"""

The io module provides the Python interfaces to stream handling. The

builtin open function is defined in this module.



At the top of the I/O hierarchy is the abstract base class IOBase. It

defines the basic interface to a stream. Note, however, that there is no

separation between reading and writing to streams; implementations are

allowed to throw an IOError if they do not support a given operation.



Extending IOBase is RawIOBase which deals simply with the reading and

writing of raw bytes to a stream. FileIO subclasses RawIOBase to provide

an interface to OS files.



BufferedIOBase deals with buffering on a raw byte stream (RawIOBase). Its

subclasses, BufferedWriter, BufferedReader, and BufferedRWPair buffer

streams that are readable, writable, and both respectively.

BufferedRandom provides a buffered interface to random access

streams. BytesIO is a simple stream of in-memory bytes.



Another IOBase subclass, TextIOBase, deals with the encoding and decoding

of streams into text. TextIOWrapper, which extends it, is a buffered text

interface to a buffered raw stream (`BufferedIOBase`). Finally, StringIO

is a in-memory stream for text.



Argument names are not part of the specification, and only the arguments

of open() are intended to be used as keyword arguments.



data:



DEFAULT_BUFFER_SIZE



   An int containing the default buffer size used by the module's buffered

   I/O classes. open() uses the file's blksize (as obtained by os.stat) if

   possible.

"""

# New I/O library conforming to PEP 3116.



# This is a prototype; hopefully eventually some of this will be

# reimplemented in C.



# XXX edge cases when switching between reading/writing

# XXX need to support 1 meaning line-buffered

# XXX whenever an argument is None, use the default value

# XXX read/write ops should check readable/writable

# XXX buffered readinto should work with arbitrary buffer objects

# XXX use incremental encoder for text output, at least for UTF-16 and UTF-8-SIG

# XXX check writable, readable and seekable in appropriate places

from __future__ import print_function

from __future__ import unicode_literals



__author__ = ("Guido van Rossum <guido@python.org>, "

              "Mike Verdone <mike.verdone@gmail.com>, "

              "Mark Russell <mark.russell@zen.co.uk>")



__all__ = ["BlockingIOError", "open", "IOBase", "RawIOBase", "FileIO",

           "BytesIO", "StringIO", "BufferedIOBase",

           "BufferedReader", "BufferedWriter", "BufferedRWPair",

           "BufferedRandom", "TextIOBase", "TextIOWrapper"]



import os

import abc

import codecs

import _fileio

import threading



# open() uses st_blksize whenever we can

DEFAULT_BUFFER_SIZE = 8 * 1024  # bytes



# py3k has only new style classes

__metaclass__ = type



class BlockingIOError(IOError):



    """Exception raised when I/O would block on a non-blocking I/O stream."""



    def __init__(self, errno, strerror, characters_written=0):

        IOError.__init__(self, errno, strerror)

        self.characters_written = characters_written





def open(file, mode="r", buffering=None, encoding=None, errors=None,

         newline=None, closefd=True):

    r"""Open file and return a stream. If the file cannot be opened, an IOError is

    raised.



    file is either a string giving the name (and the path if the file

    isn't in the current working directory) of the file to be opened or an

    integer file descriptor of the file to be wrapped. (If a file

    descriptor is given, it is closed when the returned I/O object is

    closed, unless closefd is set to False.)



    mode is an optional string that specifies the mode in which the file

    is opened. It defaults to 'r' which means open for reading in text

    mode.  Other common values are 'w' for writing (truncating the file if

    it already exists), and 'a' for appending (which on some Unix systems,

    means that all writes append to the end of the file regardless of the

    current seek position). In text mode, if encoding is not specified the

    encoding used is platform dependent. (For reading and writing raw

    bytes use binary mode and leave encoding unspecified.) The available

    modes are:



    ========= ===============================================================

    Character Meaning

    --------- ---------------------------------------------------------------

    'r'       open for reading (default)

    'w'       open for writing, truncating the file first

    'a'       open for writing, appending to the end of the file if it exists

    'b'       binary mode

    't'       text mode (default)

    '+'       open a disk file for updating (reading and writing)

    'U'       universal newline mode (for backwards compatibility; unneeded

              for new code)

    ========= ===============================================================



    The default mode is 'rt' (open for reading text). For binary random

    access, the mode 'w+b' opens and truncates the file to 0 bytes, while

    'r+b' opens the file without truncation.



    Python distinguishes between files opened in binary and text modes,

    even when the underlying operating system doesn't. Files opened in

    binary mode (appending 'b' to the mode argument) return contents as

    bytes objects without any decoding. In text mode (the default, or when

    't' is appended to the mode argument), the contents of the file are

    returned as strings, the bytes having been first decoded using a

    platform-dependent encoding or using the specified encoding if given.



    buffering is an optional integer used to set the buffering policy. By

    default full buffering is on. Pass 0 to switch buffering off (only

    allowed in binary mode), 1 to set line buffering, and an integer > 1

    for full buffering.



    encoding is the name of the encoding used to decode or encode the

    file. This should only be used in text mode. The default encoding is

    platform dependent, but any encoding supported by Python can be

    passed.  See the codecs module for the list of supported encodings.



    errors is an optional string that specifies how encoding errors are to

    be handled---this argument should not be used in binary mode. Pass

    'strict' to raise a ValueError exception if there is an encoding error

    (the default of None has the same effect), or pass 'ignore' to ignore

    errors. (Note that ignoring encoding errors can lead to data loss.)

    See the documentation for codecs.register for a list of the permitted

    encoding error strings.



    newline controls how universal newlines works (it only applies to text

    mode). It can be None, '', '\n', '\r', and '\r\n'.  It works as

    follows:



    * On input, if newline is None, universal newlines mode is

      enabled. Lines in the input can end in '\n', '\r', or '\r\n', and

      these are translated into '\n' before being returned to the

      caller. If it is '', universal newline mode is enabled, but line

      endings are returned to the caller untranslated. If it has any of

      the other legal values, input lines are only terminated by the given

      string, and the line ending is returned to the caller untranslated.



    * On output, if newline is None, any '\n' characters written are

      translated to the system default line separator, os.linesep. If

      newline is '', no translation takes place. If newline is any of the

      other legal values, any '\n' characters written are translated to

      the given string.



    If closefd is False, the underlying file descriptor will be kept open

    when the file is closed. This does not work when a file name is given

    and must be True in that case.



    open() returns a file object whose type depends on the mode, and

    through which the standard file operations such as reading and writing

    are performed. When open() is used to open a file in a text mode ('w',

    'r', 'wt', 'rt', etc.), it returns a TextIOWrapper. When used to open

    a file in a binary mode, the returned class varies: in read binary

    mode, it returns a BufferedReader; in write binary and append binary

    modes, it returns a BufferedWriter, and in read/write mode, it returns

    a BufferedRandom.



    It is also possible to use a string or bytearray as a file for both

    reading and writing. For strings StringIO can be used like a file

    opened in a text mode, and for bytes a BytesIO can be used like a file

    opened in a binary mode.

    """

    if not isinstance(file, (basestring, int)):

        raise TypeError("invalid file: %r" % file)

    if not isinstance(mode, basestring):

        raise TypeError("invalid mode: %r" % mode)

    if buffering is not None and not isinstance(buffering, int):

        raise TypeError("invalid buffering: %r" % buffering)

    if encoding is not None and not isinstance(encoding, basestring):

        raise TypeError("invalid encoding: %r" % encoding)

    if errors is not None and not isinstance(errors, basestring):

        raise TypeError("invalid errors: %r" % errors)

    modes = set(mode)

    if modes - set("arwb+tU") or len(mode) > len(modes):

        raise ValueError("invalid mode: %r" % mode)

    reading = "r" in modes

    writing = "w" in modes

    appending = "a" in modes

    updating = "+" in modes

    text = "t" in modes

    binary = "b" in modes

    if "U" in modes:

        if writing or appending:

            raise ValueError("can't use U and writing mode at once")

        reading = True

    if text and binary:

        raise ValueError("can't have text and binary mode at once")

    if reading + writing + appending > 1:

        raise ValueError("can't have read/write/append mode at once")

    if not (reading or writing or appending):

        raise ValueError("must have exactly one of read/write/append mode")

    if binary and encoding is not None:

        raise ValueError("binary mode doesn't take an encoding argument")

    if binary and errors is not None:

        raise ValueError("binary mode doesn't take an errors argument")

    if binary and newline is not None:

        raise ValueError("binary mode doesn't take a newline argument")

    raw = FileIO(file,

                 (reading and "r" or "") +

                 (writing and "w" or "") +

                 (appending and "a" or "") +

                 (updating and "+" or ""),

                 closefd)

    if buffering is None:

        buffering = -1

    line_buffering = False

    if buffering == 1 or buffering < 0 and raw.isatty():

        buffering = -1

        line_buffering = True

    if buffering < 0:

        buffering = DEFAULT_BUFFER_SIZE

        try:

            bs = os.fstat(raw.fileno()).st_blksize

        except (os.error, AttributeError):

            pass

        else:

            if bs > 1:

                buffering = bs

    if buffering < 0:

        raise ValueError("invalid buffering size")

    if buffering == 0:

        if binary:

            return raw

        raise ValueError("can't have unbuffered text I/O")

    if updating:

        buffer = BufferedRandom(raw, buffering)

    elif writing or appending:

        buffer = BufferedWriter(raw, buffering)

    elif reading:

        buffer = BufferedReader(raw, buffering)

    else:

        raise ValueError("unknown mode: %r" % mode)

    if binary:

        return buffer

    text = TextIOWrapper(buffer, encoding, errors, newline, line_buffering)

    text.mode = mode

    return text



class _DocDescriptor:

    """Helper for builtins.open.__doc__

    """

    def __get__(self, obj, typ):

        return (

            "open(file, mode='r', buffering=None, encoding=None, "

                 "errors=None, newline=None, closefd=True)\n\n" +

            open.__doc__)



class OpenWrapper:

    """Wrapper for builtins.open



    Trick so that open won't become a bound method when stored

    as a class variable (as dumbdbm does).



    See initstdio() in Python/pythonrun.c.

    """

    __doc__ = _DocDescriptor()



    def __new__(cls, *args, **kwargs):

        return open(*args, **kwargs)





class UnsupportedOperation(ValueError, IOError):

    pass





class IOBase(object):



    """The abstract base class for all I/O classes, acting on streams of

    bytes. There is no public constructor.



    This class provides dummy implementations for many methods that

    derived classes can override selectively; the default implementations

    represent a file that cannot be read, written or seeked.



    Even though IOBase does not declare read, readinto, or write because

    their signatures will vary, implementations and clients should

    consider those methods part of the interface. Also, implementations

    may raise a IOError when operations they do not support are called.



    The basic type used for binary data read from or written to a file is

    bytes. bytearrays are accepted too, and in some cases (such as

    readinto) needed. Text I/O classes work with str data.



    Note that calling any method (even inquiries) on a closed stream is

    undefined. Implementations may raise IOError in this case.



    IOBase (and its subclasses) support the iterator protocol, meaning

    that an IOBase object can be iterated over yielding the lines in a

    stream.



    IOBase also supports the :keyword:`with` statement. In this example,

    fp is closed after the suite of the with statment is complete:



    with open('spam.txt', 'r') as fp:

        fp.write('Spam and eggs!')

    """



    __metaclass__ = abc.ABCMeta



    ### Internal ###



    def _unsupported(self, name):

        """Internal: raise an exception for unsupported operations."""

        raise UnsupportedOperation("%s.%s() not supported" %

                                   (self.__class__.__name__, name))



    ### Positioning ###



    def seek(self, pos, whence = 0):

        """Change stream position.



        Change the stream position to byte offset offset. offset is

        interpreted relative to the position indicated by whence.  Values

        for whence are:



        * 0 -- start of stream (the default); offset should be zero or positive

        * 1 -- current stream position; offset may be negative

        * 2 -- end of stream; offset is usually negative



        Return the new absolute position.

        """

        self._unsupported("seek")



    def tell(self):

        """Return current stream position."""

        return self.seek(0, 1)



    def truncate(self, pos = None):

        """Truncate file to size bytes.



        Size defaults to the current IO position as reported by tell().  Return

        the new size.

        """

        self._unsupported("truncate")



    ### Flush and close ###



    def flush(self):

        """Flush write buffers, if applicable.



        This is not implemented for read-only and non-blocking streams.

        """

        # XXX Should this return the number of bytes written???



    __closed = False



    def close(self):

        """Flush and close the IO object.



        This method has no effect if the file is already closed.

        """

        if not self.__closed:

            try:

                self.flush()

            except IOError:

                pass  # If flush() fails, just give up

            self.__closed = True



    def __del__(self):

        """Destructor.  Calls close()."""

        # The try/except block is in case this is called at program

        # exit time, when it's possible that globals have already been

        # deleted, and then the close() call might fail.  Since

        # there's nothing we can do about such failures and they annoy

        # the end users, we suppress the traceback.

        try:

            self.close()

        except:

            pass



    ### Inquiries ###



    def seekable(self):

        """Return whether object supports random access.



        If False, seek(), tell() and truncate() will raise IOError.

        This method may need to do a test seek().

        """

        return False



    def _checkSeekable(self, msg=None):

        """Internal: raise an IOError if file is not seekable

        """

        if not self.seekable():

            raise IOError("File or stream is not seekable."

                          if msg is None else msg)





    def readable(self):

        """Return whether object was opened for reading.



        If False, read() will raise IOError.

        """

        return False



    def _checkReadable(self, msg=None):

        """Internal: raise an IOError if file is not readable

        """

        if not self.readable():

            raise IOError("File or stream is not readable."

                          if msg is None else msg)



    def writable(self):

        """Return whether object was opened for writing.



        If False, write() and truncate() will raise IOError.

        """

        return False



    def _checkWritable(self, msg=None):

        """Internal: raise an IOError if file is not writable

        """

        if not self.writable():

            raise IOError("File or stream is not writable."

                          if msg is None else msg)



    @property

    def closed(self):

        """closed: bool.  True iff the file has been closed.



        For backwards compatibility, this is a property, not a predicate.

        """

        return self.__closed



    def _checkClosed(self, msg=None):

        """Internal: raise an ValueError if file is closed

        """

        if self.closed:

            raise ValueError("I/O operation on closed file."

                             if msg is None else msg)



    ### Context manager ###



    def __enter__(self):

        """Context management protocol.  Returns self."""

        self._checkClosed()

        return self



    def __exit__(self, *args):

        """Context management protocol.  Calls close()"""

        self.close()



    ### Lower-level APIs ###



    # XXX Should these be present even if unimplemented?



    def fileno(self):

        """Returns underlying file descriptor if one exists.



        An IOError is raised if the IO object does not use a file descriptor.

        """

        self._unsupported("fileno")



    def isatty(self):

        """Return whether this is an 'interactive' stream.



        Return False if it can't be determined.

        """

        self._checkClosed()

        return False



    ### Readline[s] and writelines ###



    def readline(self, limit = -1):

        r"""Read and return a line from the stream.



        If limit is specified, at most limit bytes will be read.



        The line terminator is always b'\n' for binary files; for text

        files, the newlines argument to open can be used to select the line

        terminator(s) recognized.

        """

        self._checkClosed()

        if hasattr(self, "peek"):

            def nreadahead():

                readahead = self.peek(1)

                if not readahead:

                    return 1

                n = (readahead.find(b"\n") + 1) or len(readahead)

                if limit >= 0:

                    n = min(n, limit)

                return n

        else:

            def nreadahead():

                return 1

        if limit is None:

            limit = -1

        if not isinstance(limit, (int, long)):

            raise TypeError("limit must be an integer")

        res = bytearray()

        while limit < 0 or len(res) < limit:

            b = self.read(nreadahead())

            if not b:

                break

            res += b

            if res.endswith(b"\n"):

                break

        return bytes(res)



    def __iter__(self):

        self._checkClosed()

        return self



    def next(self):

        line = self.readline()

        if not line:

            raise StopIteration

        return line



    def readlines(self, hint=None):

        """Return a list of lines from the stream.



        hint can be specified to control the number of lines read: no more

        lines will be read if the total size (in bytes/characters) of all

        lines so far exceeds hint.

        """

        if hint is None:

            hint = -1

        if not isinstance(hint, (int, long)):

            raise TypeError("hint must be an integer")

        if hint <= 0:

            return list(self)

        n = 0

        lines = []

        for line in self:

            lines.append(line)

            n += len(line)

            if n >= hint:

                break

        return lines



    def writelines(self, lines):

        self._checkClosed()

        for line in lines:

            self.write(line)





class RawIOBase(IOBase):



    """Base class for raw binary I/O."""



    # The read() method is implemented by calling readinto(); derived

    # classes that want to support read() only need to implement

    # readinto() as a primitive operation.  In general, readinto() can be

    # more efficient than read().



    # (It would be tempting to also provide an implementation of

    # readinto() in terms of read(), in case the latter is a more suitable

    # primitive operation, but that would lead to nasty recursion in case

    # a subclass doesn't implement either.)



    def read(self, n = -1):

        """Read and return up to n bytes.



        Returns an empty bytes array on EOF, or None if the object is

        set not to block and has no data to read.

        """

        if n is None:

            n = -1

        if n < 0:

            return self.readall()

        b = bytearray(n.__index__())

        n = self.readinto(b)

        del b[n:]

        return bytes(b)



    def readall(self):

        """Read until EOF, using multiple read() call."""

        res = bytearray()

        while True:

            data = self.read(DEFAULT_BUFFER_SIZE)

            if not data:

                break

            res += data

        return bytes(res)



    def readinto(self, b):

        """Read up to len(b) bytes into b.



        Returns number of bytes read (0 for EOF), or None if the object

        is set not to block as has no data to read.

        """

        self._unsupported("readinto")



    def write(self, b):

        """Write the given buffer to the IO stream.



        Returns the number of bytes written, which may be less than len(b).

        """

        self._unsupported("write")





class FileIO(_fileio._FileIO, RawIOBase):



    """Raw I/O implementation for OS files."""



    # This multiply inherits from _FileIO and RawIOBase to make

    # isinstance(io.FileIO(), io.RawIOBase) return True without requiring

    # that _fileio._FileIO inherits from io.RawIOBase (which would be hard

    # to do since _fileio.c is written in C).



    def __init__(self, name, mode="r", closefd=True):

        _fileio._FileIO.__init__(self, name, mode, closefd)

        self._name = name



    def close(self):

        _fileio._FileIO.close(self)

        RawIOBase.close(self)



    @property

    def name(self):

        return self._name





class BufferedIOBase(IOBase):



    """Base class for buffered IO objects.



    The main difference with RawIOBase is that the read() method

    supports omitting the size argument, and does not have a default

    implementation that defers to readinto().



    In addition, read(), readinto() and write() may raise

    BlockingIOError if the underlying raw stream is in non-blocking

    mode and not ready; unlike their raw counterparts, they will never

    return None.



    A typical implementation should not inherit from a RawIOBase

    implementation, but wrap one.

    """



    def read(self, n = None):

        """Read and return up to n bytes.



        If the argument is omitted, None, or negative, reads and

        returns all data until EOF.



        If the argument is positive, and the underlying raw stream is

        not 'interactive', multiple raw reads may be issued to satisfy

        the byte count (unless EOF is reached first).  But for

        interactive raw streams (XXX and for pipes?), at most one raw

        read will be issued, and a short result does not imply that

        EOF is imminent.



        Returns an empty bytes array on EOF.



        Raises BlockingIOError if the underlying raw stream has no

        data at the moment.

        """

        self._unsupported("read")



    def readinto(self, b):

        """Read up to len(b) bytes into b.



        Like read(), this may issue multiple reads to the underlying raw

        stream, unless the latter is 'interactive'.



        Returns the number of bytes read (0 for EOF).



        Raises BlockingIOError if the underlying raw stream has no

        data at the moment.

        """

        # XXX This ought to work with anything that supports the buffer API

        data = self.read(len(b))

        n = len(data)

        try:

            b[:n] = data

        except TypeError as err:

            import array

            if not isinstance(b, array.array):

                raise err

            b[:n] = array.array(b'b', data)

        return n



    def write(self, b):

        """Write the given buffer to the IO stream.



        Return the number of bytes written, which is never less than

        len(b).



        Raises BlockingIOError if the buffer is full and the

        underlying raw stream cannot accept more data at the moment.

        """

        self._unsupported("write")





class _BufferedIOMixin(BufferedIOBase):



    """A mixin implementation of BufferedIOBase with an underlying raw stream.



    This passes most requests on to the underlying raw stream.  It

    does *not* provide implementations of read(), readinto() or

    write().

    """



    def __init__(self, raw):

        self.raw = raw



    ### Positioning ###



    def seek(self, pos, whence=0):

        return self.raw.seek(pos, whence)



    def tell(self):

        return self.raw.tell()



    def truncate(self, pos=None):

        # Flush the stream.  We're mixing buffered I/O with lower-level I/O,

        # and a flush may be necessary to synch both views of the current

        # file state.

        self.flush()



        if pos is None:

            pos = self.tell()

        # XXX: Should seek() be used, instead of passing the position

        # XXX  directly to truncate?

        return self.raw.truncate(pos)



    ### Flush and close ###



    def flush(self):

        self.raw.flush()



    def close(self):

        if not self.closed:

            try:

                self.flush()

            except IOError:

                pass  # If flush() fails, just give up

            self.raw.close()



    ### Inquiries ###



    def seekable(self):

        return self.raw.seekable()



    def readable(self):

        return self.raw.readable()



    def writable(self):

        return self.raw.writable()



    @property

    def closed(self):

        return self.raw.closed



    @property

    def name(self):

        return self.raw.name



    @property

    def mode(self):

        return self.raw.mode



    ### Lower-level APIs ###



    def fileno(self):

        return self.raw.fileno()



    def isatty(self):

        return self.raw.isatty()





class _BytesIO(BufferedIOBase):



    """Buffered I/O implementation using an in-memory bytes buffer."""



    # XXX More docs



    def __init__(self, initial_bytes=None):

        buf = bytearray()

        if initial_bytes is not None:

            buf += bytearray(initial_bytes)

        self._buffer = buf

        self._pos = 0



    def getvalue(self):

        """Return the bytes value (contents) of the buffer

        """

        if self.closed:

            raise ValueError("getvalue on closed file")

        return bytes(self._buffer)



    def read(self, n=None):

        if self.closed:

            raise ValueError("read from closed file")

        if n is None:

            n = -1

        if not isinstance(n, (int, long)):

            raise TypeError("argument must be an integer")

        if n < 0:

            n = len(self._buffer)

        if len(self._buffer) <= self._pos:

            return b""

        newpos = min(len(self._buffer), self._pos + n)

        b = self._buffer[self._pos : newpos]

        self._pos = newpos

        return bytes(b)



    def read1(self, n):

        """this is the same as read.

        """

        return self.read(n)



    def write(self, b):

        if self.closed:

            raise ValueError("write to closed file")

        if isinstance(b, unicode):

            raise TypeError("can't write unicode to binary stream")

        n = len(b)

        if n == 0:

            return 0

        pos = self._pos

        if pos > len(self._buffer):

            # Inserts null bytes between the current end of the file

            # and the new write position.

            padding = b'\x00' * (pos - len(self._buffer))

            self._buffer += padding

        self._buffer[pos:pos + n] = b

        self._pos += n

        return n



    def seek(self, pos, whence=0):

        if self.closed:

            raise ValueError("seek on closed file")

        try:

            pos = pos.__index__()

        except AttributeError as err:

            raise TypeError("an integer is required") # from err

        if whence == 0:

            if pos < 0:

                raise ValueError("negative seek position %r" % (pos,))

            self._pos = pos

        elif whence == 1:

            self._pos = max(0, self._pos + pos)

        elif whence == 2:

            self._pos = max(0, len(self._buffer) + pos)

        else:

            raise ValueError("invalid whence value")

        return self._pos



    def tell(self):

        if self.closed:

            raise ValueError("tell on closed file")

        return self._pos



    def truncate(self, pos=None):

        if self.closed:

            raise ValueError("truncate on closed file")

        if pos is None:

            pos = self._pos

        elif pos < 0:

            raise ValueError("negative truncate position %r" % (pos,))

        del self._buffer[pos:]

        return self.seek(pos)



    def readable(self):

        return True



    def writable(self):

        return True



    def seekable(self):

        return True



# Use the faster implementation of BytesIO if available

try:

    import _bytesio



    class BytesIO(_bytesio._BytesIO, BufferedIOBase):

        __doc__ = _bytesio._BytesIO.__doc__



except ImportError:

    BytesIO = _BytesIO





class BufferedReader(_BufferedIOMixin):



    """BufferedReader(raw[, buffer_size])



    A buffer for a readable, sequential BaseRawIO object.



    The constructor creates a BufferedReader for the given readable raw

    stream and buffer_size. If buffer_size is omitted, DEFAULT_BUFFER_SIZE

    is used.

    """



    def __init__(self, raw, buffer_size=DEFAULT_BUFFER_SIZE):

        """Create a new buffered reader using the given readable raw IO object.

        """

        raw._checkReadable()

        _BufferedIOMixin.__init__(self, raw)

        self.buffer_size = buffer_size

        self._reset_read_buf()

        self._read_lock = threading.Lock()



    def _reset_read_buf(self):

        self._read_buf = b""

        self._read_pos = 0



    def read(self, n=None):

        """Read n bytes.



        Returns exactly n bytes of data unless the underlying raw IO

        stream reaches EOF or if the call would block in non-blocking

        mode. If n is negative, read until EOF or until read() would

        block.

        """

        with self._read_lock:

            return self._read_unlocked(n)



    def _read_unlocked(self, n=None):

        nodata_val = b""

        empty_values = (b"", None)

        buf = self._read_buf

        pos = self._read_pos



        # Special case for when the number of bytes to read is unspecified.

        if n is None or n == -1:

            self._reset_read_buf()

            chunks = [buf[pos:]]  # Strip the consumed bytes.

            current_size = 0

            while True:

                # Read until EOF or until read() would block.

                chunk = self.raw.read()

                if chunk in empty_values:

                    nodata_val = chunk

                    break

                current_size += len(chunk)

                chunks.append(chunk)

            return b"".join(chunks) or nodata_val



        # The number of bytes to read is specified, return at most n bytes.

        avail = len(buf) - pos  # Length of the available buffered data.

        if n <= avail:

            # Fast path: the data to read is fully buffered.

            self._read_pos += n

            return buf[pos:pos+n]

        # Slow path: read from the stream until enough bytes are read,

        # or until an EOF occurs or until read() would block.

        chunks = [buf[pos:]]

        wanted = max(self.buffer_size, n)

        while avail < n:

            chunk = self.raw.read(wanted)

            if chunk in empty_values:

                nodata_val = chunk

                break

            avail += len(chunk)

            chunks.append(chunk)

        # n is more then avail only when an EOF occurred or when

        # read() would have blocked.

        n = min(n, avail)

        out = b"".join(chunks)

        self._read_buf = out[n:]  # Save the extra data in the buffer.

        self._read_pos = 0

        return out[:n] if out else nodata_val



    def peek(self, n=0):

        """Returns buffered bytes without advancing the position.



        The argument indicates a desired minimal number of bytes; we

        do at most one raw read to satisfy it.  We never return more

        than self.buffer_size.

        """

        with self._read_lock:

            return self._peek_unlocked(n)



    def _peek_unlocked(self, n=0):

        want = min(n, self.buffer_size)

        have = len(self._read_buf) - self._read_pos

        if have < want:

            to_read = self.buffer_size - have

            current = self.raw.read(to_read)

            if current:

                self._read_buf = self._read_buf[self._read_pos:] + current

                self._read_pos = 0

        return self._read_buf[self._read_pos:]



    def read1(self, n):

        """Reads up to n bytes, with at most one read() system call."""

        # Returns up to n bytes.  If at least one byte is buffered, we

        # only return buffered bytes.  Otherwise, we do one raw read.

        if n <= 0:

            return b""

        with self._read_lock:

            self._peek_unlocked(1)

            return self._read_unlocked(

                min(n, len(self._read_buf) - self._read_pos))



    def tell(self):

        return self.raw.tell() - len(self._read_buf) + self._read_pos



    def seek(self, pos, whence=0):

        with self._read_lock:

            if whence == 1:

                pos -= len(self._read_buf) - self._read_pos

            pos = self.raw.seek(pos, whence)

            self._reset_read_buf()

            return pos





class BufferedWriter(_BufferedIOMixin):



    """A buffer for a writeable sequential RawIO object.



    The constructor creates a BufferedWriter for the given writeable raw

    stream. If the buffer_size is not given, it defaults to

    DEAFULT_BUFFER_SIZE. If max_buffer_size is omitted, it defaults to

    twice the buffer size.

    """



    def __init__(self, raw,

                 buffer_size=DEFAULT_BUFFER_SIZE, max_buffer_size=None):

        raw._checkWritable()

        _BufferedIOMixin.__init__(self, raw)

        self.buffer_size = buffer_size

        self.max_buffer_size = (2*buffer_size

                                if max_buffer_size is None

                                else max_buffer_size)

        self._write_buf = bytearray()

        self._write_lock = threading.Lock()



    def write(self, b):

        if self.closed:

            raise ValueError("write to closed file")

        if isinstance(b, unicode):

            raise TypeError("can't write unicode to binary stream")

        with self._write_lock:

            # XXX we can implement some more tricks to try and avoid

            # partial writes

            if len(self._write_buf) > self.buffer_size:

                # We're full, so let's pre-flush the buffer

                try:

                    self._flush_unlocked()

                except BlockingIOError as e:

                    # We can't accept anything else.

                    # XXX Why not just let the exception pass through?

                    raise BlockingIOError(e.errno, e.strerror, 0)

            before = len(self._write_buf)

            self._write_buf.extend(b)

            written = len(self._write_buf) - before

            if len(self._write_buf) > self.buffer_size:

                try:

                    self._flush_unlocked()

                except BlockingIOError as e:

                    if len(self._write_buf) > self.max_buffer_size:

                        # We've hit max_buffer_size. We have to accept a

                        # partial write and cut back our buffer.

                        overage = len(self._write_buf) - self.max_buffer_size

                        self._write_buf = self._write_buf[:self.max_buffer_size]

                        raise BlockingIOError(e.errno, e.strerror, overage)

            return written



    def truncate(self, pos=None):

        with self._write_lock:

            self._flush_unlocked()

            if pos is None:

                pos = self.raw.tell()

            return self.raw.truncate(pos)



    def flush(self):

        with self._write_lock:

            self._flush_unlocked()



    def _flush_unlocked(self):

        if self.closed:

            raise ValueError("flush of closed file")

        written = 0

        try:

            while self._write_buf:

                n = self.raw.write(self._write_buf)

                del self._write_buf[:n]

                written += n

        except BlockingIOError as e:

            n = e.characters_written

            del self._write_buf[:n]

            written += n

            raise BlockingIOError(e.errno, e.strerror, written)



    def tell(self):

        return self.raw.tell() + len(self._write_buf)



    def seek(self, pos, whence=0):

        with self._write_lock:

            self._flush_unlocked()

            return self.raw.seek(pos, whence)





class BufferedRWPair(BufferedIOBase):



    """A buffered reader and writer object together.



    A buffered reader object and buffered writer object put together to

    form a sequential IO object that can read and write. This is typically

    used with a socket or two-way pipe.



    reader and writer are RawIOBase objects that are readable and

    writeable respectively. If the buffer_size is omitted it defaults to

    DEFAULT_BUFFER_SIZE. The max_buffer_size (for the buffered writer)

    defaults to twice the buffer size.

    """



    # XXX The usefulness of this (compared to having two separate IO

    # objects) is questionable.



    def __init__(self, reader, writer,

                 buffer_size=DEFAULT_BUFFER_SIZE, max_buffer_size=None):

        """Constructor.



        The arguments are two RawIO instances.

        """

        reader._checkReadable()

        writer._checkWritable()

        self.reader = BufferedReader(reader, buffer_size)

        self.writer = BufferedWriter(writer, buffer_size, max_buffer_size)



    def read(self, n=None):

        if n is None:

            n = -1

        return self.reader.read(n)



    def readinto(self, b):

        return self.reader.readinto(b)



    def write(self, b):

        return self.writer.write(b)



    def peek(self, n=0):

        return self.reader.peek(n)



    def read1(self, n):

        return self.reader.read1(n)



    def readable(self):

        return self.reader.readable()



    def writable(self):

        return self.writer.writable()



    def flush(self):

        return self.writer.flush()



    def close(self):

        self.writer.close()

        self.reader.close()



    def isatty(self):

        return self.reader.isatty() or self.writer.isatty()



    @property

    def closed(self):

        return self.writer.closed





class BufferedRandom(BufferedWriter, BufferedReader):



    """A buffered interface to random access streams.



    The constructor creates a reader and writer for a seekable stream,

    raw, given in the first argument. If the buffer_size is omitted it

    defaults to DEFAULT_BUFFER_SIZE. The max_buffer_size (for the buffered

    writer) defaults to twice the buffer size.

    """



    def __init__(self, raw,

                 buffer_size=DEFAULT_BUFFER_SIZE, max_buffer_size=None):

        raw._checkSeekable()

        BufferedReader.__init__(self, raw, buffer_size)

        BufferedWriter.__init__(self, raw, buffer_size, max_buffer_size)



    def seek(self, pos, whence=0):

        self.flush()

        # First do the raw seek, then empty the read buffer, so that

        # if the raw seek fails, we don't lose buffered data forever.

        pos = self.raw.seek(pos, whence)

        with self._read_lock:

            self._reset_read_buf()

        return pos



    def tell(self):

        if self._write_buf:

            return self.raw.tell() + len(self._write_buf)

        else:

            return BufferedReader.tell(self)



    def truncate(self, pos=None):

        if pos is None:

            pos = self.tell()

        # Use seek to flush the read buffer.

        self.seek(pos)

        return BufferedWriter.truncate(self)



    def read(self, n=None):

        if n is None:

            n = -1

        self.flush()

        return BufferedReader.read(self, n)



    def readinto(self, b):

        self.flush()

        return BufferedReader.readinto(self, b)



    def peek(self, n=0):

        self.flush()

        return BufferedReader.peek(self, n)



    def read1(self, n):

        self.flush()

        return BufferedReader.read1(self, n)



    def write(self, b):

        if self._read_buf:

            # Undo readahead

            with self._read_lock:

                self.raw.seek(self._read_pos - len(self._read_buf), 1)

                self._reset_read_buf()

        return BufferedWriter.write(self, b)





class TextIOBase(IOBase):



    """Base class for text I/O.



    This class provides a character and line based interface to stream

    I/O. There is no readinto method because Python's character strings

    are immutable. There is no public constructor.

    """



    def read(self, n = -1):

        """Read at most n characters from stream.



        Read from underlying buffer until we have n characters or we hit EOF.

        If n is negative or omitted, read until EOF.

        """

        self._unsupported("read")



    def write(self, s):

        """Write string s to stream."""

        self._unsupported("write")



    def truncate(self, pos = None):

        """Truncate size to pos."""

        self._unsupported("truncate")



    def readline(self):

        """Read until newline or EOF.



        Returns an empty string if EOF is hit immediately.

        """

        self._unsupported("readline")



    @property

    def encoding(self):

        """Subclasses should override."""

        return None



    @property

    def newlines(self):

        """Line endings translated so far.



        Only line endings translated during reading are considered.



        Subclasses should override.

        """

        return None





class IncrementalNewlineDecoder(codecs.IncrementalDecoder):

    """Codec used when reading a file in universal newlines mode.

    It wraps another incremental decoder, translating \\r\\n and \\r into \\n.

    It also records the types of newlines encountered.

    When used with translate=False, it ensures that the newline sequence is

    returned in one piece.

    """

    def __init__(self, decoder, translate, errors='strict'):

        codecs.IncrementalDecoder.__init__(self, errors=errors)

        self.translate = translate

        self.decoder = decoder

        self.seennl = 0

        self.pendingcr = False



    def decode(self, input, final=False):

        # decode input (with the eventual \r from a previous pass)

        output = self.decoder.decode(input, final=final)

        if self.pendingcr and (output or final):

            output = "\r" + output

            self.pendingcr = False



        # retain last \r even when not translating data:

        # then readline() is sure to get \r\n in one pass

        if output.endswith("\r") and not final:

            output = output[:-1]

            self.pendingcr = True



        # Record which newlines are read

        crlf = output.count('\r\n')

        cr = output.count('\r') - crlf

        lf = output.count('\n') - crlf

        self.seennl |= (lf and self._LF) | (cr and self._CR) \

                    | (crlf and self._CRLF)



        if self.translate:

            if crlf:

                output = output.replace("\r\n", "\n")

            if cr:

                output = output.replace("\r", "\n")



        return output



    def getstate(self):

        buf, flag = self.decoder.getstate()

        flag <<= 1

        if self.pendingcr:

            flag |= 1

        return buf, flag



    def setstate(self, state):

        buf, flag = state

        self.pendingcr = bool(flag & 1)

        self.decoder.setstate((buf, flag >> 1))



    def reset(self):

        self.seennl = 0

        self.pendingcr = False

        self.decoder.reset()



    _LF = 1

    _CR = 2

    _CRLF = 4



    @property

    def newlines(self):

        return (None,

                "\n",

                "\r",

                ("\r", "\n"),

                "\r\n",

                ("\n", "\r\n"),

                ("\r", "\r\n"),

                ("\r", "\n", "\r\n")

               )[self.seennl]





class TextIOWrapper(TextIOBase):



    r"""Character and line based layer over a BufferedIOBase object, buffer.



    encoding gives the name of the encoding that the stream will be

    decoded or encoded with. It defaults to locale.getpreferredencoding.



    errors determines the strictness of encoding and decoding (see the

    codecs.register) and defaults to "strict".



    newline can be None, '', '\n', '\r', or '\r\n'.  It controls the

    handling of line endings. If it is None, universal newlines is

    enabled.  With this enabled, on input, the lines endings '\n', '\r',

    or '\r\n' are translated to '\n' before being returned to the

    caller. Conversely, on output, '\n' is translated to the system

    default line separator, os.linesep. If newline is any other of its

    legal values, that newline becomes the newline when the file is read

    and it is returned untranslated. On output, '\n' is converted to the

    newline.



    If line_buffering is True, a call to flush is implied when a call to

    write contains a newline character.

    """



    _CHUNK_SIZE = 128



    def __init__(self, buffer, encoding=None, errors=None, newline=None,

                 line_buffering=False):

        if newline not in (None, "", "\n", "\r", "\r\n"):

            raise ValueError("illegal newline value: %r" % (newline,))

        if encoding is None:

            try:

                encoding = os.device_encoding(buffer.fileno())

            except (AttributeError, UnsupportedOperation):

                pass

            if encoding is None:

                try:

                    import locale

                except ImportError:

                    # Importing locale may fail if Python is being built

                    encoding = "ascii"

                else:

                    encoding = locale.getpreferredencoding()



        if not isinstance(encoding, basestring):

            raise ValueError("invalid encoding: %r" % encoding)



        if errors is None:

            errors = "strict"

        else:

            if not isinstance(errors, basestring):

                raise ValueError("invalid errors: %r" % errors)



        self.buffer = buffer

        self._line_buffering = line_buffering

        self._encoding = encoding

        self._errors = errors

        self._readuniversal = not newline

        self._readtranslate = newline is None

        self._readnl = newline

        self._writetranslate = newline != ''

        self._writenl = newline or os.linesep

        self._encoder = None

        self._decoder = None

        self._decoded_chars = ''  # buffer for text returned from decoder

        self._decoded_chars_used = 0  # offset into _decoded_chars for read()

        self._snapshot = None  # info for reconstructing decoder state

        self._seekable = self._telling = self.buffer.seekable()



    # self._snapshot is either None, or a tuple (dec_flags, next_input)

    # where dec_flags is the second (integer) item of the decoder state

    # and next_input is the chunk of input bytes that comes next after the

    # snapshot point.  We use this to reconstruct decoder states in tell().



    # Naming convention:

    #   - "bytes_..." for integer variables that count input bytes

    #   - "chars_..." for integer variables that count decoded characters



    @property

    def encoding(self):

        return self._encoding



    @property

    def errors(self):

        return self._errors



    @property

    def line_buffering(self):

        return self._line_buffering



    def seekable(self):

        return self._seekable



    def readable(self):

        return self.buffer.readable()



    def writable(self):

        return self.buffer.writable()



    def flush(self):

        self.buffer.flush()

        self._telling = self._seekable



    def close(self):

        try:

            self.flush()

        except:

            pass  # If flush() fails, just give up

        self.buffer.close()



    @property

    def closed(self):

        return self.buffer.closed



    @property

    def name(self):

        return self.buffer.name



    def fileno(self):

        return self.buffer.fileno()



    def isatty(self):

        return self.buffer.isatty()



    def write(self, s):

        if self.closed:

            raise ValueError("write to closed file")

        if not isinstance(s, unicode):

            raise TypeError("can't write %s to text stream" %

                            s.__class__.__name__)

        length = len(s)

        haslf = (self._writetranslate or self._line_buffering) and "\n" in s

        if haslf and self._writetranslate and self._writenl != "\n":

            s = s.replace("\n", self._writenl)

        encoder = self._encoder or self._get_encoder()

        # XXX What if we were just reading?

        b = encoder.encode(s)

        self.buffer.write(b)

        if self._line_buffering and (haslf or "\r" in s):

            self.flush()

        self._snapshot = None

        if self._decoder:

            self._decoder.reset()

        return length



    def _get_encoder(self):

        make_encoder = codecs.getincrementalencoder(self._encoding)

        self._encoder = make_encoder(self._errors)

        return self._encoder



    def _get_decoder(self):

        make_decoder = codecs.getincrementaldecoder(self._encoding)

        decoder = make_decoder(self._errors)

        if self._readuniversal:

            decoder = IncrementalNewlineDecoder(decoder, self._readtranslate)

        self._decoder = decoder

        return decoder



    # The following three methods implement an ADT for _decoded_chars.

    # Text returned from the decoder is buffered here until the client

    # requests it by calling our read() or readline() method.

    def _set_decoded_chars(self, chars):

        """Set the _decoded_chars buffer."""

        self._decoded_chars = chars

        self._decoded_chars_used = 0



    def _get_decoded_chars(self, n=None):

        """Advance into the _decoded_chars buffer."""

        offset = self._decoded_chars_used

        if n is None:

            chars = self._decoded_chars[offset:]

        else:

            chars = self._decoded_chars[offset:offset + n]

        self._decoded_chars_used += len(chars)

        return chars



    def _rewind_decoded_chars(self, n):

        """Rewind the _decoded_chars buffer."""

        if self._decoded_chars_used < n:

            raise AssertionError("rewind decoded_chars out of bounds")

        self._decoded_chars_used -= n



    def _read_chunk(self):

        """

        Read and decode the next chunk of data from the BufferedReader.



        The return value is True unless EOF was reached.  The decoded string

        is placed in self._decoded_chars (replacing its previous value).

        The entire input chunk is sent to the decoder, though some of it

        may remain buffered in the decoder, yet to be converted.

        """



        if self._decoder is None:

            raise ValueError("no decoder")



        if self._telling:

            # To prepare for tell(), we need to snapshot a point in the

            # file where the decoder's input buffer is empty.



            dec_buffer, dec_flags = self._decoder.getstate()

            # Given this, we know there was a valid snapshot point

            # len(dec_buffer) bytes ago with decoder state (b'', dec_flags).



        # Read a chunk, decode it, and put the result in self._decoded_chars.

        input_chunk = self.buffer.read1(self._CHUNK_SIZE)

        eof = not input_chunk

        self._set_decoded_chars(self._decoder.decode(input_chunk, eof))



        if self._telling:

            # At the snapshot point, len(dec_buffer) bytes before the read,

            # the next input to be decoded is dec_buffer + input_chunk.

            self._snapshot = (dec_flags, dec_buffer + input_chunk)



        return not eof



    def _pack_cookie(self, position, dec_flags=0,

                           bytes_to_feed=0, need_eof=0, chars_to_skip=0):

        # The meaning of a tell() cookie is: seek to position, set the

        # decoder flags to dec_flags, read bytes_to_feed bytes, feed them

        # into the decoder with need_eof as the EOF flag, then skip

        # chars_to_skip characters of the decoded result.  For most simple

        # decoders, tell() will often just give a byte offset in the file.

        return (position | (dec_flags<<64) | (bytes_to_feed<<128) |

               (chars_to_skip<<192) | bool(need_eof)<<256)



    def _unpack_cookie(self, bigint):

        rest, position = divmod(bigint, 1<<64)

        rest, dec_flags = divmod(rest, 1<<64)

        rest, bytes_to_feed = divmod(rest, 1<<64)

        need_eof, chars_to_skip = divmod(rest, 1<<64)

        return position, dec_flags, bytes_to_feed, need_eof, chars_to_skip



    def tell(self):

        if not self._seekable:

            raise IOError("underlying stream is not seekable")

        if not self._telling:

            raise IOError("telling position disabled by next() call")

        self.flush()

        position = self.buffer.tell()

        decoder = self._decoder

        if decoder is None or self._snapshot is None:

            if self._decoded_chars:

                # This should never happen.

                raise AssertionError("pending decoded text")

            return position



        # Skip backward to the snapshot point (see _read_chunk).

        dec_flags, next_input = self._snapshot

        position -= len(next_input)



        # How many decoded characters have been used up since the snapshot?

        chars_to_skip = self._decoded_chars_used

        if chars_to_skip == 0:

            # We haven't moved from the snapshot point.

            return self._pack_cookie(position, dec_flags)



        # Starting from the snapshot position, we will walk the decoder

        # forward until it gives us enough decoded characters.

        saved_state = decoder.getstate()

        try:

            # Note our initial start point.

            decoder.setstate((b'', dec_flags))

            start_pos = position

            start_flags, bytes_fed, chars_decoded = dec_flags, 0, 0

            need_eof = 0



            # Feed the decoder one byte at a time.  As we go, note the

            # nearest "safe start point" before the current location

            # (a point where the decoder has nothing buffered, so seek()

            # can safely start from there and advance to this location).

            for next_byte in next_input:

                bytes_fed += 1

                chars_decoded += len(decoder.decode(next_byte))

                dec_buffer, dec_flags = decoder.getstate()

                if not dec_buffer and chars_decoded <= chars_to_skip:

                    # Decoder buffer is empty, so this is a safe start point.

                    start_pos += bytes_fed

                    chars_to_skip -= chars_decoded

                    start_flags, bytes_fed, chars_decoded = dec_flags, 0, 0

                if chars_decoded >= chars_to_skip:

                    break

            else:

                # We didn't get enough decoded data; signal EOF to get more.

                chars_decoded += len(decoder.decode(b'', final=True))

                need_eof = 1

                if chars_decoded < chars_to_skip:

                    raise IOError("can't reconstruct logical file position")



            # The returned cookie corresponds to the last safe start point.

            return self._pack_cookie(

                start_pos, start_flags, bytes_fed, need_eof, chars_to_skip)

        finally:

            decoder.setstate(saved_state)



    def truncate(self, pos=None):

        self.flush()

        if pos is None:

            pos = self.tell()

        self.seek(pos)

        return self.buffer.truncate()



    def seek(self, cookie, whence=0):

        if self.closed:

            raise ValueError("tell on closed file")

        if not self._seekable:

            raise IOError("underlying stream is not seekable")

        if whence == 1: # seek relative to current position

            if cookie != 0:

                raise IOError("can't do nonzero cur-relative seeks")

            # Seeking to the current position should attempt to

            # sync the underlying buffer with the current position.

            whence = 0

            cookie = self.tell()

        if whence == 2: # seek relative to end of file

            if cookie != 0:

                raise IOError("can't do nonzero end-relative seeks")

            self.flush()

            position = self.buffer.seek(0, 2)

            self._set_decoded_chars('')

            self._snapshot = None

            if self._decoder:

                self._decoder.reset()

            return position

        if whence != 0:

            raise ValueError("invalid whence (%r, should be 0, 1 or 2)" %

                             (whence,))

        if cookie < 0:

            raise ValueError("negative seek position %r" % (cookie,))

        self.flush()



        # The strategy of seek() is to go back to the safe start point

        # and replay the effect of read(chars_to_skip) from there.

        start_pos, dec_flags, bytes_to_feed, need_eof, chars_to_skip = \

            self._unpack_cookie(cookie)



        # Seek back to the safe start point.

        self.buffer.seek(start_pos)

        self._set_decoded_chars('')

        self._snapshot = None



        # Restore the decoder to its state from the safe start point.

        if self._decoder or dec_flags or chars_to_skip:

            self._decoder = self._decoder or self._get_decoder()

            self._decoder.setstate((b'', dec_flags))

            self._snapshot = (dec_flags, b'')



        if chars_to_skip:

            # Just like _read_chunk, feed the decoder and save a snapshot.

            input_chunk = self.buffer.read(bytes_to_feed)

            self._set_decoded_chars(

                self._decoder.decode(input_chunk, need_eof))

            self._snapshot = (dec_flags, input_chunk)



            # Skip chars_to_skip of the decoded characters.

            if len(self._decoded_chars) < chars_to_skip:

                raise IOError("can't restore logical file position")

            self._decoded_chars_used = chars_to_skip



        return cookie



    def read(self, n=None):

        if n is None:

            n = -1

        decoder = self._decoder or self._get_decoder()

        if n < 0:

            # Read everything.

            result = (self._get_decoded_chars() +

                      decoder.decode(self.buffer.read(), final=True))

            self._set_decoded_chars('')

            self._snapshot = None

            return result

        else:

            # Keep reading chunks until we have n characters to return.

            eof = False

            result = self._get_decoded_chars(n)

            while len(result) < n and not eof:

                eof = not self._read_chunk()

                result += self._get_decoded_chars(n - len(result))

            return result



    def next(self):

        self._telling = False

        line = self.readline()

        if not line:

            self._snapshot = None

            self._telling = self._seekable

            raise StopIteration

        return line



    def readline(self, limit=None):

        if self.closed:

            raise ValueError("read from closed file")

        if limit is None:

            limit = -1

        if not isinstance(limit, (int, long)):

            raise TypeError("limit must be an integer")



        # Grab all the decoded text (we will rewind any extra bits later).

        line = self._get_decoded_chars()



        start = 0

        decoder = self._decoder or self._get_decoder()



        pos = endpos = None

        while True:

            if self._readtranslate:

                # Newlines are already translated, only search for \n

                pos = line.find('\n', start)

                if pos >= 0:

                    endpos = pos + 1

                    break

                else:

                    start = len(line)



            elif self._readuniversal:

                # Universal newline search. Find any of \r, \r\n, \n

                # The decoder ensures that \r\n are not split in two pieces



                # In C we'd look for these in parallel of course.

                nlpos = line.find("\n", start)

                crpos = line.find("\r", start)

                if crpos == -1:

                    if nlpos == -1:

                        # Nothing found

                        start = len(line)

                    else:

                        # Found \n

                        endpos = nlpos + 1

                        break

                elif nlpos == -1:

                    # Found lone \r

                    endpos = crpos + 1

                    break

                elif nlpos < crpos:

                    # Found \n

                    endpos = nlpos + 1

                    break

                elif nlpos == crpos + 1:

                    # Found \r\n

                    endpos = crpos + 2

                    break

                else:

                    # Found \r

                    endpos = crpos + 1

                    break

            else:

                # non-universal

                pos = line.find(self._readnl)

                if pos >= 0:

                    endpos = pos + len(self._readnl)

                    break



            if limit >= 0 and len(line) >= limit:

                endpos = limit  # reached length limit

                break



            # No line ending seen yet - get more data

            more_line = ''

            while self._read_chunk():

                if self._decoded_chars:

                    break

            if self._decoded_chars:

                line += self._get_decoded_chars()

            else:

                # end of file

                self._set_decoded_chars('')

                self._snapshot = None

                return line



        if limit >= 0 and endpos > limit:

            endpos = limit  # don't exceed limit



        # Rewind _decoded_chars to just after the line ending we found.

        self._rewind_decoded_chars(len(line) - endpos)

        return line[:endpos]



    @property

    def newlines(self):

        return self._decoder.newlines if self._decoder else None



class StringIO(TextIOWrapper):



    """An in-memory stream for text. The initial_value argument sets the

    value of object. The other arguments are like those of TextIOWrapper's

    constructor.

    """



    def __init__(self, initial_value="", encoding="utf-8",

                 errors="strict", newline="\n"):

        super(StringIO, self).__init__(BytesIO(),

                                       encoding=encoding,

                                       errors=errors,

                                       newline=newline)

        # Issue #5645: make universal newlines semantics the same as in the

        # C version, even under Windows.

        if newline is None:

            self._writetranslate = False

        if initial_value:

            if not isinstance(initial_value, unicode):

                initial_value = unicode(initial_value)

            self.write(initial_value)

            self.seek(0)



    def getvalue(self):

        self.flush()

        return self.buffer.getvalue().decode(self._encoding, self._errors)

