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cpython/Lib/lzma.py /
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| """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 | |
| import os | |
| from _lzma import * | |
| from _lzma import _encode_filter_properties, _decode_filter_properties | |
| import _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) |