352 lines
11 KiB
Python
352 lines
11 KiB
Python
# -*- coding: utf-8 -*-
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r"""
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werkzeug.contrib.iterio
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~~~~~~~~~~~~~~~~~~~~~~~
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This module implements a :class:`IterIO` that converts an iterator into
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a stream object and the other way round. Converting streams into
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iterators requires the `greenlet`_ module.
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To convert an iterator into a stream all you have to do is to pass it
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directly to the :class:`IterIO` constructor. In this example we pass it
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a newly created generator::
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def foo():
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yield "something\n"
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yield "otherthings"
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stream = IterIO(foo())
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print stream.read() # read the whole iterator
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The other way round works a bit different because we have to ensure that
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the code execution doesn't take place yet. An :class:`IterIO` call with a
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callable as first argument does two things. The function itself is passed
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an :class:`IterIO` stream it can feed. The object returned by the
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:class:`IterIO` constructor on the other hand is not an stream object but
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an iterator::
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def foo(stream):
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stream.write("some")
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stream.write("thing")
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stream.flush()
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stream.write("otherthing")
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iterator = IterIO(foo)
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print iterator.next() # prints something
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print iterator.next() # prints otherthing
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iterator.next() # raises StopIteration
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.. _greenlet: https://github.com/python-greenlet/greenlet
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:copyright: (c) 2014 by the Werkzeug Team, see AUTHORS for more details.
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:license: BSD, see LICENSE for more details.
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"""
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try:
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import greenlet
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except ImportError:
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greenlet = None
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from werkzeug._compat import implements_iterator
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def _mixed_join(iterable, sentinel):
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"""concatenate any string type in an intelligent way."""
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iterator = iter(iterable)
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first_item = next(iterator, sentinel)
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if isinstance(first_item, bytes):
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return first_item + b''.join(iterator)
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return first_item + u''.join(iterator)
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def _newline(reference_string):
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if isinstance(reference_string, bytes):
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return b'\n'
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return u'\n'
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@implements_iterator
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class IterIO(object):
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"""Instances of this object implement an interface compatible with the
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standard Python :class:`file` object. Streams are either read-only or
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write-only depending on how the object is created.
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If the first argument is an iterable a file like object is returned that
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returns the contents of the iterable. In case the iterable is empty
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read operations will return the sentinel value.
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If the first argument is a callable then the stream object will be
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created and passed to that function. The caller itself however will
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not receive a stream but an iterable. The function will be be executed
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step by step as something iterates over the returned iterable. Each
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call to :meth:`flush` will create an item for the iterable. If
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:meth:`flush` is called without any writes in-between the sentinel
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value will be yielded.
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Note for Python 3: due to the incompatible interface of bytes and
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streams you should set the sentinel value explicitly to an empty
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bytestring (``b''``) if you are expecting to deal with bytes as
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otherwise the end of the stream is marked with the wrong sentinel
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value.
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.. versionadded:: 0.9
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`sentinel` parameter was added.
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"""
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def __new__(cls, obj, sentinel=''):
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try:
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iterator = iter(obj)
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except TypeError:
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return IterI(obj, sentinel)
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return IterO(iterator, sentinel)
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def __iter__(self):
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return self
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def tell(self):
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if self.closed:
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raise ValueError('I/O operation on closed file')
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return self.pos
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def isatty(self):
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if self.closed:
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raise ValueError('I/O operation on closed file')
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return False
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def seek(self, pos, mode=0):
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if self.closed:
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raise ValueError('I/O operation on closed file')
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raise IOError(9, 'Bad file descriptor')
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def truncate(self, size=None):
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if self.closed:
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raise ValueError('I/O operation on closed file')
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raise IOError(9, 'Bad file descriptor')
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def write(self, s):
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if self.closed:
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raise ValueError('I/O operation on closed file')
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raise IOError(9, 'Bad file descriptor')
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def writelines(self, list):
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if self.closed:
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raise ValueError('I/O operation on closed file')
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raise IOError(9, 'Bad file descriptor')
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def read(self, n=-1):
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if self.closed:
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raise ValueError('I/O operation on closed file')
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raise IOError(9, 'Bad file descriptor')
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def readlines(self, sizehint=0):
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if self.closed:
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raise ValueError('I/O operation on closed file')
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raise IOError(9, 'Bad file descriptor')
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def readline(self, length=None):
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if self.closed:
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raise ValueError('I/O operation on closed file')
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raise IOError(9, 'Bad file descriptor')
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def flush(self):
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if self.closed:
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raise ValueError('I/O operation on closed file')
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raise IOError(9, 'Bad file descriptor')
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def __next__(self):
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if self.closed:
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raise StopIteration()
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line = self.readline()
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if not line:
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raise StopIteration()
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return line
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class IterI(IterIO):
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"""Convert an stream into an iterator."""
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def __new__(cls, func, sentinel=''):
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if greenlet is None:
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raise RuntimeError('IterI requires greenlet support')
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stream = object.__new__(cls)
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stream._parent = greenlet.getcurrent()
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stream._buffer = []
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stream.closed = False
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stream.sentinel = sentinel
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stream.pos = 0
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def run():
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func(stream)
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stream.close()
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g = greenlet.greenlet(run, stream._parent)
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while 1:
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rv = g.switch()
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if not rv:
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return
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yield rv[0]
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def close(self):
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if not self.closed:
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self.closed = True
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self._flush_impl()
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def write(self, s):
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if self.closed:
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raise ValueError('I/O operation on closed file')
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if s:
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self.pos += len(s)
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self._buffer.append(s)
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def writelines(self, list):
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for item in list:
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self.write(item)
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def flush(self):
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if self.closed:
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raise ValueError('I/O operation on closed file')
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self._flush_impl()
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def _flush_impl(self):
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data = _mixed_join(self._buffer, self.sentinel)
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self._buffer = []
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if not data and self.closed:
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self._parent.switch()
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else:
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self._parent.switch((data,))
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class IterO(IterIO):
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"""Iter output. Wrap an iterator and give it a stream like interface."""
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def __new__(cls, gen, sentinel=''):
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self = object.__new__(cls)
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self._gen = gen
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self._buf = None
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self.sentinel = sentinel
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self.closed = False
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self.pos = 0
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return self
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def __iter__(self):
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return self
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def _buf_append(self, string):
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'''Replace string directly without appending to an empty string,
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avoiding type issues.'''
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if not self._buf:
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self._buf = string
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else:
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self._buf += string
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def close(self):
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if not self.closed:
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self.closed = True
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if hasattr(self._gen, 'close'):
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self._gen.close()
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def seek(self, pos, mode=0):
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if self.closed:
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raise ValueError('I/O operation on closed file')
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if mode == 1:
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pos += self.pos
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elif mode == 2:
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self.read()
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self.pos = min(self.pos, self.pos + pos)
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return
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elif mode != 0:
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raise IOError('Invalid argument')
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buf = []
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try:
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tmp_end_pos = len(self._buf)
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while pos > tmp_end_pos:
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item = next(self._gen)
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tmp_end_pos += len(item)
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buf.append(item)
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except StopIteration:
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pass
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if buf:
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self._buf_append(_mixed_join(buf, self.sentinel))
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self.pos = max(0, pos)
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def read(self, n=-1):
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if self.closed:
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raise ValueError('I/O operation on closed file')
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if n < 0:
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self._buf_append(_mixed_join(self._gen, self.sentinel))
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result = self._buf[self.pos:]
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self.pos += len(result)
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return result
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new_pos = self.pos + n
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buf = []
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try:
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tmp_end_pos = 0 if self._buf is None else len(self._buf)
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while new_pos > tmp_end_pos or (self._buf is None and not buf):
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item = next(self._gen)
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tmp_end_pos += len(item)
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buf.append(item)
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except StopIteration:
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pass
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if buf:
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self._buf_append(_mixed_join(buf, self.sentinel))
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if self._buf is None:
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return self.sentinel
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new_pos = max(0, new_pos)
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try:
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return self._buf[self.pos:new_pos]
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finally:
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self.pos = min(new_pos, len(self._buf))
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def readline(self, length=None):
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if self.closed:
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raise ValueError('I/O operation on closed file')
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nl_pos = -1
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if self._buf:
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nl_pos = self._buf.find(_newline(self._buf), self.pos)
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buf = []
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try:
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if self._buf is None:
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pos = self.pos
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else:
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pos = len(self._buf)
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while nl_pos < 0:
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item = next(self._gen)
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local_pos = item.find(_newline(item))
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buf.append(item)
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if local_pos >= 0:
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nl_pos = pos + local_pos
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break
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pos += len(item)
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except StopIteration:
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pass
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if buf:
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self._buf_append(_mixed_join(buf, self.sentinel))
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if self._buf is None:
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return self.sentinel
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if nl_pos < 0:
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new_pos = len(self._buf)
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else:
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new_pos = nl_pos + 1
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if length is not None and self.pos + length < new_pos:
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new_pos = self.pos + length
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try:
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return self._buf[self.pos:new_pos]
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finally:
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self.pos = min(new_pos, len(self._buf))
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def readlines(self, sizehint=0):
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total = 0
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lines = []
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line = self.readline()
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while line:
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lines.append(line)
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total += len(line)
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if 0 < sizehint <= total:
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break
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line = self.readline()
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return lines
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