Gzip Consumer Class
January 27, 2003 | Fredrik Lundh
The following consumer class provides gzip decoding on the fly. The consumer acts like a filter, passing decoded data on to another consumer object.
The consumer’s feed and close methods may raise IOError or zlib.error exceptions, if the input data is not a valid gzip stream.
Note that this class delegates all method calls to the underlying target consumer. This allows you to use GzipConsumer(consumer) instead of a plain consumer, in many cases.
The GzipConsumer Class
# File: GzipConsumer.py class GzipConsumer: def __init__(self, consumer): self.__consumer = consumer self.__decoder = None self.__data = "" def __getattr__(self, key): # delegate unknown methods/attributes return getattr(self.__consumer, key) def feed(self, data): if self.__decoder is None: # check if we have a full gzip header data = self.__data + data try: i = 10 flag = ord(data[3]) if flag & 4: # extra x = ord(data[i]) + 256*ord(data[i+1]) i = i + 2 + x if flag & 8: # filename while ord(data[i]): i = i + 1 i = i + 1 if flag & 16: # comment while ord(data[i]): i = i + 1 i = i + 1 if flag & 2: # crc i = i + 2 if len(data) < i: raise IndexError("not enough data") if data[:3] != "\x1f\x8b\x08": raise IOError("invalid gzip data") data = data[i:] except IndexError: self.__data = data return # need more data import zlib self.__data = "" self.__decoder = zlib.decompressobj(-zlib.MAX_WBITS) data = self.__decoder.decompress(data) if data: self.__consumer.feed(data) def close(self): if self.__decoder: data = self.__decoder.flush() if data: self.__consumer.feed(data) self.__consumer.close()
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