diff options
Diffstat (limited to 'Lib/lzma.py')
| -rw-r--r-- | Lib/lzma.py | 130 |
1 files changed, 86 insertions, 44 deletions
diff --git a/Lib/lzma.py b/Lib/lzma.py index 1a1b065..b2e2f7e 100644 --- a/Lib/lzma.py +++ b/Lib/lzma.py @@ -55,7 +55,7 @@ class LZMAFile(io.BufferedIOBase): be an existing file object to read from or write to. mode can be "r" for reading (default), "w" for (over)writing, or - "a" for appending. These can equivalently be given as "rb", "wb", + "a" for appending. These can equivalently be given as "rb", "wb" and "ab" respectively. format specifies the container format to use for the file. @@ -110,7 +110,8 @@ class LZMAFile(io.BufferedIOBase): # stream will need a separate decompressor object. self._init_args = {"format":format, "filters":filters} self._decompressor = LZMADecompressor(**self._init_args) - self._buffer = None + self._buffer = b"" + self._buffer_offset = 0 elif mode in ("w", "wb", "a", "ab"): if format is None: format = FORMAT_XZ @@ -143,7 +144,7 @@ class LZMAFile(io.BufferedIOBase): try: if self._mode in (_MODE_READ, _MODE_READ_EOF): self._decompressor = None - self._buffer = None + self._buffer = b"" elif self._mode == _MODE_WRITE: self._fp.write(self._compressor.flush()) self._compressor = None @@ -187,15 +188,18 @@ class LZMAFile(io.BufferedIOBase): raise ValueError("I/O operation on closed file") def _check_can_read(self): - if not self.readable(): + if self._mode not in (_MODE_READ, _MODE_READ_EOF): + self._check_not_closed() raise io.UnsupportedOperation("File not open for reading") def _check_can_write(self): - if not self.writable(): + if self._mode != _MODE_WRITE: + self._check_not_closed() raise io.UnsupportedOperation("File not open for writing") def _check_can_seek(self): - if not self.readable(): + if self._mode not in (_MODE_READ, _MODE_READ_EOF): + self._check_not_closed() raise io.UnsupportedOperation("Seeking is only supported " "on files open for reading") if not self._fp.seekable(): @@ -204,16 +208,13 @@ class LZMAFile(io.BufferedIOBase): # Fill the readahead buffer if it is empty. Returns False on EOF. def _fill_buffer(self): + if self._mode == _MODE_READ_EOF: + return False # Depending on the input data, our call to the decompressor may not # return any data. In this case, try again after reading another block. - while True: - if self._buffer: - return True - - if self._decompressor.unused_data: - rawblock = self._decompressor.unused_data - else: - rawblock = self._fp.read(_BUFFER_SIZE) + while self._buffer_offset == len(self._buffer): + rawblock = (self._decompressor.unused_data or + self._fp.read(_BUFFER_SIZE)) if not rawblock: if self._decompressor.eof: @@ -229,30 +230,48 @@ class LZMAFile(io.BufferedIOBase): self._decompressor = LZMADecompressor(**self._init_args) self._buffer = self._decompressor.decompress(rawblock) + self._buffer_offset = 0 + return True # Read data until EOF. # If return_data is false, consume the data without returning it. def _read_all(self, return_data=True): + # The loop assumes that _buffer_offset is 0. Ensure that this is true. + self._buffer = self._buffer[self._buffer_offset:] + self._buffer_offset = 0 + blocks = [] while self._fill_buffer(): if return_data: blocks.append(self._buffer) self._pos += len(self._buffer) - self._buffer = None + self._buffer = b"" if return_data: return b"".join(blocks) # Read a block of up to n bytes. # If return_data is false, consume the data without returning it. def _read_block(self, n, return_data=True): + # If we have enough data buffered, return immediately. + end = self._buffer_offset + n + if end <= len(self._buffer): + data = self._buffer[self._buffer_offset : end] + self._buffer_offset = end + self._pos += len(data) + return data if return_data else None + + # The loop assumes that _buffer_offset is 0. Ensure that this is true. + self._buffer = self._buffer[self._buffer_offset:] + self._buffer_offset = 0 + blocks = [] while n > 0 and self._fill_buffer(): if n < len(self._buffer): data = self._buffer[:n] - self._buffer = self._buffer[n:] + self._buffer_offset = n else: data = self._buffer - self._buffer = None + self._buffer = b"" if return_data: blocks.append(data) self._pos += len(data) @@ -267,9 +286,9 @@ class LZMAFile(io.BufferedIOBase): The exact number of bytes returned is unspecified. """ self._check_can_read() - if self._mode == _MODE_READ_EOF or not self._fill_buffer(): + if not self._fill_buffer(): return b"" - return self._buffer + return self._buffer[self._buffer_offset:] def read(self, size=-1): """Read up to size uncompressed bytes from the file. @@ -278,7 +297,7 @@ class LZMAFile(io.BufferedIOBase): Returns b"" if the file is already at EOF. """ self._check_can_read() - if self._mode == _MODE_READ_EOF or size == 0: + if size == 0: return b"" elif size < 0: return self._read_all() @@ -295,18 +314,40 @@ class LZMAFile(io.BufferedIOBase): # this does not give enough data for the decompressor to make progress. # In this case we make multiple reads, to avoid returning b"". self._check_can_read() - if (size == 0 or self._mode == _MODE_READ_EOF or - not self._fill_buffer()): + if (size == 0 or + # Only call _fill_buffer() if the buffer is actually empty. + # This gives a significant speedup if *size* is small. + (self._buffer_offset == len(self._buffer) and not self._fill_buffer())): return b"" - if 0 < size < len(self._buffer): - data = self._buffer[:size] - self._buffer = self._buffer[size:] + if size > 0: + data = self._buffer[self._buffer_offset : + self._buffer_offset + size] + self._buffer_offset += len(data) else: - data = self._buffer - self._buffer = None + data = self._buffer[self._buffer_offset:] + self._buffer = b"" + self._buffer_offset = 0 self._pos += len(data) return data + def readline(self, size=-1): + """Read a line of uncompressed bytes from the file. + + The terminating newline (if present) is retained. If size is + non-negative, no more than size bytes will be read (in which + case the line may be incomplete). Returns b'' if already at EOF. + """ + self._check_can_read() + # Shortcut for the common case - the whole line is in the buffer. + if size < 0: + end = self._buffer.find(b"\n", self._buffer_offset) + 1 + if end > 0: + line = self._buffer[self._buffer_offset : end] + self._buffer_offset = end + self._pos += len(line) + return line + return io.BufferedIOBase.readline(self, size) + def write(self, data): """Write a bytes object to the file. @@ -326,7 +367,8 @@ class LZMAFile(io.BufferedIOBase): self._mode = _MODE_READ self._pos = 0 self._decompressor = LZMADecompressor(**self._init_args) - self._buffer = None + self._buffer = b"" + self._buffer_offset = 0 def seek(self, offset, whence=0): """Change the file position. @@ -365,8 +407,7 @@ class LZMAFile(io.BufferedIOBase): offset -= self._pos # Read and discard data until we reach the desired position. - if self._mode != _MODE_READ_EOF: - self._read_block(offset, return_data=False) + self._read_block(offset, return_data=False) return self._pos @@ -381,23 +422,24 @@ def open(filename, mode="rb", *, encoding=None, errors=None, newline=None): """Open an LZMA-compressed file in binary or text mode. - filename can be either an actual file name (given as a str or bytes object), - in which case the named file is opened, or it can be an existing file object - to read from or write to. + filename can be either an actual file name (given as a str or bytes + object), in which case the named file is opened, or it can be an + existing file object to read from or write to. - The mode argument can be "r", "rb" (default), "w", "wb", "a", or "ab" for - binary mode, or "rt", "wt" or "at" for text mode. + The mode argument can be "r", "rb" (default), "w", "wb", "a" or "ab" + for binary mode, or "rt", "wt" or "at" for text mode. - The format, check, preset and filters arguments specify the compression - settings, as for LZMACompressor, LZMADecompressor and LZMAFile. + The format, check, preset and filters arguments specify the + compression settings, as for LZMACompressor, LZMADecompressor and + LZMAFile. - For binary mode, this function is equivalent to the LZMAFile constructor: - LZMAFile(filename, mode, ...). In this case, the encoding, errors and - newline arguments must not be provided. + For binary mode, this function is equivalent to the LZMAFile + constructor: LZMAFile(filename, mode, ...). In this case, the + encoding, errors and newline arguments must not be provided. For text mode, a LZMAFile object is created, and wrapped in an - io.TextIOWrapper instance with the specified encoding, error handling - behavior, and line ending(s). + io.TextIOWrapper instance with the specified encoding, error + handling behavior, and line ending(s). """ if "t" in mode: @@ -427,7 +469,7 @@ def compress(data, format=FORMAT_XZ, check=-1, preset=None, filters=None): Refer to LZMACompressor's docstring for a description of the optional arguments *format*, *check*, *preset* and *filters*. - For incremental compression, use an LZMACompressor object instead. + For incremental compression, use an LZMACompressor instead. """ comp = LZMACompressor(format, check, preset, filters) return comp.compress(data) + comp.flush() @@ -439,7 +481,7 @@ def decompress(data, format=FORMAT_AUTO, memlimit=None, filters=None): Refer to LZMADecompressor's docstring for a description of the optional arguments *format*, *check* and *filters*. - For incremental decompression, use a LZMADecompressor object instead. + For incremental decompression, use an LZMADecompressor instead. """ results = [] while True: |