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import errno
import os
import select
import struct
import six
try:
from ..transport import NpipeSocket
except ImportError:
NpipeSocket = type(None)
class SocketError(Exception):
pass
def read(socket, n=4096):
"""
Reads at most n bytes from socket
"""
recoverable_errors = (errno.EINTR, errno.EDEADLK, errno.EWOULDBLOCK)
# wait for data to become available
if not isinstance(socket, NpipeSocket):
select.select([socket], [], [])
try:
if hasattr(socket, 'recv'):
return socket.recv(n)
return os.read(socket.fileno(), n)
except EnvironmentError as e:
if e.errno not in recoverable_errors:
raise
def read_exactly(socket, n):
"""
Reads exactly n bytes from socket
Raises SocketError if there isn't enough data
"""
data = six.binary_type()
while len(data) < n:
next_data = read(socket, n - len(data))
if not next_data:
raise SocketError("Unexpected EOF")
data += next_data
return data
def next_frame_size(socket):
"""
Returns the size of the next frame of data waiting to be read from socket,
according to the protocol defined here:
https://docs.docker.com/engine/reference/api/docker_remote_api_v1.24/#/attach-to-a-container
"""
try:
data = read_exactly(socket, 8)
except SocketError:
return 0
_, actual = struct.unpack('>BxxxL', data)
return actual
def frames_iter(socket):
"""
Returns a generator of frames read from socket
"""
n = next_frame_size(socket)
while n > 0:
yield read(socket, n)
n = next_frame_size(socket)
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