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bc6c12c72a
No longer use len() to get the length of the input data. For some buffer protocol objects, the length obtained by using len() is wrong.
361 lines
13 KiB
Python
361 lines
13 KiB
Python
"""Interface to the liblzma compression library.
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This module provides a class for reading and writing compressed files,
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classes for incremental (de)compression, and convenience functions for
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one-shot (de)compression.
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These classes and functions support both the XZ and legacy LZMA
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container formats, as well as raw compressed data streams.
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"""
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__all__ = [
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"CHECK_NONE", "CHECK_CRC32", "CHECK_CRC64", "CHECK_SHA256",
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"CHECK_ID_MAX", "CHECK_UNKNOWN",
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"FILTER_LZMA1", "FILTER_LZMA2", "FILTER_DELTA", "FILTER_X86", "FILTER_IA64",
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"FILTER_ARM", "FILTER_ARMTHUMB", "FILTER_POWERPC", "FILTER_SPARC",
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"FORMAT_AUTO", "FORMAT_XZ", "FORMAT_ALONE", "FORMAT_RAW",
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"MF_HC3", "MF_HC4", "MF_BT2", "MF_BT3", "MF_BT4",
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"MODE_FAST", "MODE_NORMAL", "PRESET_DEFAULT", "PRESET_EXTREME",
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"LZMACompressor", "LZMADecompressor", "LZMAFile", "LZMAError",
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"open", "compress", "decompress", "is_check_supported",
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]
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import builtins
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import io
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import os
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from _lzma import *
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from _lzma import _encode_filter_properties, _decode_filter_properties
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import _compression
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_MODE_CLOSED = 0
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_MODE_READ = 1
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# Value 2 no longer used
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_MODE_WRITE = 3
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class LZMAFile(_compression.BaseStream):
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"""A file object providing transparent LZMA (de)compression.
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An LZMAFile can act as a wrapper for an existing file object, or
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refer directly to a named file on disk.
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Note that LZMAFile provides a *binary* file interface - data read
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is returned as bytes, and data to be written must be given as bytes.
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"""
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def __init__(self, filename=None, mode="r", *,
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format=None, check=-1, preset=None, filters=None):
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"""Open an LZMA-compressed file in binary mode.
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filename can be either an actual file name (given as a str,
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bytes, or PathLike object), in which case the named file is
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opened, or it can be an existing file object to read from or
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write to.
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mode can be "r" for reading (default), "w" for (over)writing,
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"x" for creating exclusively, or "a" for appending. These can
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equivalently be given as "rb", "wb", "xb" and "ab" respectively.
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format specifies the container format to use for the file.
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If mode is "r", this defaults to FORMAT_AUTO. Otherwise, the
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default is FORMAT_XZ.
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check specifies the integrity check to use. This argument can
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only be used when opening a file for writing. For FORMAT_XZ,
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the default is CHECK_CRC64. FORMAT_ALONE and FORMAT_RAW do not
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support integrity checks - for these formats, check must be
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omitted, or be CHECK_NONE.
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When opening a file for reading, the *preset* argument is not
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meaningful, and should be omitted. The *filters* argument should
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also be omitted, except when format is FORMAT_RAW (in which case
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it is required).
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When opening a file for writing, the settings used by the
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compressor can be specified either as a preset compression
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level (with the *preset* argument), or in detail as a custom
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filter chain (with the *filters* argument). For FORMAT_XZ and
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FORMAT_ALONE, the default is to use the PRESET_DEFAULT preset
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level. For FORMAT_RAW, the caller must always specify a filter
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chain; the raw compressor does not support preset compression
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levels.
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preset (if provided) should be an integer in the range 0-9,
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optionally OR-ed with the constant PRESET_EXTREME.
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filters (if provided) should be a sequence of dicts. Each dict
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should have an entry for "id" indicating ID of the filter, plus
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additional entries for options to the filter.
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"""
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self._fp = None
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self._closefp = False
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self._mode = _MODE_CLOSED
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if mode in ("r", "rb"):
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if check != -1:
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raise ValueError("Cannot specify an integrity check "
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"when opening a file for reading")
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if preset is not None:
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raise ValueError("Cannot specify a preset compression "
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"level when opening a file for reading")
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if format is None:
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format = FORMAT_AUTO
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mode_code = _MODE_READ
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elif mode in ("w", "wb", "a", "ab", "x", "xb"):
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if format is None:
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format = FORMAT_XZ
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mode_code = _MODE_WRITE
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self._compressor = LZMACompressor(format=format, check=check,
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preset=preset, filters=filters)
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self._pos = 0
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else:
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raise ValueError("Invalid mode: {!r}".format(mode))
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if isinstance(filename, (str, bytes, os.PathLike)):
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if "b" not in mode:
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mode += "b"
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self._fp = builtins.open(filename, mode)
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self._closefp = True
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self._mode = mode_code
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elif hasattr(filename, "read") or hasattr(filename, "write"):
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self._fp = filename
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self._mode = mode_code
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else:
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raise TypeError("filename must be a str, bytes, file or PathLike object")
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if self._mode == _MODE_READ:
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raw = _compression.DecompressReader(self._fp, LZMADecompressor,
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trailing_error=LZMAError, format=format, filters=filters)
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self._buffer = io.BufferedReader(raw)
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def close(self):
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"""Flush and close the file.
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May be called more than once without error. Once the file is
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closed, any other operation on it will raise a ValueError.
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"""
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if self._mode == _MODE_CLOSED:
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return
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try:
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if self._mode == _MODE_READ:
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self._buffer.close()
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self._buffer = None
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elif self._mode == _MODE_WRITE:
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self._fp.write(self._compressor.flush())
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self._compressor = None
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finally:
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try:
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if self._closefp:
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self._fp.close()
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finally:
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self._fp = None
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self._closefp = False
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self._mode = _MODE_CLOSED
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@property
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def closed(self):
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"""True if this file is closed."""
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return self._mode == _MODE_CLOSED
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def fileno(self):
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"""Return the file descriptor for the underlying file."""
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self._check_not_closed()
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return self._fp.fileno()
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def seekable(self):
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"""Return whether the file supports seeking."""
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return self.readable() and self._buffer.seekable()
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def readable(self):
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"""Return whether the file was opened for reading."""
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self._check_not_closed()
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return self._mode == _MODE_READ
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def writable(self):
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"""Return whether the file was opened for writing."""
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self._check_not_closed()
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return self._mode == _MODE_WRITE
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def peek(self, size=-1):
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"""Return buffered data without advancing the file position.
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Always returns at least one byte of data, unless at EOF.
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The exact number of bytes returned is unspecified.
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"""
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self._check_can_read()
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# Relies on the undocumented fact that BufferedReader.peek() always
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# returns at least one byte (except at EOF)
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return self._buffer.peek(size)
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def read(self, size=-1):
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"""Read up to size uncompressed bytes from the file.
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If size is negative or omitted, read until EOF is reached.
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Returns b"" if the file is already at EOF.
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"""
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self._check_can_read()
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return self._buffer.read(size)
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def read1(self, size=-1):
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"""Read up to size uncompressed bytes, while trying to avoid
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making multiple reads from the underlying stream. Reads up to a
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buffer's worth of data if size is negative.
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Returns b"" if the file is at EOF.
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"""
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self._check_can_read()
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if size < 0:
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size = io.DEFAULT_BUFFER_SIZE
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return self._buffer.read1(size)
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def readline(self, size=-1):
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"""Read a line of uncompressed bytes from the file.
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The terminating newline (if present) is retained. If size is
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non-negative, no more than size bytes will be read (in which
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case the line may be incomplete). Returns b'' if already at EOF.
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"""
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self._check_can_read()
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return self._buffer.readline(size)
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def __iter__(self):
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self._check_can_read()
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return self._buffer.__iter__()
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def write(self, data):
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"""Write a bytes object to the file.
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Returns the number of uncompressed bytes written, which is
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always the length of data in bytes. Note that due to buffering,
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the file on disk may not reflect the data written until close()
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is called.
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"""
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self._check_can_write()
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if isinstance(data, (bytes, bytearray)):
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length = len(data)
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else:
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# accept any data that supports the buffer protocol
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data = memoryview(data)
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length = data.nbytes
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compressed = self._compressor.compress(data)
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self._fp.write(compressed)
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self._pos += length
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return length
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def seek(self, offset, whence=io.SEEK_SET):
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"""Change the file position.
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The new position is specified by offset, relative to the
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position indicated by whence. Possible values for whence are:
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0: start of stream (default): offset must not be negative
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1: current stream position
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2: end of stream; offset must not be positive
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Returns the new file position.
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Note that seeking is emulated, so depending on the parameters,
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this operation may be extremely slow.
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"""
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self._check_can_seek()
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return self._buffer.seek(offset, whence)
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def tell(self):
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"""Return the current file position."""
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self._check_not_closed()
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if self._mode == _MODE_READ:
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return self._buffer.tell()
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return self._pos
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def open(filename, mode="rb", *,
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format=None, check=-1, preset=None, filters=None,
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encoding=None, errors=None, newline=None):
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"""Open an LZMA-compressed file in binary or text mode.
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filename can be either an actual file name (given as a str, bytes,
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or PathLike object), in which case the named file is opened, or it
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can be an existing file object to read from or write to.
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The mode argument can be "r", "rb" (default), "w", "wb", "x", "xb",
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"a", or "ab" for binary mode, or "rt", "wt", "xt", or "at" for text
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mode.
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The format, check, preset and filters arguments specify the
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compression settings, as for LZMACompressor, LZMADecompressor and
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LZMAFile.
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For binary mode, this function is equivalent to the LZMAFile
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constructor: LZMAFile(filename, mode, ...). In this case, the
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encoding, errors and newline arguments must not be provided.
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For text mode, an LZMAFile object is created, and wrapped in an
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io.TextIOWrapper instance with the specified encoding, error
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handling behavior, and line ending(s).
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"""
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if "t" in mode:
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if "b" in mode:
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raise ValueError("Invalid mode: %r" % (mode,))
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else:
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if encoding is not None:
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raise ValueError("Argument 'encoding' not supported in binary mode")
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if errors is not None:
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raise ValueError("Argument 'errors' not supported in binary mode")
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if newline is not None:
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raise ValueError("Argument 'newline' not supported in binary mode")
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lz_mode = mode.replace("t", "")
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binary_file = LZMAFile(filename, lz_mode, format=format, check=check,
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preset=preset, filters=filters)
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if "t" in mode:
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encoding = io.text_encoding(encoding)
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return io.TextIOWrapper(binary_file, encoding, errors, newline)
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else:
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return binary_file
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def compress(data, format=FORMAT_XZ, check=-1, preset=None, filters=None):
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"""Compress a block of data.
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Refer to LZMACompressor's docstring for a description of the
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optional arguments *format*, *check*, *preset* and *filters*.
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For incremental compression, use an LZMACompressor instead.
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"""
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comp = LZMACompressor(format, check, preset, filters)
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return comp.compress(data) + comp.flush()
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def decompress(data, format=FORMAT_AUTO, memlimit=None, filters=None):
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"""Decompress a block of data.
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Refer to LZMADecompressor's docstring for a description of the
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optional arguments *format*, *check* and *filters*.
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For incremental decompression, use an LZMADecompressor instead.
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"""
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results = []
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while True:
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decomp = LZMADecompressor(format, memlimit, filters)
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try:
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res = decomp.decompress(data)
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except LZMAError:
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if results:
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break # Leftover data is not a valid LZMA/XZ stream; ignore it.
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else:
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raise # Error on the first iteration; bail out.
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results.append(res)
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if not decomp.eof:
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raise LZMAError("Compressed data ended before the "
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"end-of-stream marker was reached")
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data = decomp.unused_data
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if not data:
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break
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return b"".join(results)
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