634 lines
22 KiB
Python
634 lines
22 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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__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 U32(i):
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"""Return i as an unsigned integer, assuming it fits in 32 bits.
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If it's >= 2GB when viewed as a 32-bit unsigned int, return a long.
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"""
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if i < 0:
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i += 1 << 32
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return i
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def LOWU32(i):
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"""Return the low-order 32 bits, as a non-negative int"""
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return i & 0xFFFFFFFF
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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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def read32(input):
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return struct.unpack("<I", input.read(4))[0]
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def open(filename, mode="rb", compresslevel=9):
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"""Shorthand for GzipFile(filename, mode, compresslevel).
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The filename argument is required; mode defaults to 'rb'
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and compresslevel defaults to 9.
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"""
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return GzipFile(filename, mode, compresslevel)
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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'', readprevious=False):
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if self._read is None:
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self._buffer = prepend
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elif readprevious and len(prepend) <= self._read:
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self._read -= len(prepend)
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return
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else:
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self._buffer = self._buffer[read:] + prepend
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self._length = len(self._buffer)
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self._read = 0
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def unused(self):
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if self._read is None:
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return b''
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return self._buffer[self._read:]
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def seek(self, offset, whence=0):
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# This is only ever called with offset=whence=0
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if whence == 1 and self._read is not None:
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if 0 <= offset + self._read <= self._length:
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self._read += offset
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return
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else:
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offset += self._length - self._read
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self._read = None
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self._buffer = None
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return self.file.seek(offset, whence)
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def __getattr__(self, name):
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return getattr(self.file, name)
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class GzipFile(io.BufferedIOBase):
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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 readinto() and truncate() methods.
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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, wrap your GzipFile with an io.TextIOWrapper.
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"""
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myfileobj = None
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max_read_chunk = 10 * 1024 * 1024 # 10Mb
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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, a StringIO 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 includes 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', or 'wb',
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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', and 'a' and 'ab'.
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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 stream when compressing. All gzip compressed streams
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are required to contain a timestamp. If omitted or None, the
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current time is used. This module ignores the timestamp when
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decompressing; however, some programs, such as gunzip, make use
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of it. The format of the timestamp is the same as that of the
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return value of time.time() and of the st_mtime member of the
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object returned by os.stat().
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"""
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if mode and ('t' in mode or 'U' in mode):
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raise IOError("Mode " + mode + " not supported")
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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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if hasattr(fileobj, 'mode'): mode = fileobj.mode
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else: mode = 'rb'
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if mode[0:1] == 'r':
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self.mode = READ
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# Set flag indicating start of a new member
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self._new_member = True
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# Buffer data read from gzip file. extrastart is offset in
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# stream where buffer starts. extrasize is number of
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# bytes remaining in buffer from current stream position.
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self.extrabuf = b""
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self.extrasize = 0
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self.extrastart = 0
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self.name = filename
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# Starts small, scales exponentially
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self.min_readsize = 100
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fileobj = _PaddedFile(fileobj)
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elif mode[0:1] == 'w' or mode[0:1] == 'a':
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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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else:
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raise IOError("Mode " + mode + " not supported")
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self.fileobj = fileobj
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self.offset = 0
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self.mtime = mtime
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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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def __repr__(self):
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fileobj = self.fileobj
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if isinstance(fileobj, _PaddedFile):
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fileobj = fileobj.file
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s = repr(fileobj)
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return '<gzip ' + s[1:-1] + ' ' + hex(id(self)) + '>'
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def _check_closed(self):
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"""Raises a ValueError if the underlying file object has been closed.
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"""
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if self.closed:
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raise ValueError('I/O operation on closed file.')
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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"") & 0xffffffff
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self.size = 0
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self.writebuf = []
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self.bufsize = 0
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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.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 _init_read(self):
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self.crc = zlib.crc32(b"") & 0xffffffff
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self.size = 0
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def _read_gzip_header(self):
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magic = self.fileobj.read(2)
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if magic == b'':
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raise EOFError("Reached EOF")
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if magic != b'\037\213':
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raise IOError('Not a gzipped file')
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method = ord( self.fileobj.read(1) )
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if method != 8:
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raise IOError('Unknown compression method')
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flag = ord( self.fileobj.read(1) )
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self.mtime = read32(self.fileobj)
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# extraflag = self.fileobj.read(1)
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# os = self.fileobj.read(1)
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self.fileobj.read(2)
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if flag & FEXTRA:
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# Read & discard the extra field, if present
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xlen = ord(self.fileobj.read(1))
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xlen = xlen + 256*ord(self.fileobj.read(1))
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self.fileobj.read(xlen)
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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.fileobj.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.fileobj.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.fileobj.read(2) # Read & discard the 16-bit header CRC
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unused = self.fileobj.unused()
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if unused:
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uncompress = self.decompress.decompress(unused)
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self._add_read_data(uncompress)
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def write(self,data):
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self._check_closed()
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if self.mode != WRITE:
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import errno
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raise IOError(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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# Convert data type if called by io.BufferedWriter.
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if isinstance(data, memoryview):
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data = data.tobytes()
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if len(data) > 0:
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self.size = self.size + len(data)
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self.crc = zlib.crc32(data, self.crc) & 0xffffffff
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self.fileobj.write( self.compress.compress(data) )
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self.offset += len(data)
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return len(data)
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def read(self, size=-1):
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self._check_closed()
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if self.mode != READ:
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import errno
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raise IOError(errno.EBADF, "read() on write-only GzipFile object")
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if self.extrasize <= 0 and self.fileobj is None:
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return b''
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readsize = 1024
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if size < 0: # get the whole thing
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try:
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while True:
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self._read(readsize)
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readsize = min(self.max_read_chunk, readsize * 2)
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except EOFError:
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size = self.extrasize
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else: # just get some more of it
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try:
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while size > self.extrasize:
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self._read(readsize)
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readsize = min(self.max_read_chunk, readsize * 2)
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except EOFError:
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if size > self.extrasize:
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size = self.extrasize
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offset = self.offset - self.extrastart
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chunk = self.extrabuf[offset: offset + size]
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self.extrasize = self.extrasize - size
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self.offset += size
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return chunk
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def peek(self, n):
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if self.mode != READ:
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import errno
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raise IOError(errno.EBADF, "peek() on write-only GzipFile object")
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# Do not return ridiculously small buffers, for one common idiom
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# is to call peek(1) and expect more bytes in return.
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if n < 100:
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n = 100
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if self.extrasize == 0:
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if self.fileobj is None:
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return b''
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try:
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# Ensure that we don't return b"" if we haven't reached EOF.
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while self.extrasize == 0:
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# 1024 is the same buffering heuristic used in read()
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self._read(max(n, 1024))
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except EOFError:
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pass
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offset = self.offset - self.extrastart
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remaining = self.extrasize
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assert remaining == len(self.extrabuf) - offset
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return self.extrabuf[offset:offset + n]
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def _unread(self, buf):
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self.extrasize = len(buf) + self.extrasize
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self.offset -= len(buf)
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def _read(self, size=1024):
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if self.fileobj is None:
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raise EOFError("Reached EOF")
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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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self._read_gzip_header()
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self.decompress = zlib.decompressobj(-zlib.MAX_WBITS)
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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.fileobj.read(size)
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# If the EOF has been reached, flush the decompression object
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# and mark this object as finished.
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if buf == b"":
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uncompress = self.decompress.flush()
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# Prepend the already read bytes to the fileobj to they can be
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# seen by _read_eof()
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self.fileobj.prepend(self.decompress.unused_data, True)
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self._read_eof()
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self._add_read_data( uncompress )
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raise EOFError('Reached EOF')
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uncompress = self.decompress.decompress(buf)
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self._add_read_data( uncompress )
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if self.decompress.unused_data != b"":
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# Ending case: we've come to the end of a member in the file,
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# so seek back to the start of the unused data, finish up
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# this member, and read a new gzip header.
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# Prepend the already read bytes to the fileobj to they can be
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# seen by _read_eof() and _read_gzip_header()
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self.fileobj.prepend(self.decompress.unused_data, True)
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# Check the CRC and file size, and set the flag so we read
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# a new member on the next call
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self._read_eof()
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self._new_member = True
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def _add_read_data(self, data):
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self.crc = zlib.crc32(data, self.crc) & 0xffffffff
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offset = self.offset - self.extrastart
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self.extrabuf = self.extrabuf[offset:] + data
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self.extrasize = self.extrasize + len(data)
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self.extrastart = self.offset
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self.size = self.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 = read32(self.fileobj)
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isize = read32(self.fileobj) # may exceed 2GB
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if crc32 != self.crc:
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raise IOError("CRC check failed %s != %s" % (hex(crc32),
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hex(self.crc)))
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elif isize != (self.size & 0xffffffff):
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raise IOError("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.fileobj.read(1)
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if c:
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self.fileobj.prepend(c, True)
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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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if self.fileobj is None:
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return
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if self.mode == WRITE:
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self.fileobj.write(self.compress.flush())
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write32u(self.fileobj, self.crc)
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# self.size may exceed 2GB, or even 4GB
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write32u(self.fileobj, self.size & 0xffffffff)
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self.fileobj = None
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elif self.mode == READ:
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self.fileobj = None
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if self.myfileobj:
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self.myfileobj.close()
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self.myfileobj = None
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def flush(self,zlib_mode=zlib.Z_SYNC_FLUSH):
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self._check_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 IOError("Can't rewind in write mode")
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self.fileobj.seek(0)
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self._new_member = True
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self.extrabuf = b""
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self.extrasize = 0
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self.extrastart = 0
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self.offset = 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=0):
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if whence:
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if whence == 1:
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offset = self.offset + offset
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|
else:
|
|
raise ValueError('Seek from end not supported')
|
|
if self.mode == WRITE:
|
|
if offset < self.offset:
|
|
raise IOError('Negative seek in write mode')
|
|
count = offset - self.offset
|
|
chunk = bytes(1024)
|
|
for i in range(count // 1024):
|
|
self.write(chunk)
|
|
self.write(bytes(count % 1024))
|
|
elif self.mode == READ:
|
|
if offset < self.offset:
|
|
# for negative seek, rewind and do positive seek
|
|
self.rewind()
|
|
count = offset - self.offset
|
|
for i in range(count // 1024):
|
|
self.read(1024)
|
|
self.read(count % 1024)
|
|
|
|
return self.offset
|
|
|
|
def readline(self, size=-1):
|
|
if size < 0:
|
|
# Shortcut common case - newline found in buffer.
|
|
offset = self.offset - self.extrastart
|
|
i = self.extrabuf.find(b'\n', offset) + 1
|
|
if i > 0:
|
|
self.extrasize -= i - offset
|
|
self.offset += i - offset
|
|
return self.extrabuf[offset: i]
|
|
|
|
size = sys.maxsize
|
|
readsize = self.min_readsize
|
|
else:
|
|
readsize = size
|
|
bufs = []
|
|
while size != 0:
|
|
c = self.read(readsize)
|
|
i = c.find(b'\n')
|
|
|
|
# We set i=size to break out of the loop under two
|
|
# conditions: 1) there's no newline, and the chunk is
|
|
# larger than size, or 2) there is a newline, but the
|
|
# resulting line would be longer than 'size'.
|
|
if (size <= i) or (i == -1 and len(c) > size):
|
|
i = size - 1
|
|
|
|
if i >= 0 or c == b'':
|
|
bufs.append(c[:i + 1]) # Add portion of last chunk
|
|
self._unread(c[i + 1:]) # Push back rest of chunk
|
|
break
|
|
|
|
# Append chunk to list, decrease 'size',
|
|
bufs.append(c)
|
|
size = size - len(c)
|
|
readsize = min(size, readsize * 2)
|
|
if readsize > self.min_readsize:
|
|
self.min_readsize = min(readsize, self.min_readsize * 2, 512)
|
|
return b''.join(bufs) # Return resulting line
|
|
|
|
|
|
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()
|