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"""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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_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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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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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 |
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else: |
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raise |
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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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