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572 lines
20 KiB
Python
572 lines
20 KiB
Python
"""Functions that read and write gzipped files.
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The user of the file doesn't have to worry about the compression,
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but random access is not allowed."""
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# based on Andrew Kuchling's minigzip.py distributed with the zlib module
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import struct, sys, time, os
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import zlib
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import builtins
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import io
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import _compression
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__all__ = ["GzipFile", "open", "compress", "decompress"]
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FTEXT, FHCRC, FEXTRA, FNAME, FCOMMENT = 1, 2, 4, 8, 16
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READ, WRITE = 1, 2
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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 gzip-compressed file in binary or text mode.
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The filename argument can be an actual filename (a str or bytes object), or
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an existing file object to read from or write to.
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The mode argument can be "r", "rb", "w", "wb", "x", "xb", "a" or "ab" for
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binary mode, or "rt", "wt", "xt" or "at" for text mode. The default mode is
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"rb", and the default compresslevel is 9.
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For binary mode, this function is equivalent to the GzipFile constructor:
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GzipFile(filename, mode, compresslevel). In this case, the encoding, errors
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and newline arguments must not be provided.
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For text mode, a GzipFile object is created, and wrapped in an
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io.TextIOWrapper instance with the specified encoding, error handling
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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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gz_mode = mode.replace("t", "")
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if isinstance(filename, (str, bytes)):
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binary_file = GzipFile(filename, gz_mode, compresslevel)
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elif hasattr(filename, "read") or hasattr(filename, "write"):
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binary_file = GzipFile(None, gz_mode, compresslevel, filename)
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else:
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raise TypeError("filename must be a str or bytes object, or a file")
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if "t" in mode:
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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 write32u(output, value):
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# The L format writes the bit pattern correctly whether signed
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# or unsigned.
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output.write(struct.pack("<L", value))
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class _PaddedFile:
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"""Minimal read-only file object that prepends a string to the contents
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of an actual file. Shouldn't be used outside of gzip.py, as it lacks
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essential functionality."""
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def __init__(self, f, prepend=b''):
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self._buffer = prepend
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self._length = len(prepend)
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self.file = f
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self._read = 0
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def read(self, size):
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if self._read is None:
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return self.file.read(size)
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if self._read + size <= self._length:
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read = self._read
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self._read += size
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return self._buffer[read:self._read]
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else:
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read = self._read
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self._read = None
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return self._buffer[read:] + \
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self.file.read(size-self._length+read)
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def prepend(self, prepend=b''):
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if self._read is None:
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self._buffer = prepend
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else: # Assume data was read since the last prepend() call
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self._read -= len(prepend)
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return
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self._length = len(self._buffer)
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self._read = 0
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def seek(self, off):
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self._read = None
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self._buffer = None
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return self.file.seek(off)
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def seekable(self):
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return True # Allows fast-forwarding even in unseekable streams
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class GzipFile(_compression.BaseStream):
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"""The GzipFile class simulates most of the methods of a file object with
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the exception of the truncate() method.
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This class only supports opening files in binary mode. If you need to open a
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compressed file in text mode, use the gzip.open() function.
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"""
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# Overridden with internal file object to be closed, if only a filename
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# is passed in
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myfileobj = None
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def __init__(self, filename=None, mode=None,
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compresslevel=9, fileobj=None, mtime=None):
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"""Constructor for the GzipFile class.
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At least one of fileobj and filename must be given a
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non-trivial value.
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The new class instance is based on fileobj, which can be a regular
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file, an io.BytesIO object, or any other object which simulates a file.
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It defaults to None, in which case filename is opened to provide
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a file object.
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When fileobj is not None, the filename argument is only used to be
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included in the gzip file header, which may include the original
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filename of the uncompressed file. It defaults to the filename of
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fileobj, if discernible; otherwise, it defaults to the empty string,
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and in this case the original filename is not included in the header.
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The mode argument can be any of 'r', 'rb', 'a', 'ab', 'w', 'wb', 'x', or
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'xb' depending on whether the file will be read or written. The default
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is the mode of fileobj if discernible; otherwise, the default is 'rb'.
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A mode of 'r' is equivalent to one of 'rb', and similarly for 'w' and
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'wb', 'a' and 'ab', and 'x' and 'xb'.
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The compresslevel argument is an integer from 0 to 9 controlling the
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level of compression; 1 is fastest and produces the least compression,
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and 9 is slowest and produces the most compression. 0 is no compression
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at all. The default is 9.
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The mtime argument is an optional numeric timestamp to be written
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to the last modification time field in the stream when compressing.
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If omitted or None, the current time is used.
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"""
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if mode and ('t' in mode or 'U' in mode):
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raise ValueError("Invalid mode: {!r}".format(mode))
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if mode and 'b' not in mode:
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mode += 'b'
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if fileobj is None:
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fileobj = self.myfileobj = builtins.open(filename, mode or 'rb')
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if filename is None:
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filename = getattr(fileobj, 'name', '')
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if not isinstance(filename, (str, bytes)):
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filename = ''
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if mode is None:
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mode = getattr(fileobj, 'mode', 'rb')
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if mode.startswith('r'):
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self.mode = READ
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raw = _GzipReader(fileobj)
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self._buffer = io.BufferedReader(raw)
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self.name = filename
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elif mode.startswith(('w', 'a', 'x')):
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self.mode = WRITE
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self._init_write(filename)
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self.compress = zlib.compressobj(compresslevel,
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zlib.DEFLATED,
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-zlib.MAX_WBITS,
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zlib.DEF_MEM_LEVEL,
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0)
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self._write_mtime = mtime
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else:
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raise ValueError("Invalid mode: {!r}".format(mode))
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self.fileobj = fileobj
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if self.mode == WRITE:
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self._write_gzip_header()
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@property
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def filename(self):
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import warnings
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warnings.warn("use the name attribute", DeprecationWarning, 2)
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if self.mode == WRITE and self.name[-3:] != ".gz":
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return self.name + ".gz"
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return self.name
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@property
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def mtime(self):
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"""Last modification time read from stream, or None"""
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return self._buffer.raw._last_mtime
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def __repr__(self):
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s = repr(self.fileobj)
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return '<gzip ' + s[1:-1] + ' ' + hex(id(self)) + '>'
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def _init_write(self, filename):
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self.name = filename
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self.crc = zlib.crc32(b"")
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self.size = 0
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self.writebuf = []
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self.bufsize = 0
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self.offset = 0 # Current file offset for seek(), tell(), etc
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def _write_gzip_header(self):
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self.fileobj.write(b'\037\213') # magic header
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self.fileobj.write(b'\010') # compression method
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try:
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# RFC 1952 requires the FNAME field to be Latin-1. Do not
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# include filenames that cannot be represented that way.
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fname = os.path.basename(self.name)
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if not isinstance(fname, bytes):
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fname = fname.encode('latin-1')
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if fname.endswith(b'.gz'):
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fname = fname[:-3]
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except UnicodeEncodeError:
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fname = b''
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flags = 0
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if fname:
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flags = FNAME
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self.fileobj.write(chr(flags).encode('latin-1'))
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mtime = self._write_mtime
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if mtime is None:
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mtime = time.time()
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write32u(self.fileobj, int(mtime))
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self.fileobj.write(b'\002')
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self.fileobj.write(b'\377')
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if fname:
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self.fileobj.write(fname + b'\000')
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def write(self,data):
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self._check_not_closed()
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if self.mode != WRITE:
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import errno
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raise OSError(errno.EBADF, "write() on read-only GzipFile object")
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if self.fileobj is None:
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raise ValueError("write() on closed GzipFile object")
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if isinstance(data, bytes):
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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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if length > 0:
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self.fileobj.write(self.compress.compress(data))
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self.size += length
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self.crc = zlib.crc32(data, self.crc)
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self.offset += length
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return length
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def read(self, size=-1):
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self._check_not_closed()
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if self.mode != READ:
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import errno
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raise OSError(errno.EBADF, "read() on write-only GzipFile object")
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return self._buffer.read(size)
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def read1(self, size=-1):
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"""Implements BufferedIOBase.read1()
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Reads up to a buffer's worth of data is size is negative."""
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self._check_not_closed()
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if self.mode != READ:
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import errno
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raise OSError(errno.EBADF, "read1() on write-only GzipFile object")
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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 peek(self, n):
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self._check_not_closed()
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if self.mode != READ:
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import errno
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raise OSError(errno.EBADF, "peek() on write-only GzipFile object")
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return self._buffer.peek(n)
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@property
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def closed(self):
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return self.fileobj is None
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def close(self):
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fileobj = self.fileobj
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if fileobj is None:
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return
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self.fileobj = None
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try:
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if self.mode == WRITE:
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fileobj.write(self.compress.flush())
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write32u(fileobj, self.crc)
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# self.size may exceed 2GB, or even 4GB
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write32u(fileobj, self.size & 0xffffffff)
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elif self.mode == READ:
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self._buffer.close()
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finally:
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myfileobj = self.myfileobj
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if myfileobj:
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self.myfileobj = None
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myfileobj.close()
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def flush(self,zlib_mode=zlib.Z_SYNC_FLUSH):
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self._check_not_closed()
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if self.mode == WRITE:
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# Ensure the compressor's buffer is flushed
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self.fileobj.write(self.compress.flush(zlib_mode))
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self.fileobj.flush()
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def fileno(self):
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"""Invoke the underlying file object's fileno() method.
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This will raise AttributeError if the underlying file object
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doesn't support fileno().
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"""
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return self.fileobj.fileno()
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def rewind(self):
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'''Return the uncompressed stream file position indicator to the
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beginning of the file'''
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if self.mode != READ:
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raise OSError("Can't rewind in write mode")
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self._buffer.seek(0)
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def readable(self):
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return self.mode == READ
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def writable(self):
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return self.mode == WRITE
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def seekable(self):
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return True
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def seek(self, offset, whence=io.SEEK_SET):
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if self.mode == WRITE:
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if whence != io.SEEK_SET:
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if whence == io.SEEK_CUR:
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offset = self.offset + offset
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else:
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raise ValueError('Seek from end not supported')
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if offset < self.offset:
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raise OSError('Negative seek in write mode')
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count = offset - self.offset
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chunk = bytes(1024)
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for i in range(count // 1024):
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self.write(chunk)
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self.write(bytes(count % 1024))
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elif self.mode == READ:
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self._check_not_closed()
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return self._buffer.seek(offset, whence)
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return self.offset
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def readline(self, size=-1):
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self._check_not_closed()
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return self._buffer.readline(size)
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class _GzipReader(_compression.DecompressReader):
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def __init__(self, fp):
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super().__init__(_PaddedFile(fp), zlib.decompressobj,
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wbits=-zlib.MAX_WBITS)
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# Set flag indicating start of a new member
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self._new_member = True
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self._last_mtime = None
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def _init_read(self):
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self._crc = zlib.crc32(b"")
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self._stream_size = 0 # Decompressed size of unconcatenated stream
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def _read_exact(self, n):
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'''Read exactly *n* bytes from `self._fp`
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This method is required because self._fp may be unbuffered,
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i.e. return short reads.
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'''
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data = self._fp.read(n)
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while len(data) < n:
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b = self._fp.read(n - len(data))
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if not b:
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raise EOFError("Compressed file ended before the "
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"end-of-stream marker was reached")
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data += b
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return data
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def _read_gzip_header(self):
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magic = self._fp.read(2)
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if magic == b'':
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return False
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if magic != b'\037\213':
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raise OSError('Not a gzipped file (%r)' % magic)
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(method, flag,
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self._last_mtime) = struct.unpack("<BBIxx", self._read_exact(8))
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if method != 8:
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raise OSError('Unknown compression method')
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if flag & FEXTRA:
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# Read & discard the extra field, if present
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extra_len, = struct.unpack("<H", self._read_exact(2))
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self._read_exact(extra_len)
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if flag & FNAME:
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# Read and discard a null-terminated string containing the filename
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while True:
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s = self._fp.read(1)
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if not s or s==b'\000':
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break
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if flag & FCOMMENT:
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# Read and discard a null-terminated string containing a comment
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while True:
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s = self._fp.read(1)
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if not s or s==b'\000':
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break
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if flag & FHCRC:
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self._read_exact(2) # Read & discard the 16-bit header CRC
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return True
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def read(self, size=-1):
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if size < 0:
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return self.readall()
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# size=0 is special because decompress(max_length=0) is not supported
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if not size:
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return b""
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# For certain input data, a single
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# call to decompress() may not return
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# any data. In this case, retry until we get some data or reach EOF.
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while True:
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if self._decompressor.eof:
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# Ending case: we've come to the end of a member in the file,
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# so finish up this member, and read a new gzip header.
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# Check the CRC and file size, and set the flag so we read
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# a new member
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self._read_eof()
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self._new_member = True
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self._decompressor = self._decomp_factory(
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**self._decomp_args)
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if self._new_member:
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# If the _new_member flag is set, we have to
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# jump to the next member, if there is one.
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self._init_read()
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if not self._read_gzip_header():
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self._size = self._pos
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return b""
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self._new_member = False
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# Read a chunk of data from the file
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buf = self._fp.read(io.DEFAULT_BUFFER_SIZE)
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uncompress = self._decompressor.decompress(buf, size)
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if self._decompressor.unconsumed_tail != b"":
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self._fp.prepend(self._decompressor.unconsumed_tail)
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elif self._decompressor.unused_data != b"":
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# Prepend the already read bytes to the fileobj so they can
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# be seen by _read_eof() and _read_gzip_header()
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self._fp.prepend(self._decompressor.unused_data)
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if uncompress != b"":
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break
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if buf == b"":
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raise EOFError("Compressed file ended before the "
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"end-of-stream marker was reached")
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self._add_read_data( uncompress )
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self._pos += len(uncompress)
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return uncompress
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def _add_read_data(self, data):
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self._crc = zlib.crc32(data, self._crc)
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self._stream_size = self._stream_size + len(data)
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def _read_eof(self):
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# We've read to the end of the file
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# We check the that the computed CRC and size of the
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# uncompressed data matches the stored values. Note that the size
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# stored is the true file size mod 2**32.
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crc32, isize = struct.unpack("<II", self._read_exact(8))
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if crc32 != self._crc:
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raise OSError("CRC check failed %s != %s" % (hex(crc32),
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hex(self._crc)))
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elif isize != (self._stream_size & 0xffffffff):
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raise OSError("Incorrect length of data produced")
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# Gzip files can be padded with zeroes and still have archives.
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# Consume all zero bytes and set the file position to the first
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# non-zero byte. See http://www.gzip.org/#faq8
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c = b"\x00"
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while c == b"\x00":
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c = self._fp.read(1)
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if c:
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self._fp.prepend(c)
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def _rewind(self):
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super()._rewind()
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self._new_member = True
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|
def compress(data, compresslevel=9):
|
|
"""Compress data in one shot and return the compressed string.
|
|
Optional argument is the compression level, in range of 0-9.
|
|
"""
|
|
buf = io.BytesIO()
|
|
with GzipFile(fileobj=buf, mode='wb', compresslevel=compresslevel) as f:
|
|
f.write(data)
|
|
return buf.getvalue()
|
|
|
|
def decompress(data):
|
|
"""Decompress a gzip compressed string in one shot.
|
|
Return the decompressed string.
|
|
"""
|
|
with GzipFile(fileobj=io.BytesIO(data)) as f:
|
|
return f.read()
|
|
|
|
|
|
def _test():
|
|
# Act like gzip; with -d, act like gunzip.
|
|
# The input file is not deleted, however, nor are any other gzip
|
|
# options or features supported.
|
|
args = sys.argv[1:]
|
|
decompress = args and args[0] == "-d"
|
|
if decompress:
|
|
args = args[1:]
|
|
if not args:
|
|
args = ["-"]
|
|
for arg in args:
|
|
if decompress:
|
|
if arg == "-":
|
|
f = GzipFile(filename="", mode="rb", fileobj=sys.stdin.buffer)
|
|
g = sys.stdout.buffer
|
|
else:
|
|
if arg[-3:] != ".gz":
|
|
print("filename doesn't end in .gz:", repr(arg))
|
|
continue
|
|
f = open(arg, "rb")
|
|
g = builtins.open(arg[:-3], "wb")
|
|
else:
|
|
if arg == "-":
|
|
f = sys.stdin.buffer
|
|
g = GzipFile(filename="", mode="wb", fileobj=sys.stdout.buffer)
|
|
else:
|
|
f = builtins.open(arg, "rb")
|
|
g = open(arg + ".gz", "wb")
|
|
while True:
|
|
chunk = f.read(1024)
|
|
if not chunk:
|
|
break
|
|
g.write(chunk)
|
|
if g is not sys.stdout.buffer:
|
|
g.close()
|
|
if f is not sys.stdin.buffer:
|
|
f.close()
|
|
|
|
if __name__ == '__main__':
|
|
_test()
|