54 lines
1.6 KiB
Python
54 lines
1.6 KiB
Python
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"""
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Defines utility methods for working with gzip streams.
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"""
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import zlib
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import time
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# Window size for decompressing GZIP streams.
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# This results in ZLIB automatically detecting the GZIP headers.
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# http://stackoverflow.com/questions/3122145/zlib-error-error-3-while-decompressing-incorrect-header-check/22310760#22310760
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ZLIB_GZIP_WINDOW = zlib.MAX_WBITS | 32
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CHUNK_SIZE = 5 * 1024 * 1024
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class SizeInfo(object):
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def __init__(self):
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self.uncompressed_size = 0
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self.compressed_size = 0
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self.is_valid = True
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def calculate_size_handler():
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""" Returns an object and a SocketReader handler. The handler will gunzip the data it receives,
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adding the size found to the object.
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"""
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size_info = SizeInfo()
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decompressor = zlib.decompressobj(ZLIB_GZIP_WINDOW)
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def fn(buf):
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if not size_info.is_valid:
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return
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# Note: We set a maximum CHUNK_SIZE to prevent the decompress from taking too much
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# memory. As a result, we have to loop until the unconsumed tail is empty.
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current_data = buf
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size_info.compressed_size += len(current_data)
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while len(current_data) > 0:
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try:
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size_info.uncompressed_size += len(decompressor.decompress(current_data, CHUNK_SIZE))
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except:
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# The gzip stream is not valid for some reason.
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size_info.uncompressed_size = None
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size_info.is_valid = False
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return
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current_data = decompressor.unconsumed_tail
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# Make sure we allow the scheduler to do other work if we get stuck in this tight loop.
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if len(current_data) > 0:
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time.sleep(0)
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return size_info, fn
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