Pin zstandard to latest version 0.23.0

[pyup-bot]

This PR pins zstandard to the latest release 0.23.0.

Changelog

0.22.0

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

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

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

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.

0.16.0

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

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

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

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

This release should contain no functional changes compared to 0.14.0. The only expected difference with this version is Python 3.9 wheels are now being produced.

0.14.0

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. See release notes at https://github.com/facebook/zstd/releases/tag/v1.4.5.
* ``setup.py`` is now executable.
* Python code reformatted with black using 80 character line lengths.

0.13.0

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

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.

0.11.0

New Features
------------

* zstd library upgraded from 1.3.6 to 1.3.8.
* ``ZstdCompressor.stream_reader()``, ``ZstdCompressor.stream_writer()``, ``ZstdDecompressor.stream_reader()``, and ``ZstdDecompressor.stream_writer()`` should now completely implement the ``io.RawIOBase`` interface, allowing them to be used as fully-featured streams. One can combine an instance with say an ``io.TextIOWrapper``, ``codecs.StreamReader``, or ``codecs.StreamWriter`` to transparently convert between binary and textual data or apply encodings to data. A stream reader or writer should interoperate with any Python code that accepts a stream-like object. Please note that some implementation details may change slightly in the future in order to ensure better compatibility with the stream interfaces.
* ``ZstdDecompressor.stream_reader()`` can now read inputs that have multiple zstd *frames*. Look for future releases to improve support for reading sources with multiple *frames*.

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

Bug Fixes
---------

* ``zstd_cffi.py`` added to ``setup.py`` (60).

Changes
-------

* Change some integer casts to avoid ``ssize_t`` (61).

0.10.1

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

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
-------

* ``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

This release contains packaging improvements. No changes to the Python library code were made in this release.

0.9.0

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
------------

* Bundlded 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

* Fixed memory leak in ``ZstdCompressor.copy_stream()`` (40).
* Fixed memory leak in ``ZstdDecompressor.copy_stream()`` (35).

0.8.1

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

0.8.0

* 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.

Links

• PyPI: https://pypi.org/project/zstandard
• Changelog: https://data.safetycli.com/changelogs/zstandard/
• Repo: https://github.com/indygreg/python-zstandard