diff options
Diffstat (limited to 'Lib/lzma.py')
| -rw-r--r-- | Lib/lzma.py | 226 |
1 files changed, 30 insertions, 196 deletions
diff --git a/Lib/lzma.py b/Lib/lzma.py index f1d3958179..7dff1c319a 100644 --- a/Lib/lzma.py +++ b/Lib/lzma.py @@ -25,17 +25,16 @@ import builtins import io from _lzma import * from _lzma import _encode_filter_properties, _decode_filter_properties +import _compression _MODE_CLOSED = 0 _MODE_READ = 1 -_MODE_READ_EOF = 2 +# Value 2 no longer used _MODE_WRITE = 3 -_BUFFER_SIZE = 8192 - -class LZMAFile(io.BufferedIOBase): +class LZMAFile(_compression.BaseStream): """A file object providing transparent LZMA (de)compression. @@ -92,8 +91,6 @@ class LZMAFile(io.BufferedIOBase): self._fp = None self._closefp = False self._mode = _MODE_CLOSED - self._pos = 0 - self._size = -1 if mode in ("r", "rb"): if check != -1: @@ -105,19 +102,13 @@ class LZMAFile(io.BufferedIOBase): if format is None: format = FORMAT_AUTO mode_code = _MODE_READ - # Save the args to pass to the LZMADecompressor initializer. - # If the file contains multiple compressed streams, each - # stream will need a separate decompressor object. - self._init_args = {"format":format, "filters":filters} - self._decompressor = LZMADecompressor(**self._init_args) - self._buffer = b"" - self._buffer_offset = 0 elif mode in ("w", "wb", "a", "ab", "x", "xb"): if format is None: format = FORMAT_XZ mode_code = _MODE_WRITE self._compressor = LZMACompressor(format=format, check=check, preset=preset, filters=filters) + self._pos = 0 else: raise ValueError("Invalid mode: {!r}".format(mode)) @@ -133,6 +124,11 @@ class LZMAFile(io.BufferedIOBase): else: raise TypeError("filename must be a str or bytes object, or a file") + if self._mode == _MODE_READ: + raw = _compression.DecompressReader(self._fp, LZMADecompressor, + trailing_error=LZMAError, format=format, filters=filters) + self._buffer = io.BufferedReader(raw) + def close(self): """Flush and close the file. @@ -142,9 +138,9 @@ class LZMAFile(io.BufferedIOBase): if self._mode == _MODE_CLOSED: return try: - if self._mode in (_MODE_READ, _MODE_READ_EOF): - self._decompressor = None - self._buffer = b"" + if self._mode == _MODE_READ: + self._buffer.close() + self._buffer = None elif self._mode == _MODE_WRITE: self._fp.write(self._compressor.flush()) self._compressor = None @@ -169,123 +165,18 @@ class LZMAFile(io.BufferedIOBase): def seekable(self): """Return whether the file supports seeking.""" - return self.readable() and self._fp.seekable() + return self.readable() and self._buffer.seekable() def readable(self): """Return whether the file was opened for reading.""" self._check_not_closed() - return self._mode in (_MODE_READ, _MODE_READ_EOF) + return self._mode == _MODE_READ def writable(self): """Return whether the file was opened for writing.""" self._check_not_closed() return self._mode == _MODE_WRITE - # Mode-checking helper functions. - - def _check_not_closed(self): - if self.closed: - raise ValueError("I/O operation on closed file") - - def _check_can_read(self): - 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 self._mode != _MODE_WRITE: - self._check_not_closed() - raise io.UnsupportedOperation("File not open for writing") - - def _check_can_seek(self): - 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(): - raise io.UnsupportedOperation("The underlying file object " - "does not support seeking") - - # 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 self._buffer_offset == len(self._buffer): - rawblock = (self._decompressor.unused_data or - self._fp.read(_BUFFER_SIZE)) - - if not rawblock: - if self._decompressor.eof: - self._mode = _MODE_READ_EOF - self._size = self._pos - return False - else: - raise EOFError("Compressed file ended before the " - "end-of-stream marker was reached") - - if self._decompressor.eof: - # Continue to next stream. - self._decompressor = LZMADecompressor(**self._init_args) - try: - self._buffer = self._decompressor.decompress(rawblock) - except LZMAError: - # Trailing data isn't a valid compressed stream; ignore it. - self._mode = _MODE_READ_EOF - self._size = self._pos - return False - else: - 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 = 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_offset = n - else: - data = self._buffer - self._buffer = b"" - if return_data: - blocks.append(data) - self._pos += len(data) - n -= len(data) - if return_data: - return b"".join(blocks) - def peek(self, size=-1): """Return buffered data without advancing the file position. @@ -293,9 +184,9 @@ class LZMAFile(io.BufferedIOBase): The exact number of bytes returned is unspecified. """ self._check_can_read() - if not self._fill_buffer(): - return b"" - return self._buffer[self._buffer_offset:] + # Relies on the undocumented fact that BufferedReader.peek() always + # returns at least one byte (except at EOF) + return self._buffer.peek(size) def read(self, size=-1): """Read up to size uncompressed bytes from the file. @@ -304,38 +195,19 @@ class LZMAFile(io.BufferedIOBase): Returns b"" if the file is already at EOF. """ self._check_can_read() - if size == 0: - return b"" - elif size < 0: - return self._read_all() - else: - return self._read_block(size) + return self._buffer.read(size) def read1(self, size=-1): """Read up to size uncompressed bytes, while trying to avoid - making multiple reads from the underlying stream. + making multiple reads from the underlying stream. Reads up to a + buffer's worth of data if size is negative. Returns b"" if the file is at EOF. """ - # Usually, read1() calls _fp.read() at most once. However, sometimes - # 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 - # 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 size > 0: - data = self._buffer[self._buffer_offset : - self._buffer_offset + size] - self._buffer_offset += len(data) - else: - data = self._buffer[self._buffer_offset:] - self._buffer = b"" - self._buffer_offset = 0 - self._pos += len(data) - return data + if size < 0: + size = io.DEFAULT_BUFFER_SIZE + return self._buffer.read1(size) def readline(self, size=-1): """Read a line of uncompressed bytes from the file. @@ -345,15 +217,7 @@ class LZMAFile(io.BufferedIOBase): 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) + return self._buffer.readline(size) def write(self, data): """Write a bytes object to the file. @@ -368,16 +232,7 @@ class LZMAFile(io.BufferedIOBase): self._pos += len(data) return len(data) - # Rewind the file to the beginning of the data stream. - def _rewind(self): - self._fp.seek(0, 0) - self._mode = _MODE_READ - self._pos = 0 - self._decompressor = LZMADecompressor(**self._init_args) - self._buffer = b"" - self._buffer_offset = 0 - - def seek(self, offset, whence=0): + def seek(self, offset, whence=io.SEEK_SET): """Change the file position. The new position is specified by offset, relative to the @@ -389,38 +244,17 @@ class LZMAFile(io.BufferedIOBase): Returns the new file position. - Note that seeking is emulated, sp depending on the parameters, + Note that seeking is emulated, so depending on the parameters, this operation may be extremely slow. """ self._check_can_seek() - - # Recalculate offset as an absolute file position. - if whence == 0: - pass - elif whence == 1: - offset = self._pos + offset - elif whence == 2: - # Seeking relative to EOF - we need to know the file's size. - if self._size < 0: - self._read_all(return_data=False) - offset = self._size + offset - else: - raise ValueError("Invalid value for whence: {}".format(whence)) - - # Make it so that offset is the number of bytes to skip forward. - if offset < self._pos: - self._rewind() - else: - offset -= self._pos - - # Read and discard data until we reach the desired position. - self._read_block(offset, return_data=False) - - return self._pos + return self._buffer.seek(offset, whence) def tell(self): """Return the current file position.""" self._check_not_closed() + if self._mode == _MODE_READ: + return self._buffer.tell() return self._pos @@ -445,7 +279,7 @@ def open(filename, mode="rb", *, 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 + For text mode, an LZMAFile object is created, and wrapped in an io.TextIOWrapper instance with the specified encoding, error handling behavior, and line ending(s). |