cpython/Lib/io.py

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"""New I/O library conforming to PEP 3116.
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This is a prototype; hopefully eventually some of this will be
reimplemented in C.
Conformance of alternative implementations: all arguments are intended
to be positional-only except the arguments of the open() function.
Argument names except those of the open() function are not part of the
specification. Instance variables and methods whose name starts with
a leading underscore are not part of the specification (except "magic"
names like __iter__). Only the top-level names listed in the __all__
variable are part of the specification.
XXX edge cases when switching between reading/writing
XXX need to default buffer size to 1 if isatty()
XXX need to support 1 meaning line-buffered
XXX don't use assert to validate input requirements
XXX whenever an argument is None, use the default value
XXX read/write ops should check readable/writable
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"""
__author__ = ("Guido van Rossum <guido@python.org>, "
"Mike Verdone <mike.verdone@gmail.com>, "
"Mark Russell <mark.russell@zen.co.uk>")
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__all__ = ["BlockingIOError", "open", "IOBase", "RawIOBase", "FileIO",
"SocketIO", "BytesIO", "StringIO", "BufferedIOBase",
"BufferedReader", "BufferedWriter", "BufferedRWPair",
"BufferedRandom", "TextIOBase", "TextIOWrapper"]
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import os
import sys
import codecs
import _fileio
import warnings
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try:
import cPickle as pickle
except ImportError:
import pickle
# XXX Shouldn't we use st_blksize whenever we can?
DEFAULT_BUFFER_SIZE = 8 * 1024 # bytes
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, newline=None):
"""Replacement for the built-in open function.
Args:
file: string giving the name of the file to be opened;
or integer file descriptor of the file to be wrapped (*).
mode: optional mode string; see below.
buffering: optional int >= 0 giving the buffer size; values
can be: 0 = unbuffered, 1 = line buffered,
larger = fully buffered.
Keywords (for text modes only; *must* be given as keyword arguments):
encoding: optional string giving the text encoding.
newline: optional newlines specifier; must be None, '\n' or '\r\n';
specifies the line ending expected on input and written on
output. If None, use universal newlines on input and
use os.linesep on output.
(*) If a file descriptor is given, it is closed when the returned
I/O object is closed. If you don't want this to happen, use
os.dup() to create a duplicate file descriptor.
Mode strings characters:
'r': open for reading (default)
'w': open for writing, truncating the file first
'a': open for writing, appending to the end if the file exists
'b': binary mode
't': text mode (default)
'+': open a disk file for updating (implies reading and writing)
'U': universal newline mode (for backwards compatibility)
Constraints:
- encoding must not be given when a binary mode is given
- buffering must not be zero when a text mode is given
Returns:
Depending on the mode and buffering arguments, either a raw
binary stream, a buffered binary stream, or a buffered text
stream, open for reading and/or writing.
"""
# XXX Don't use asserts for these checks; raise TypeError or ValueError
assert isinstance(file, (basestring, int)), repr(file)
assert isinstance(mode, basestring), repr(mode)
assert buffering is None or isinstance(buffering, int), repr(buffering)
assert encoding is None or isinstance(encoding, basestring), repr(encoding)
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modes = set(mode)
if modes - set("arwb+tU") or len(mode) > len(modes):
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raise ValueError("invalid mode: %r" % mode)
reading = "r" in modes
writing = "w" in modes
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appending = "a" in modes
updating = "+" in modes
text = "t" in modes
binary = "b" in modes
if "U" in modes and not (reading or writing or appending):
reading = True
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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 newline is not None:
raise ValueError("binary mode doesn't take a newline argument")
raw = FileIO(file,
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(reading and "r" or "") +
(writing and "w" or "") +
(appending and "a" or "") +
(updating and "+" or ""))
if buffering is None:
buffering = DEFAULT_BUFFER_SIZE
# XXX Should default to line buffering if os.isatty(raw.fileno())
try:
bs = os.fstat(raw.fileno()).st_blksize
except (os.error, AttributeError):
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pass
else:
if bs > 1:
buffering = bs
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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:
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buffer = BufferedWriter(raw, buffering)
else:
assert reading
buffer = BufferedReader(raw, buffering)
if binary:
return buffer
return TextIOWrapper(buffer, encoding, newline)
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class IOBase:
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"""Base class for all I/O classes.
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.
This does not define read(), readinto() and write(), nor
readline() and friends, since their signatures vary per layer.
Not that calling any method (even inquiries) on a closed file is
undefined. Implementations may raise IOError in this case.
"""
### Internal ###
def _unsupported(self, name: str) -> IOError:
"""Internal: raise an exception for unsupported operations."""
raise IOError("%s.%s() not supported" % (self.__class__.__name__,
name))
### Positioning ###
def seek(self, pos: int, whence: int = 0) -> int:
"""seek(pos: int, whence: int = 0) -> int. Change stream position.
Seek to byte offset pos relative to position indicated by whence:
0 Start of stream (the default). pos should be >= 0;
1 Current position - whence may be negative;
2 End of stream - whence usually negative.
Returns the new absolute position.
"""
self._unsupported("seek")
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def tell(self) -> int:
"""tell() -> int. Return current stream position."""
return self.seek(0, 1)
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def truncate(self, pos: int = None) -> int:
"""truncate(size: int = None) -> int. Truncate file to size bytes.
Size defaults to the current IO position as reported by tell().
Returns the new size.
"""
self._unsupported("truncate")
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### Flush and close ###
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def flush(self) -> None:
"""flush() -> None. Flushes write buffers, if applicable.
This is a no-op for read-only and non-blocking streams.
"""
__closed = False
def close(self) -> None:
"""close() -> None. Flushes and closes the IO object.
This must be idempotent. It should also set a flag for the
'closed' property (see below) to test.
"""
if not self.__closed:
self.__closed = True
self.flush()
def __del__(self) -> None:
"""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) -> bool:
"""seekable() -> bool. Return whether object supports random access.
If False, seek(), tell() and truncate() will raise IOError.
This method may need to do a test seek().
"""
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return False
def readable(self) -> bool:
"""readable() -> bool. Return whether object was opened for reading.
If False, read() will raise IOError.
"""
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return False
def writable(self) -> bool:
"""writable() -> bool. Return whether object was opened for writing.
If False, write() and truncate() will raise IOError.
"""
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return False
@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
### Context manager ###
def __enter__(self) -> "IOBase": # That's a forward reference
"""Context management protocol. Returns self."""
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return self
def __exit__(self, *args) -> None:
"""Context management protocol. Calls close()"""
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self.close()
### Lower-level APIs ###
# XXX Should these be present even if unimplemented?
def fileno(self) -> int:
"""fileno() -> int. Returns underlying file descriptor if one exists.
Raises IOError if the IO object does not use a file descriptor.
"""
self._unsupported("fileno")
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def isatty(self) -> bool:
"""isatty() -> int. Returns whether this is an 'interactive' stream.
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Returns False if we don't know.
"""
return False
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class RawIOBase(IOBase):
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"""Base class for raw binary I/O.
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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().
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(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.)
"""
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def read(self, n: int) -> bytes:
"""read(n: int) -> bytes. Read and return up to n bytes.
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Returns an empty bytes array on EOF, or None if the object is
set not to block and has no data to read.
"""
b = bytes(n.__index__())
n = self.readinto(b)
del b[n:]
return b
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def readinto(self, b: bytes) -> int:
"""readinto(b: bytes) -> int. Read up to len(b) bytes into b.
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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: bytes) -> int:
"""write(b: bytes) -> int. Write the given buffer to the IO stream.
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Returns the number of bytes written, which may be less than len(b).
"""
self._unsupported("write")
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class FileIO(_fileio._FileIO, RawIOBase):
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"""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 close(self):
_fileio._FileIO.close(self)
RawIOBase.close(self)
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class SocketIO(RawIOBase):
"""Raw I/O implementation for stream sockets."""
# XXX More docs
# XXX Hook this up to socket.py
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def __init__(self, sock, mode):
assert mode in ("r", "w", "rw")
RawIOBase.__init__(self)
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self._sock = sock
self._mode = mode
def readinto(self, b):
return self._sock.recv_into(b)
def write(self, b):
return self._sock.send(b)
def close(self):
if not self.closed:
RawIOBase.close()
self._sock.close()
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def readable(self):
return "r" in self._mode
def writable(self):
return "w" in self._mode
def fileno(self):
return self._sock.fileno()
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: int = -1) -> bytes:
"""read(n: int = -1) -> bytes. Read and return up to n bytes.
If the argument is omitted, 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: bytes) -> int:
"""readinto(b: bytes) -> int. 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' (XXX or a
pipe?).
Returns the number of bytes read (0 for EOF).
Raises BlockingIOError if the underlying raw stream has no
data at the moment.
"""
data = self.read(len(b))
n = len(data)
b[:n] = data
return n
def write(self, b: bytes) -> int:
"""write(b: bytes) -> int. Write the given buffer to the IO stream.
Returns 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):
return self.raw.truncate(pos)
### Flush and close ###
def flush(self):
self.raw.flush()
def close(self):
self.flush()
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
### Lower-level APIs ###
def fileno(self):
return self.raw.fileno()
def isatty(self):
return self.raw.isatty()
class _MemoryIOMixin(BufferedIOBase):
# XXX docstring
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def __init__(self, buffer):
self._buffer = buffer
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self._pos = 0
def getvalue(self):
return self._buffer
def read(self, n=-1):
assert n is not None
if n < 0:
n = len(self._buffer)
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newpos = min(len(self._buffer), self._pos + n)
b = self._buffer[self._pos : newpos]
self._pos = newpos
return b
def write(self, b):
n = len(b)
newpos = self._pos + n
self._buffer[self._pos:newpos] = b
self._pos = newpos
return n
def seek(self, pos, whence=0):
if whence == 0:
self._pos = max(0, pos)
elif whence == 1:
self._pos = max(0, self._pos + pos)
elif whence == 2:
self._pos = max(0, len(self._buffer) + pos)
else:
raise IOError("invalid whence value")
return self._pos
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def tell(self):
return self._pos
def truncate(self, pos=None):
if pos is None:
pos = self._pos
else:
self._pos = max(0, pos)
del self._buffer[pos:]
return pos
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def readable(self):
return True
def writable(self):
return True
def seekable(self):
return True
class BytesIO(_MemoryIOMixin):
"""Buffered I/O implementation using a bytes buffer, like StringIO."""
# XXX More docs
def __init__(self, inital_bytes=None):
buffer = b""
if inital_bytes is not None:
buffer += inital_bytes
_MemoryIOMixin.__init__(self, buffer)
# XXX This should inherit from TextIOBase
class StringIO(_MemoryIOMixin):
"""Buffered I/O implementation using a string buffer, like StringIO."""
# XXX More docs
# Reuses the same code as BytesIO, just with a string rather that
# bytes as the _buffer value.
# XXX This doesn't work; _MemoryIOMixin's write() and truncate()
# methods assume the buffer is mutable. Simply redefining those
# to use slice concatenation will make it awfully slow (in fact,
# quadratic in the number of write() calls).
def __init__(self, inital_string=None):
buffer = ""
if inital_string is not None:
buffer += inital_string
_MemoryIOMixin.__init__(self, buffer)
def readinto(self, b: bytes) -> int:
self._unsupported("readinto")
class BufferedReader(_BufferedIOMixin):
"""Buffer for a readable sequential RawIO object."""
def __init__(self, raw, buffer_size=DEFAULT_BUFFER_SIZE):
"""Create a new buffered reader using the given readable raw IO object.
"""
assert raw.readable()
_BufferedIOMixin.__init__(self, raw)
self._read_buf = b""
self.buffer_size = buffer_size
def read(self, n=-1):
"""Read n bytes.
Returns exactly n bytes of data unless the underlying raw IO
stream reaches EOF of if the call would block in non-blocking
mode. If n is negative, read until EOF or until read() would
block.
"""
assert n is not None
nodata_val = b""
while n < 0 or len(self._read_buf) < n:
to_read = max(self.buffer_size,
n if n is not None else 2*len(self._read_buf))
current = self.raw.read(to_read)
if current in (b"", None):
nodata_val = current
break
self._read_buf += current
if self._read_buf:
if n < 0:
n = len(self._read_buf)
out = self._read_buf[:n]
self._read_buf = self._read_buf[n:]
else:
out = nodata_val
return out
def tell(self):
return self.raw.tell() - len(self._read_buf)
def seek(self, pos, whence=0):
if whence == 1:
pos -= len(self._read_buf)
pos = self.raw.seek(pos, whence)
self._read_buf = b""
return pos
class BufferedWriter(_BufferedIOMixin):
# XXX docstring
def __init__(self, raw,
buffer_size=DEFAULT_BUFFER_SIZE, max_buffer_size=None):
assert raw.writable()
_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 = b""
def write(self, b):
# 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()
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)
self._write_buf.extend(b)
if len(self._write_buf) > self.buffer_size:
try:
self.flush()
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 len(b)
def flush(self):
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):
self.flush()
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.
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.
"""
assert reader.readable()
assert writer.writable()
self.reader = BufferedReader(reader, buffer_size)
self.writer = BufferedWriter(writer, buffer_size, max_buffer_size)
def read(self, 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 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):
# XXX docstring
def __init__(self, raw,
buffer_size=DEFAULT_BUFFER_SIZE, max_buffer_size=None):
assert raw.seekable()
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)
self._read_buf = b""
return pos
def tell(self):
if (self._write_buf):
return self.raw.tell() + len(self._write_buf)
else:
return self.raw.tell() - len(self._read_buf)
def read(self, n=-1):
self.flush()
return BufferedReader.read(self, n)
def readinto(self, b):
self.flush()
return BufferedReader.readinto(self, b)
def write(self, b):
if self._read_buf:
self.raw.seek(-len(self._read_buf), 1) # Undo readahead
self._read_buf = b""
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, as character strings are immutable.
"""
def read(self, n: int = -1) -> str:
"""read(n: int = -1) -> str. 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: str) -> int:
"""write(s: str) -> int. Write string s to stream."""
self._unsupported("write")
def truncate(self, pos: int = None) -> int:
"""truncate(pos: int = None) -> int. Truncate size to pos."""
self.flush()
if pos is None:
pos = self.tell()
self.seek(pos)
return self.buffer.truncate()
def readline(self) -> str:
"""readline() -> str. Read until newline or EOF.
Returns an empty string if EOF is hit immediately.
"""
self._unsupported("readline")
def __iter__(self) -> "TextIOBase": # That's a forward reference
"""__iter__() -> Iterator. Return line iterator (actually just self).
"""
return self
def next(self) -> str:
"""Same as readline() except raises StopIteration on immediate EOF."""
line = self.readline()
if not line:
raise StopIteration
return line
# The following are provided for backwards compatibility
def readlines(self, hint=None):
if hint is None:
return list(self)
n = 0
lines = []
while not lines or n < hint:
line = self.readline()
if not line:
break
lines.append(line)
n += len(line)
return lines
def writelines(self, lines):
for line in lines:
self.write(line)
class TextIOWrapper(TextIOBase):
"""Buffered text stream.
Character and line based layer over a BufferedIOBase object.
"""
_CHUNK_SIZE = 128
def __init__(self, buffer, encoding=None, newline=None):
if newline not in (None, "\n", "\r\n"):
raise ValueError("illegal newline value: %r" % (newline,))
if encoding is None:
# XXX This is questionable
encoding = sys.getfilesystemencoding() or "latin-1"
self.buffer = buffer
self._encoding = encoding
self._newline = newline or os.linesep
self._fix_newlines = newline is None
self._decoder = None
self._decoder_in_rest_pickle = None
self._pending = ""
self._snapshot = None
self._seekable = self._telling = self.buffer.seekable()
# A word about _snapshot. This attribute is either None, or a
# tuple (decoder_pickle, readahead, pending) where decoder_pickle
# is a pickled decoder state, readahead is the chunk of bytes that
# was read, and pending is the characters that were rendered by
# the decoder after feeding it those bytes. We use this to
# reconstruct intermediate decoder states in tell().
def _seekable(self):
return self._seekable
def flush(self):
self.buffer.flush()
self._telling = self._seekable
def close(self):
self.flush()
self.buffer.close()
@property
def closed(self):
return self.buffer.closed
def fileno(self):
return self.buffer.fileno()
def write(self, s: str):
# XXX What if we were just reading?
b = s.encode(self._encoding)
if isinstance(b, str):
b = bytes(b)
n = self.buffer.write(b)
if "\n" in s:
self.flush()
self._snapshot = self._decoder = None
return len(s)
def _get_decoder(self):
make_decoder = codecs.getincrementaldecoder(self._encoding)
if make_decoder is None:
raise IOError("Can't find an incremental decoder for encoding %s" %
self._encoding)
decoder = self._decoder = make_decoder() # XXX: errors
if isinstance(decoder, codecs.BufferedIncrementalDecoder):
# XXX Hack: make the codec use bytes instead of strings
decoder.buffer = b""
self._decoder_in_rest_pickle = pickle.dumps(decoder, 2) # For tell()
return decoder
def _read_chunk(self):
assert self._decoder is not None
if not self._telling:
readahead = self.buffer.read(self._CHUNK_SIZE)
pending = self._decoder.decode(readahead, not readahead)
return readahead, pending
decoder_state = pickle.dumps(self._decoder, 2)
readahead = self.buffer.read(self._CHUNK_SIZE)
pending = self._decoder.decode(readahead, not readahead)
self._snapshot = (decoder_state, readahead, pending)
return readahead, pending
def _encode_decoder_state(self, ds, pos):
if ds == self._decoder_in_rest_pickle:
return pos
x = 0
for i in bytes(ds):
x = x<<8 | i
return (x<<64) | pos
def _decode_decoder_state(self, pos):
x, pos = divmod(pos, 1<<64)
if not x:
return None, pos
b = b""
while x:
b.append(x&0xff)
x >>= 8
return str(b[::-1]), pos
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()
if self._decoder is None or self._snapshot is None:
assert self._pending == ""
return position
decoder_state, readahead, pending = self._snapshot
position -= len(readahead)
needed = len(pending) - len(self._pending)
if not needed:
return self._encode_decoder_state(decoder_state, position)
decoder = pickle.loads(decoder_state)
n = 0
bb = bytes(1)
for i, bb[0] in enumerate(readahead):
n += len(decoder.decode(bb))
if n >= needed:
decoder_state = pickle.dumps(decoder, 2)
return self._encode_decoder_state(decoder_state, position+i+1)
raise IOError("Can't reconstruct logical file position")
def seek(self, pos, whence=0):
if not self._seekable:
raise IOError("Underlying stream is not seekable")
if whence == 1:
if pos != 0:
raise IOError("Can't do nonzero cur-relative seeks")
pos = self.tell()
whence = 0
if whence == 2:
if pos != 0:
raise IOError("Can't do nonzero end-relative seeks")
self.flush()
pos = self.buffer.seek(0, 2)
self._snapshot = None
self._pending = ""
self._decoder = None
return pos
if whence != 0:
raise ValueError("Invalid whence (%r, should be 0, 1 or 2)" %
(whence,))
if pos < 0:
raise ValueError("Negative seek position %r" % (pos,))
self.flush()
orig_pos = pos
ds, pos = self._decode_decoder_state(pos)
if not ds:
self.buffer.seek(pos)
self._snapshot = None
self._pending = ""
self._decoder = None
return pos
decoder = pickle.loads(ds)
self.buffer.seek(pos)
self._snapshot = (ds, b"", "")
self._pending = ""
if not self._decoder_in_rest_pickle:
self._get_decoder() # For its side effect
self._decoder = decoder
return orig_pos
def read(self, n: int = -1):
decoder = self._decoder or self._get_decoder()
res = self._pending
if n < 0:
res += decoder.decode(self.buffer.read(), True)
self._pending = ""
self._snapshot = None
return res
else:
while len(res) < n:
readahead, pending = self._read_chunk()
res += pending
if not readahead:
break
self._pending = res[n:]
return res[:n]
def next(self) -> str:
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 limit is not None:
# XXX Hack to support limit argument, for backwards compatibility
line = self.readline()
if len(line) <= limit:
return line
line, self._pending = line[:limit], line[limit:] + self._pending
return line
line = self._pending
start = 0
decoder = self._decoder or self._get_decoder()
while True:
# In C we'd look for these in parallel of course.
nlpos = line.find("\n", start)
crpos = line.find("\r", start)
if nlpos >= 0 and crpos >= 0:
endpos = min(nlpos, crpos)
else:
endpos = nlpos if nlpos >= 0 else crpos
if endpos != -1:
endc = line[endpos]
if endc == "\n":
ending = "\n"
break
# We've seen \r - is it standalone, \r\n or \r at end of line?
if endpos + 1 < len(line):
if line[endpos+1] == "\n":
ending = "\r\n"
else:
ending = "\r"
break
# There might be a following \n in the next block of data ...
start = endpos
else:
start = len(line)
# No line ending seen yet - get more data
while True:
readahead, pending = self._read_chunk()
more_line = pending
if more_line or not readahead:
break
if not more_line:
ending = ""
endpos = len(line)
break
line += more_line
nextpos = endpos + len(ending)
self._pending = line[nextpos:]
# XXX Update self.newlines here if we want to support that
if self._fix_newlines and ending not in ("\n", ""):
return line[:endpos] + "\n"
else:
return line[:nextpos]