"""

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

seperation 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:

            raw._name = file

            raw._mode = mode

            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:

        buffer.name = file

        buffer.mode = mode

        return buffer

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

    text.name = file

    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()