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# Copyright 2009, 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.
"""Dispatch Web Socket request.
"""
import os
import re
import util
_SOURCE_PATH_PATTERN = re.compile(r'(?i)_wsh\.py$')
_SOURCE_SUFFIX = '_wsh.py'
_DO_EXTRA_HANDSHAKE_HANDLER_NAME = 'web_socket_do_extra_handshake'
_TRANSFER_DATA_HANDLER_NAME = 'web_socket_transfer_data'
class DispatchError(Exception):
"""Exception in dispatching Web Socket request."""
pass
def _normalize_path(path):
"""Normalize path.
Args:
path: the path to normalize.
Path is converted to the absolute path.
The input path can use either '\\' or '/' as the separator.
The normalized path always uses '/' regardless of the platform.
"""
path = path.replace('\\', os.path.sep)
path = os.path.realpath(path)
path = path.replace('\\', '/')
return path
def _path_to_resource_converter(base_dir):
base_dir = _normalize_path(base_dir)
base_len = len(base_dir)
suffix_len = len(_SOURCE_SUFFIX)
def converter(path):
if not path.endswith(_SOURCE_SUFFIX):
return None
path = _normalize_path(path)
if not path.startswith(base_dir):
return None
return path[base_len:-suffix_len]
return converter
def _source_file_paths(directory):
"""Yield Web Socket Handler source file names in the given directory."""
for root, unused_dirs, files in os.walk(directory):
for base in files:
path = os.path.join(root, base)
if _SOURCE_PATH_PATTERN.search(path):
yield path
def _source(source_str):
"""Source a handler definition string."""
global_dic = {}
try:
exec source_str in global_dic
except Exception:
raise DispatchError('Error in sourcing handler:' +
util.get_stack_trace())
return (_extract_handler(global_dic, _DO_EXTRA_HANDSHAKE_HANDLER_NAME),
_extract_handler(global_dic, _TRANSFER_DATA_HANDLER_NAME))
def _extract_handler(dic, name):
if name not in dic:
raise DispatchError('%s is not defined.' % name)
handler = dic[name]
if not callable(handler):
raise DispatchError('%s is not callable.' % name)
return handler
class Dispatcher(object):
"""Dispatches Web Socket requests.
This class maintains a map from resource name to handlers.
"""
def __init__(self, root_dir, scan_dir=None):
"""Construct an instance.
Args:
root_dir: The directory where handler definition files are
placed.
scan_dir: The directory where handler definition files are
searched. scan_dir must be a directory under root_dir,
including root_dir itself. If scan_dir is None, root_dir
is used as scan_dir. scan_dir can be useful in saving
scan time when root_dir contains many subdirectories.
"""
self._handlers = {}
self._source_warnings = []
if scan_dir is None:
scan_dir = root_dir
if not os.path.realpath(scan_dir).startswith(
os.path.realpath(root_dir)):
raise DispatchError('scan_dir:%s must be a directory under '
'root_dir:%s.' % (scan_dir, root_dir))
self._source_files_in_dir(root_dir, scan_dir)
def source_warnings(self):
"""Return warnings in sourcing handlers."""
return self._source_warnings
def do_extra_handshake(self, request):
"""Do extra checking in Web Socket handshake.
Select a handler based on request.uri and call its
web_socket_do_extra_handshake function.
Args:
request: mod_python request.
"""
do_extra_handshake_, unused_transfer_data = self._handler(request)
try:
do_extra_handshake_(request)
except Exception, e:
util.prepend_message_to_exception(
'%s raised exception for %s: ' % (
_DO_EXTRA_HANDSHAKE_HANDLER_NAME,
request.ws_resource),
e)
raise
def transfer_data(self, request):
"""Let a handler transfer_data with a Web Socket client.
Select a handler based on request.ws_resource and call its
web_socket_transfer_data function.
Args:
request: mod_python request.
"""
unused_do_extra_handshake, transfer_data_ = self._handler(request)
try:
transfer_data_(request)
except Exception, e:
util.prepend_message_to_exception(
'%s raised exception for %s: ' % (
_TRANSFER_DATA_HANDLER_NAME, request.ws_resource),
e)
raise
def _handler(self, request):
try:
ws_resource_path = request.ws_resource.split('?', 1)[0]
return self._handlers[ws_resource_path]
except KeyError:
raise DispatchError('No handler for: %r' % request.ws_resource)
def _source_files_in_dir(self, root_dir, scan_dir):
"""Source all the handler source files in the scan_dir directory.
The resource path is determined relative to root_dir.
"""
to_resource = _path_to_resource_converter(root_dir)
for path in _source_file_paths(scan_dir):
try:
handlers = _source(open(path).read())
except DispatchError, e:
self._source_warnings.append('%s: %s' % (path, e))
continue
self._handlers[to_resource(path)] = handlers
# vi:sts=4 sw=4 et
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