view contrib/python-zstandard/make_cffi.py @ 37056:861e9d37e56e

wireproto: buffer output frames when in half duplex mode

Previously, when told that a response was ready, the server reactor
would instruct the caller to send frames immediately. This was OK
as an initial implementation. But it would not work for half-duplex
connections where the sender can't receive until all data has been
transmitted - such as httplib based clients.

In this commit, we teach the reactor that output frames should
be buffered until end of input is seen. This required a new
event to inform the reactor of end of input. The result from that
event will instruct the consumer to send all buffered frames.

The HTTP server is buffered by default.

This change effectively hides the complexity of buffering within
the reactor so that transports need not be concerned about it.
This helps keep the transports "dumb" and will make implementing
multiple requests-responses per atomic exchange (like an HTTP
request) much simpler.

Differential Revision: https://phab.mercurial-scm.org/D2860

# 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 distutils.ccompiler
import os
import re
import subprocess
import tempfile


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/pool.c',
    'common/threading.c',
    'common/xxhash.c',
    'common/zstd_common.c',
    'compress/fse_compress.c',
    'compress/huf_compress.c',
    'compress/zstd_compress.c',
    'compress/zstdmt_compress.c',
    'decompress/huf_decompress.c',
    'decompress/zstd_decompress.c',
    'dictBuilder/cover.c',
    'dictBuilder/divsufsort.c',
    'dictBuilder/zdict.c',
)]

# Headers whose preprocessed output will be fed into cdef().
HEADERS = [os.path.join(HERE, 'zstd', *p) for p in (
    ('zstd.h',),
    ('compress', 'zstdmt_compress.h'),
    ('dictBuilder', 'zdict.h'),
)]

INCLUDE_DIRS = [os.path.join(HERE, d) for d in (
    'zstd',
    'zstd/common',
    'zstd/compress',
    'zstd/decompress',
    'zstd/dictBuilder',
)]

# cffi can't parse some of the primitives in zstd.h. So we invoke the
# preprocessor and feed its output into cffi.
compiler = distutils.ccompiler.new_compiler()

# Needed for MSVC.
if hasattr(compiler, 'initialize'):
    compiler.initialize()

# Distutils doesn't set compiler.preprocessor, so invoke the preprocessor
# manually.
if compiler.compiler_type == 'unix':
    args = list(compiler.executables['compiler'])
    args.extend([
        '-E',
        '-DZSTD_STATIC_LINKING_ONLY',
        '-DZDICT_STATIC_LINKING_ONLY',
    ])
elif compiler.compiler_type == 'msvc':
    args = [compiler.cc]
    args.extend([
        '/EP',
        '/DZSTD_STATIC_LINKING_ONLY',
        '/DZDICT_STATIC_LINKING_ONLY',
    ])
else:
    raise Exception('unsupported compiler type: %s' % compiler.compiler_type)

def preprocess(path):
    with open(path, 'rb') as fh:
        lines = []
        for l in fh:
            # zstd.h includes <stddef.h>, which is also included by cffi's
            # boilerplate. This can lead to duplicate declarations. So we strip
            # this include from the preprocessor invocation.
            #
            # The same things happens for including zstd.h, so give it the same
            # treatment.
            #
            # We define ZSTD_STATIC_LINKING_ONLY, which is redundant with the inline
            # #define in zstdmt_compress.h and results in a compiler warning. So drop
            # the inline #define.
            if l.startswith((b'#include <stddef.h>',
                             b'#include "zstd.h"',
                             b'#define ZSTD_STATIC_LINKING_ONLY')):
                continue

            # ZSTDLIB_API may not be defined if we dropped zstd.h. It isn't
            # important so just filter it out.
            if l.startswith(b'ZSTDLIB_API'):
                l = l[len(b'ZSTDLIB_API '):]

            lines.append(l)

    fd, input_file = tempfile.mkstemp(suffix='.h')
    os.write(fd, b''.join(lines))
    os.close(fd)

    try:
        process = subprocess.Popen(args + [input_file], stdout=subprocess.PIPE)
        output = process.communicate()[0]
        ret = process.poll()
        if ret:
            raise Exception('preprocessor exited with error')

        return output
    finally:
        os.unlink(input_file)


def normalize_output(output):
    lines = []
    for line in output.splitlines():
        # CFFI's parser doesn't like __attribute__ on UNIX compilers.
        if line.startswith(b'__attribute__ ((visibility ("default"))) '):
            line = line[len(b'__attribute__ ((visibility ("default"))) '):]

        if line.startswith(b'__attribute__((deprecated('):
            continue
        elif b'__declspec(deprecated(' in line:
            continue

        lines.append(line)

    return b'\n'.join(lines)


ffi = cffi.FFI()
# *_DISABLE_DEPRECATE_WARNINGS prevents the compiler from emitting a warning
# when cffi uses the function. Since we statically link against zstd, even
# if we use the deprecated functions it shouldn't be a huge problem.
ffi.set_source('_zstd_cffi', '''
#include "mem.h"
#define ZSTD_STATIC_LINKING_ONLY
#include "zstd.h"
#define ZDICT_STATIC_LINKING_ONLY
#define ZDICT_DISABLE_DEPRECATE_WARNINGS
#include "zdict.h"
#include "zstdmt_compress.h"
''', sources=SOURCES, include_dirs=INCLUDE_DIRS)

DEFINE = re.compile(b'^\\#define ([a-zA-Z0-9_]+) ')

sources = []

# Feed normalized preprocessor output for headers into the cdef parser.
for header in HEADERS:
    preprocessed = preprocess(header)
    sources.append(normalize_output(preprocessed))

    # #define's are effectively erased as part of going through preprocessor.
    # So perform a manual pass to re-add those to the cdef source.
    with open(header, 'rb') as fh:
        for line in fh:
            line = line.strip()
            m = DEFINE.match(line)
            if not m:
                continue

            if m.group(1) == b'ZSTD_STATIC_LINKING_ONLY':
                continue

            # The parser doesn't like some constants with complex values.
            if m.group(1) in (b'ZSTD_LIB_VERSION', b'ZSTD_VERSION_STRING'):
                continue

            # The ... is magic syntax by the cdef parser to resolve the
            # value at compile time.
            sources.append(m.group(0) + b' ...')

cdeflines = b'\n'.join(sources).splitlines()
cdeflines = [l for l in cdeflines if l.strip()]
ffi.cdef(b'\n'.join(cdeflines).decode('latin1'))

if __name__ == '__main__':
    ffi.compile()