibility Notes

• This will likely be the final version supporting Python 2.7. Future releases will likely only work on Python 3.5+. See #109 for more context.
• There is a significant possibility that future versions will use Rust - instead of C - for compiled code. See #110 for more context.

Bug Fixes

• Some internal fields of C structs are now explicitly initialized. (Possible fix for #105.)
• The make_cffi.py script used to build the CFFI bindings now calls distutils.sysconfig.customize_compiler() so compiler customizations (such as honoring the CC environment variable) are performed. Patch by @Arfrever. (#103)
• The make_cffi.py script now sets LC_ALL=C when invoking the preprocessor in an attempt to normalize output to ASCII. (#95)

Changes

• Bundled zstandard library upgraded from 1.4.4 to 1.4.5.
• setup.py is now executable.
• Python code reformatted with black using 80 character line lengths.

0.13.0 (released 2019-12-28)

Changes

• pytest-xdist pytest extension is now installed so tests can be run in parallel.
• CI now builds manylinux2010 and manylinux2014 binary wheels instead of a mix of manylinux2010 and manylinux1.
• Official support for Python 3.8 has been added.
• Bundled zstandard library upgraded from 1.4.3 to 1.4.4.
• Python code has been reformatted with black.

0.12.0 (released 2019-09-15)

Backwards Compatibility Notes

• Support for Python 3.4 has been dropped since Python 3.4 is no longer a supported Python version upstream. (But it will likely continue to work until Python 2.7 support is dropped and we port to Python 3.5+ APIs.)

Bug Fixes

• Fix ZstdDecompressor.__init__ on 64-bit big-endian systems (#91).
• Fix memory leak in ZstdDecompressionReader.seek() (#82).

Changes

• CI transitioned to Azure Pipelines (from AppVeyor and Travis CI).
• Switched to pytest for running tests (from nose).
• Bundled zstandard library upgraded from 1.3.8 to 1.4.3.

0.11.1 (released 2019-05-14)

• Fix memory leak in ZstdDecompressionReader.seek() (#82).

0.11.0 (released 2019-02-24)

Backwards Compatibility Notes

• ZstdDecompressor.read() now allows reading sizes of -1 or 0 and defaults to -1, per the documented behavior of io.RawIOBase.read(). Previously, we required an argument that was a positive value.
• The readline(), readlines(), __iter__, and __next__ methods of ZstdDecompressionReader() now raise io.UnsupportedOperation instead of NotImplementedError.
• ZstdDecompressor.stream_reader() now accepts a read_across_frames argument. The default value will likely be changed in a future release and consumers are advised to pass the argument to avoid unwanted change of behavior in the future.
• setup.py now always disables the CFFI backend if the installed CFFI package does not meet the minimum version requirements. Before, it was possible for the CFFI backend to be generated and a run-time error to occur.
• In the CFFI backend, CompressionReader and DecompressionReader were renamed to ZstdCompressionReader and ZstdDecompressionReader, respectively so naming is identical to the C extension. This should have no meaningful end-user impact, as instances aren't meant to be constructed directly.
• ZstdDecompressor.stream_writer() now accepts a write_return_read argument to control whether write() returns the number of bytes read from the source / written to the decompressor. It defaults to off, which preserves the existing behavior of returning the number of bytes emitted from the decompressor. The default will change in a future release so behavior aligns with the specified behavior of io.RawIOBase.
• ZstdDecompressionWriter.__exit__ now calls self.close(). This will result in that stream plus the underlying stream being closed as well. If this behavior is not desirable, do not use instances as context managers.
• ZstdCompressor.stream_writer() now accepts a write_return_read argument to control whether write() returns the number of bytes read from the source / written to the compressor. It defaults to off, which preserves the existing behavior of returning the number of bytes emitted from the compressor. The default will change in a future release so behavior aligns with the specified behavior of io.RawIOBase.
• ZstdCompressionWriter.__exit__ now calls self.close(). This will result in that stream plus any underlying stream being closed as well. If this behavior is not desirable, do not use instances as context managers.
• ZstdDecompressionWriter no longer requires being used as a context manager (#57).
• ZstdCompressionWriter no longer requires being used as a context manager (#57).
• The overlap_size_log attribute on CompressionParameters instances has been deprecated and will be removed in a future release. The overlap_log attribute should be used instead.
• The overlap_size_log argument to CompressionParameters has been deprecated and will be removed in a future release. The overlap_log argument should be used instead.
• The ldm_hash_every_log attribute on CompressionParameters instances has been deprecated and will be removed in a future release. The ldm_hash_rate_log attribute should be used instead.
• The ldm_hash_every_log argument to CompressionParameters has been deprecated and will be removed in a future release. The ldm_hash_rate_log argument should be used instead.
• The compression_strategy argument to CompressionParameters has been deprecated and will be removed in a future release. The strategy argument should be used instead.
• The SEARCHLENGTH_MIN and SEARCHLENGTH_MAX constants are deprecated and will be removed in a future release. Use MINMATCH_MIN and MINMATCH_MAX instead.
• The zstd_cffi module has been renamed to zstandard.cffi. As had been documented in the README file since the 0.9.0 release, the module should not be imported directly at its new location. Instead, import zstandard to cause an appropriate backend module to be loaded automatically.

Bug Fixes

• CFFI backend could encounter a failure when sending an empty chunk into ZstdDecompressionObj.decompress(). The issue has been fixed.
• CFFI backend could encounter an error when calling ZstdDecompressionReader.read() if there was data remaining in an internal buffer. The issue has been fixed. (#71)

Changes

• ZstDecompressionObj.decompress() now properly handles empty inputs in the CFFI backend.
• ZstdCompressionReader now implements read1() and readinto1(). These are part of the io.BufferedIOBase interface.
• ZstdCompressionReader has gained a readinto(b) method for reading compressed output into an existing buffer.
• ZstdCompressionReader.read() now defaults to size=-1 and accepts read sizes of -1 and 0. The new behavior aligns with the documented behavior of io.RawIOBase.
• ZstdCompressionReader now implements readall(). Previously, this method raised NotImplementedError.
• ZstdDecompressionReader now implements read1() and readinto1(). These are part of the io.BufferedIOBase interface.
• ZstdDecompressionReader.read() now defaults to size=-1 and accepts read sizes of -1 and 0. The new behavior aligns with the documented behavior of io.RawIOBase.
• ZstdDecompressionReader() now implements readall(). Previously, this method raised NotImplementedError.
• The readline(), readlines(), __iter__, and __next__ methods of ZstdDecompressionReader() now raise io.UnsupportedOperation instead of NotImplementedError. This reflects a decision to never implement text-based I/O on (de)compressors and keep the low-level API operating in the binary domain. (#13)
• README.rst now documented how to achieve linewise iteration using an io.TextIOWrapper with a ZstdDecompressionReader.
• ZstdDecompressionReader has gained a readinto(b) method for reading decompressed output into an existing buffer. This allows chaining to an io.TextIOWrapper on Python 3 without using an io.BufferedReader.
• ZstdDecompressor.stream_reader() now accepts a read_across_frames argument to control behavior when the input data has multiple zstd frames. When False (the default for backwards compatibility), a read() will stop when the end of a zstd frame is encountered. When True, read() can potentially return data spanning multiple zstd frames. The default will likely be changed to True in a future release.
• setup.py now performs CFFI version sniffing and disables the CFFI backend if CFFI is too old. Previously, we only used install_requires to enforce the CFFI version and not all build modes would properly enforce the minimum CFFI version. (#69)
• CFFI's ZstdDecompressionReader.read() now properly handles data remaining in any internal buffer. Before, repeated read() could result in random errors. (#71)
• Upgraded various Python packages in CI environment.
• Upgrade to hypothesis 4.5.11.
• In the CFFI backend, CompressionReader and DecompressionReader were renamed to ZstdCompressionReader and ZstdDecompressionReader, respectively.
• ZstdDecompressor.stream_writer() now accepts a write_return_read argument to control whether write() returns the number of bytes read from the source. It defaults to False to preserve backwards compatibility.
• ZstdDecompressor.stream_writer() now implements the io.RawIOBase interface and behaves as a proper stream object.
• ZstdCompressor.stream_writer() now accepts a write_return_read argument to control whether write() returns the number of bytes read from the source. It defaults to False to preserve backwards compatibility.
• ZstdCompressionWriter now implements the io.RawIOBase interface and behaves as a proper stream object. close() will now close the stream and the underlying stream (if possible). __exit__ will now call close(). Methods like writable() and fileno() are implemented.
• ZstdDecompressionWriter no longer must be used as a context manager.
• ZstdCompressionWriter no longer must be used as a context manager. When not using as a context manager, it is important to call flush(FRAME_FRAME) or the compression stream won't be properly terminated and decoders may complain about malformed input.
• ZstdCompressionWriter.flush() (what is returned from ZstdCompressor.stream_writer()) now accepts an argument controlling the flush behavior. Its value can be one of the new constants FLUSH_BLOCK or FLUSH_FRAME.
• ZstdDecompressionObj instances now have a flush([length=None]) method. This provides parity with standard library equivalent types. (#65)
• CompressionParameters no longer redundantly store individual compression parameters on each instance. Instead, compression parameters are stored inside the underlying ZSTD_CCtx_params instance. Attributes for obtaining parameters are now properties rather than instance variables.
• Exposed the STRATEGY_BTULTRA2 constant.
• CompressionParameters instances now expose an overlap_log attribute. This behaves identically to the overlap_size_log attribute.
• CompressionParameters() now accepts an overlap_log argument that behaves identically to the overlap_size_log argument. An error will be raised if both arguments are specified.
• CompressionParameters instances now expose an ldm_hash_rate_log attribute. This behaves identically to the ldm_hash_every_log attribute.
• CompressionParameters() now accepts a ldm_hash_rate_log argument that behaves identically to the ldm_hash_every_log argument. An error will be raised if both arguments are specified.
• CompressionParameters() now accepts a strategy argument that behaves identically to the compression_strategy argument. An error will be raised if both arguments are specified.
• The MINMATCH_MIN and MINMATCH_MAX constants were added. They are semantically equivalent to the old SEARCHLENGTH_MIN and SEARCHLENGTH_MAX constants.
• Bundled zstandard library upgraded from 1.3.7 to 1.3.8.
• setup.py denotes support for Python 3.7 (Python 3.7 was supported and tested in the 0.10 release).
• zstd_cffi module has been renamed to zstandard.cffi.
• ZstdCompressor.stream_writer() now reuses a buffer in order to avoid allocating a new buffer for every operation. This should result in faster performance in cases where write() or flush() are being called frequently. (#62)
• Bundled zstandard library upgraded from 1.3.6 to 1.3.7.

0.10.2 (released 2018-11-03)

Bug Fixes

• zstd_cffi.py added to setup.py (#60).

Changes

• Change some integer casts to avoid ssize_t (#61).

0.10.1 (released 2018-10-08)

Backwards Compatibility Notes

• ZstdCompressor.stream_reader().closed is now a property instead of a method (#58).
• ZstdDecompressor.stream_reader().closed is now a property instead of a method (#58).

Changes

• Stop attempting to package Python 3.6 for Miniconda. The latest version of Miniconda is using Python 3.7. The Python 3.6 Miniconda packages were a lie since this were built against Python 3.7.
• ZstdCompressor.stream_reader()'s and ZstdDecompressor.stream_reader()'s closed attribute is now a read-only property instead of a method. This now properly matches the IOBase API and allows instances to be used in more places that accept IOBase instances.

0.10.0 (released 2018-10-08)

Backwards Compatibility Notes

• ZstdDecompressor.stream_reader().read() now consistently requires an argument in both the C and CFFI backends. Before, the CFFI implementation would assume a default value of -1, which was later rejected.
• The compress_literals argument and attribute has been removed from zstd.ZstdCompressionParameters because it was removed by the zstd 1.3.5 API.
• ZSTD_CCtx_setParametersUsingCCtxParams() is no longer called on every operation performed against ZstdCompressor instances. The reason for this change is that the zstd 1.3.5 API no longer allows this without calling ZSTD_CCtx_resetParameters() first. But if we called ZSTD_CCtx_resetParameters() on every operation, we'd have to redo potentially expensive setup when using dictionaries. We now call ZSTD_CCtx_reset() on every operation and don't attempt to change compression parameters.
• Objects returned by ZstdCompressor.stream_reader() no longer need to be used as a context manager. The context manager interface still exists and its behavior is unchanged.
• Objects returned by ZstdDecompressor.stream_reader() no longer need to be used as a context manager. The context manager interface still exists and its behavior is unchanged.

Bug Fixes

• ZstdDecompressor.decompressobj().decompress() should now return all data from internal buffers in more scenarios. Before, it was possible for data to remain in internal buffers. This data would be emitted on a subsequent call to decompress(). The overall output stream would still be valid. But if callers were expecting input data to exactly map to output data (say the producer had used flush(COMPRESSOBJ_FLUSH_BLOCK) and was attempting to map input chunks to output chunks), then the previous behavior would be wrong. The new behavior is such that output from flush(COMPRESSOBJ_FLUSH_BLOCK) fed into decompressobj().decompress() should produce all available compressed input.
• ZstdDecompressor.stream_reader().read() should no longer segfault after a previous context manager resulted in error (#56).
• ZstdCompressor.compressobj().flush(COMPRESSOBJ_FLUSH_BLOCK) now returns all data necessary to flush a block. Before, it was possible for the flush() to not emit all data necessary to fully represent a block. This would mean decompressors wouldn't be able to decompress all data that had been fed into the compressor and flush()'ed. (#55).

New Features

• New module constants BLOCKSIZELOG_MAX, BLOCKSIZE_MAX, TARGETLENGTH_MAX that expose constants from libzstd.
• New ZstdCompressor.chunker() API for manually feeding data into a compressor and emitting chunks of a fixed size. Like compressobj(), the API doesn't impose restrictions on the input or output types for the data streams. Unlike compressobj(), it ensures output chunks are of a fixed size. This makes this API useful when the compressed output is being fed into an I/O layer, where uniform write sizes are useful.
• ZstdCompressor.stream_reader() no longer needs to be used as a context manager (#34).
• ZstdDecompressor.stream_reader() no longer needs to be used as a context manager (#34).
• Bundled zstandard library upgraded from 1.3.4 to 1.3.6.

Changes

• Added zstd_cffi.py and NEWS.rst to MANIFEST.in.
• zstandard.__version__ is now defined (#50).
• Upgrade pip, setuptools, wheel, and cibuildwheel packages to latest versions.
• Upgrade various packages used in CI to latest versions. Notably tox (in order to support Python 3.7).
• Use relative paths in setup.py to appease Python 3.7 (#51).
• Added CI for Python 3.7.

0.9.1 (released 2018-06-04)

• Debian packaging support.
• Fix typo in setup.py (#44).
• Support building with mingw compiler (#46).

0.9.0 (released 2018-04-08)

Backwards Compatibility Notes

• CFFI 1.11 or newer is now required (previous requirement was 1.8).
• The primary module is now zstandard. Please change imports of zstd and zstd_cffi to import zstandard. See the README for more. Support for importing the old names will be dropped in the next release.
• ZstdCompressor.read_from() and ZstdDecompressor.read_from() have been renamed to read_to_iter(). read_from() is aliased to the new name and will be deleted in a future release.
• Support for Python 2.6 has been removed.
• Support for Python 3.3 has been removed.
• The selectivity argument to train_dictionary() has been removed, as the feature disappeared from zstd 1.3.
• Support for legacy dictionaries has been removed. Cover dictionaries are now the default. train_cover_dictionary() has effectively been renamed to train_dictionary().
• The allow_empty argument from ZstdCompressor.compress() has been deleted and the method now allows empty inputs to be compressed by default.
• estimate_compression_context_size() has been removed. Use CompressionParameters.estimated_compression_context_size() instead.
• get_compression_parameters() has been removed. Use CompressionParameters.from_level() instead.
• The arguments to CompressionParameters.__init__() have changed. If you were using positional arguments before, the positions now map to different arguments. It is recommended to use keyword arguments to construct CompressionParameters instances.
• TARGETLENGTH_MAX constant has been removed (it disappeared from zstandard 1.3.4).
• ZstdCompressor.write_to() and ZstdDecompressor.write_to() have been renamed to ZstdCompressor.stream_writer() and ZstdDecompressor.stream_writer(), respectively. The old names are still aliased, but will be removed in the next major release.
• Content sizes are written into frame headers by default (ZstdCompressor(write_content_size=True) is now the default).
• CompressionParameters has been renamed to ZstdCompressionParameters for consistency with other types. The old name is an alias and will be removed in the next major release.

Bug Fixes

• Fixed memory leak in ZstdCompressor.copy_stream() (#40) (from 0.8.2).
• Fixed memory leak in ZstdDecompressor.copy_stream() (#35) (from 0.8.2).
• Fixed memory leak of ZSTD_DDict instances in CFFI's ZstdDecompressor.

New Features

• Bundled zstandard library upgraded from 1.1.3 to 1.3.4. This delivers various bug fixes and performance improvements. It also gives us access to newer features.
• Support for negative compression levels.
• Support for long distance matching (facilitates compression ratios that approach LZMA).
• Supporting for reading empty zstandard frames (with an embedded content size of 0).
• Support for writing and partial support for reading zstandard frames without a magic header.
• New stream_reader() API that exposes the io.RawIOBase interface (allows you to .read() from a file-like object).
• Several minor features, bug fixes, and performance enhancements.
• Wheels for Linux and macOS are now provided with releases.

Changes

• Functions accepting bytes data now use the buffer protocol and can accept more types (like memoryview and bytearray) (#26).
• Add #includes so compilation on OS X and BSDs works (#20).
• New ZstdDecompressor.stream_reader() API to obtain a read-only i/o stream of decompressed data for a source.
• New ZstdCompressor.stream_reader() API to obtain a read-only i/o stream of compressed data for a source.
• Renamed ZstdDecompressor.read_from() to ZstdDecompressor.read_to_iter(). The old name is still available.
• Renamed ZstdCompressor.read_from() to ZstdCompressor.read_to_iter(). read_from() is still available at its old location.
• Introduce the zstandard module to import and re-export the C or CFFI backend as appropriate. Behavior can be controlled via the PYTHON_ZSTANDARD_IMPORT_POLICY environment variable. See README for usage info.
• Vendored version of zstd upgraded to 1.3.4.
• Added module constants CONTENTSIZE_UNKNOWN and CONTENTSIZE_ERROR.
• Add STRATEGY_BTULTRA compression strategy constant.
• Switch from deprecated ZSTD_getDecompressedSize() to ZSTD_getFrameContentSize() replacement.
• ZstdCompressor.compress() can now compress empty inputs without requiring special handling.
• ZstdCompressor and ZstdDecompressor now have a memory_size() method for determining the current memory utilization of the underlying zstd primitive.
• train_dictionary() has new arguments and functionality for trying multiple variations of COVER parameters and selecting the best one.
• Added module constants LDM_MINMATCH_MIN, LDM_MINMATCH_MAX, and LDM_BUCKETSIZELOG_MAX.
• Converted all consumers to the zstandard new advanced API, which uses ZSTD_compress_generic()
• CompressionParameters.__init__ now accepts several more arguments, including support for long distance matching.
• ZstdCompressionDict.__init__ now accepts a dict_type argument that controls how the dictionary should be interpreted. This can be used to force the use of content-only dictionaries or to require the presence of the dictionary magic header.
• ZstdCompressionDict.precompute_compress() can be used to precompute the compression dictionary so it can efficiently be used with multiple ZstdCompressor instances.
• Digested dictionaries are now stored in ZstdCompressionDict instances, created automatically on first use, and automatically reused by all ZstdDecompressor instances bound to that dictionary.
• All meaningful functions now accept keyword arguments.
• ZstdDecompressor.decompressobj() now accepts a write_size argument to control how much work to perform on every decompressor invocation.
• ZstdCompressor.write_to() now exposes a tell(), which exposes the total number of bytes written so far.
• ZstdDecompressor.stream_reader() now supports seek() when moving forward in the stream.
• Removed TARGETLENGTH_MAX constant.
• Added frame_header_size(data) function.
• Added frame_content_size(data) function.
• Consumers of ZSTD_decompress* have been switched to the new advanced decompression API.
• ZstdCompressor and ZstdCompressionParams can now be constructed with negative compression levels.
• ZstdDecompressor now accepts a max_window_size argument to limit the amount of memory required for decompression operations.
• FORMAT_ZSTD1 and FORMAT_ZSTD1_MAGICLESS constants to be used with the format compression parameter to control whether the frame magic header is written.
• ZstdDecompressor now accepts a format argument to control the expected frame format.
• ZstdCompressor now has a frame_progression() method to return information about the current compression operation.
• Error messages in CFFI no longer have b'' literals.
• Compiler warnings and underlying overflow issues on 32-bit platforms have been fixed.
• Builds in CI now build with compiler warnings as errors. This should hopefully fix new compiler warnings from being introduced.
• Make ZstdCompressor(write_content_size=True) and CompressionParameters(write_content_size=True) the default.
• CompressionParameters has been renamed to ZstdCompressionParameters.

0.8.2 (released 2018-02-22)

• Fixed memory leak in ZstdCompressor.copy_stream() (#40).
• Fixed memory leak in ZstdDecompressor.copy_stream() (#35).

0.8.1 (released 2017-04-08)

• Add #includes so compilation on OS X and BSDs works (#20).

0.8.0 (released 2017-03-08)

• CompressionParameters now has a estimated_compression_context_size() method. zstd.estimate_compression_context_size() is now deprecated and slated for removal.
• Implemented a lot of fuzzing tests.
• CompressionParameters instances now perform extra validation by calling ZSTD_checkCParams() at construction time.
• multi_compress_to_buffer() API for compressing multiple inputs as a single operation, as efficiently as possible.
• ZSTD_CStream instances are now used across multiple operations on ZstdCompressor instances, resulting in much better performance for APIs that do streaming.
• ZSTD_DStream instances are now used across multiple operations on ZstdDecompressor instances, resulting in much better performance for APIs that do streaming.
• train_dictionary() now releases the GIL.
• Support for training dictionaries using the COVER algorithm.
• multi_decompress_to_buffer() API for decompressing multiple frames as a single operation, as efficiently as possible.
• Support for multi-threaded compression.
• Disable deprecation warnings when compiling CFFI module.
• Fixed memory leak in train_dictionary().
• Removed DictParameters type.
• train_dictionary() now accepts keyword arguments instead of a DictParameters instance to control dictionary generation.

0.7.0 (released 2017-02-07)

• Added zstd.get_frame_parameters() to obtain info about a zstd frame.
• Added ZstdDecompressor.decompress_content_dict_chain() for efficient decompression of content-only dictionary chains.
• CFFI module fully implemented; all tests run against both C extension and CFFI implementation.
• Vendored version of zstd updated to 1.1.3.
• Use ZstdDecompressor.decompress() now uses ZSTD_createDDict_byReference() to avoid extra memory allocation of dict data.
• Add function names to error messages (by using ":name" in PyArg_Parse* functions).
• Reuse decompression context across operations. Previously, we created a new ZSTD_DCtx for each decompress(). This was measured to slow down decompression by 40-200MB/s. The API guarantees say ZstdDecompressor is not thread safe. So we reuse the ZSTD_DCtx across operations and make things faster in the process.
• ZstdCompressor.write_to()'s compress() and flush() methods now return number of bytes written.
• ZstdDecompressor.write_to()'s write() method now returns the number of bytes written to the underlying output object.
• CompressionParameters instances now expose their values as attributes.
• CompressionParameters instances no longer are subscriptable nor behave as tuples (backwards incompatible). Use attributes to obtain values.
• DictParameters instances now expose their values as attributes.

0.6.0 (released 2017-01-14)

• Support for legacy zstd protocols (build time opt in feature).
• Automation improvements to test against Python 3.6, latest versions of Tox, more deterministic AppVeyor behavior.
• CFFI "parser" improved to use a compiler preprocessor instead of rewriting source code manually.
• Vendored version of zstd updated to 1.1.2.
• Documentation improvements.
• Introduce a bench.py script for performing (crude) benchmarks.
• ZSTD_CCtx instances are now reused across multiple compress() operations.
• ZstdCompressor.write_to() now has a flush() method.
• ZstdCompressor.compressobj()'s flush() method now accepts an argument to flush a block (as opposed to ending the stream).
• Disallow compress(b'') when writing content sizes by default (issue #11).

0.5.2 (released 2016-11-12)

• more packaging fixes for source distribution

0.5.1 (released 2016-11-12)

• setup_zstd.py is included in the source distribution

0.5.0 (released 2016-11-10)

• Vendored version of zstd updated to 1.1.1.
• Continuous integration for Python 3.6 and 3.7
• Continuous integration for Conda
• Added compression and decompression APIs providing similar interfaces to the standard library zlib and bz2 modules. This allows coding to a common interface.
• zstd.__version__ is now defined.
• read_from() on various APIs now accepts objects implementing the buffer protocol.
• read_from() has gained a skip_bytes argument. This allows callers to pass in an existing buffer with a header without having to create a slice or a new object.
• Implemented ZstdCompressionDict.as_bytes().
• Python's memory allocator is now used instead of malloc().
• Low-level zstd data structures are reused in more instances, cutting down on overhead for certain operations.
• distutils boilerplate for obtaining an Extension instance has now been refactored into a standalone setup_zstd.py file. This allows other projects with setup.py files to reuse the distutils code for this project without copying code.
• The monolithic zstd.c file has been split into a header file defining types and separate .c source files for the implementation.

Older History

2016-08-31 - Zstandard 1.0.0 is released and Gregory starts hacking on a Python extension for use by the Mercurial project. A very hacky prototype is sent to the mercurial-devel list for RFC.

2016-09-03 - Most functionality from Zstandard C API implemented. Source code published on https://github.com/indygreg/python-zstandard. Travis-CI automation configured. 0.0.1 release on PyPI.

2016-09-05 - After the API was rounded out a bit and support for Python 2.6 and 2.7 was added, version 0.1 was released to PyPI.

2016-09-05 - After the compressor and decompressor APIs were changed, 0.2 was released to PyPI.

2016-09-10 - 0.3 is released with a bunch of new features. ZstdCompressor now accepts arguments controlling frame parameters. The source size can now be declared when performing streaming compression. ZstdDecompressor.decompress() is implemented. Compression dictionaries are now cached when using the simple compression and decompression APIs. Memory size APIs added. ZstdCompressor.read_from() and ZstdDecompressor.read_from() have been implemented. This rounds out the major compression/decompression APIs planned by the author.

2016-10-02 - 0.3.3 is released with a bug fix for read_from not fully decoding a zstd frame (issue #2).

2016-10-02 - 0.4.0 is released with zstd 1.1.0, support for custom read and write buffer sizes, and a few bug fixes involving failure to read/write all data when buffer sizes were too small to hold remaining data.

2016-11-10 - 0.5.0 is released with zstd 1.1.1 and other enhancements.