cpython/Lib/codecs.py at 3.5 · python/cpython · GitHub

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""" codecs -- Python Codec Registry, API and helpers.

Written by Marc-Andre Lemburg (mal@lemburg.com).

"""#"

import builtins, sys

### Registry and builtin stateless codec functions

try:

from _codecs import *

except ImportError as why:

raise SystemError('Failed to load the builtin codecs: %s' % why)

__all__ = ["register", "lookup", "open", "EncodedFile", "BOM", "BOM_BE",

"BOM_LE", "BOM32_BE", "BOM32_LE", "BOM64_BE", "BOM64_LE",

"BOM_UTF8", "BOM_UTF16", "BOM_UTF16_LE", "BOM_UTF16_BE",

"BOM_UTF32", "BOM_UTF32_LE", "BOM_UTF32_BE",

"CodecInfo", "Codec", "IncrementalEncoder", "IncrementalDecoder",

"StreamReader", "StreamWriter",

"StreamReaderWriter", "StreamRecoder",

"getencoder", "getdecoder", "getincrementalencoder",

"getincrementaldecoder", "getreader", "getwriter",

"encode", "decode", "iterencode", "iterdecode",

"strict_errors", "ignore_errors", "replace_errors",

"xmlcharrefreplace_errors",

"backslashreplace_errors", "namereplace_errors",

"register_error", "lookup_error"]

### Constants

# Byte Order Mark (BOM = ZERO WIDTH NO-BREAK SPACE = U+FEFF)

# and its possible byte string values

# for UTF8/UTF16/UTF32 output and little/big endian machines

# UTF-8

BOM_UTF8 = b'\xef\xbb\xbf'

# UTF-16, little endian

BOM_LE = BOM_UTF16_LE = b'\xff\xfe'

# UTF-16, big endian

BOM_BE = BOM_UTF16_BE = b'\xfe\xff'

# UTF-32, little endian

BOM_UTF32_LE = b'\xff\xfe\x00\x00'

# UTF-32, big endian

BOM_UTF32_BE = b'\x00\x00\xfe\xff'

if sys.byteorder == 'little':

# UTF-16, native endianness

BOM = BOM_UTF16 = BOM_UTF16_LE

# UTF-32, native endianness

BOM_UTF32 = BOM_UTF32_LE

else:

# UTF-16, native endianness

BOM = BOM_UTF16 = BOM_UTF16_BE

# UTF-32, native endianness

BOM_UTF32 = BOM_UTF32_BE

# Old broken names (don't use in new code)

BOM32_LE = BOM_UTF16_LE

BOM32_BE = BOM_UTF16_BE

BOM64_LE = BOM_UTF32_LE

BOM64_BE = BOM_UTF32_BE

### Codec base classes (defining the API)

class CodecInfo(tuple):

"""Codec details when looking up the codec registry"""

# Private API to allow Python 3.4 to blacklist the known non-Unicode

# codecs in the standard library. A more general mechanism to

# reliably distinguish test encodings from other codecs will hopefully

# be defined for Python 3.5

# See http://bugs.python.org/issue19619

_is_text_encoding = True # Assume codecs are text encodings by default

def __new__(cls, encode, decode, streamreader=None, streamwriter=None,

incrementalencoder=None, incrementaldecoder=None, name=None,

*, _is_text_encoding=None):

self = tuple.__new__(cls, (encode, decode, streamreader, streamwriter))

self.name = name

self.encode = encode

self.decode = decode

self.incrementalencoder = incrementalencoder

self.incrementaldecoder = incrementaldecoder

self.streamwriter = streamwriter

self.streamreader = streamreader

if _is_text_encoding is not None:

self._is_text_encoding = _is_text_encoding

return self

def __repr__(self):

return "<%s.%s object for encoding %s at %#x>" % \

(self.__class__.__module__, self.__class__.__qualname__,

self.name, id(self))

class Codec:

""" Defines the interface for stateless encoders/decoders.

The .encode()/.decode() methods may use different error

handling schemes by providing the errors argument. These

string values are predefined:

'strict' - raise a ValueError error (or a subclass)

'ignore' - ignore the character and continue with the next

'replace' - replace with a suitable replacement character;

Python will use the official U+FFFD REPLACEMENT

CHARACTER for the builtin Unicode codecs on

decoding and '?' on encoding.

'surrogateescape' - replace with private code points U+DCnn.

'xmlcharrefreplace' - Replace with the appropriate XML

character reference (only for encoding).

'backslashreplace' - Replace with backslashed escape sequences.

'namereplace' - Replace with \\N{...} escape sequences

(only for encoding).

The set of allowed values can be extended via register_error.

"""

def encode(self, input, errors='strict'):

""" Encodes the object input and returns a tuple (output

object, length consumed).

errors defines the error handling to apply. It defaults to

'strict' handling.

The method may not store state in the Codec instance. Use

StreamWriter for codecs which have to keep state in order to

make encoding efficient.

The encoder must be able to handle zero length input and

return an empty object of the output object type in this

situation.

"""

raise NotImplementedError

def decode(self, input, errors='strict'):

""" Decodes the object input and returns a tuple (output

object, length consumed).

input must be an object which provides the bf_getreadbuf

buffer slot. Python strings, buffer objects and memory

mapped files are examples of objects providing this slot.

errors defines the error handling to apply. It defaults to

'strict' handling.

The method may not store state in the Codec instance. Use

StreamReader for codecs which have to keep state in order to

make decoding efficient.

The decoder must be able to handle zero length input and

return an empty object of the output object type in this

situation.

"""

raise NotImplementedError

class IncrementalEncoder(object):

"""

An IncrementalEncoder encodes an input in multiple steps. The input can

be passed piece by piece to the encode() method. The IncrementalEncoder

remembers the state of the encoding process between calls to encode().

"""

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

"""

Creates an IncrementalEncoder instance.

The IncrementalEncoder may use different error handling schemes by

providing the errors keyword argument. See the module docstring

for a list of possible values.

"""

self.errors = errors

self.buffer = ""

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

"""

Encodes input and returns the resulting object.

"""

raise NotImplementedError

def reset(self):

"""

Resets the encoder to the initial state.

"""

def getstate(self):

"""

Return the current state of the encoder.

"""

return 0

def setstate(self, state):

"""

Set the current state of the encoder. state must have been

returned by getstate().

"""

class BufferedIncrementalEncoder(IncrementalEncoder):

"""

This subclass of IncrementalEncoder can be used as the baseclass for an

incremental encoder if the encoder must keep some of the output in a

buffer between calls to encode().

"""

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

IncrementalEncoder.__init__(self, errors)

# unencoded input that is kept between calls to encode()

self.buffer = ""

def _buffer_encode(self, input, errors, final):

# Overwrite this method in subclasses: It must encode input

# and return an (output, length consumed) tuple

raise NotImplementedError

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

# encode input (taking the buffer into account)

data = self.buffer + input

(result, consumed) = self._buffer_encode(data, self.errors, final)

# keep unencoded input until the next call

self.buffer = data[consumed:]

return result

def reset(self):

IncrementalEncoder.reset(self)

self.buffer = ""

def getstate(self):

return self.buffer or 0

def setstate(self, state):

self.buffer = state or ""

class IncrementalDecoder(object):

"""

An IncrementalDecoder decodes an input in multiple steps. The input can

be passed piece by piece to the decode() method. The IncrementalDecoder

remembers the state of the decoding process between calls to decode().

"""

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

"""

Create an IncrementalDecoder instance.

The IncrementalDecoder may use different error handling schemes by

providing the errors keyword argument. See the module docstring

for a list of possible values.

"""

self.errors = errors

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

"""

Decode input and returns the resulting object.

"""

raise NotImplementedError

def reset(self):

"""

Reset the decoder to the initial state.

"""

def getstate(self):

"""

Return the current state of the decoder.

This must be a (buffered_input, additional_state_info) tuple.

buffered_input must be a bytes object containing bytes that

were passed to decode() that have not yet been converted.

additional_state_info must be a non-negative integer

representing the state of the decoder WITHOUT yet having

processed the contents of buffered_input. In the initial state

and after reset(), getstate() must return (b"", 0).

"""

return (b"", 0)

def setstate(self, state):

"""

Set the current state of the decoder.

state must have been returned by getstate(). The effect of

setstate((b"", 0)) must be equivalent to reset().

"""

class BufferedIncrementalDecoder(IncrementalDecoder):

"""

This subclass of IncrementalDecoder can be used as the baseclass for an

incremental decoder if the decoder must be able to handle incomplete

byte sequences.

"""

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

IncrementalDecoder.__init__(self, errors)

# undecoded input that is kept between calls to decode()

self.buffer = b""

def _buffer_decode(self, input, errors, final):

# Overwrite this method in subclasses: It must decode input

# and return an (output, length consumed) tuple

raise NotImplementedError

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

# decode input (taking the buffer into account)

data = self.buffer + input

(result, consumed) = self._buffer_decode(data, self.errors, final)

# keep undecoded input until the next call

self.buffer = data[consumed:]

return result

def reset(self):

IncrementalDecoder.reset(self)

self.buffer = b""

def getstate(self):

# additional state info is always 0

return (self.buffer, 0)

def setstate(self, state):

# ignore additional state info

self.buffer = state[0]

# The StreamWriter and StreamReader class provide generic working

# interfaces which can be used to implement new encoding submodules

# very easily. See encodings/utf_8.py for an example on how this is

# done.

class StreamWriter(Codec):

def __init__(self, stream, errors='strict'):

""" Creates a StreamWriter instance.

stream must be a file-like object open for writing.

The StreamWriter may use different error handling

schemes by providing the errors keyword argument. These

parameters are predefined:

'strict' - raise a ValueError (or a subclass)

'ignore' - ignore the character and continue with the next

'replace'- replace with a suitable replacement character

'xmlcharrefreplace' - Replace with the appropriate XML

character reference.

'backslashreplace' - Replace with backslashed escape

sequences.

'namereplace' - Replace with \\N{...} escape sequences.

The set of allowed parameter values can be extended via

register_error.

"""

self.stream = stream

self.errors = errors

def write(self, object):

""" Writes the object's contents encoded to self.stream.

"""

data, consumed = self.encode(object, self.errors)

self.stream.write(data)

def writelines(self, list):

""" Writes the concatenated list of strings to the stream

using .write().

"""

self.write(''.join(list))

def reset(self):

""" Flushes and resets the codec buffers used for keeping state.

Calling this method should ensure that the data on the

output is put into a clean state, that allows appending

of new fresh data without having to rescan the whole

stream to recover state.

"""

pass

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

self.stream.seek(offset, whence)

if whence == 0 and offset == 0:

self.reset()

def __getattr__(self, name,

getattr=getattr):

""" Inherit all other methods from the underlying stream.

"""

return getattr(self.stream, name)

def __enter__(self):

return self

def __exit__(self, type, value, tb):

self.stream.close()

###

class StreamReader(Codec):

charbuffertype = str

def __init__(self, stream, errors='strict'):

""" Creates a StreamReader instance.

stream must be a file-like object open for reading.

The StreamReader may use different error handling

schemes by providing the errors keyword argument. These

parameters are predefined:

'strict' - raise a ValueError (or a subclass)

'ignore' - ignore the character and continue with the next

'replace'- replace with a suitable replacement character

'backslashreplace' - Replace with backslashed escape sequences;

The set of allowed parameter values can be extended via

register_error.

"""

self.stream = stream

self.errors = errors

self.bytebuffer = b""

self._empty_charbuffer = self.charbuffertype()

self.charbuffer = self._empty_charbuffer

self.linebuffer = None

def decode(self, input, errors='strict'):

raise NotImplementedError

def read(self, size=-1, chars=-1, firstline=False):

""" Decodes data from the stream self.stream and returns the

resulting object.

chars indicates the number of decoded code points or bytes to

return. read() will never return more data than requested,

but it might return less, if there is not enough available.

size indicates the approximate maximum number of decoded

bytes or code points to read for decoding. The decoder

can modify this setting as appropriate. The default value

-1 indicates to read and decode as much as possible. size

is intended to prevent having to decode huge files in one

step.

If firstline is true, and a UnicodeDecodeError happens

after the first line terminator in the input only the first line

will be returned, the rest of the input will be kept until the

next call to read().

The method should use a greedy read strategy, meaning that

it should read as much data as is allowed within the

definition of the encoding and the given size, e.g. if

optional encoding endings or state markers are available

on the stream, these should be read too.

"""

# If we have lines cached, first merge them back into characters

if self.linebuffer:

self.charbuffer = self._empty_charbuffer.join(self.linebuffer)

self.linebuffer = None

# read until we get the required number of characters (if available)

while True:

# can the request be satisfied from the character buffer?

if chars >= 0:

if len(self.charbuffer) >= chars:

break

elif size >= 0:

if len(self.charbuffer) >= size:

break

# we need more data

if size < 0:

newdata = self.stream.read()

else:

newdata = self.stream.read(size)

# decode bytes (those remaining from the last call included)

data = self.bytebuffer + newdata

if not data:

break

try:

newchars, decodedbytes = self.decode(data, self.errors)

except UnicodeDecodeError as exc:

if firstline:

newchars, decodedbytes = \

self.decode(data[:exc.start], self.errors)

lines = newchars.splitlines(keepends=True)

if len(lines)<=1:

raise

else:

raise

# keep undecoded bytes until the next call

self.bytebuffer = data[decodedbytes:]

# put new characters in the character buffer

self.charbuffer += newchars

# there was no data available

if not newdata:

break

if chars < 0:

# Return everything we've got

result = self.charbuffer

self.charbuffer = self._empty_charbuffer

else:

# Return the first chars characters

result = self.charbuffer[:chars]

self.charbuffer = self.charbuffer[chars:]

return result

def readline(self, size=None, keepends=True):

""" Read one line from the input stream and return the

decoded data.

size, if given, is passed as size argument to the

read() method.

"""

# If we have lines cached from an earlier read, return

# them unconditionally

if self.linebuffer:

line = self.linebuffer[0]

del self.linebuffer[0]

if len(self.linebuffer) == 1:

# revert to charbuffer mode; we might need more data

# next time

self.charbuffer = self.linebuffer[0]

self.linebuffer = None

if not keepends:

line = line.splitlines(keepends=False)[0]

return line

readsize = size or 72

line = self._empty_charbuffer

# If size is given, we call read() only once

while True:

data = self.read(readsize, firstline=True)

if data:

# If we're at a "\r" read one extra character (which might

# be a "\n") to get a proper line ending. If the stream is

# temporarily exhausted we return the wrong line ending.

if (isinstance(data, str) and data.endswith("\r")) or \

(isinstance(data, bytes) and data.endswith(b"\r")):

data += self.read(size=1, chars=1)

line += data

lines = line.splitlines(keepends=True)

if lines:

if len(lines) > 1:

# More than one line result; the first line is a full line

# to return

line = lines[0]

del lines[0]

if len(lines) > 1:

# cache the remaining lines

lines[-1] += self.charbuffer

self.linebuffer = lines

self.charbuffer = None

else:

# only one remaining line, put it back into charbuffer

self.charbuffer = lines[0] + self.charbuffer

if not keepends:

line = line.splitlines(keepends=False)[0]

break

line0withend = lines[0]

line0withoutend = lines[0].splitlines(keepends=False)[0]

if line0withend != line0withoutend: # We really have a line end

# Put the rest back together and keep it until the next call

self.charbuffer = self._empty_charbuffer.join(lines[1:]) + \

self.charbuffer

if keepends:

line = line0withend

else:

line = line0withoutend

break

# we didn't get anything or this was our only try

if not data or size is not None:

if line and not keepends:

line = line.splitlines(keepends=False)[0]

break

if readsize < 8000:

readsize *= 2

return line

def readlines(self, sizehint=None, keepends=True):

""" Read all lines available on the input stream

and return them as a list.

Line breaks are implemented using the codec's decoder

method and are included in the list entries.

sizehint, if given, is ignored since there is no efficient

way to finding the true end-of-line.

"""

data = self.read()

return data.splitlines(keepends)

def reset(self):

""" Resets the codec buffers used for keeping state.

Note that no stream repositioning should take place.

This method is primarily intended to be able to recover

from decoding errors.

"""

self.bytebuffer = b""

self.charbuffer = self._empty_charbuffer

self.linebuffer = None

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

""" Set the input stream's current position.

Resets the codec buffers used for keeping state.

"""

self.stream.seek(offset, whence)

self.reset()

def __next__(self):

""" Return the next decoded line from the input stream."""

line = self.readline()

if line:

return line

raise StopIteration

def __iter__(self):

return self

def __getattr__(self, name,

getattr=getattr):

""" Inherit all other methods from the underlying stream.

"""

return getattr(self.stream, name)

def __enter__(self):

return self

def __exit__(self, type, value, tb):

self.stream.close()

###

class StreamReaderWriter:

""" StreamReaderWriter instances allow wrapping streams which

work in both read and write modes.

The design is such that one can use the factory functions

returned by the codec.lookup() function to construct the

instance.

"""

# Optional attributes set by the file wrappers below

encoding = 'unknown'

def __init__(self, stream, Reader, Writer, errors='strict'):

""" Creates a StreamReaderWriter instance.

stream must be a Stream-like object.

Reader, Writer must be factory functions or classes

providing the StreamReader, StreamWriter interface resp.

Error handling is done in the same way as defined for the

StreamWriter/Readers.

"""

self.stream = stream

self.reader = Reader(stream, errors)

self.writer = Writer(stream, errors)

self.errors = errors

def read(self, size=-1):

return self.reader.read(size)

def readline(self, size=None):

return self.reader.readline(size)

def readlines(self, sizehint=None):

return self.reader.readlines(sizehint)

def __next__(self):

""" Return the next decoded line from the input stream."""

return next(self.reader)

def __iter__(self):

return self

def write(self, data):

return self.writer.write(data)

def writelines(self, list):

return self.writer.writelines(list)

def reset(self):

self.reader.reset()

self.writer.reset()

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

self.stream.seek(offset, whence)

self.reader.reset()

if whence == 0 and offset == 0:

self.writer.reset()

def __getattr__(self, name,

getattr=getattr):

""" Inherit all other methods from the underlying stream.

"""

return getattr(self.stream, name)

# these are needed to make "with codecs.open(...)" work properly

def __enter__(self):

return self

def __exit__(self, type, value, tb):

self.stream.close()

###

class StreamRecoder:

""" StreamRecoder instances translate data from one encoding to another.

They use the complete set of APIs returned by the

codecs.lookup() function to implement their task.

Data written to the StreamRecoder is first decoded into an

intermediate format (depending on the "decode" codec) and then

written to the underlying stream using an instance of the provided

Writer class.

In the other direction, data is read from the underlying stream using

a Reader instance and then encoded and returned to the caller.

"""

# Optional attributes set by the file wrappers below

data_encoding = 'unknown'

file_encoding = 'unknown'

def __init__(self, stream, encode, decode, Reader, Writer,

errors='strict'):

""" Creates a StreamRecoder instance which implements a two-way

conversion: encode and decode work on the frontend (the

data visible to .read() and .write()) while Reader and Writer

work on the backend (the data in stream).

You can use these objects to do transparent

transcodings from e.g. latin-1 to utf-8 and back.

stream must be a file-like object.

encode and decode must adhere to the Codec interface; Reader and

Writer must be factory functions or classes providing the

StreamReader and StreamWriter interfaces resp.

Error handling is done in the same way as defined for the

StreamWriter/Readers.

"""

self.stream = stream

self.encode = encode

self.decode = decode

self.reader = Reader(stream, errors)

self.writer = Writer(stream, errors)

self.errors = errors

def read(self, size=-1):

data = self.reader.read(size)

data, bytesencoded = self.encode(data, self.errors)

return data

def readline(self, size=None):

if size is None:

data = self.reader.readline()

else:

data = self.reader.readline(size)

data, bytesencoded = self.encode(data, self.errors)

return data

def readlines(self, sizehint=None):

data = self.reader.read()

data, bytesencoded = self.encode(data, self.errors)

return data.splitlines(keepends=True)

def __next__(self):

""" Return the next decoded line from the input stream."""

data = next(self.reader)

data, bytesencoded = self.encode(data, self.errors)

return data

def __iter__(self):

return self

def write(self, data):

data, bytesdecoded = self.decode(data, self.errors)

return self.writer.write(data)

def writelines(self, list):

data = ''.join(list)

data, bytesdecoded = self.decode(data, self.errors)

return self.writer.write(data)

def reset(self):

self.reader.reset()

self.writer.reset()

def __getattr__(self, name,

getattr=getattr):

""" Inherit all other methods from the underlying stream.

"""

return getattr(self.stream, name)

def __enter__(self):

return self

def __exit__(self, type, value, tb):

self.stream.close()

### Shortcuts

def open(filename, mode='r', encoding=None, errors='strict', buffering=1):

""" Open an encoded file using the given mode and return

a wrapped version providing transparent encoding/decoding.

Note: The wrapped version will only accept the object format

defined by the codecs, i.e. Unicode objects for most builtin

codecs. Output is also codec dependent and will usually be

Unicode as well.

Underlying encoded files are always opened in binary mode.

The default file mode is 'r', meaning to open the file in read mode.

encoding specifies the encoding which is to be used for the

file.

errors may be given to define the error handling. It defaults

to 'strict' which causes ValueErrors to be raised in case an

encoding error occurs.

buffering has the same meaning as for the builtin open() API.

It defaults to line buffered.

The returned wrapped file object provides an extra attribute

.encoding which allows querying the used encoding. This

attribute is only available if an encoding was specified as

parameter.

"""

if encoding is not None and \

'b' not in mode:

# Force opening of the file in binary mode

mode = mode + 'b'

file = builtins.open(filename, mode, buffering)

if encoding is None:

return file

info = lookup(encoding)

srw = StreamReaderWriter(file, info.streamreader, info.streamwriter, errors)

# Add attributes to simplify introspection

srw.encoding = encoding

return srw

def EncodedFile(file, data_encoding, file_encoding=None, errors='strict'):

""" Return a wrapped version of file which provides transparent

encoding translation.

Data written to the wrapped file is decoded according

to the given data_encoding and then encoded to the underlying

file using file_encoding. The intermediate data type

will usually be Unicode but depends on the specified codecs.

Bytes read from the file are decoded using file_encoding and then

passed back to the caller encoded using data_encoding.

If file_encoding is not given, it defaults to data_encoding.

errors may be given to define the error handling. It defaults

to 'strict' which causes ValueErrors to be raised in case an

encoding error occurs.

The returned wrapped file object provides two extra attributes

.data_encoding and .file_encoding which reflect the given

parameters of the same name. The attributes can be used for

introspection by Python programs.

"""

if file_encoding is None:

file_encoding = data_encoding

data_info = lookup(data_encoding)

file_info = lookup(file_encoding)

sr = StreamRecoder(file, data_info.encode, data_info.decode,

file_info.streamreader, file_info.streamwriter, errors)

# Add attributes to simplify introspection

sr.data_encoding = data_encoding

sr.file_encoding = file_encoding

return sr

### Helpers for codec lookup

def getencoder(encoding):

""" Lookup up the codec for the given encoding and return

its encoder function.

Raises a LookupError in case the encoding cannot be found.

"""

return lookup(encoding).encode

def getdecoder(encoding):

""" Lookup up the codec for the given encoding and return

its decoder function.

Raises a LookupError in case the encoding cannot be found.

"""

return lookup(encoding).decode

def getincrementalencoder(encoding):

""" Lookup up the codec for the given encoding and return

its IncrementalEncoder class or factory function.

Raises a LookupError in case the encoding cannot be found

or the codecs doesn't provide an incremental encoder.

"""

encoder = lookup(encoding).incrementalencoder

if encoder is None:

raise LookupError(encoding)

return encoder

def getincrementaldecoder(encoding):

""" Lookup up the codec for the given encoding and return

its IncrementalDecoder class or factory function.

Raises a LookupError in case the encoding cannot be found

or the codecs doesn't provide an incremental decoder.

"""

decoder = lookup(encoding).incrementaldecoder

if decoder is None:

raise LookupError(encoding)

return decoder

def getreader(encoding):

""" Lookup up the codec for the given encoding and return

its StreamReader class or factory function.

Raises a LookupError in case the encoding cannot be found.

"""

return lookup(encoding).streamreader

def getwriter(encoding):

View remainder of file in raw view

cpython/Lib/codecs.py at 3.5 · python/cpython · GitHub

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