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20be6ba61a
* Introduces `compression` package for https://peps.python.org/pep-0784/ This commit introduces the `compression` package, specified in PEP 784 to re-export the `lzma`, `bz2`, `gzip`, and `zlib` modules. Introduction of `compression.zstd` will be completed in a future commit once the `_zstd` module is merged. This commit also moves the `_compression` private module to `compression._common._streams`. * Re-exports existing module docstrings.
352 lines
12 KiB
Python
352 lines
12 KiB
Python
"""Interface to the libbzip2 compression library.
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This module provides a file interface, classes for incremental
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(de)compression, and functions for one-shot (de)compression.
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"""
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__all__ = ["BZ2File", "BZ2Compressor", "BZ2Decompressor",
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"open", "compress", "decompress"]
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__author__ = "Nadeem Vawda <nadeem.vawda@gmail.com>"
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from builtins import open as _builtin_open
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from compression._common import _streams
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import io
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import os
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from _bz2 import BZ2Compressor, BZ2Decompressor
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# Value 0 no longer used
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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 BZ2File(_streams.BaseStream):
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"""A file object providing transparent bzip2 (de)compression.
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A BZ2File can act as a wrapper for an existing file object, or refer
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directly to a named file on disk.
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Note that BZ2File provides a *binary* file interface - data read is
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returned as bytes, and data to be written should be given as bytes.
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"""
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def __init__(self, filename, mode="r", *, compresslevel=9):
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"""Open a bzip2-compressed file.
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If filename is a str, bytes, or PathLike object, it gives the
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name of the file to be opened. Otherwise, it should be a file
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object, which will be used to read or write the compressed data.
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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'.
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If mode is 'w', 'x' or 'a', compresslevel can be a number between 1
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and 9 specifying the level of compression: 1 produces the least
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compression, and 9 (default) produces the most compression.
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If mode is 'r', the input file may be the concatenation of
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multiple compressed streams.
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"""
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self._fp = None
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self._closefp = False
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self._mode = None
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if not (1 <= compresslevel <= 9):
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raise ValueError("compresslevel must be between 1 and 9")
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if mode in ("", "r", "rb"):
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mode = "rb"
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mode_code = _MODE_READ
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elif mode in ("w", "wb"):
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mode = "wb"
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mode_code = _MODE_WRITE
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self._compressor = BZ2Compressor(compresslevel)
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elif mode in ("x", "xb"):
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mode = "xb"
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mode_code = _MODE_WRITE
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self._compressor = BZ2Compressor(compresslevel)
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elif mode in ("a", "ab"):
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mode = "ab"
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mode_code = _MODE_WRITE
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self._compressor = BZ2Compressor(compresslevel)
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else:
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raise ValueError("Invalid mode: %r" % (mode,))
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if isinstance(filename, (str, bytes, os.PathLike)):
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self._fp = _builtin_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 = _streams.DecompressReader(self._fp,
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BZ2Decompressor, trailing_error=OSError)
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self._buffer = io.BufferedReader(raw)
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else:
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self._pos = 0
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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.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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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._buffer = None
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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._fp is None
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@property
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def name(self):
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self._check_not_closed()
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return self._fp.name
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@property
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def mode(self):
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return 'wb' if self._mode == _MODE_WRITE else 'rb'
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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, n=0):
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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()
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# always returns at least one byte (except at EOF), independent
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# of the value of n
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return self._buffer.peek(n)
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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 readinto(self, b):
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"""Read bytes into b.
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Returns the number of bytes read (0 for EOF).
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"""
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self._check_can_read()
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return self._buffer.readinto(b)
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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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if not isinstance(size, int):
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if not hasattr(size, "__index__"):
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raise TypeError("Integer argument expected")
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size = size.__index__()
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self._check_can_read()
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return self._buffer.readline(size)
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def readlines(self, size=-1):
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"""Read a list of lines of uncompressed bytes from the file.
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size can be specified to control the number of lines read: no
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further lines will be read once the total size of the lines read
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so far equals or exceeds size.
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"""
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if not isinstance(size, int):
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if not hasattr(size, "__index__"):
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raise TypeError("Integer argument expected")
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size = size.__index__()
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self._check_can_read()
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return self._buffer.readlines(size)
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def write(self, data):
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"""Write a byte string 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 writelines(self, seq):
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"""Write a sequence of byte strings to the file.
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Returns the number of uncompressed bytes written.
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seq can be any iterable yielding byte strings.
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Line separators are not added between the written byte strings.
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"""
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return _streams.BaseStream.writelines(self, seq)
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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. 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", compresslevel=9,
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encoding=None, errors=None, newline=None):
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"""Open a bzip2-compressed file in binary or text mode.
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The filename argument can be an actual filename (a str, bytes, or
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PathLike object), or an existing file object to read from or write
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to.
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The mode argument can be "r", "rb", "w", "wb", "x", "xb", "a" or
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"ab" for binary mode, or "rt", "wt", "xt" or "at" for text mode.
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The default mode is "rb", and the default compresslevel is 9.
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For binary mode, this function is equivalent to the BZ2File
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constructor: BZ2File(filename, mode, compresslevel). In this case,
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the encoding, errors and newline arguments must not be provided.
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For text mode, a BZ2File 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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bz_mode = mode.replace("t", "")
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binary_file = BZ2File(filename, bz_mode, compresslevel=compresslevel)
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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, compresslevel=9):
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"""Compress a block of data.
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compresslevel, if given, must be a number between 1 and 9.
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For incremental compression, use a BZ2Compressor object instead.
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"""
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comp = BZ2Compressor(compresslevel)
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return comp.compress(data) + comp.flush()
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def decompress(data):
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"""Decompress a block of data.
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For incremental decompression, use a BZ2Decompressor object instead.
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"""
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results = []
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while data:
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decomp = BZ2Decompressor()
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try:
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res = decomp.decompress(data)
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except OSError:
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if results:
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break # Leftover data is not a valid bzip2 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 ValueError("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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return b"".join(results)
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