112 lines
3.5 KiB
Python
112 lines
3.5 KiB
Python
|
""" Python 'utf-8-sig' Codec
|
||
|
|
This work similar to UTF-8 with the following changes:
|
||
|
|
|
||
|
|
* On encoding/writing a UTF-8 encoded BOM will be prepended/written as the
|
||
|
|
first three bytes.
|
||
|
|
|
||
|
|
* On decoding/reading if the first three bytes are a UTF-8 encoded BOM, these
|
||
|
|
bytes will be skipped.
|
||
|
|
"""
|
||
|
|
import codecs
|
||
|
|
|
||
|
|
### Codec APIs
|
||
|
|
|
||
|
|
def encode(input, errors='strict'):
|
||
|
|
return (codecs.BOM_UTF8 + codecs.utf_8_encode(input, errors)[0], len(input))
|
||
|
|
|
||
|
|
def decode(input, errors='strict'):
|
||
|
|
prefix = 0
|
||
|
|
if input[:3] == codecs.BOM_UTF8:
|
||
|
|
input = input[3:]
|
||
|
|
prefix = 3
|
||
|
|
(output, consumed) = codecs.utf_8_decode(input, errors, True)
|
||
|
|
return (output, consumed+prefix)
|
||
|
|
|
||
|
|
class IncrementalEncoder(codecs.IncrementalEncoder):
|
||
|
|
def __init__(self, errors='strict'):
|
||
|
|
codecs.IncrementalEncoder.__init__(self, errors)
|
||
|
|
self.first = True
|
||
|
|
|
||
|
|
def encode(self, input, final=False):
|
||
|
|
if self.first:
|
||
|
|
self.first = False
|
||
|
|
return codecs.BOM_UTF8 + codecs.utf_8_encode(input, self.errors)[0]
|
||
|
|
else:
|
||
|
|
return codecs.utf_8_encode(input, self.errors)[0]
|
||
|
|
|
||
|
|
def reset(self):
|
||
|
|
codecs.IncrementalEncoder.reset(self)
|
||
|
|
self.first = True
|
||
|
|
|
||
|
|
class IncrementalDecoder(codecs.BufferedIncrementalDecoder):
|
||
|
|
def __init__(self, errors='strict'):
|
||
|
|
codecs.BufferedIncrementalDecoder.__init__(self, errors)
|
||
|
|
self.first = True
|
||
|
|
|
||
|
|
def _buffer_decode(self, input, errors, final):
|
||
|
|
if self.first:
|
||
|
|
if len(input) < 3:
|
||
|
|
if codecs.BOM_UTF8.startswith(input):
|
||
|
|
# not enough data to decide if this really is a BOM
|
||
|
|
# => try again on the next call
|
||
|
|
return (u"", 0)
|
||
|
|
else:
|
||
|
|
self.first = None
|
||
|
|
else:
|
||
|
|
self.first = None
|
||
|
|
if input[:3] == codecs.BOM_UTF8:
|
||
|
|
(output, consumed) = codecs.utf_8_decode(input[3:], errors, final)
|
||
|
|
return (output, consumed+3)
|
||
|
|
return codecs.utf_8_decode(input, errors, final)
|
||
|
|
|
||
|
|
def reset(self):
|
||
|
|
codecs.BufferedIncrementalDecoder.reset(self)
|
||
|
|
self.first = True
|
||
|
|
|
||
|
|
class StreamWriter(codecs.StreamWriter):
|
||
|
|
def reset(self):
|
||
|
|
codecs.StreamWriter.reset(self)
|
||
|
|
try:
|
||
|
|
del self.encode
|
||
|
|
except AttributeError:
|
||
|
|
pass
|
||
|
|
|
||
|
|
def encode(self, input, errors='strict'):
|
||
|
|
self.encode = codecs.utf_8_encode
|
||
|
|
return encode(input, errors)
|
||
|
|
|
||
|
|
class StreamReader(codecs.StreamReader):
|
||
|
|
def reset(self):
|
||
|
|
codecs.StreamReader.reset(self)
|
||
|
|
try:
|
||
|
|
del self.decode
|
||
|
|
except AttributeError:
|
||
|
|
pass
|
||
|
|
|
||
|
|
def decode(self, input, errors='strict'):
|
||
|
|
if len(input) < 3:
|
||
|
|
if codecs.BOM_UTF8.startswith(input):
|
||
|
|
# not enough data to decide if this is a BOM
|
||
|
|
# => try again on the next call
|
||
|
|
return (u"", 0)
|
||
|
|
elif input[:3] == codecs.BOM_UTF8:
|
||
|
|
self.decode = codecs.utf_8_decode
|
||
|
|
(output, consumed) = codecs.utf_8_decode(input[3:],errors)
|
||
|
|
return (output, consumed+3)
|
||
|
|
# (else) no BOM present
|
||
|
|
self.decode = codecs.utf_8_decode
|
||
|
|
return codecs.utf_8_decode(input, errors)
|
||
|
|
|
||
|
|
### encodings module API
|
||
|
|
|
||
|
|
def getregentry():
|
||
|
|
return codecs.CodecInfo(
|
||
|
|
name='utf-8-sig',
|
||
|
|
encode=encode,
|
||
|
|
decode=decode,
|
||
|
|
incrementalencoder=IncrementalEncoder,
|
||
|
|
incrementaldecoder=IncrementalDecoder,
|
||
|
|
streamreader=StreamReader,
|
||
|
|
streamwriter=StreamWriter,
|
||
|
|
)
|