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-rw-r--r--Lib/encodings/utf_8_sig.py57
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diff --git a/Lib/encodings/utf_8_sig.py b/Lib/encodings/utf_8_sig.py
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+++ b/Lib/encodings/utf_8_sig.py
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+""" 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.startswith(codecs.BOM_UTF8):
+ input = input[3:]
+ prefix = 3
+ (output, consumed) = codecs.utf_8_decode(input, errors, True)
+ return (output, consumed+prefix)
+
+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 and codecs.BOM_UTF8.startswith(input):
+ # not enough data to decide if this is a BOM
+ # => try again on the next call
+ return (u"", 0)
+ self.decode = codecs.utf_8_decode
+ return decode(input, errors)
+
+### encodings module API
+
+def getregentry():
+
+ return (encode,decode,StreamReader,StreamWriter)