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# dockerpty: io.py # # Copyright 2014 Chris Corbyn <chris@w3style.co.uk> # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. # You may obtain a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # See the License for the specific language governing permissions and # limitations under the License. import os import fcntl import errno import struct import select as builtin_select import six def set_blocking(fd, blocking=True): """ Set the given file-descriptor blocking or non-blocking. Returns the original blocking status. """ old_flag = fcntl.fcntl(fd, fcntl.F_GETFL) if blocking: new_flag = old_flag & ~ os.O_NONBLOCK else: new_flag = old_flag | os.O_NONBLOCK fcntl.fcntl(fd, fcntl.F_SETFL, new_flag) return not bool(old_flag & os.O_NONBLOCK) def select(read_streams, write_streams, timeout=0): """ Select the streams from `read_streams` that are ready for reading, and streams from `write_streams` ready for writing. Uses `select.select()` internally but only returns two lists of ready streams. """ exception_streams = [] try: return builtin_select.select( read_streams, write_streams, exception_streams, timeout, )[0:2] except builtin_select.error as e: # POSIX signals interrupt select() no = e.errno if six.PY3 else e[0] if no == errno.EINTR: return ([], []) else: raise e class Stream(object): """ Generic Stream class. This is a file-like abstraction on top of os.read() and os.write(), which add consistency to the reading of sockets and files alike. """ """ Recoverable IO/OS Errors. """ ERRNO_RECOVERABLE = [ errno.EINTR, errno.EDEADLK, errno.EWOULDBLOCK, ] def __init__(self, fd): """ Initialize the Stream for the file descriptor `fd`. The `fd` object must have a `fileno()` method. """ self.fd = fd self.buffer = b'' self.close_requested = False self.closed = False def fileno(self): """ Return the fileno() of the file descriptor. """ return self.fd.fileno() def set_blocking(self, value): if hasattr(self.fd, 'setblocking'): self.fd.setblocking(value) return True else: return set_blocking(self.fd, value) def read(self, n=4096): """ Return `n` bytes of data from the Stream, or None at end of stream. """ while True: try: if hasattr(self.fd, 'recv'): return self.fd.recv(n) return os.read(self.fd.fileno(), n) except EnvironmentError as e: if e.errno not in Stream.ERRNO_RECOVERABLE: raise e def write(self, data): """ Write `data` to the Stream. Not all data may be written right away. Use select to find when the stream is writeable, and call do_write() to flush the internal buffer. """ if not data: return None self.buffer += data self.do_write() return len(data) def do_write(self): """ Flushes as much pending data from the internal write buffer as possible. """ while True: try: written = 0 if hasattr(self.fd, 'send'): written = self.fd.send(self.buffer) else: written = os.write(self.fd.fileno(), self.buffer) self.buffer = self.buffer[written:] # try to close after writes if a close was requested if self.close_requested and len(self.buffer) == 0: self.close() return written except EnvironmentError as e: if e.errno not in Stream.ERRNO_RECOVERABLE: raise e def needs_write(self): """ Returns True if the stream has data waiting to be written. """ return len(self.buffer) > 0 def close(self): self.close_requested = True # We don't close the fd immediately, as there may still be data pending # to write. if not self.closed and len(self.buffer) == 0: self.closed = True if hasattr(self.fd, 'close'): self.fd.close() else: os.close(self.fd.fileno()) def __repr__(self): return "{cls}({fd})".format(cls=type(self).__name__, fd=self.fd) class Demuxer(object): """ Wraps a multiplexed Stream to read in data demultiplexed. Docker multiplexes streams together when there is no PTY attached, by sending an 8-byte header, followed by a chunk of data. The first 4 bytes of the header denote the stream from which the data came (i.e. 0x01 = stdout, 0x02 = stderr). Only the first byte of these initial 4 bytes is used. The next 4 bytes indicate the length of the following chunk of data as an integer in big endian format. This much data must be consumed before the next 8-byte header is read. """ def __init__(self, stream): """ Initialize a new Demuxer reading from `stream`. """ self.stream = stream self.remain = 0 def fileno(self): """ Returns the fileno() of the underlying Stream. This is useful for select() to work. """ return self.stream.fileno() def set_blocking(self, value): return self.stream.set_blocking(value) def read(self, n=4096): """ Read up to `n` bytes of data from the Stream, after demuxing. Less than `n` bytes of data may be returned depending on the available payload, but the number of bytes returned will never exceed `n`. Because demuxing involves scanning 8-byte headers, the actual amount of data read from the underlying stream may be greater than `n`. """ size = self._next_packet_size(n) if size <= 0: return else: data = six.binary_type() while len(data) < size: nxt = self.stream.read(size - len(data)) if not nxt: # the stream has closed, return what data we got return data data = data + nxt return data def write(self, data): """ Delegates the the underlying Stream. """ return self.stream.write(data) def needs_write(self): """ Delegates to underlying Stream. """ if hasattr(self.stream, 'needs_write'): return self.stream.needs_write() return False def do_write(self): """ Delegates to underlying Stream. """ if hasattr(self.stream, 'do_write'): return self.stream.do_write() return False def close(self): """ Delegates to underlying Stream. """ return self.stream.close() def _next_packet_size(self, n=0): size = 0 if self.remain > 0: size = min(n, self.remain) self.remain -= size else: data = six.binary_type() while len(data) < 8: nxt = self.stream.read(8 - len(data)) if not nxt: # The stream has closed, there's nothing more to read return 0 data = data + nxt if data is None: return 0 if len(data) == 8: __, actual = struct.unpack('>BxxxL', data) size = min(n, actual) self.remain = actual - size return size def __repr__(self): return "{cls}({stream})".format(cls=type(self).__name__, stream=self.stream) class Pump(object): """ Stream pump class. A Pump wraps two Streams, reading from one and and writing its data into the other, much like a pipe but manually managed. This abstraction is used to facilitate piping data between the file descriptors associated with the tty and those associated with a container's allocated pty. Pumps are selectable based on the 'read' end of the pipe. """ def __init__(self, from_stream, to_stream, wait_for_output=True, propagate_close=True): """ Initialize a Pump with a Stream to read from and another to write to. `wait_for_output` is a flag that says that we need to wait for EOF on the from_stream in order to consider this pump as "done". """ self.from_stream = from_stream self.to_stream = to_stream self.eof = False self.wait_for_output = wait_for_output self.propagate_close = propagate_close def fileno(self): """ Returns the `fileno()` of the reader end of the Pump. This is useful to allow Pumps to function with `select()`. """ return self.from_stream.fileno() def set_blocking(self, value): return self.from_stream.set_blocking(value) def flush(self, n=4096): """ Flush `n` bytes of data from the reader Stream to the writer Stream. Returns the number of bytes that were actually flushed. A return value of zero is not an error. If EOF has been reached, `None` is returned. """ try: read = self.from_stream.read(n) if read is None or len(read) == 0: self.eof = True if self.propagate_close: self.to_stream.close() return None return self.to_stream.write(read) except OSError as e: if e.errno != errno.EPIPE: raise e def is_done(self): """ Returns True if the read stream is done (either it's returned EOF or the pump doesn't have wait_for_output set), and the write side does not have pending bytes to send. """ return (not self.wait_for_output or self.eof) and \ not (hasattr(self.to_stream, 'needs_write') and self.to_stream.needs_write()) def __repr__(self): return "{cls}(from={from_stream}, to={to_stream})".format( cls=type(self).__name__, from_stream=self.from_stream, to_stream=self.to_stream)