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Diffstat (limited to 'Lib/lzma.py')
| -rw-r--r-- | Lib/lzma.py | 454 |
1 files changed, 454 insertions, 0 deletions
diff --git a/Lib/lzma.py b/Lib/lzma.py new file mode 100644 index 0000000..1a1b065 --- /dev/null +++ b/Lib/lzma.py @@ -0,0 +1,454 @@ +"""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 = None + 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 = None + 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 not self.readable(): + raise io.UnsupportedOperation("File not open for reading") + + def _check_can_write(self): + if not self.writable(): + raise io.UnsupportedOperation("File not open for writing") + + def _check_can_seek(self): + if not self.readable(): + 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): + # 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) + + 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) + + # Read data until EOF. + # If return_data is false, consume the data without returning it. + def _read_all(self, return_data=True): + blocks = [] + while self._fill_buffer(): + if return_data: + blocks.append(self._buffer) + self._pos += len(self._buffer) + self._buffer = None + 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): + blocks = [] + while n > 0 and self._fill_buffer(): + if n < len(self._buffer): + data = self._buffer[:n] + self._buffer = self._buffer[n:] + else: + data = self._buffer + self._buffer = None + 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 self._mode == _MODE_READ_EOF or not self._fill_buffer(): + return b"" + return self._buffer + + 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 self._mode == _MODE_READ_EOF or 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 self._mode == _MODE_READ_EOF or + not self._fill_buffer()): + return b"" + if 0 < size < len(self._buffer): + data = self._buffer[:size] + self._buffer = self._buffer[size:] + else: + data = self._buffer + self._buffer = None + self._pos += len(data) + return data + + 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 = None + + 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. + if self._mode != _MODE_READ_EOF: + 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 object 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 a LZMADecompressor object 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 |