Haibo Huang | d883030 | 2020-03-03 10:09:46 -0800 | [diff] [blame] | 1 | """Abstract Protocol base classes.""" |
| 2 | |
| 3 | __all__ = ( |
| 4 | 'BaseProtocol', 'Protocol', 'DatagramProtocol', |
| 5 | 'SubprocessProtocol', 'BufferedProtocol', |
| 6 | ) |
| 7 | |
| 8 | |
| 9 | class BaseProtocol: |
| 10 | """Common base class for protocol interfaces. |
| 11 | |
| 12 | Usually user implements protocols that derived from BaseProtocol |
| 13 | like Protocol or ProcessProtocol. |
| 14 | |
| 15 | The only case when BaseProtocol should be implemented directly is |
| 16 | write-only transport like write pipe |
| 17 | """ |
| 18 | |
| 19 | __slots__ = () |
| 20 | |
| 21 | def connection_made(self, transport): |
| 22 | """Called when a connection is made. |
| 23 | |
| 24 | The argument is the transport representing the pipe connection. |
| 25 | To receive data, wait for data_received() calls. |
| 26 | When the connection is closed, connection_lost() is called. |
| 27 | """ |
| 28 | |
| 29 | def connection_lost(self, exc): |
| 30 | """Called when the connection is lost or closed. |
| 31 | |
| 32 | The argument is an exception object or None (the latter |
| 33 | meaning a regular EOF is received or the connection was |
| 34 | aborted or closed). |
| 35 | """ |
| 36 | |
| 37 | def pause_writing(self): |
| 38 | """Called when the transport's buffer goes over the high-water mark. |
| 39 | |
| 40 | Pause and resume calls are paired -- pause_writing() is called |
| 41 | once when the buffer goes strictly over the high-water mark |
| 42 | (even if subsequent writes increases the buffer size even |
| 43 | more), and eventually resume_writing() is called once when the |
| 44 | buffer size reaches the low-water mark. |
| 45 | |
| 46 | Note that if the buffer size equals the high-water mark, |
| 47 | pause_writing() is not called -- it must go strictly over. |
| 48 | Conversely, resume_writing() is called when the buffer size is |
| 49 | equal or lower than the low-water mark. These end conditions |
| 50 | are important to ensure that things go as expected when either |
| 51 | mark is zero. |
| 52 | |
| 53 | NOTE: This is the only Protocol callback that is not called |
| 54 | through EventLoop.call_soon() -- if it were, it would have no |
| 55 | effect when it's most needed (when the app keeps writing |
| 56 | without yielding until pause_writing() is called). |
| 57 | """ |
| 58 | |
| 59 | def resume_writing(self): |
| 60 | """Called when the transport's buffer drains below the low-water mark. |
| 61 | |
| 62 | See pause_writing() for details. |
| 63 | """ |
| 64 | |
| 65 | |
| 66 | class Protocol(BaseProtocol): |
| 67 | """Interface for stream protocol. |
| 68 | |
| 69 | The user should implement this interface. They can inherit from |
| 70 | this class but don't need to. The implementations here do |
| 71 | nothing (they don't raise exceptions). |
| 72 | |
| 73 | When the user wants to requests a transport, they pass a protocol |
| 74 | factory to a utility function (e.g., EventLoop.create_connection()). |
| 75 | |
| 76 | When the connection is made successfully, connection_made() is |
| 77 | called with a suitable transport object. Then data_received() |
| 78 | will be called 0 or more times with data (bytes) received from the |
| 79 | transport; finally, connection_lost() will be called exactly once |
| 80 | with either an exception object or None as an argument. |
| 81 | |
| 82 | State machine of calls: |
| 83 | |
| 84 | start -> CM [-> DR*] [-> ER?] -> CL -> end |
| 85 | |
| 86 | * CM: connection_made() |
| 87 | * DR: data_received() |
| 88 | * ER: eof_received() |
| 89 | * CL: connection_lost() |
| 90 | """ |
| 91 | |
| 92 | __slots__ = () |
| 93 | |
| 94 | def data_received(self, data): |
| 95 | """Called when some data is received. |
| 96 | |
| 97 | The argument is a bytes object. |
| 98 | """ |
| 99 | |
| 100 | def eof_received(self): |
| 101 | """Called when the other end calls write_eof() or equivalent. |
| 102 | |
| 103 | If this returns a false value (including None), the transport |
| 104 | will close itself. If it returns a true value, closing the |
| 105 | transport is up to the protocol. |
| 106 | """ |
| 107 | |
| 108 | |
| 109 | class BufferedProtocol(BaseProtocol): |
| 110 | """Interface for stream protocol with manual buffer control. |
| 111 | |
Haibo Huang | d883030 | 2020-03-03 10:09:46 -0800 | [diff] [blame] | 112 | Event methods, such as `create_server` and `create_connection`, |
| 113 | accept factories that return protocols that implement this interface. |
| 114 | |
| 115 | The idea of BufferedProtocol is that it allows to manually allocate |
| 116 | and control the receive buffer. Event loops can then use the buffer |
| 117 | provided by the protocol to avoid unnecessary data copies. This |
| 118 | can result in noticeable performance improvement for protocols that |
| 119 | receive big amounts of data. Sophisticated protocols can allocate |
| 120 | the buffer only once at creation time. |
| 121 | |
| 122 | State machine of calls: |
| 123 | |
| 124 | start -> CM [-> GB [-> BU?]]* [-> ER?] -> CL -> end |
| 125 | |
| 126 | * CM: connection_made() |
| 127 | * GB: get_buffer() |
| 128 | * BU: buffer_updated() |
| 129 | * ER: eof_received() |
| 130 | * CL: connection_lost() |
| 131 | """ |
| 132 | |
| 133 | __slots__ = () |
| 134 | |
| 135 | def get_buffer(self, sizehint): |
| 136 | """Called to allocate a new receive buffer. |
| 137 | |
| 138 | *sizehint* is a recommended minimal size for the returned |
| 139 | buffer. When set to -1, the buffer size can be arbitrary. |
| 140 | |
| 141 | Must return an object that implements the |
| 142 | :ref:`buffer protocol <bufferobjects>`. |
| 143 | It is an error to return a zero-sized buffer. |
| 144 | """ |
| 145 | |
| 146 | def buffer_updated(self, nbytes): |
| 147 | """Called when the buffer was updated with the received data. |
| 148 | |
| 149 | *nbytes* is the total number of bytes that were written to |
| 150 | the buffer. |
| 151 | """ |
| 152 | |
| 153 | def eof_received(self): |
| 154 | """Called when the other end calls write_eof() or equivalent. |
| 155 | |
| 156 | If this returns a false value (including None), the transport |
| 157 | will close itself. If it returns a true value, closing the |
| 158 | transport is up to the protocol. |
| 159 | """ |
| 160 | |
| 161 | |
| 162 | class DatagramProtocol(BaseProtocol): |
| 163 | """Interface for datagram protocol.""" |
| 164 | |
| 165 | __slots__ = () |
| 166 | |
| 167 | def datagram_received(self, data, addr): |
| 168 | """Called when some datagram is received.""" |
| 169 | |
| 170 | def error_received(self, exc): |
| 171 | """Called when a send or receive operation raises an OSError. |
| 172 | |
| 173 | (Other than BlockingIOError or InterruptedError.) |
| 174 | """ |
| 175 | |
| 176 | |
| 177 | class SubprocessProtocol(BaseProtocol): |
| 178 | """Interface for protocol for subprocess calls.""" |
| 179 | |
| 180 | __slots__ = () |
| 181 | |
| 182 | def pipe_data_received(self, fd, data): |
| 183 | """Called when the subprocess writes data into stdout/stderr pipe. |
| 184 | |
| 185 | fd is int file descriptor. |
| 186 | data is bytes object. |
| 187 | """ |
| 188 | |
| 189 | def pipe_connection_lost(self, fd, exc): |
| 190 | """Called when a file descriptor associated with the child process is |
| 191 | closed. |
| 192 | |
| 193 | fd is the int file descriptor that was closed. |
| 194 | """ |
| 195 | |
| 196 | def process_exited(self): |
| 197 | """Called when subprocess has exited.""" |
| 198 | |
| 199 | |
| 200 | def _feed_data_to_buffered_proto(proto, data): |
| 201 | data_len = len(data) |
| 202 | while data_len: |
| 203 | buf = proto.get_buffer(data_len) |
| 204 | buf_len = len(buf) |
| 205 | if not buf_len: |
| 206 | raise RuntimeError('get_buffer() returned an empty buffer') |
| 207 | |
| 208 | if buf_len >= data_len: |
| 209 | buf[:data_len] = data |
| 210 | proto.buffer_updated(data_len) |
| 211 | return |
| 212 | else: |
| 213 | buf[:buf_len] = data[:buf_len] |
| 214 | proto.buffer_updated(buf_len) |
| 215 | data = data[buf_len:] |
| 216 | data_len = len(data) |