JezK
Edit File: pipe.py
# -*- coding: utf-8 -*- # Copyright (C) 2013 Sebastian Wiesner <lunaryorn@gmail.com> # This library is free software; you can redistribute it and/or modify it # under the terms of the GNU Lesser General Public License as published by the # Free Software Foundation; either version 2.1 of the License, or (at your # option) any later version. # This library is distributed in the hope that it will be useful, but WITHOUT # ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or # FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License # for more details. # You should have received a copy of the GNU Lesser General Public License # along with this library; if not, write to the Free Software Foundation, # Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA """ pyudev._os.pipe =============== Fallback implementations for pipe. 1. pipe2 from python os module 2. pipe2 from libc 3. pipe from python os module The Pipe class wraps the chosen implementation. .. moduleauthor:: Sebastian Wiesner <lunaryorn@gmail.com> """ # isort: STDLIB import fcntl import os from functools import partial # isort: LOCAL from pyudev._ctypeslib.libc import ERROR_CHECKERS, FD_PAIR, SIGNATURES from pyudev._ctypeslib.utils import load_ctypes_library # Define O_CLOEXEC, if not present in os already O_CLOEXEC = getattr(os, "O_CLOEXEC", 0o2000000) def _pipe2_ctypes(libc, flags): """A ``pipe2`` implementation using ``pipe2`` from ctypes. ``libc`` is a :class:`ctypes.CDLL` object for libc. ``flags`` is an integer providing the flags to ``pipe2``. Return a pair of file descriptors ``(r, w)``. """ fds = FD_PAIR() libc.pipe2(fds, flags) return fds[0], fds[1] def _pipe2_by_pipe(flags): """A ``pipe2`` implementation using :func:`os.pipe`. ``flags`` is an integer providing the flags to ``pipe2``. .. warning:: This implementation is not atomic! Return a pair of file descriptors ``(r, w)``. """ fds = os.pipe() if flags & os.O_NONBLOCK != 0: for file_descriptor in fds: set_fd_status_flag(file_descriptor, os.O_NONBLOCK) if flags & O_CLOEXEC != 0: for file_descriptor in fds: set_fd_flag(file_descriptor, O_CLOEXEC) return fds def _get_pipe2_implementation(): """ Find the appropriate implementation for ``pipe2``. Return a function implementing ``pipe2``.""" if hasattr(os, "pipe2"): return os.pipe2 # pylint: disable=no-member try: libc = load_ctypes_library("libc", SIGNATURES, ERROR_CHECKERS) return ( partial(_pipe2_ctypes, libc) if hasattr(libc, "pipe2") else _pipe2_by_pipe ) except ImportError: return _pipe2_by_pipe _PIPE2 = _get_pipe2_implementation() def set_fd_flag(fd, flag): # pylint: disable=invalid-name """Set a flag on a file descriptor. ``fd`` is the file descriptor or file object, ``flag`` the flag as integer. """ flags = fcntl.fcntl(fd, fcntl.F_GETFD, 0) fcntl.fcntl(fd, fcntl.F_SETFD, flags | flag) def set_fd_status_flag(fd, flag): # pylint: disable=invalid-name """Set a status flag on a file descriptor. ``fd`` is the file descriptor or file object, ``flag`` the flag as integer. """ flags = fcntl.fcntl(fd, fcntl.F_GETFL, 0) fcntl.fcntl(fd, fcntl.F_SETFL, flags | flag) class Pipe: """A unix pipe. A pipe object provides two file objects: :attr:`source` is a readable file object, and :attr:`sink` a writeable. Bytes written to :attr:`sink` appear at :attr:`source`. Open a pipe with :meth:`open()`. """ @classmethod def open(cls): """Open and return a new :class:`Pipe`. The pipe uses non-blocking IO.""" source, sink = _PIPE2(os.O_NONBLOCK | O_CLOEXEC) return cls(source, sink) def __init__(self, source_fd, sink_fd): """Create a new pipe object from the given file descriptors. ``source_fd`` is a file descriptor for the readable side of the pipe, ``sink_fd`` is a file descriptor for the writeable side.""" self.source = os.fdopen(source_fd, "rb", 0) self.sink = os.fdopen(sink_fd, "wb", 0) def close(self): """Closes both sides of the pipe.""" try: self.source.close() finally: self.sink.close()