1

# read a stream from a fifo

     2

     3

from twisted.internet import reactor, interfaces

     4

from twisted.python import log

     5

from zope.interface import implements

     6

     7

import os, fcntl, errno

     8

     9

class EOF (Exception) : pass

    10

    11

BUF_SIZE = 2048

    12

    13

class Fifo (object) :

    14

    implements(interfaces.IReadDescriptor)

    15

    16

    def __init__ (self, path) :

    17

        self.path = path

    18

        self.fd = None

    19

    20

        self._open()

    21

    22

    def _open (self) :

    23

        self.fd = os.open(self.path, os.O_RDONLY | os.O_NONBLOCK)

    24

    25

        reactor.addReader(self)

    26

    27

    def close (self) :

    28

        if self.fd :

    29

            reactor.removeReader(self)

    30

            os.close(self.fd)

    31

    32

            self.fd = None

    33

    34

    def reopen (self) :

    35

        """

    36

            Close and re-open the fifo. This is useful for handling EOF

    37

        """

    38

        self.close()

    39

        self._open()

    40

    41

    def _read (self, length) :

    42

    43

        try :

    44

            data = os.read(self.fd, length)

    45

    46

        except OSError, e :

    47

            if e.errno == errno.EAGAIN :

    48

                return None

    49

            else :

    50

                raise

    51

    52

        if not data :

    53

            raise EOF()

    54

    55

        return data

    56

    57

    def fileno (self) :

    58

        return self.fd

    59

    60

    def doRead (self) :

    61

        while True :

    62

            try :

    63

                data = self._read(BUF_SIZE)

    64

            except EOF :

    65

                self.handleEOF()

    66

                return

    67

    68

            if data :

    69

                self.dataReceived(data)

    70

            else :

    71

                break

    72

    73

    def dataReceived (self, data) :

    74

        pass

    75

    76

    def handleEOF (self) :

    77

        pass

    78

    79

    def connectionLost (self, reason) :

    80

        self.close()

    81

    82

    def logPrefix (self) :

    83

        return "fifo(%s)" % (self.path, )

    84

    85

    def __del__ (self) :

    86

        """

    87

            !!! this is important

    88

        """

    89

        self.close()

    90