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Issue #22982: Improve BOM handling when seeking to multiple positions of a writable text file.

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This commit is contained in:
Antoine Pitrou 2015-04-13 20:02:33 +02:00
commit 56452eea39
4 changed files with 52 additions and 15 deletions
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26
Lib/_pyio.py
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@ -2275,6 +2275,19 @@ class TextIOWrapper(TextIOBase):
return buffer
def seek(self, cookie, whence=0):
def _reset_encoder(position):
"""Reset the encoder (merely useful for proper BOM handling)"""
try:
encoder = self._encoder or self._get_encoder()
except LookupError:
# Sometimes the encoder doesn't exist
pass
else:
if position != 0:
encoder.setstate(0)
else:
encoder.reset()
if self.closed:
raise ValueError("tell on closed file")
if not self._seekable:
@ -2295,6 +2308,7 @@ class TextIOWrapper(TextIOBase):
self._snapshot = None
if self._decoder:
self._decoder.reset()
_reset_encoder(position)
return position
if whence != 0:
raise ValueError("unsupported whence (%r)" % (whence,))
@ -2332,17 +2346,7 @@ class TextIOWrapper(TextIOBase):
raise OSError("can't restore logical file position")
self._decoded_chars_used = chars_to_skip
# Finally, reset the encoder (merely useful for proper BOM handling)
try:
encoder = self._encoder or self._get_encoder()
except LookupError:
# Sometimes the encoder doesn't exist
pass
else:
if cookie != 0:
encoder.setstate(0)
else:
encoder.reset()
_reset_encoder(cookie)
return cookie
def read(self, size=None):