twisted.internet.process.ProcessWriter(abstract.FileDescriptor) class documentation

Part of twisted.internet.process (View In Hierarchy)

Known subclasses: twisted.test.test_process.DumbProcessWriter

(Internal) Helper class to write into a Process's input pipe.

I am a helper which describes a selectable asynchronous writer to a process's input pipe, including stdin.

Instance Variable enableReadHack A flag which determines how readability on this write descriptor will be handled. If True, then readability may indicate the reader for this write descriptor has been closed (ie, the connection has been lost). If False, then readability events are ignored.
Method __init__ Initialize, specifying a Process instance to connect to.
Method fileno Return the fileno() of my process's stdin.
Method writeSomeData Write some data to the open process.
Method write Reliably write some data.
Method doRead The only way a write pipe can become "readable" is at EOF, because the child has closed it, and we're using a reactor which doesn't distinguish between readable and closed (such as the select reactor).
Method connectionLost See abstract.FileDescriptor.connectionLost.

Inherited from FileDescriptor:

Method doWrite Called when data can be written.
Method writeConnectionLost Indicates write connection was lost.
Method readConnectionLost Indicates read connection was lost.
Method writeSequence Reliably write a sequence of data.
Method loseConnection Close the connection at the next available opportunity.
Method loseWriteConnection Undocumented
Method stopReading Stop waiting for read availability.
Method stopWriting Stop waiting for write availability.
Method startReading Start waiting for read availability.
Method startWriting Start waiting for write availability.
Method stopConsuming Stop consuming data.
Method resumeProducing Resume producing data.
Method pauseProducing Pause producing data.
Method stopProducing Stop producing data.
Method _postLoseConnection Called after a loseConnection(), when all data has been written.
Method _closeWriteConnection Undocumented
Method _isSendBufferFull Determine whether the user-space send buffer for this transport is full or not.
Method _maybePauseProducer Possibly pause a producer, if there is one and the send buffer is full.

Inherited from _ConsumerMixin (via FileDescriptor):

Instance Variable producer None if no producer is registered, otherwise the registered producer.
Instance Variable producerPaused A flag indicating whether the producer is currently paused. (type: bool)
Instance Variable streamingProducer 0 A flag indicating whether the producer was registered as a streaming (ie push) producer or not (ie a pull producer). This will determine whether the consumer may ever need to pause and resume it, or if it can merely call resumeProducing on it when buffer space is available.
Instance Variable streamingProducer bool or int
Method registerProducer Register to receive data from a producer.
Method unregisterProducer Stop consuming data from a producer, without disconnecting.

Inherited from _LogOwner (via FileDescriptor):

Method logPrefix Override this method to insert custom logging behavior. Its return value will be inserted in front of every line. It may be called more times than the number of output lines.
Method _getLogPrefix Determine the log prefix to use for messages related to applicationObject, which may or may not be an interfaces.ILoggingContext provider.
enableReadHack =
A flag which determines how readability on this write descriptor will be handled. If True, then readability may indicate the reader for this write descriptor has been closed (ie, the connection has been lost). If False, then readability events are ignored.
def __init__(self, reactor, proc, name, fileno, forceReadHack=False):
overrides twisted.internet.abstract.FileDescriptor.__init__

Initialize, specifying a Process instance to connect to.

def fileno(self):
from twisted.internet.interfaces.IFileDescriptor
overrides twisted.internet.abstract.FileDescriptor.fileno

Return the fileno() of my process's stdin.

def writeSomeData(self, data):
overrides twisted.internet.abstract.FileDescriptor.writeSomeData

Write some data to the open process.

def write(self, data):
from twisted.internet.interfaces.IConsumer
overrides twisted.internet.abstract.FileDescriptor.write

Reliably write some data.

The data is buffered until the underlying file descriptor is ready for writing. If there is more than self.bufferSize data in the buffer and this descriptor has a registered streaming producer, its pauseProducing() method will be called.

def doRead(self):
from twisted.internet.interfaces.IReadDescriptor
overrides twisted.internet.abstract.FileDescriptor.doRead

The only way a write pipe can become "readable" is at EOF, because the child has closed it, and we're using a reactor which doesn't distinguish between readable and closed (such as the select reactor).

Except that's not true on linux < 2.6.11. It has the following characteristics: write pipe is completely empty => POLLOUT (writable in select), write pipe is not completely empty => POLLIN (readable in select), write pipe's reader closed => POLLIN|POLLERR (readable and writable in select)

That's what this funky code is for. If linux was not broken, this function could be simply "return CONNECTION_LOST".

def connectionLost(self, reason):
from twisted.internet.interfaces.IFileDescriptor
overrides twisted.internet.abstract.FileDescriptor.connectionLost

See abstract.FileDescriptor.connectionLost.

API Documentation for twisted, generated by pydoctor at 2020-03-25 17:34:30.