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lzma.py12.9 KB · 356 lines
"""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 forone-shot (de)compression. These classes and functions support both the XZ and legacy LZMAcontainer 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 builtinsimport ioimport osfrom _lzma import *from _lzma import _encode_filter_properties, _decode_filter_propertiesimport _compression  _MODE_CLOSED   = 0_MODE_READ     = 1# Value 2 no longer used_MODE_WRITE    = 3  class LZMAFile(_compression.BaseStream):     """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,        bytes, or PathLike 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,        "x" for creating exclusively, or "a" for appending. These can        equivalently be given as "rb", "wb", "xb" 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         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        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))         if isinstance(filename, (str, bytes, os.PathLike)):            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, bytes, file or PathLike object")         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.         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 == _MODE_READ:                self._buffer.close()                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._buffer.seekable()     def readable(self):        """Return whether the file was opened for reading."""        self._check_not_closed()        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     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()        # 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.         If size is negative or omitted, read until EOF is reached.        Returns b"" if the file is already at EOF.        """        self._check_can_read()        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. Reads up to a        buffer's worth of data if size is negative.         Returns b"" if the file is at EOF.        """        self._check_can_read()        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.         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()        return self._buffer.readline(size)     def write(self, data):        """Write a bytes object to the file.         Returns the number of uncompressed bytes written, which is        always the length of data in bytes. Note that due to buffering,        the file on disk may not reflect the data written until close()        is called.        """        self._check_can_write()        if isinstance(data, (bytes, bytearray)):            length = len(data)        else:            # accept any data that supports the buffer protocol            data = memoryview(data)            length = data.nbytes         compressed = self._compressor.compress(data)        self._fp.write(compressed)        self._pos += length        return length     def seek(self, offset, whence=io.SEEK_SET):        """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, so depending on the parameters,        this operation may be extremely slow.        """        self._check_can_seek()        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  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, bytes,    or PathLike 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", "x", "xb",    "a", or "ab" for binary mode, or "rt", "wt", "xt", 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, an 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)        try:            res = decomp.decompress(data)        except LZMAError:            if results:                break  # Leftover data is not a valid LZMA/XZ stream; ignore it.            else:                raise  # Error on the first iteration; bail out.        results.append(res)        if not decomp.eof:            raise LZMAError("Compressed data ended before the "                            "end-of-stream marker was reached")        data = decomp.unused_data        if not data:            break    return b"".join(results)