posixfile.py

"""Extended file operations available in POSIX.

f = posixfile.open(filename, [mode, [bufsize]])
      will create a new posixfile object

f = posixfile.fileopen(fileobject)
      will create a posixfile object from a builtin file object

f.file()
      will return the original builtin file object

f.dup()
      will return a new file object based on a new filedescriptor

f.dup2(fd)
      will return a new file object based on the given filedescriptor

f.flags(mode)
      will turn on the associated flag (merge)
      mode can contain the following characters:

  (character representing a flag)
      a       append only flag
      c       close on exec flag
      n       no delay flag
      s       synchronization flag
  (modifiers)
      !       turn flags 'off' instead of default 'on'
      =       copy flags 'as is' instead of default 'merge'
      ?       return a string in which the characters represent the flags
              that are set

      note: - the '!' and '=' modifiers are mutually exclusive.
            - the '?' modifier will return the status of the flags after they
              have been changed by other characters in the mode string

f.lock(mode [, len [, start [, whence]]])
      will (un)lock a region
      mode can contain the following characters:

  (character representing type of lock)
      u       unlock
      r       read lock
      w       write lock
  (modifiers)
      |       wait until the lock can be granted
      ?       return the first lock conflicting with the requested lock
              or 'None' if there is no conflict. The lock returned is in the
              format (mode, len, start, whence, pid) where mode is a
              character representing the type of lock ('r' or 'w')

      note: - the '?' modifier prevents a region from being locked; it is
              query only
"""

class _posixfile_:
    """File wrapper class that provides extra POSIX file routines."""

    states = ['open', 'closed']

    #
    # Internal routines
    #
    def __repr__(self):
        file = self._file_
        return "<%s posixfile '%s', mode '%s' at %s>" % \
                (self.states[file.closed], file.name, file.mode, \
                 hex(id(self))[2:])

    #
    # Initialization routines
    #
    def open(self, name, mode='r', bufsize=-1):
        import __builtin__
        return self.fileopen(__builtin__.open(name, mode, bufsize))

    def fileopen(self, file):
        if `type(file)` != "<type 'file'>":
            raise TypeError, 'posixfile.fileopen() arg must be file object'
        self._file_  = file
        # Copy basic file methods
        for method in file.__methods__:
            setattr(self, method, getattr(file, method))
        return self

    #
    # New methods
    #
    def file(self):
        return self._file_

    def dup(self):
        import posix

        try: ignore = posix.fdopen
        except: raise AttributeError, 'dup() method unavailable'

        return posix.fdopen(posix.dup(self._file_.fileno()), self._file_.mode)

    def dup2(self, fd):
        import posix

        try: ignore = posix.fdopen
        except: raise AttributeError, 'dup() method unavailable'

        posix.dup2(self._file_.fileno(), fd)
        return posix.fdopen(fd, self._file_.mode)

    def flags(self, *which):
        import fcntl, FCNTL

        if which:
            if len(which) > 1:
                raise TypeError, 'Too many arguments'
            which = which[0]
        else: which = '?'

        l_flags = 0
        if 'n' in which: l_flags = l_flags | FCNTL.O_NDELAY
        if 'a' in which: l_flags = l_flags | FCNTL.O_APPEND
        if 's' in which: l_flags = l_flags | FCNTL.O_SYNC

        file = self._file_

        if '=' not in which:
            cur_fl = fcntl.fcntl(file.fileno(), FCNTL.F_GETFL, 0)
            if '!' in which: l_flags = cur_fl & ~ l_flags
            else: l_flags = cur_fl | l_flags

        l_flags = fcntl.fcntl(file.fileno(), FCNTL.F_SETFL, l_flags)

        if 'c' in which:
            arg = ('!' not in which)    # 0 is don't, 1 is do close on exec
            l_flags = fcntl.fcntl(file.fileno(), FCNTL.F_SETFD, arg)

        if '?' in which:
            which = ''                  # Return current flags
            l_flags = fcntl.fcntl(file.fileno(), FCNTL.F_GETFL, 0)
            if FCNTL.O_APPEND & l_flags: which = which + 'a'
            if fcntl.fcntl(file.fileno(), FCNTL.F_GETFD, 0) & 1:
                which = which + 'c'
            if FCNTL.O_NDELAY & l_flags: which = which + 'n'
            if FCNTL.O_SYNC & l_flags: which = which + 's'
            return which

    def lock(self, how, *args):
        import struct, fcntl, FCNTL

        if 'w' in how: l_type = FCNTL.F_WRLCK
        elif 'r' in how: l_type = FCNTL.F_RDLCK
        elif 'u' in how: l_type = FCNTL.F_UNLCK
        else: raise TypeError, 'no type of lock specified'

        if '|' in how: cmd = FCNTL.F_SETLKW
        elif '?' in how: cmd = FCNTL.F_GETLK
        else: cmd = FCNTL.F_SETLK

        l_whence = 0
        l_start = 0
        l_len = 0

        if len(args) == 1:
            l_len = args[0]
        elif len(args) == 2:
            l_len, l_start = args
        elif len(args) == 3:
            l_len, l_start, l_whence = args
        elif len(args) > 3:
            raise TypeError, 'too many arguments'

        # Hack by davem@magnet.com to get locking to go on freebsd;
        # additions for AIX by Vladimir.Marangozov@imag.fr
        import sys, os
        if sys.platform in ('netbsd1',
                            'openbsd2',
                            'freebsd2', 'freebsd3', 'freebsd4', 'freebsd5',
                            'bsdos2', 'bsdos3', 'bsdos4'):
            flock = struct.pack('lxxxxlxxxxlhh', \
                  l_start, l_len, os.getpid(), l_type, l_whence)
        elif sys.platform in ['aix3', 'aix4']:
            flock = struct.pack('hhlllii', \
                  l_type, l_whence, l_start, l_len, 0, 0, 0)
        else:
            flock = struct.pack('hhllhh', \
                  l_type, l_whence, l_start, l_len, 0, 0)

        flock = fcntl.fcntl(self._file_.fileno(), cmd, flock)

        if '?' in how:
            if sys.platform in ('netbsd1',
                                'openbsd2',
                                'freebsd2', 'freebsd3', 'freebsd4', 'freebsd5',
                                'bsdos2', 'bsdos3', 'bsdos4'):
                l_start, l_len, l_pid, l_type, l_whence = \
                    struct.unpack('lxxxxlxxxxlhh', flock)
            elif sys.platform in ['aix3', 'aix4']:
                l_type, l_whence, l_start, l_len, l_sysid, l_pid, l_vfs = \
                    struct.unpack('hhlllii', flock)
            elif sys.platform == "linux2":
                l_type, l_whence, l_start, l_len, l_pid, l_sysid = \
                    struct.unpack('hhllhh', flock)
            else:
                l_type, l_whence, l_start, l_len, l_sysid, l_pid = \
                    struct.unpack('hhllhh', flock)

            if l_type != FCNTL.F_UNLCK:
                if l_type == FCNTL.F_RDLCK:
                    return 'r', l_len, l_start, l_whence, l_pid
                else:
                    return 'w', l_len, l_start, l_whence, l_pid

def open(name, mode='r', bufsize=-1):
    """Public routine to open a file as a posixfile object."""
    return _posixfile_().open(name, mode, bufsize)

def fileopen(file):
    """Public routine to get a posixfile object from a Python file object."""
    return _posixfile_().fileopen(file)

#
# Constants
#
SEEK_SET = 0
SEEK_CUR = 1
SEEK_END = 2

#
# End of posixfile.py
#