Class _GzipReader

Lib/gzip.py:524–619

class _GzipReader(_streams.DecompressReader):
    def __init__(self, fp):
        super().__init__(_PaddedFile(fp), zlib._ZlibDecompressor,
                         wbits=-zlib.MAX_WBITS)
        # Set flag indicating start of a new member
        self._new_member = True
        self._last_mtime = None

    def _init_read(self):
        self._crc = zlib.crc32(b"")
        self._stream_size = 0  # Decompressed size of unconcatenated stream

    def _read_gzip_header(self):
        last_mtime = _read_gzip_header(self._fp)
        if last_mtime is None:
            return False
        self._last_mtime = last_mtime
        return True

    def read(self, size=-1):
        if size < 0:
            return self.readall()
        # size=0 is special because decompress(max_length=0) is not supported
        if not size:
            return b""

        # For certain input data, a single
        # call to decompress() may not return
        # any data. In this case, retry until we get some data or reach EOF.
        while True:
            if self._decompressor.eof:
                # Ending case: we've come to the end of a member in the file,
                # so finish up this member, and read a new gzip header.
                # Check the CRC and file size, and set the flag so we read
                # a new member
                self._read_eof()
                self._new_member = True
                self._decompressor = self._decomp_factory(
                    **self._decomp_args)

            if self._new_member:
                # If the _new_member flag is set, we have to
                # jump to the next member, if there is one.
                self._init_read()
                if not self._read_gzip_header():
                    self._size = self._pos
                    return b""
                self._new_member = False

            # Read a chunk of data from the file
            if self._decompressor.needs_input:
                buf = self._fp.read(READ_BUFFER_SIZE)
                uncompress = self._decompressor.decompress(buf, size)
            else:
                uncompress = self._decompressor.decompress(b"", size)

            if self._decompressor.unused_data != b"":
                # Prepend the already read bytes to the fileobj so they can