# Copyright 2011, Google Inc.
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are
# met:
#
# * Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
# * Redistributions in binary form must reproduce the above
# copyright notice, this list of conditions and the following disclaimer
# in the documentation and/or other materials provided with the
# distribution.
# * Neither the name of Google Inc. nor the names of its
# contributors may be used to endorse or promote products derived from
# this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
"""WebSocket utilities.
"""
import errno
# Import hash classes from a module available and recommended for each Python
# version and re-export those symbol. Use sha and md5 module in Python 2.4, and
# hashlib module in Python 2.6.
try:
import hashlib
md5_hash = hashlib.md5
sha1_hash = hashlib.sha1
except ImportError:
import md5
import sha
md5_hash = md5.md5
sha1_hash = sha.sha
import StringIO
import logging
import os
import re
import socket
import traceback
import zlib
def get_stack_trace():
"""Get the current stack trace as string.
This is needed to support Python 2.3.
TODO: Remove this when we only support Python 2.4 and above.
Use traceback.format_exc instead.
"""
out = StringIO.StringIO()
traceback.print_exc(file=out)
return out.getvalue()
def prepend_message_to_exception(message, exc):
"""Prepend message to the exception."""
exc.args = (message + str(exc),)
return
def __translate_interp(interp, cygwin_path):
"""Translate interp program path for Win32 python to run cygwin program
(e.g. perl). Note that it doesn't support path that contains space,
which is typically true for Unix, where #!-script is written.
For Win32 python, cygwin_path is a directory of cygwin binaries.
Args:
interp: interp command line
cygwin_path: directory name of cygwin binary, or None
Returns:
translated interp command line.
"""
if not cygwin_path:
return interp
m = re.match('^[^ ]*/([^ ]+)( .*)?', interp)
if m:
cmd = os.path.join(cygwin_path, m.group(1))
return cmd + m.group(2)
return interp
def get_script_interp(script_path, cygwin_path=None):
"""Gets #!-interpreter command line from the script.
It also fixes command path. When Cygwin Python is used, e.g. in WebKit,
it could run "/usr/bin/perl -wT hello.pl".
When Win32 Python is used, e.g. in Chromium, it couldn't. So, fix
"/usr/bin/perl" to "<cygwin_path>\perl.exe".
Args:
script_path: pathname of the script
cygwin_path: directory name of cygwin binary, or None
Returns:
#!-interpreter command line, or None if it is not #!-script.
"""
fp = open(script_path)
line = fp.readline()
fp.close()
m = re.match('^#!(.*)', line)
if m:
return __translate_interp(m.group(1), cygwin_path)
return None
def wrap_popen3_for_win(cygwin_path):
"""Wrap popen3 to support #!-script on Windows.
Args:
cygwin_path: path for cygwin binary if command path is needed to be
translated. None if no translation required.
"""
__orig_popen3 = os.popen3
def __wrap_popen3(cmd, mode='t', bufsize=-1):
cmdline = cmd.split(' ')
interp = get_script_interp(cmdline[0], cygwin_path)
if interp:
cmd = interp + ' ' + cmd
return __orig_popen3(cmd, mode, bufsize)
os.popen3 = __wrap_popen3
def hexify(s):
return ' '.join(map(lambda x: '%02x' % ord(x), s))
def get_class_logger(o):
return logging.getLogger(
'%s.%s' % (o.__class__.__module__, o.__class__.__name__))
class NoopMasker(object):
"""A masking object that has the same interface as RepeatedXorMasker but
just returns the string passed in without making any change.
"""
def __init__(self):
pass
def mask(self, s):
return s
class DeflateRequest(object):
"""A wrapper class for request object to intercept send and recv to perform
deflate compression and decompression transparently.
"""
def __init__(self, request):
self._request = request
self.connection = DeflateConnection(request.connection)
def __getattribute__(self, name):
if name in ('_request', 'connection'):
return object.__getattribute__(self, name)
return self._request.__getattribute__(name)
def __setattr__(self, name, value):
if name in ('_request', 'connection'):
return object.__setattr__(self, name, value)
return self._request.__setattr__(name, value)
# By making wbits option negative, we can suppress CMF/FLG (2 octet) and
# ADLER32 (4 octet) fields of zlib so that we can use zlib module just as
# deflate library. DICTID won't be added as far as we don't set dictionary.
# LZ77 window of 32K will be used for both compression and decompression.
# For decompression, we can just use 32K to cover any windows size. For
# compression, we use 32K so receivers must use 32K.
#
# Compression level is Z_DEFAULT_COMPRESSION. We don't have to match level
# to decode.
#
# See zconf.h, deflate.cc, inflate.cc of zlib library, and zlibmodule.c of
# Python. See also RFC1950 (ZLIB 3.3).
class _Deflater(object):
def __init__(self, window_bits):
self._logger = get_class_logger(self)
self._compress = zlib.compressobj(
zlib.Z_DEFAULT_COMPRESSION, zlib.DEFLATED, -window_bits)
def compress_and_flush(self, bytes):
compressed_bytes = self._compress.compress(bytes)
compressed_bytes += self._compress.flush(zlib.Z_SYNC_FLUSH)
self._logger.debug('Compress input %r', bytes)
self._logger.debug('Compress result %r', compressed_bytes)
return compressed_bytes
class _Inflater(object):
def __init__(self):
self._logger = get_class_logger(self)
self._unconsumed = ''
self.reset()
def decompress(self, size):
if not (size == -1 or size > 0):
raise Exception('size must be -1 or positive')
data = ''
while True:
if size == -1:
data += self._decompress.decompress(self._unconsumed)
# See Python bug http://bugs.python.org/issue12050 to
# understand why the same code cannot be used for updating
# self._unconsumed for here and else block.
self._unconsumed = ''
else:
data += self._decompress.decompress(
self._unconsumed, size - len(data))
self._unconsumed = self._decompress.unconsumed_tail
if self._decompress.unused_data:
# Encountered a last block (i.e. a block with BFINAL = 1) and
# found a new stream (unused_data). We cannot use the same
# zlib.Decompress object for the new stream. Create a new
# Decompress object to decompress the new one.
#
# It's fine to ignore unconsumed_tail if unused_data is not
# empty.
self._unconsumed = self._decompress.unused_data
self.reset()
if size >= 0 and len(data) == size:
# data is filled. Don't call decompress again.
break
else:
# Re-invoke Decompress.decompress to try to decompress all
# available bytes before invoking read which blocks until
# any new byte is available.
continue
else:
# Here, since unused_data is empty, even if unconsumed_tail is
# not empty, bytes of requested length are already in data. We
# don't have to "continue" here.
break
if data:
self._logger.debug('Decompressed %r', data)
return data
def append(self, data):
self._logger.debug('Appended %r', data)
self._unconsumed += data
def reset(self):
self._logger.debug('Reset')
self._decompress = zlib.decompressobj(-zlib.MAX_WBITS)
# Compresses/decompresses given octets using the method introduced in RFC1979.
class _RFC1979Deflater(object):
"""A compressor class that applies DEFLATE to given byte sequence and
flushes using the algorithm described in the RFC1979 section 2.1.
"""
def __init__(self, window_bits, no_context_takeover):
self._deflater = None
if window_bits is None:
window_bits = zlib.MAX_WBITS
self._window_bits = window_bits
self._no_context_takeover = no_context_takeover
def filter(self, bytes):
if self._deflater is None or self._no_context_takeover:
self._deflater = _Deflater(self._window_bits)
# Strip last 4 octets which is LEN and NLEN field of a non-compressed
# block added for Z_SYNC_FLUSH.
return self._deflater.compress_and_flush(bytes)[:-4]
class _RFC1979Inflater(object):
"""A decompressor class for byte sequence compressed and flushed following
the algorithm described in the RFC1979 section 2.1.
"""
def __init__(self):
self._inflater = _Inflater()
def filter(self, bytes):
# Restore stripped LEN and NLEN field of a non-compressed block added
# for Z_SYNC_FLUSH.
self._inflater.append(bytes + '\x00\x00\xff\xff')
return self._inflater.decompress(-1)
class DeflateSocket(object):
"""A wrapper class for socket object to intercept send and recv to perform
deflate compression and decompression transparently.
"""
# Size of the buffer passed to recv to receive compressed data.
_RECV_SIZE = 4096
def __init__(self, socket):
self._socket = socket
self._logger = get_class_logger(self)
self._deflater = _Deflater(zlib.MAX_WBITS)
self._inflater = _Inflater()
def recv(self, size):
"""Receives data from the socket specified on the construction up
to the specified size. Once any data is available, returns it even
if it's smaller than the specified size.
"""
# TODO(tyoshino): Allow call with size=0. It should block until any
# decompressed data is available.
if size <= 0:
raise Exception('Non-positive size passed')
while True:
data = self._inflater.decompress(size)
if len(data) != 0:
return data
read_data = self._socket.recv(DeflateSocket._RECV_SIZE)
if not read_data:
return ''
self._inflater.append(read_data)
def sendall(self, bytes):
self.send(bytes)
def send(self, bytes):
self._socket.sendall(self._deflater.compress_and_flush(bytes))
return len(bytes)
class DeflateConnection(object):
"""A wrapper class for request object to intercept write and read to
perform deflate compression and decompression transparently.
"""
def __init__(self, connection):
self._connection = connection
self._logger = get_class_logger(self)
self._deflater = _Deflater(zlib.MAX_WBITS)
self._inflater = _Inflater()
def get_remote_addr(self):
return self._connection.remote_addr
remote_addr = property(get_remote_addr)
def put_bytes(self, bytes):
self.write(bytes)
def read(self, size=-1):
"""Reads at most size bytes. Blocks until there's at least one byte
available.
"""
# TODO(tyoshino): Allow call with size=0.
if not (size == -1 or size > 0):
raise Exception('size must be -1 or positive')
data = ''
while True:
if size == -1:
data += self._inflater.decompress(-1)
else:
data += self._inflater.decompress(size - len(data))
if size >= 0 and len(data) != 0:
break
# TODO(tyoshino): Make this read efficient by some workaround.
#
# In 3.0.3 and prior of mod_python, read blocks until length bytes
# was read. We don't know the exact size to read while using
# deflate, so read byte-by-byte.
#
# _StandaloneRequest.read that ultimately performs
# socket._fileobject.read also blocks until length bytes was read
read_data = self._connection.read(1)
if not read_data:
break
self._inflater.append(read_data)
return data
def write(self, bytes):
self._connection.write(self._deflater.compress_and_flush(bytes))
def _is_ewouldblock_errno(error_number):
"""Returns True iff error_number indicates that receive operation would
block. To make this portable, we check availability of errno and then
compare them.
"""
for error_name in ['WSAEWOULDBLOCK', 'EWOULDBLOCK', 'EAGAIN']:
if (error_name in dir(errno) and
error_number == getattr(errno, error_name)):
return True
return False
def drain_received_data(raw_socket):
# Set the socket non-blocking.
original_timeout = raw_socket.gettimeout()
raw_socket.settimeout(0.0)
drained_data = []
# Drain until the socket is closed or no data is immediately
# available for read.
while True:
try:
data = raw_socket.recv(1)
if not data:
break
drained_data.append(data)
except socket.error, e:
# e can be either a pair (errno, string) or just a string (or
# something else) telling what went wrong. We suppress only
# the errors that indicates that the socket blocks. Those
# exceptions can be parsed as a pair (errno, string).
try:
error_number, message = e
except:
# Failed to parse socket.error.
raise e
if _is_ewouldblock_errno(error_number):
break
else:
raise e
# Rollback timeout value.
raw_socket.settimeout(original_timeout)
return ''.join(drained_data)
# vi:sts=4 sw=4 et