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io.py
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io.py
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# curio/io.py
#
# Curio is primarily concerned with the scheduling of tasks. In
# particular, the kernel does not actually perform any I/O. It merely
# blocks tasks that need to wait for reading or writing. To actually
# perform I/O, you use the existing file and socket abstractions
# already provided by the Python standard library. The only
# difference is that you need to take extra steps to manage their
# non-blocking behavior. The classes in this file provide wrappers
# around socket-like and file-like objects. Methods responsible for
# reading/writing have a small amount of extra logic to added to
# handle their scheduling. Other methods are simply passed through to
# the original object via delegation.
#
# It's important to emphasize that these classes can be applied to
# *ANY* existing socket-like or file-like object as long as it
# represents a real system-level file (must have a fileno() method)
# and can be used with the underlying I/O selector. For example, the
# Socket class can wrap a normal socket or an SSL socket--it doesn't
# matter which. Similarly, the Stream class can wrap normal files,
# files created from sockets, pipes, and other file-like abstractions.
#
# No assumption is made about system compatibility (Unix vs. Windows).
# The main compatibility concern would be at the level of the I/O
# selector used by the kernel. For example, can it detect I/O events
# on the provided file or socket? If so, it will probably work here.
__all__ = ['Socket', 'FileStream', 'SocketStream']
# -- Standard Library
from socket import SOL_SOCKET, SO_ERROR
from contextlib import contextmanager
import io
import os
# -- Curio
from .traps import _read_wait, _write_wait
from . import errors
from . import thread
# Exceptions raised for non-blocking I/O. For normal sockets, blocking operations
# normally just raise BlockingIOError. For SSL sockets, more specific exceptions
# are raised. Here we're just making some aliases for the possible exceptions.
try:
from ssl import SSLWantReadError, SSLWantWriteError
WantRead = (BlockingIOError, InterruptedError, SSLWantReadError)
WantWrite = (BlockingIOError, InterruptedError, SSLWantWriteError)
except ImportError:
WantRead = (BlockingIOError, InterruptedError)
WantWrite = (BlockingIOError, InterruptedError)
# Wrapper class around an integer file descriptor. This is used
# to take advantage of an I/O scheduling performance optimization
# in the kernel. If a non-integer file object is given, the
# kernel is able to reuse prior registrations on the event loop.
# The reason this wrapper class is used is that even though an
# integer file descriptor might be reused by the host OS,
# instances of _Fd will not be reused. Thus, if a file is closed
# and a new file opened on the same descriptor, it will be
# detected as a different file.
#
# See also: https://github.com/dabeaz/curio/issues/104
class _Fd(object):
__slots__ = ('fd',)
def __init__(self, fd):
self.fd = fd
def fileno(self):
return self.fd
def __int__(self):
return self.fd
def __repr__(self):
return f'<fd={self.fd!r}>'
# There is a certain amount of repetition in this class. It can
# probably be shortened with some sort of decorator magic. On the
# other, the KISSS (Keep it Stupid Simple Stupid) principle might be a
# better policy--just in case someone needs to debug it.
class Socket(object):
'''
Non-blocking wrapper around a socket object. The original socket is put
into a non-blocking mode when it's wrapped.
'''
def __init__(self, sock):
self._socket = sock
self._socket.setblocking(False)
self._fileno = _Fd(sock.fileno())
# Commonly used bound methods
self._socket_send = sock.send
self._socket_recv = sock.recv
def __repr__(self):
return f'<curio.Socket {self._socket!r}>'
def __getattr__(self, name):
return getattr(self._socket, name)
def fileno(self):
return int(self._fileno)
def settimeout(self, seconds):
raise RuntimeError('Use timeout_after() to set a timeout')
def gettimeout(self):
return None
def dup(self):
return type(self)(self._socket.dup())
def makefile(self, mode, buffering=0, *, encoding=None, errors=None, newline=None):
if 'b' not in mode:
raise RuntimeError('File can only be created in binary mode')
f = self._socket.makefile(mode, buffering=buffering)
return FileStream(f)
def as_stream(self):
'''
Create a stream-based interface to the socket.
'''
return SocketStream(self._socket)
@contextmanager
def blocking(self):
'''
Allow temporary access to the underlying socket in blocking mode
'''
try:
self._socket.setblocking(True)
yield self._socket
finally:
self._socket.setblocking(False)
async def recv(self, maxsize, flags=0):
while True:
try:
return self._socket_recv(maxsize, flags)
except WantRead:
await _read_wait(self._fileno)
except WantWrite: # pragma: no cover
await _write_wait(self._fileno)
async def recv_into(self, buffer, nbytes=0, flags=0):
while True:
try:
return self._socket.recv_into(buffer, nbytes, flags)
except WantRead:
await _read_wait(self._fileno)
except WantWrite: # pragma: no cover
await _write_wait(self._fileno)
async def send(self, data, flags=0):
while True:
try:
return self._socket_send(data, flags)
except WantWrite:
await _write_wait(self._fileno)
except WantRead: # pragma: no cover
await _read_wait(self._fileno)
async def sendall(self, data, flags=0):
with memoryview(data).cast('B') as buffer:
total_sent = 0
try:
while buffer:
try:
nsent = self._socket_send(buffer, flags)
total_sent += nsent
buffer = buffer[nsent:]
except WantWrite:
await _write_wait(self._fileno)
except WantRead: # pragma: no cover
await _read_wait(self._fileno)
except errors.CancelledError as e:
e.bytes_sent = total_sent
raise
async def accept(self):
while True:
try:
client, addr = self._socket.accept()
return type(self)(client), addr
except WantRead:
await _read_wait(self._fileno)
async def connect_ex(self, address):
try:
await self.connect(address)
return 0
except OSError as e:
return e.errno
async def connect(self, address):
try:
result = self._socket.connect(address)
if getattr(self, 'do_handshake_on_connect', False):
await self.do_handshake()
return result
except WantWrite:
await _write_wait(self._fileno)
err = self._socket.getsockopt(SOL_SOCKET, SO_ERROR)
if err != 0:
raise OSError(err, f'Connect call failed {address}')
if getattr(self, 'do_handshake_on_connect', False):
await self.do_handshake()
async def recvfrom(self, buffersize, flags=0):
while True:
try:
return self._socket.recvfrom(buffersize, flags)
except WantRead:
await _read_wait(self._fileno)
except WantWrite:
await _write_wait(self._fileno)
async def recvfrom_into(self, buffer, bytes=0, flags=0):
while True:
try:
return self._socket.recvfrom_into(buffer, bytes, flags)
except WantRead:
await _read_wait(self._fileno)
except WantWrite: # pragma: no cover
await _write_wait(self._fileno)
async def sendto(self, bytes, flags_or_address, address=None):
if address:
flags = flags_or_address
else:
address = flags_or_address
flags = 0
while True:
try:
return self._socket.sendto(bytes, flags, address)
except WantWrite:
await _write_wait(self._fileno)
except WantRead: # pragma: no cover
await _read_wait(self._fileno)
async def recvmsg(self, bufsize, ancbufsize=0, flags=0):
while True:
try:
return self._socket.recvmsg(bufsize, ancbufsize, flags)
except WantRead:
await _read_wait(self._fileno)
async def recvmsg_into(self, buffers, ancbufsize=0, flags=0):
while True:
try:
return self._socket.recvmsg_into(buffers, ancbufsize, flags)
except WantRead:
await _read_wait(self._fileno)
async def sendmsg(self, buffers, ancdata=(), flags=0, address=None):
while True:
try:
return self._socket.sendmsg(buffers, ancdata, flags, address)
except WantRead:
await _write_wait(self._fileno)
# Special functions for SSL
async def do_handshake(self):
while True:
try:
return self._socket.do_handshake()
except WantRead:
await _read_wait(self._fileno)
except WantWrite:
await _write_wait(self._fileno)
# Design discussion. Why make close() async? Partly it's to make the
# programming interface highly uniform with the other methods (all of which
# involve an await). It's also to provide consistency with the Stream
# API below which requires an asynchronous close to properly flush I/O
# buffers.
async def close(self):
if self._socket:
self._socket.close()
self._socket = None
self._fileno = -1
# This is declared as async for the same reason as close()
async def shutdown(self, how):
if self._socket:
self._socket.shutdown(how)
async def __aenter__(self):
self._socket.__enter__()
return self
async def __aexit__(self, *args):
if self._socket:
self._socket.__exit__(*args)
def __enter__(self):
return thread.AWAIT(self.__aenter__())
def __exit__(self, *args):
return thread.AWAIT(self.__aexit__(*args))
MAX_READ = 65536
class StreamBase(object):
'''
Base class for file-like objects.
'''
def __init__(self, fileobj):
self._file = fileobj
self._fileno = _Fd(fileobj.fileno())
self._buffer = bytearray()
def __repr__(self):
return f'<curio.{type(self).__name__} {self._file!r}>'
def fileno(self):
return int(self._fileno)
# ---- Methods that must be implemented in child classes
async def _read(self, maxbytes=-1): # pragma: no cover
raise NotImplementedError()
async def write(self, data): # pragma: no cover
raise NotImplementedError()
# ---- General I/O methods for streams
async def read(self, maxbytes=-1):
buf = self._buffer
if buf:
if maxbytes < 0 or len(buf) <= maxbytes:
data = bytes(buf)
buf.clear()
else:
data = bytes(buf[:maxbytes])
del buf[:maxbytes]
else:
data = await self._read(maxbytes)
return data
async def readall(self):
chunks = []
maxread = 65536
if self._buffer:
chunks.append(bytes(self._buffer))
self._buffer.clear()
while True:
try:
chunk = await self.read(maxread)
except errors.CancelledError as e:
e.bytes_read = b''.join(chunks)
raise
if not chunk:
return b''.join(chunks)
chunks.append(chunk)
if len(chunk) == maxread:
maxread *= 2
async def read_exactly(self, nbytes):
chunks = []
while nbytes > 0:
try:
chunk = await self.read(nbytes)
except errors.CancelledError as e:
e.bytes_read = b''.join(chunks)
raise
if not chunk:
e = EOFError('Unexpected end of data')
e.bytes_read = b''.join(chunks)
raise e
chunks.append(chunk)
nbytes -= len(chunk)
return b''.join(chunks)
async def readinto(self, memory):
with memoryview(memory).cast('B') as view:
remaining = len(view)
total_read = 0
# It's possible that there is data already buffered on this stream.
# If so, we have to copy into the memory buffer first.
buffered = len(self._buffer)
tocopy = remaining if (remaining < buffered) else buffered
if tocopy:
view[:tocopy] = self._buffer[:tocopy]
del self._buffer[:tocopy]
remaining -= tocopy
total_read += tocopy
# To emulate behavior of synchronous readinto(), we read all available
# bytes up to the buffer size.
while remaining > 0:
try:
nrecv = self._readinto_impl(view[total_read:total_read+remaining])
# On proper file objects, None might be returned to indicate blocking
if nrecv is None:
await _read_wait(self._fileno)
elif nrecv == 0:
break
else:
total_read += nrecv
remaining -= nrecv
except WantRead:
await _read_wait(self._fileno)
except WantWrite:
await _write_wait(self._fileno)
return total_read
async def readline(self, maxlen=None):
while True:
nl_index = self._buffer.find(b'\n')
if nl_index >= 0:
resp = bytes(self._buffer[:nl_index + 1])
del self._buffer[:nl_index + 1]
return resp
data = await self._read(MAX_READ)
if data == b'':
resp = bytes(self._buffer)
self._buffer.clear()
return resp
self._buffer.extend(data)
async def readlines(self):
lines = []
try:
async for line in self:
lines.append(line)
return lines
except errors.CancelledError as e:
e.lines_read = lines
raise
async def writelines(self, lines):
nwritten = 0
for line in lines:
try:
await self.write(line)
nwritten += len(line)
except errors.CancelledError as e:
e.bytes_written += nwritten
raise
async def flush(self):
pass
# Why async close()? If the underlying file is buffered, the contents need
# to be flushed first--a process that might cause a BlockingIOError. In
# that case, we have to suspend briefly until the buffers free up space.
async def close(self):
await self.flush()
if self._file:
self._file.close()
self._file = None
self._fileno = -1
def __aiter__(self):
return self
async def __anext__(self):
line = await self.readline()
if line:
return line
else:
raise StopAsyncIteration
async def __aenter__(self):
return self
async def __aexit__(self, *args):
await self.close()
def __iter__(self):
return thread.AWAIT(self.__aiter__())
def __next__(self):
try:
return thread.AWAIT(self.__anext__())
except StopAsyncIteration:
raise StopIteration
def __enter__(self):
return thread.AWAIT(self.__aenter__())
def __exit__(self, *args):
return thread.AWAIT(self.__exit__(*args))
class FileStream(StreamBase):
'''
Wrapper around a file-like object. File is put into non-blocking mode.
The underlying file must be in binary mode.
'''
def __init__(self, fileobj):
assert not isinstance(fileobj, io.TextIOBase), 'Only binary mode files allowed'
super().__init__(fileobj)
os.set_blocking(int(self._fileno), False)
# Common bound methods
self._file_read = fileobj.read
self._readinto_impl = getattr(fileobj, 'readinto', None)
self._file_write = fileobj.write
@contextmanager
def blocking(self):
'''
Allow temporary access to the underlying file in blocking mode
'''
if self._buffer:
raise IOError('There is unread buffered data.')
try:
os.set_blocking(int(self._fileno), True)
yield self._file
finally:
os.set_blocking(int(self._fileno), False)
async def _read(self, maxbytes=-1):
while True:
# In non-blocking mode, a file-like object might return None if no data is
# available. Alternatively, we'll catch the usual blocking exceptions just to be safe
try:
data = self._file_read(maxbytes)
if data is None:
await _read_wait(self._fileno)
else:
return data
except WantRead:
await _read_wait(self._fileno)
except WantWrite: # pragma: no cover
await _write_wait(self._fileno)
async def write(self, data):
nwritten = 0
view = memoryview(data).cast('B')
try:
while view:
try:
nbytes = self._file_write(view)
if nbytes is None:
raise BlockingIOError()
nwritten += nbytes
view = view[nbytes:]
except WantWrite as e:
if hasattr(e, 'characters_written'):
nwritten += e.characters_written
view = view[e.characters_written:]
await _write_wait(self._fileno)
except WantRead: # pragma: no cover
await _read_wait(self._fileno)
return nwritten
except errors.CancelledError as e:
e.bytes_written = nwritten
raise
async def flush(self):
if not self._file:
return
while True:
try:
return self._file.flush()
except WantWrite:
await _write_wait(self._fileno)
except WantRead:
await _read_wait(self._fileno)
class SocketStream(StreamBase):
'''
Stream wrapper for a socket.
'''
def __init__(self, sock):
super().__init__(sock)
sock.setblocking(False)
# Common bound methods
self._socket_recv = sock.recv
self._readinto_impl = sock.recv_into
self._socket_send = sock.send
@contextmanager
def blocking(self):
'''
Allow temporary access to the underlying file in blocking mode
'''
if self._buffer:
raise IOError('There is unread buffered data.')
try:
self._file.setblocking(True)
yield open(int(self._fileno), 'rb+', buffering=0, closefd=False)
finally:
self._file.setblocking(False)
async def _read(self, maxbytes=-1):
while True:
try:
data = self._socket_recv(maxbytes if maxbytes > 0 else MAX_READ)
return data
except WantRead:
await _read_wait(self._fileno)
except WantWrite: # pragma: no cover
await _write_wait(self._fileno)
async def write(self, data):
nwritten = 0
view = memoryview(data).cast('B')
try:
while view:
try:
nbytes = self._socket_send(view)
nwritten += nbytes
view = view[nbytes:]
except WantWrite:
await _write_wait(self._fileno)
except WantRead: # pragma: no cover
await _read_wait(self._fileno)
return nwritten
except errors.CancelledError as e:
e.bytes_written = nwritten
raise
# Wherein the structure of space-time folds in upon itself and ties
# itself into a fractal threaded knot, code beyond this point abides.
#
# These classes are for performing I/O within Async Threads.
# Currently undocumented and experimental. Use at your own risk.
class SyncSocket(object):
def __init__(self, sock):
self._socket = sock
self._socket.setblocking(False)
self._fileno = _Fd(sock.fileno())
# Commonly used bound methods
self._socket_send = sock.send
self._socket_recv = sock.recv
def __repr__(self):
return f'<curio.SyncSocket {self._socket!r}>'
def __getattr__(self, name):
return getattr(self._socket, name)
def fileno(self):
return int(self._fileno)
def settimeout(self, seconds):
if seconds:
raise RuntimeError('Use timeout_after() to set a timeout')
def gettimeout(self):
return None
def dup(self):
return type(self)(self._socket.dup())
def makefile(self, mode, buffering=0, *, encoding=None, errors=None, newline=None):
if 'b' not in mode:
raise RuntimeError('File can only be created in binary mode')
f = self._socket.makefile(mode, buffering=buffering)
return SyncFileStream(f)
def as_stream(self):
return SyncSocketStream(self._socket)
def recv(self, maxsize, flags=0):
while True:
try:
return self._socket_recv(maxsize, flags)
except WantRead:
thread.AWAIT(_read_wait, self._fileno)
except WantWrite:
thread.AWAIT(_write_wait, self._fileno)
def recv_into(self, buffer, nbytes=0, flags=0):
while True:
try:
return self._socket.recv_into(buffer, nbytes, flags)
except WantRead:
thread.AWAIT(_read_wait, self._fileno)
except WantWrite:
thread.AWAIT(_write_wait, self._fileno)
def send(self, data, flags=0):
while True:
try:
return self._socket_send(data, flags)
except WantWrite:
thread.AWAIT(_write_wait, self._fileno)
except WantRead:
thread.AWAIT(_read_wait, self._fileno)
def sendall(self, data, flags=0):
with memoryview(data).cast('B') as buffer:
total_sent = 0
try:
while buffer:
try:
nsent = self._socket_send(buffer, flags)
total_sent += nsent
buffer = buffer[nsent:]
except WantWrite:
thread.AWAIT(_write_wait, self._fileno)
except WantRead:
thread.AWAIT(_read_wait, self._fileno)
except errors.CancelledError as e:
e.bytes_sent = total_sent
raise
def accept(self):
while True:
try:
client, addr = self._socket.accept()
return type(self)(client), addr
except WantRead:
thread.AWAIT(_read_wait, self._fileno)
def connect_ex(self, address):
try:
self.connect(address)
return 0
except OSError as e:
return e.errno
def connect(self, address):
try:
result = self._socket.connect(address)
if getattr(self, 'do_handshake_on_connect', False):
self.do_handshake()
return result
except WantWrite:
thread.AWAIT(_write_wait, self._fileno)
err = self._socket.getsockopt(SOL_SOCKET, SO_ERROR)
if err != 0:
raise OSError(err, f'Connect call failed {address}')
if getattr(self, 'do_handshake_on_connect', False):
self.do_handshake()
def recvfrom(self, buffersize, flags=0):
while True:
try:
return self._socket.recvfrom(buffersize, flags)
except WantRead:
thread.AWAIT(_read_wait, self._fileno)
except WantWrite:
thread.AWAIT(_write_wait, self._fileno)
def recvfrom_into(self, buffer, bytes=0, flags=0):
while True:
try:
return self._socket.recvfrom_into(buffer, bytes, flags)
except WantRead:
thread.AWAIT(_read_wait, self._fileno)
except WantWrite:
thread.AWAIT(_write_wait, self._fileno)
def sendto(self, bytes, flags_or_address, address=None):
if address:
flags = flags_or_address
else:
address = flags_or_address
flags = 0
while True:
try:
return self._socket.sendto(bytes, flags, address)
except WantWrite:
thread.AWAIT(_write_wait, self._fileno)
except WantRead:
thread.AWAIT(_read_wait, self._fileno)
def recvmsg(self, bufsize, ancbufsize=0, flags=0):
while True:
try:
return self._socket.recvmsg(bufsize, ancbufsize, flags)
except WantRead:
thread.AWAIT(_read_wait, self._fileno)
def recvmsg_into(self, buffers, ancbufsize=0, flags=0):
while True:
try:
return self._socket.recvmsg_into(buffers, ancbufsize, flags)
except WantRead:
thread.AWAIT(_read_wait, self._fileno)
def sendmsg(self, buffers, ancdata=(), flags=0, address=None):
while True:
try:
return self._socket.sendmsg(buffers, ancdata, flags, address)
except WantRead:
thread.AWAIT(_write_wait, self._fileno)
# Special functions for SSL
def do_handshake(self):
while True:
try:
return self._socket.do_handshake()
except WantRead:
thread.AWAIT(_read_wait, self._fileno)
except WantWrite:
thread.AWAIT(_write_wait, self._fileno)
def close(self):
if self._socket:
self._socket.close()
self._socket = None
self._fileno = -1
def shutdown(self, how):
if self._socket:
self._socket.shutdown(how)
class SyncStreamBase(object):
def __init__(self, fileobj):
self._file = fileobj
self._fileno = _Fd(fileobj.fileno())
self._buffer = bytearray()
def __repr__(self):
return f'<curio.{type(self).__name__} {self._file!r}>'
def fileno(self):
return int(self._fileno)
# ---- Methods that must be implemented in child classes
def _read(self, maxbytes=-1):
raise NotImplementedError()
def write(self, data):
raise NotImplementedError()
# ---- General I/O methods for streams
def read(self, maxbytes=-1):
buf = self._buffer
if buf:
if maxbytes < 0 or len(buf) <= maxbytes:
data = bytes(buf)
buf.clear()
else:
data = bytes(buf[:maxbytes])
del buf[:maxbytes]
else:
data = self._read(maxbytes)
return data
def readall(self):
chunks = []
maxread = 65536
if self._buffer:
chunks.append(bytes(self._buffer))
self._buffer.clear()
while True:
try:
chunk = self.read(maxread)
except errors.CancelledError as e:
e.bytes_read = b''.join(chunks)
raise
if not chunk:
return b''.join(chunks)
chunks.append(chunk)
if len(chunk) == maxread:
maxread *= 2
def read_exactly(self, nbytes):
chunks = []
while nbytes > 0:
try:
chunk = self.read(nbytes)
except errors.CancelledError as e:
e.bytes_read = b''.join(chunks)
raise
if not chunk:
e = EOFError('Unexpected end of data')
e.bytes_read = b''.join(chunks)
raise e
chunks.append(chunk)
nbytes -= len(chunk)
return b''.join(chunks)
def readinto(self, memory):
with memoryview(memory).cast('B') as view:
remaining = len(view)
total_read = 0
# It's possible that there is data already buffered on this stream.
# If so, we have to copy into the memory buffer first.
buffered = len(self._buffer)
tocopy = remaining if (remaining < buffered) else buffered
if tocopy:
view[:tocopy] = self._buffer[:tocopy]
del self._buffer[:tocopy]
remaining -= tocopy
total_read += tocopy
# To emulate behavior of synchronous readinto(), we read all available
# bytes up to the buffer size.
while remaining > 0:
try:
nrecv = self._readinto_impl(view[total_read:total_read+remaining])
# On proper file objects, None might be returned to indicate blocking
if nrecv is None:
thread.AWAIT(_read_wait, self._fileno)
elif nrecv == 0:
break
else:
total_read += nrecv
remaining -= nrecv
except WantRead:
thread.AWAIT(_read_wait, self._fileno)
except WantWrite:
thread.AWAIT(_write_wait, self._fileno)
return total_read
def readline(self, maxlen=None):
while True:
nl_index = self._buffer.find(b'\n')
if nl_index >= 0:
resp = bytes(self._buffer[:nl_index + 1])
del self._buffer[:nl_index + 1]
return resp
data = self._read(MAX_READ)
if data == b'':
resp = bytes(self._buffer)
self._buffer.clear()
return resp
self._buffer.extend(data)
def readlines(self):
lines = []
try:
for line in self:
lines.append(line)
return lines
except errors.CancelledError as e:
e.lines_read = lines
raise
def writelines(self, lines):
nwritten = 0
for line in lines:
try:
self.write(line)
nwritten += len(line)
except errors.CancelledError as e:
e.bytes_written += nwritten
raise
def flush(self):
pass
def close(self):
self.flush()
if self._file:
self._file.close()
self._file = None
self._fileno = -1
def __iter__(self):
return self
def __next__(self):
line = self.readline()
if line:
return line
else:
raise StopIteration
def __enter__(self):
return self
def __exit__(self, *args):
return self.close()
class SyncFileStream(SyncStreamBase):
def __init__(self, fileobj):
assert not isinstance(fileobj, io.TextIOBase), 'Only binary mode files allowed'
super().__init__(fileobj)
os.set_blocking(int(self._fileno), False)
# Common bound methods
self._file_read = fileobj.read
self._readinto_impl = getattr(fileobj, 'readinto', None)