1# Copyright 2011, Google Inc.
2# All rights reserved.
3#
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5# modification, are permitted provided that the following conditions are
6# met:
7#
8#     * Redistributions of source code must retain the above copyright
9# notice, this list of conditions and the following disclaimer.
10#     * Redistributions in binary form must reproduce the above
11# copyright notice, this list of conditions and the following disclaimer
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13# distribution.
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16# this software without specific prior written permission.
17#
18# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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22# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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24# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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27# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
28# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29
30
31"""Base stream class.
32"""
33
34
35# Note: request.connection.write/read are used in this module, even though
36# mod_python document says that they should be used only in connection
37# handlers. Unfortunately, we have no other options. For example,
38# request.write/read are not suitable because they don't allow direct raw bytes
39# writing/reading.
40
41
42import socket
43
44from mod_pywebsocket import util
45
46
47# Exceptions
48
49
50class ConnectionTerminatedException(Exception):
51    """This exception will be raised when a connection is terminated
52    unexpectedly.
53    """
54
55    pass
56
57
58class InvalidFrameException(ConnectionTerminatedException):
59    """This exception will be raised when we received an invalid frame we
60    cannot parse.
61    """
62
63    pass
64
65
66class BadOperationException(Exception):
67    """This exception will be raised when send_message() is called on
68    server-terminated connection or receive_message() is called on
69    client-terminated connection.
70    """
71
72    pass
73
74
75class UnsupportedFrameException(Exception):
76    """This exception will be raised when we receive a frame with flag, opcode
77    we cannot handle. Handlers can just catch and ignore this exception and
78    call receive_message() again to continue processing the next frame.
79    """
80
81    pass
82
83
84class InvalidUTF8Exception(Exception):
85    """This exception will be raised when we receive a text frame which
86    contains invalid UTF-8 strings.
87    """
88
89    pass
90
91
92class StreamBase(object):
93    """Base stream class."""
94
95    def __init__(self, request):
96        """Construct an instance.
97
98        Args:
99            request: mod_python request.
100        """
101
102        self._logger = util.get_class_logger(self)
103
104        self._request = request
105
106    def _read(self, length):
107        """Reads length bytes from connection. In case we catch any exception,
108        prepends remote address to the exception message and raise again.
109
110        Raises:
111            ConnectionTerminatedException: when read returns empty string.
112        """
113
114        try:
115            read_bytes = self._request.connection.read(length)
116            if not read_bytes:
117                raise ConnectionTerminatedException(
118                    'Receiving %d byte failed. Peer (%r) closed connection' %
119                    (length, (self._request.connection.remote_addr,)))
120            return read_bytes
121        except socket.error, e:
122            # Catch a socket.error. Because it's not a child class of the
123            # IOError prior to Python 2.6, we cannot omit this except clause.
124            # Use %s rather than %r for the exception to use human friendly
125            # format.
126            raise ConnectionTerminatedException(
127                'Receiving %d byte failed. socket.error (%s) occurred' %
128                (length, e))
129        except IOError, e:
130            # Also catch an IOError because mod_python throws it.
131            raise ConnectionTerminatedException(
132                'Receiving %d byte failed. IOError (%s) occurred' %
133                (length, e))
134
135    def _write(self, bytes_to_write):
136        """Writes given bytes to connection. In case we catch any exception,
137        prepends remote address to the exception message and raise again.
138        """
139
140        try:
141            self._request.connection.write(bytes_to_write)
142        except Exception, e:
143            util.prepend_message_to_exception(
144                    'Failed to send message to %r: ' %
145                            (self._request.connection.remote_addr,),
146                    e)
147            raise
148
149    def receive_bytes(self, length):
150        """Receives multiple bytes. Retries read when we couldn't receive the
151        specified amount.
152
153        Raises:
154            ConnectionTerminatedException: when read returns empty string.
155        """
156
157        read_bytes = []
158        while length > 0:
159            new_read_bytes = self._read(length)
160            read_bytes.append(new_read_bytes)
161            length -= len(new_read_bytes)
162        return ''.join(read_bytes)
163
164    def _read_until(self, delim_char):
165        """Reads bytes until we encounter delim_char. The result will not
166        contain delim_char.
167
168        Raises:
169            ConnectionTerminatedException: when read returns empty string.
170        """
171
172        read_bytes = []
173        while True:
174            ch = self._read(1)
175            if ch == delim_char:
176                break
177            read_bytes.append(ch)
178        return ''.join(read_bytes)
179
180
181# vi:sts=4 sw=4 et
182