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James Taylor
285
python/gevent/_fileobjectposix.py
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285
python/gevent/_fileobjectposix.py
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from __future__ import absolute_import
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import os
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import io
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from io import BufferedReader
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from io import BufferedWriter
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from io import BytesIO
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from io import DEFAULT_BUFFER_SIZE
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from io import RawIOBase
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from io import UnsupportedOperation
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from gevent._fileobjectcommon import cancel_wait_ex
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from gevent._fileobjectcommon import FileObjectBase
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from gevent.hub import get_hub
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from gevent.os import _read
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from gevent.os import _write
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from gevent.os import ignored_errors
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from gevent.os import make_nonblocking
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class GreenFileDescriptorIO(RawIOBase):
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# Note that RawIOBase has a __del__ method that calls
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# self.close(). (In C implementations like CPython, this is
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# the type's tp_dealloc slot; prior to Python 3, the object doesn't
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# appear to have a __del__ method, even though it functionally does)
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_read_event = None
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_write_event = None
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def __init__(self, fileno, mode='r', closefd=True):
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RawIOBase.__init__(self) # Python 2: pylint:disable=no-member,non-parent-init-called
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self._closed = False
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self._closefd = closefd
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self._fileno = fileno
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make_nonblocking(fileno)
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self._readable = 'r' in mode
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self._writable = 'w' in mode
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self.hub = get_hub()
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io_watcher = self.hub.loop.io
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if self._readable:
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self._read_event = io_watcher(fileno, 1)
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if self._writable:
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self._write_event = io_watcher(fileno, 2)
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self._seekable = None
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def readable(self):
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return self._readable
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def writable(self):
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return self._writable
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def seekable(self):
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if self._seekable is None:
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try:
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os.lseek(self._fileno, 0, os.SEEK_CUR)
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except OSError:
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self._seekable = False
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else:
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self._seekable = True
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return self._seekable
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def fileno(self):
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return self._fileno
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@property
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def closed(self):
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return self._closed
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def close(self):
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if self._closed:
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return
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self.flush()
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self._closed = True
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if self._readable:
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self.hub.cancel_wait(self._read_event, cancel_wait_ex)
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if self._writable:
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self.hub.cancel_wait(self._write_event, cancel_wait_ex)
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fileno = self._fileno
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if self._closefd:
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self._fileno = None
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os.close(fileno)
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# RawIOBase provides a 'read' method that will call readall() if
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# the `size` was missing or -1 and otherwise call readinto(). We
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# want to take advantage of this to avoid single byte reads when
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# possible. This is highlighted by a bug in BufferedIOReader that
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# calls read() in a loop when its readall() method is invoked;
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# this was fixed in Python 3.3. See
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# https://github.com/gevent/gevent/issues/675)
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def __read(self, n):
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if not self._readable:
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raise UnsupportedOperation('read')
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while True:
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try:
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return _read(self._fileno, n)
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except (IOError, OSError) as ex:
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if ex.args[0] not in ignored_errors:
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raise
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self.hub.wait(self._read_event)
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def readall(self):
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ret = BytesIO()
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while True:
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data = self.__read(DEFAULT_BUFFER_SIZE)
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if not data:
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break
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ret.write(data)
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return ret.getvalue()
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def readinto(self, b):
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data = self.__read(len(b))
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n = len(data)
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try:
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b[:n] = data
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except TypeError as err:
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import array
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if not isinstance(b, array.array):
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raise err
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b[:n] = array.array(b'b', data)
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return n
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def write(self, b):
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if not self._writable:
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raise UnsupportedOperation('write')
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while True:
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try:
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return _write(self._fileno, b)
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except (IOError, OSError) as ex:
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if ex.args[0] not in ignored_errors:
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raise
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self.hub.wait(self._write_event)
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def seek(self, offset, whence=0):
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return os.lseek(self._fileno, offset, whence)
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class FlushingBufferedWriter(BufferedWriter):
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def write(self, b):
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ret = BufferedWriter.write(self, b)
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self.flush()
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return ret
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class FileObjectPosix(FileObjectBase):
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"""
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A file-like object that operates on non-blocking files but
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provides a synchronous, cooperative interface.
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.. caution::
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This object is only effective wrapping files that can be used meaningfully
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with :func:`select.select` such as sockets and pipes.
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In general, on most platforms, operations on regular files
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(e.g., ``open('a_file.txt')``) are considered non-blocking
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already, even though they can take some time to complete as
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data is copied to the kernel and flushed to disk: this time
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is relatively bounded compared to sockets or pipes, though.
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A :func:`~os.read` or :func:`~os.write` call on such a file
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will still effectively block for some small period of time.
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Therefore, wrapping this class around a regular file is
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unlikely to make IO gevent-friendly: reading or writing large
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amounts of data could still block the event loop.
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If you'll be working with regular files and doing IO in large
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chunks, you may consider using
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:class:`~gevent.fileobject.FileObjectThread` or
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:func:`~gevent.os.tp_read` and :func:`~gevent.os.tp_write` to bypass this
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concern.
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.. note::
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Random read/write (e.g., ``mode='rwb'``) is not supported.
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For that, use :class:`io.BufferedRWPair` around two instance of this
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class.
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.. tip::
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Although this object provides a :meth:`fileno` method and so
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can itself be passed to :func:`fcntl.fcntl`, setting the
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:data:`os.O_NONBLOCK` flag will have no effect (reads will
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still block the greenlet, although other greenlets can run).
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However, removing that flag *will cause this object to no
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longer be cooperative* (other greenlets will no longer run).
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You can use the internal ``fileio`` attribute of this object
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(a :class:`io.RawIOBase`) to perform non-blocking byte reads.
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Note, however, that once you begin directly using this
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attribute, the results from using methods of *this* object
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are undefined, especially in text mode. (See :issue:`222`.)
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.. versionchanged:: 1.1
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Now uses the :mod:`io` package internally. Under Python 2, previously
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used the undocumented class :class:`socket._fileobject`. This provides
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better file-like semantics (and portability to Python 3).
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.. versionchanged:: 1.2a1
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Document the ``fileio`` attribute for non-blocking reads.
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"""
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#: platform specific default for the *bufsize* parameter
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default_bufsize = io.DEFAULT_BUFFER_SIZE
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def __init__(self, fobj, mode='rb', bufsize=-1, close=True):
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"""
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:param fobj: Either an integer fileno, or an object supporting the
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usual :meth:`socket.fileno` method. The file *will* be
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put in non-blocking mode using :func:`gevent.os.make_nonblocking`.
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:keyword str mode: The manner of access to the file, one of "rb", "rU" or "wb"
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(where the "b" or "U" can be omitted).
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If "U" is part of the mode, IO will be done on text, otherwise bytes.
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:keyword int bufsize: If given, the size of the buffer to use. The default
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value means to use a platform-specific default
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Other values are interpreted as for the :mod:`io` package.
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Buffering is ignored in text mode.
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.. versionchanged:: 1.2a1
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A bufsize of 0 in write mode is no longer forced to be 1.
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Instead, the underlying buffer is flushed after every write
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operation to simulate a bufsize of 0. In gevent 1.0, a
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bufsize of 0 was flushed when a newline was written, while
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in gevent 1.1 it was flushed when more than one byte was
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written. Note that this may have performance impacts.
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"""
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if isinstance(fobj, int):
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fileno = fobj
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fobj = None
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else:
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fileno = fobj.fileno()
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if not isinstance(fileno, int):
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raise TypeError('fileno must be int: %r' % fileno)
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orig_mode = mode
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mode = (mode or 'rb').replace('b', '')
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if 'U' in mode:
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self._translate = True
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mode = mode.replace('U', '')
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else:
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self._translate = False
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if len(mode) != 1 and mode not in 'rw': # pragma: no cover
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# Python 3 builtin `open` raises a ValueError for invalid modes;
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# Python 2 ignores it. In the past, we raised an AssertionError, if __debug__ was
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# enabled (which it usually was). Match Python 3 because it makes more sense
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# and because __debug__ may not be enabled.
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# NOTE: This is preventing a mode like 'rwb' for binary random access;
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# that code was never tested and was explicitly marked as "not used"
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raise ValueError('mode can only be [rb, rU, wb], not %r' % (orig_mode,))
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self._fobj = fobj
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# This attribute is documented as available for non-blocking reads.
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self.fileio = GreenFileDescriptorIO(fileno, mode, closefd=close)
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self._orig_bufsize = bufsize
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if bufsize < 0 or bufsize == 1:
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bufsize = self.default_bufsize
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elif bufsize == 0:
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bufsize = 1
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if mode == 'r':
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IOFamily = BufferedReader
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else:
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assert mode == 'w'
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IOFamily = BufferedWriter
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if self._orig_bufsize == 0:
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# We could also simply pass self.fileio as *io*, but this way
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# we at least consistently expose a BufferedWriter in our *io*
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# attribute.
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IOFamily = FlushingBufferedWriter
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super(FileObjectPosix, self).__init__(IOFamily(self.fileio, bufsize), close)
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def _do_close(self, fobj, closefd):
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try:
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fobj.close()
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# self.fileio already knows whether or not to close the
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# file descriptor
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self.fileio.close()
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finally:
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self._fobj = None
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self.fileio = None
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def __iter__(self):
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return self._io
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