| """Interface to the liblzma compression library. |
| |
| This module provides a class for reading and writing compressed files, |
| classes for incremental (de)compression, and convenience functions for |
| one-shot (de)compression. |
| |
| These classes and functions support both the XZ and legacy LZMA |
| container formats, as well as raw compressed data streams. |
| """ |
| |
| __all__ = [ |
| "CHECK_NONE", "CHECK_CRC32", "CHECK_CRC64", "CHECK_SHA256", |
| "CHECK_ID_MAX", "CHECK_UNKNOWN", |
| "FILTER_LZMA1", "FILTER_LZMA2", "FILTER_DELTA", "FILTER_X86", "FILTER_IA64", |
| "FILTER_ARM", "FILTER_ARMTHUMB", "FILTER_POWERPC", "FILTER_SPARC", |
| "FORMAT_AUTO", "FORMAT_XZ", "FORMAT_ALONE", "FORMAT_RAW", |
| "MF_HC3", "MF_HC4", "MF_BT2", "MF_BT3", "MF_BT4", |
| "MODE_FAST", "MODE_NORMAL", "PRESET_DEFAULT", "PRESET_EXTREME", |
| |
| "LZMACompressor", "LZMADecompressor", "LZMAFile", "LZMAError", |
| "open", "compress", "decompress", "is_check_supported", |
| ] |
| |
| import builtins |
| import io |
| from _lzma import * |
| from _lzma import _encode_filter_properties, _decode_filter_properties |
| |
| |
| _MODE_CLOSED = 0 |
| _MODE_READ = 1 |
| _MODE_READ_EOF = 2 |
| _MODE_WRITE = 3 |
| |
| _BUFFER_SIZE = 8192 |
| |
| |
| class LZMAFile(io.BufferedIOBase): |
| |
| """A file object providing transparent LZMA (de)compression. |
| |
| An LZMAFile can act as a wrapper for an existing file object, or |
| refer directly to a named file on disk. |
| |
| Note that LZMAFile provides a *binary* file interface - data read |
| is returned as bytes, and data to be written must be given as bytes. |
| """ |
| |
| def __init__(self, filename=None, mode="r", *, |
| format=None, check=-1, preset=None, filters=None): |
| """Open an LZMA-compressed file in binary 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. |
| |
| mode can be "r" for reading (default), "w" for (over)writing, or |
| "a" for appending. These can equivalently be given as "rb", "wb" |
| and "ab" respectively. |
| |
| format specifies the container format to use for the file. |
| If mode is "r", this defaults to FORMAT_AUTO. Otherwise, the |
| default is FORMAT_XZ. |
| |
| check specifies the integrity check to use. This argument can |
| only be used when opening a file for writing. For FORMAT_XZ, |
| the default is CHECK_CRC64. FORMAT_ALONE and FORMAT_RAW do not |
| support integrity checks - for these formats, check must be |
| omitted, or be CHECK_NONE. |
| |
| When opening a file for reading, the *preset* argument is not |
| meaningful, and should be omitted. The *filters* argument should |
| also be omitted, except when format is FORMAT_RAW (in which case |
| it is required). |
| |
| When opening a file for writing, the settings used by the |
| compressor can be specified either as a preset compression |
| level (with the *preset* argument), or in detail as a custom |
| filter chain (with the *filters* argument). For FORMAT_XZ and |
| FORMAT_ALONE, the default is to use the PRESET_DEFAULT preset |
| level. For FORMAT_RAW, the caller must always specify a filter |
| chain; the raw compressor does not support preset compression |
| levels. |
| |
| preset (if provided) should be an integer in the range 0-9, |
| optionally OR-ed with the constant PRESET_EXTREME. |
| |
| filters (if provided) should be a sequence of dicts. Each dict |
| should have an entry for "id" indicating ID of the filter, plus |
| additional entries for options to the filter. |
| """ |
| self._fp = None |
| self._closefp = False |
| self._mode = _MODE_CLOSED |
| self._pos = 0 |
| self._size = -1 |
| |
| if mode in ("r", "rb"): |
| if check != -1: |
| raise ValueError("Cannot specify an integrity check " |
| "when opening a file for reading") |
| if preset is not None: |
| raise ValueError("Cannot specify a preset compression " |
| "level when opening a file for reading") |
| 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"): |
| if format is None: |
| format = FORMAT_XZ |
| mode_code = _MODE_WRITE |
| self._compressor = LZMACompressor(format=format, check=check, |
| preset=preset, filters=filters) |
| else: |
| raise ValueError("Invalid mode: {!r}".format(mode)) |
| |
| if isinstance(filename, (str, bytes)): |
| if "b" not in mode: |
| mode += "b" |
| self._fp = builtins.open(filename, mode) |
| self._closefp = True |
| self._mode = mode_code |
| elif hasattr(filename, "read") or hasattr(filename, "write"): |
| self._fp = filename |
| self._mode = mode_code |
| else: |
| raise TypeError("filename must be a str or bytes object, or a file") |
| |
| def close(self): |
| """Flush and close the file. |
| |
| May be called more than once without error. Once the file is |
| closed, any other operation on it will raise a ValueError. |
| """ |
| if self._mode == _MODE_CLOSED: |
| return |
| try: |
| if self._mode in (_MODE_READ, _MODE_READ_EOF): |
| self._decompressor = None |
| self._buffer = b"" |
| elif self._mode == _MODE_WRITE: |
| self._fp.write(self._compressor.flush()) |
| self._compressor = None |
| finally: |
| try: |
| if self._closefp: |
| self._fp.close() |
| finally: |
| self._fp = None |
| self._closefp = False |
| self._mode = _MODE_CLOSED |
| |
| @property |
| def closed(self): |
| """True if this file is closed.""" |
| return self._mode == _MODE_CLOSED |
| |
| def fileno(self): |
| """Return the file descriptor for the underlying file.""" |
| self._check_not_closed() |
| return self._fp.fileno() |
| |
| def seekable(self): |
| """Return whether the file supports seeking.""" |
| return self.readable() and self._fp.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) |
| |
| 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") |
| |
| # Continue to next stream. |
| if self._decompressor.eof: |
| 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 = 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. |
| |
| Always returns at least one byte of data, unless at EOF. |
| 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:] |
| |
| def read(self, size=-1): |
| """Read up to size uncompressed bytes from the file. |
| |
| If size is negative or omitted, read until EOF is reached. |
| 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) |
| |
| def read1(self, size=-1): |
| """Read up to size uncompressed bytes, while trying to avoid |
| making multiple reads from the underlying stream. |
| |
| 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 |
| |
| 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. |
| |
| Returns the number of uncompressed bytes written, which is |
| always len(data). Note that due to buffering, the file on disk |
| may not reflect the data written until close() is called. |
| """ |
| self._check_can_write() |
| compressed = self._compressor.compress(data) |
| self._fp.write(compressed) |
| 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): |
| """Change the file position. |
| |
| The new position is specified by offset, relative to the |
| position indicated by whence. Possible values for whence are: |
| |
| 0: start of stream (default): offset must not be negative |
| 1: current stream position |
| 2: end of stream; offset must not be positive |
| |
| Returns the new file position. |
| |
| Note that seeking is emulated, sp 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 |
| |
| def tell(self): |
| """Return the current file position.""" |
| self._check_not_closed() |
| return self._pos |
| |
| |
| def open(filename, mode="rb", *, |
| format=None, check=-1, preset=None, filters=None, |
| 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. |
| |
| 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. |
| |
| 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). |
| |
| """ |
| if "t" in mode: |
| if "b" in mode: |
| raise ValueError("Invalid mode: %r" % (mode,)) |
| else: |
| if encoding is not None: |
| raise ValueError("Argument 'encoding' not supported in binary mode") |
| if errors is not None: |
| raise ValueError("Argument 'errors' not supported in binary mode") |
| if newline is not None: |
| raise ValueError("Argument 'newline' not supported in binary mode") |
| |
| lz_mode = mode.replace("t", "") |
| binary_file = LZMAFile(filename, lz_mode, format=format, check=check, |
| preset=preset, filters=filters) |
| |
| if "t" in mode: |
| return io.TextIOWrapper(binary_file, encoding, errors, newline) |
| else: |
| return binary_file |
| |
| |
| def compress(data, format=FORMAT_XZ, check=-1, preset=None, filters=None): |
| """Compress a block of data. |
| |
| Refer to LZMACompressor's docstring for a description of the |
| optional arguments *format*, *check*, *preset* and *filters*. |
| |
| For incremental compression, use an LZMACompressor instead. |
| """ |
| comp = LZMACompressor(format, check, preset, filters) |
| return comp.compress(data) + comp.flush() |
| |
| |
| def decompress(data, format=FORMAT_AUTO, memlimit=None, filters=None): |
| """Decompress a block of data. |
| |
| Refer to LZMADecompressor's docstring for a description of the |
| optional arguments *format*, *check* and *filters*. |
| |
| For incremental decompression, use an LZMADecompressor instead. |
| """ |
| results = [] |
| while True: |
| decomp = LZMADecompressor(format, memlimit, filters) |
| results.append(decomp.decompress(data)) |
| if not decomp.eof: |
| raise LZMAError("Compressed data ended before the " |
| "end-of-stream marker was reached") |
| if not decomp.unused_data: |
| return b"".join(results) |
| # There is unused data left over. Proceed to next stream. |
| data = decomp.unused_data |