zstd: vendor python-zstandard 0.5.0
As the commit message for the previous changeset says, we wish
for zstd to be a 1st class citizen in Mercurial. To make that
happen, we need to enable Python to talk to the zstd C API. And
that requires bindings.
This commit vendors a copy of existing Python bindings. Why do we
need to vendor? As the commit message of the previous commit says,
relying on systems in the wild to have the bindings or zstd present
is a losing proposition. By distributing the zstd and bindings with
Mercurial, we significantly increase our chances that zstd will
work. Since zstd will deliver a better end-user experience by
achieving better performance, this benefits our users. Another
reason is that the Python bindings still aren't stable and the
API is somewhat fluid. While Mercurial could be coded to target
multiple versions of the Python bindings, it is safer to bundle
an explicit, known working version.
The added Python bindings are mostly a fully-featured interface
to the zstd C API. They allow one-shot operations, streaming,
reading and writing from objects implements the file object
protocol, dictionary compression, control over low-level compression
parameters, and more. The Python bindings work on Python 2.6,
2.7, and 3.3+ and have been tested on Linux and Windows. There are
CFFI bindings, but they are lacking compared to the C extension.
Upstream work will be needed before we can support zstd with PyPy.
But it will be possible.
The files added in this commit come from Git commit
e637c1b214d5f869cf8116c550dcae23ec13b677 from
https://github.com/indygreg/python-zstandard and are added without
modifications. Some files from the upstream repository have been
omitted, namely files related to continuous integration.
In the spirit of full disclosure, I'm the maintainer of the
"python-zstandard" project and have authored 100% of the code
added in this commit. Unfortunately, the Python bindings have
not been formally code reviewed by anyone. While I've tested
much of the code thoroughly (I even have tests that fuzz APIs),
there's a good chance there are bugs, memory leaks, not well
thought out APIs, etc. If someone wants to review the code and
send feedback to the GitHub project, it would be greatly
appreciated.
Despite my involvement with both projects, my opinions of code
style differ from Mercurial's. The code in this commit introduces
numerous code style violations in Mercurial's linters. So, the code
is excluded from most lints. However, some violations I agree with.
These have been added to the known violations ignore list for now.
# Copyright (c) 2016-present, Gregory Szorc
# All rights reserved.
#
# This software may be modified and distributed under the terms
# of the BSD license. See the LICENSE file for details.
from __future__ import absolute_import
import cffi
import os
HERE = os.path.abspath(os.path.dirname(__file__))
SOURCES = ['zstd/%s' % p for p in (
'common/entropy_common.c',
'common/error_private.c',
'common/fse_decompress.c',
'common/xxhash.c',
'common/zstd_common.c',
'compress/fse_compress.c',
'compress/huf_compress.c',
'compress/zbuff_compress.c',
'compress/zstd_compress.c',
'decompress/huf_decompress.c',
'decompress/zbuff_decompress.c',
'decompress/zstd_decompress.c',
'dictBuilder/divsufsort.c',
'dictBuilder/zdict.c',
)]
INCLUDE_DIRS = [os.path.join(HERE, d) for d in (
'zstd',
'zstd/common',
'zstd/compress',
'zstd/decompress',
'zstd/dictBuilder',
)]
with open(os.path.join(HERE, 'zstd', 'zstd.h'), 'rb') as fh:
zstd_h = fh.read()
ffi = cffi.FFI()
ffi.set_source('_zstd_cffi', '''
/* needed for typedefs like U32 references in zstd.h */
#include "mem.h"
#define ZSTD_STATIC_LINKING_ONLY
#include "zstd.h"
''',
sources=SOURCES, include_dirs=INCLUDE_DIRS)
# Rather than define the API definitions from zstd.h inline, munge the
# source in a way that cdef() will accept.
lines = zstd_h.splitlines()
lines = [l.rstrip() for l in lines if l.strip()]
# Strip preprocessor directives - they aren't important for our needs.
lines = [l for l in lines
if not l.startswith((b'#if', b'#else', b'#endif', b'#include'))]
# Remove extern C block
lines = [l for l in lines if l not in (b'extern "C" {', b'}')]
# The version #defines don't parse and aren't necessary. Strip them.
lines = [l for l in lines if not l.startswith((
b'#define ZSTD_H_235446',
b'#define ZSTD_LIB_VERSION',
b'#define ZSTD_QUOTE',
b'#define ZSTD_EXPAND_AND_QUOTE',
b'#define ZSTD_VERSION_STRING',
b'#define ZSTD_VERSION_NUMBER'))]
# The C parser also doesn't like some constant defines referencing
# other constants.
# TODO we pick the 64-bit constants here. We should assert somewhere
# we're compiling for 64-bit.
def fix_constants(l):
if l.startswith(b'#define ZSTD_WINDOWLOG_MAX '):
return b'#define ZSTD_WINDOWLOG_MAX 27'
elif l.startswith(b'#define ZSTD_CHAINLOG_MAX '):
return b'#define ZSTD_CHAINLOG_MAX 28'
elif l.startswith(b'#define ZSTD_HASHLOG_MAX '):
return b'#define ZSTD_HASHLOG_MAX 27'
elif l.startswith(b'#define ZSTD_CHAINLOG_MAX '):
return b'#define ZSTD_CHAINLOG_MAX 28'
elif l.startswith(b'#define ZSTD_CHAINLOG_MIN '):
return b'#define ZSTD_CHAINLOG_MIN 6'
elif l.startswith(b'#define ZSTD_SEARCHLOG_MAX '):
return b'#define ZSTD_SEARCHLOG_MAX 26'
elif l.startswith(b'#define ZSTD_BLOCKSIZE_ABSOLUTEMAX '):
return b'#define ZSTD_BLOCKSIZE_ABSOLUTEMAX 131072'
else:
return l
lines = map(fix_constants, lines)
# ZSTDLIB_API isn't handled correctly. Strip it.
lines = [l for l in lines if not l.startswith(b'# define ZSTDLIB_API')]
def strip_api(l):
if l.startswith(b'ZSTDLIB_API '):
return l[len(b'ZSTDLIB_API '):]
else:
return l
lines = map(strip_api, lines)
source = b'\n'.join(lines)
ffi.cdef(source.decode('latin1'))
if __name__ == '__main__':
ffi.compile()