Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 1 | """Stream-related things.""" |
| 2 | |
| 3 | __all__ = ['StreamReader', 'StreamReaderProtocol', 'open_connection'] |
| 4 | |
| 5 | import collections |
| 6 | |
| 7 | from . import events |
| 8 | from . import futures |
| 9 | from . import protocols |
| 10 | from . import tasks |
| 11 | |
| 12 | |
| 13 | _DEFAULT_LIMIT = 2**16 |
| 14 | |
| 15 | |
| 16 | @tasks.coroutine |
| 17 | def open_connection(host=None, port=None, *, |
| 18 | loop=None, limit=_DEFAULT_LIMIT, **kwds): |
| 19 | """A wrapper for create_connection() returning a (reader, writer) pair. |
| 20 | |
| 21 | The reader returned is a StreamReader instance; the writer is a |
| 22 | Transport. |
| 23 | |
| 24 | The arguments are all the usual arguments to create_connection() |
| 25 | except protocol_factory; most common are positional host and port, |
| 26 | with various optional keyword arguments following. |
| 27 | |
| 28 | Additional optional keyword arguments are loop (to set the event loop |
| 29 | instance to use) and limit (to set the buffer limit passed to the |
| 30 | StreamReader). |
| 31 | |
| 32 | (If you want to customize the StreamReader and/or |
| 33 | StreamReaderProtocol classes, just copy the code -- there's |
| 34 | really nothing special here except some convenience.) |
| 35 | """ |
| 36 | if loop is None: |
| 37 | loop = events.get_event_loop() |
| 38 | reader = StreamReader(limit=limit, loop=loop) |
| 39 | protocol = StreamReaderProtocol(reader) |
| 40 | transport, _ = yield from loop.create_connection( |
| 41 | lambda: protocol, host, port, **kwds) |
| 42 | return reader, transport # (reader, writer) |
| 43 | |
| 44 | |
| 45 | class StreamReaderProtocol(protocols.Protocol): |
| 46 | """Trivial helper class to adapt between Protocol and StreamReader. |
| 47 | |
| 48 | (This is a helper class instead of making StreamReader itself a |
| 49 | Protocol subclass, because the StreamReader has other potential |
| 50 | uses, and to prevent the user of the StreamReader to accidentally |
| 51 | call inappropriate methods of the protocol.) |
| 52 | """ |
| 53 | |
| 54 | def __init__(self, stream_reader): |
| 55 | self.stream_reader = stream_reader |
| 56 | |
| 57 | def connection_made(self, transport): |
| 58 | self.stream_reader.set_transport(transport) |
| 59 | |
| 60 | def connection_lost(self, exc): |
| 61 | if exc is None: |
| 62 | self.stream_reader.feed_eof() |
| 63 | else: |
| 64 | self.stream_reader.set_exception(exc) |
| 65 | |
| 66 | def data_received(self, data): |
| 67 | self.stream_reader.feed_data(data) |
| 68 | |
| 69 | def eof_received(self): |
| 70 | self.stream_reader.feed_eof() |
| 71 | |
| 72 | |
| 73 | class StreamReader: |
| 74 | |
| 75 | def __init__(self, limit=_DEFAULT_LIMIT, loop=None): |
| 76 | # The line length limit is a security feature; |
| 77 | # it also doubles as half the buffer limit. |
| 78 | self.limit = limit |
| 79 | if loop is None: |
| 80 | loop = events.get_event_loop() |
| 81 | self.loop = loop |
| 82 | self.buffer = collections.deque() # Deque of bytes objects. |
| 83 | self.byte_count = 0 # Bytes in buffer. |
| 84 | self.eof = False # Whether we're done. |
| 85 | self.waiter = None # A future. |
| 86 | self._exception = None |
| 87 | self._transport = None |
| 88 | self._paused = False |
| 89 | |
| 90 | def exception(self): |
| 91 | return self._exception |
| 92 | |
| 93 | def set_exception(self, exc): |
| 94 | self._exception = exc |
| 95 | |
| 96 | waiter = self.waiter |
| 97 | if waiter is not None: |
| 98 | self.waiter = None |
| 99 | if not waiter.cancelled(): |
| 100 | waiter.set_exception(exc) |
| 101 | |
| 102 | def set_transport(self, transport): |
| 103 | assert self._transport is None, 'Transport already set' |
| 104 | self._transport = transport |
| 105 | |
| 106 | def _maybe_resume_transport(self): |
| 107 | if self._paused and self.byte_count <= self.limit: |
| 108 | self._paused = False |
Guido van Rossum | 57497ad | 2013-10-18 07:58:20 -0700 | [diff] [blame^] | 109 | self._transport.resume_reading() |
Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 110 | |
| 111 | def feed_eof(self): |
| 112 | self.eof = True |
| 113 | waiter = self.waiter |
| 114 | if waiter is not None: |
| 115 | self.waiter = None |
| 116 | if not waiter.cancelled(): |
| 117 | waiter.set_result(True) |
| 118 | |
| 119 | def feed_data(self, data): |
| 120 | if not data: |
| 121 | return |
| 122 | |
| 123 | self.buffer.append(data) |
| 124 | self.byte_count += len(data) |
| 125 | |
| 126 | waiter = self.waiter |
| 127 | if waiter is not None: |
| 128 | self.waiter = None |
| 129 | if not waiter.cancelled(): |
| 130 | waiter.set_result(False) |
| 131 | |
| 132 | if (self._transport is not None and |
| 133 | not self._paused and |
| 134 | self.byte_count > 2*self.limit): |
| 135 | try: |
Guido van Rossum | 57497ad | 2013-10-18 07:58:20 -0700 | [diff] [blame^] | 136 | self._transport.pause_reading() |
Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 137 | except NotImplementedError: |
| 138 | # The transport can't be paused. |
| 139 | # We'll just have to buffer all data. |
| 140 | # Forget the transport so we don't keep trying. |
| 141 | self._transport = None |
| 142 | else: |
| 143 | self._paused = True |
| 144 | |
| 145 | @tasks.coroutine |
| 146 | def readline(self): |
| 147 | if self._exception is not None: |
| 148 | raise self._exception |
| 149 | |
| 150 | parts = [] |
| 151 | parts_size = 0 |
| 152 | not_enough = True |
| 153 | |
| 154 | while not_enough: |
| 155 | while self.buffer and not_enough: |
| 156 | data = self.buffer.popleft() |
| 157 | ichar = data.find(b'\n') |
| 158 | if ichar < 0: |
| 159 | parts.append(data) |
| 160 | parts_size += len(data) |
| 161 | else: |
| 162 | ichar += 1 |
| 163 | head, tail = data[:ichar], data[ichar:] |
| 164 | if tail: |
| 165 | self.buffer.appendleft(tail) |
| 166 | not_enough = False |
| 167 | parts.append(head) |
| 168 | parts_size += len(head) |
| 169 | |
| 170 | if parts_size > self.limit: |
| 171 | self.byte_count -= parts_size |
| 172 | self._maybe_resume_transport() |
| 173 | raise ValueError('Line is too long') |
| 174 | |
| 175 | if self.eof: |
| 176 | break |
| 177 | |
| 178 | if not_enough: |
| 179 | assert self.waiter is None |
| 180 | self.waiter = futures.Future(loop=self.loop) |
| 181 | try: |
| 182 | yield from self.waiter |
| 183 | finally: |
| 184 | self.waiter = None |
| 185 | |
| 186 | line = b''.join(parts) |
| 187 | self.byte_count -= parts_size |
| 188 | self._maybe_resume_transport() |
| 189 | |
| 190 | return line |
| 191 | |
| 192 | @tasks.coroutine |
| 193 | def read(self, n=-1): |
| 194 | if self._exception is not None: |
| 195 | raise self._exception |
| 196 | |
| 197 | if not n: |
| 198 | return b'' |
| 199 | |
| 200 | if n < 0: |
| 201 | while not self.eof: |
| 202 | assert not self.waiter |
| 203 | self.waiter = futures.Future(loop=self.loop) |
| 204 | try: |
| 205 | yield from self.waiter |
| 206 | finally: |
| 207 | self.waiter = None |
| 208 | else: |
| 209 | if not self.byte_count and not self.eof: |
| 210 | assert not self.waiter |
| 211 | self.waiter = futures.Future(loop=self.loop) |
| 212 | try: |
| 213 | yield from self.waiter |
| 214 | finally: |
| 215 | self.waiter = None |
| 216 | |
| 217 | if n < 0 or self.byte_count <= n: |
| 218 | data = b''.join(self.buffer) |
| 219 | self.buffer.clear() |
| 220 | self.byte_count = 0 |
| 221 | self._maybe_resume_transport() |
| 222 | return data |
| 223 | |
| 224 | parts = [] |
| 225 | parts_bytes = 0 |
| 226 | while self.buffer and parts_bytes < n: |
| 227 | data = self.buffer.popleft() |
| 228 | data_bytes = len(data) |
| 229 | if n < parts_bytes + data_bytes: |
| 230 | data_bytes = n - parts_bytes |
| 231 | data, rest = data[:data_bytes], data[data_bytes:] |
| 232 | self.buffer.appendleft(rest) |
| 233 | |
| 234 | parts.append(data) |
| 235 | parts_bytes += data_bytes |
| 236 | self.byte_count -= data_bytes |
| 237 | self._maybe_resume_transport() |
| 238 | |
| 239 | return b''.join(parts) |
| 240 | |
| 241 | @tasks.coroutine |
| 242 | def readexactly(self, n): |
| 243 | if self._exception is not None: |
| 244 | raise self._exception |
| 245 | |
| 246 | if n <= 0: |
| 247 | return b'' |
| 248 | |
| 249 | while self.byte_count < n and not self.eof: |
| 250 | assert not self.waiter |
| 251 | self.waiter = futures.Future(loop=self.loop) |
| 252 | try: |
| 253 | yield from self.waiter |
| 254 | finally: |
| 255 | self.waiter = None |
| 256 | |
| 257 | return (yield from self.read(n)) |