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https://github.com/python/cpython
synced 2024-10-05 11:14:57 +00:00
In TextIOWrapper:
- Switch from consuming _decoded_text to advancing an offset into it. - Fix readline() interaction with seek/tell. - Fix readline() handling of 'limit' argument. Add tests for seek/tell after readline().
This commit is contained in:
Ka-Ping Yee
parent
f44c7e8996
commit
30cc83832d
146
Lib/io.py
146
Lib/io.py
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@ -1180,14 +1180,14 @@ def __init__(self, buffer, encoding=None, errors=None, newline=None,
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self._encoder = None
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self._decoder = None
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self._decoded_text = "" # buffer for text produced by decoder
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self._decoded_text_offset = 0 # offset to text returned by read()
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self._snapshot = None # info for reconstructing decoder state
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self._seekable = self._telling = self.buffer.seekable()
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# A word about _snapshot. This attribute is either None, or a tuple
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# (decoder_state, input_chunk, decoded_chars) where decoder_state is
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# the second (integer) item of the decoder state, input_chunk is the
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# chunk of bytes that was read, and decoded_chars is the number of
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# characters rendered by the decoder after feeding it those bytes.
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# (decoder_state, next_input) where decoder_state is the second
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# (integer) item of the decoder state, and next_input is the chunk
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# of bytes that comes after the snapshot point in the input.
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# We use this to reconstruct intermediate decoder states in tell().
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# Naming convention:
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@ -1271,10 +1271,10 @@ def _read_chunk(self):
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"""
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Read and decode the next chunk of data from the BufferedReader.
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Return a tuple of two elements: all the bytes that were read, and
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the decoded string produced by the decoder. (The entire input
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chunk is sent to the decoder, but some of it may remain buffered
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in the decoder, yet to be converted.)
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The return value is True unless EOF was reached. The decoded string
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is placed in self._decoded_text (replacing its previous value).
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(The entire input chunk is sent to the decoder, though some of it
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may remain buffered in the decoder, yet to be converted.)
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"""
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if self._decoder is None:
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@ -1283,8 +1283,9 @@ def _read_chunk(self):
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# No one should call tell(), so don't bother taking a snapshot.
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input_chunk = self.buffer.read1(self._CHUNK_SIZE)
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eof = not input_chunk
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decoded = self._decoder.decode(input_chunk, eof)
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return (input_chunk, decoded)
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self._decoded_text = self._decoder.decode(input_chunk, eof)
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self._decoded_text_offset = 0
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return not eof
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# The cookie returned by tell() cannot include the contents of
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# the decoder's buffer, so we need to snapshot a point in the
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@ -1298,16 +1299,15 @@ def _read_chunk(self):
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input_chunk = self.buffer.read1(self._CHUNK_SIZE)
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eof = not input_chunk
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decoded = self._decoder.decode(input_chunk, eof)
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self._decoded_text = self._decoder.decode(input_chunk, eof)
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self._decoded_text_offset = 0
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# At the snapshot point len(dec_buffer) bytes ago, the next input
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# to be passed to the decoder is dec_buffer + input_chunk. Save
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# len(decoded) so that later, tell() can figure out how much
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# decoded data has been used up by TextIOWrapper.read().
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self._snapshot = (dec_flags, dec_buffer + input_chunk, len(decoded))
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return (input_chunk, decoded)
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# At the snapshot point, len(dec_buffer) bytes ago, the next input
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# to be passed to the decoder is dec_buffer + input_chunk.
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self._snapshot = (dec_flags, dec_buffer + input_chunk)
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return not eof
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def _encode_tell_cookie(self, position, dec_flags=0,
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def _pack_cookie(self, position, dec_flags=0,
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feed_bytes=0, need_eof=0, skip_chars=0):
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# The meaning of a tell() cookie is: seek to position, set the
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# decoder flags to dec_flags, read feed_bytes bytes, feed them
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@ -1317,7 +1317,7 @@ def _encode_tell_cookie(self, position, dec_flags=0,
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return (position | (dec_flags<<64) | (feed_bytes<<128) |
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(skip_chars<<192) | bool(need_eof)<<256)
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def _decode_tell_cookie(self, bigint):
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def _unpack_cookie(self, bigint):
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rest, position = divmod(bigint, 1<<64)
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rest, dec_flags = divmod(rest, 1<<64)
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rest, feed_bytes = divmod(rest, 1<<64)
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@ -1339,14 +1339,14 @@ def tell(self):
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return position
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# Skip backward to the snapshot point (see _read_chunk).
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dec_flags, next_input, decoded_chars = self._snapshot
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dec_flags, next_input = self._snapshot
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position -= len(next_input)
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# How many decoded characters have been consumed since the snapshot?
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skip_chars = decoded_chars - len(self._decoded_text)
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# How many decoded characters have been returned since the snapshot?
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skip_chars = self._decoded_text_offset
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if skip_chars == 0:
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# We haven't moved from the snapshot point.
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return self._encode_tell_cookie(position, dec_flags)
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return self._pack_cookie(position, dec_flags)
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# Walk the decoder forward, one byte at a time, to find the minimum
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# input necessary to give us the decoded characters we need to skip.
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@ -1373,8 +1373,8 @@ def tell(self):
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if decoded_chars >= skip_chars:
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break
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else:
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# We didn't get enough decoded data; send EOF to get more.
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decoded = decoder.decode(b"", True)
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# We didn't get enough decoded data; signal EOF to get more.
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decoded = decoder.decode(b"", final=True)
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decoded_chars += len(decoded)
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need_eof = 1
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if decoded_chars < skip_chars:
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@ -1385,7 +1385,7 @@ def tell(self):
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position += safe_fed_bytes
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fed_bytes -= safe_fed_bytes
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skip_chars -= safe_decoded_chars
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return self._encode_tell_cookie(
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return self._pack_cookie(
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position, dec_flags, fed_bytes, need_eof, skip_chars)
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finally:
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decoder.setstate(saved_state)
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@ -1405,8 +1405,7 @@ def seek(self, cookie, whence=0):
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raise IOError("can't do nonzero end-relative seeks")
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self.flush()
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position = self.buffer.seek(0, 2)
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self._decoded_text = ""
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self._snapshot = None
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self._clear_decoded_text()
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if self._decoder:
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self._decoder.reset()
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return position
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@ -1419,48 +1418,70 @@ def seek(self, cookie, whence=0):
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# Seek back to the snapshot point.
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position, dec_flags, feed_bytes, need_eof, skip_chars = \
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self._decode_tell_cookie(cookie)
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self._unpack_cookie(cookie)
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self.buffer.seek(position)
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self._decoded_text = ""
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self._snapshot = None
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self._clear_decoded_text()
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if self._decoder or dec_flags or feed_bytes or need_eof:
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# Restore the decoder flags to their values from the snapshot.
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self._decoder = self._decoder or self._get_decoder()
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self._decoder.setstate((b"", dec_flags))
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self._snapshot = (dec_flags, b'')
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if feed_bytes or need_eof:
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# Feed feed_bytes bytes to the decoder.
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input_chunk = self.buffer.read(feed_bytes)
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decoded = self._decoder.decode(input_chunk, need_eof)
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if len(decoded) < skip_chars:
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self._decoded_text = self._decoder.decode(input_chunk, need_eof)
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if len(self._decoded_text) < skip_chars:
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raise IOError("can't restore logical file position")
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# Skip skip_chars of the decoded characters.
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self._decoded_text = decoded[skip_chars:]
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self._decoded_text_offset = skip_chars
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# Restore the snapshot.
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self._snapshot = (dec_flags, input_chunk, len(decoded))
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self._snapshot = (dec_flags, input_chunk)
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return cookie
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def _clear_decoded_text(self):
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"""Reset the _decoded_text buffer."""
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self._decoded_text = ''
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self._decoded_text_offset = 0
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self._snapshot = None
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def _emit_decoded_text(self, n=None):
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"""Advance into the _decoded_text buffer."""
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offset = self._decoded_text_offset
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if n is None:
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text = self._decoded_text[offset:]
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else:
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text = self._decoded_text[offset:offset + n]
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self._decoded_text_offset += len(text)
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return text
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def _unemit_decoded_text(self, n):
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"""Rewind the _decoded_text buffer."""
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if self._decoded_text_offset < n:
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raise AssertionError("unemit out of bounds")
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self._decoded_text_offset -= n
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def read(self, n=None):
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if n is None:
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n = -1
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decoder = self._decoder or self._get_decoder()
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result = self._decoded_text
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if n < 0:
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result += decoder.decode(self.buffer.read(), True)
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self._decoded_text = ""
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self._snapshot = None
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# Read everything.
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result = (self._emit_decoded_text() +
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decoder.decode(self.buffer.read(), final=True))
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self._clear_decoded_text()
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return result
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else:
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while len(result) < n:
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input_chunk, decoded = self._read_chunk()
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result += decoded
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if not input_chunk:
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break
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self._decoded_text = result[n:]
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return result[:n]
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# Keep reading chunks until we have n characters to return.
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eof = False
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result = self._emit_decoded_text(n)
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while len(result) < n and not eof:
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eof = not self._read_chunk()
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result += self._emit_decoded_text(n - len(result))
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return result
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def __next__(self):
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self._telling = False
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@ -1474,21 +1495,20 @@ def __next__(self):
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def readline(self, limit=None):
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if limit is None:
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limit = -1
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if limit >= 0:
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# XXX Hack to support limit argument, for backwards compatibility
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line = self.readline()
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if len(line) <= limit:
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return line
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line, self._decoded_text = \
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line[:limit], line[limit:] + self._decoded_text
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return line
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line = self._decoded_text
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# Grab all the decoded text (we will rewind any extra bits later).
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line = self._emit_decoded_text()
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start = 0
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decoder = self._decoder or self._get_decoder()
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pos = endpos = None
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while True:
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if limit >= 0 and len(line) >= limit:
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# Length limit has been reached.
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endpos = limit
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break
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if self._readtranslate:
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# Newlines are already translated, only search for \n
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pos = line.find('\n', start)
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@ -1538,20 +1558,18 @@ def readline(self, limit=None):
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# No line ending seen yet - get more data
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more_line = ''
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while True:
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readahead, pending = self._read_chunk()
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more_line = pending
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if more_line or not readahead:
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while self._read_chunk():
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if self._decoded_text:
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break
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if more_line:
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line += more_line
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if self._decoded_text:
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line += self._emit_decoded_text()
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else:
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# end of file
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self._decoded_text = ''
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self._snapshot = None
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self._clear_decoded_text()
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return line
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self._decoded_text = line[endpos:]
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# Rewind _decoded_text to just after the line ending we found.
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self._unemit_decoded_text(len(line) - endpos)
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return line[:endpos]
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@property
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@ -590,7 +590,9 @@ class StatefulIncrementalDecoderTest(unittest.TestCase):
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# I=0, O=3
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(b'i.o3.x.xyz.toolong.', False, 'x--.xyz.too.'),
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# I=6, O=3
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(b'i.o3.i6.abcdefghijklmnop', True, 'abc.ghi.mno.')
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(b'i.o3.i6.abcdefghijklmnop', True, 'abc.ghi.mno.'),
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# I=5, O=8 with newlines
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(b'i.o8.i5.abc\ndef\nghy\nz', True, 'abc\nd---.ef\ngh---.y\nz-----.')
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]
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def testDecoder(self):
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@ -890,8 +892,8 @@ def lookupTestDecoder(name):
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return codecs.CodecInfo(
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name='test_decoder', encode=None, decode=None,
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incrementalencoder=None,
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streamreader=None, streamwriter=None,
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incrementaldecoder=StatefulIncrementalDecoder)
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incrementaldecoder=StatefulIncrementalDecoder,
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streamreader=None, streamwriter=None)
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def testSeekAndTellWithData(data, min_pos=0):
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"""Tell/seek to various points within a data stream and ensure
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@ -903,16 +905,42 @@ def testSeekAndTellWithData(data, min_pos=0):
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decoded = f.read()
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f.close()
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for i in range(min_pos, len(decoded) + 1): # seek positions
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for j in [1, 5, len(decoded) - i]: # read lengths
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# Use read() to move to various positions in the input;
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# then tell, read some more data, and seek back.
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for i in range(min_pos, len(decoded) + 1): # to read before tell
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for j in [1, 5, len(decoded)]: # to read after tell
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f = io.open(test_support.TESTFN, encoding='test_decoder')
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self.assertEquals(f.read(i), decoded[:i])
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cookie = f.tell()
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self.assertEquals(f.read(j), decoded[i:i + j])
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f.seek(cookie)
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self.assertEquals(f.tell(), cookie)
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self.assertEquals(f.read(), decoded[i:])
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f.close()
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lines = len(decoded.split('\n'))
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# Use readline() to move to various positions in the input;
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# then tell, read some more data, and seek back.
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for limit in [-1, 4, 128]: # 'limit' argument for readline()
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for j in [1, 5, len(decoded)]: # to read after tell()
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f = io.open(test_support.TESTFN, encoding='test_decoder')
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text = ''
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for k in range(lines): # repeatedly call readline()
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line = f.readline(limit=limit)
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if limit >= 0:
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self.assert_(len(line) <= limit)
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text += line
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i = len(text)
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self.assertEquals(text, decoded[:i])
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cookie = f.tell()
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self.assertEquals(f.read(j), decoded[i:i + j])
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f.seek(cookie)
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self.assertEquals(f.tell(), cookie)
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self.assertEquals(f.read(), decoded[i:])
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f.seek(cookie)
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f.close()
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# Register a special incremental decoder for testing.
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codecs.register(lookupTestDecoder)
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self.codecEnabled = 1
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