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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.
349 lines
12 KiB
Python
349 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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import io
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import os
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import _compression
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from _bz2 import BZ2Compressor, BZ2Decompressor
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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 BZ2File(_compression.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 = _MODE_CLOSED
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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 = _compression.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._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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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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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._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, 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 __iter__(self):
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self._check_can_read()
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return self._buffer.__iter__()
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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 _compression.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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