"""
Defines utility methods for working with gzip streams.
import zlib
import time
# Window size for decompressing GZIP streams.
# This results in ZLIB automatically detecting the GZIP headers.
# http://stackoverflow.com/questions/3122145/zlib-error-error-3-while-decompressing-incorrect-header-check/22310760#22310760
ZLIB_GZIP_WINDOW = zlib.MAX_WBITS | 32
CHUNK_SIZE = 5 * 1024 * 1024
class SizeInfo(object):
def __init__(self):
self.uncompressed_size = 0
self.compressed_size = 0
def calculate_size_handler():
""" Returns an object and a SocketReader handler. The handler will gunzip the data it receives,
adding the size found to the object.
size_info = SizeInfo()
decompressor = zlib.decompressobj(ZLIB_GZIP_WINDOW)
def fn(buf):
# Note: We set a maximum CHUNK_SIZE to prevent the decompress from taking too much
# memory. As a result, we have to loop until the unconsumed tail is empty.
current_data = buf
size_info.compressed_size += len(current_data)
while len(current_data) > 0:
size_info.uncompressed_size += len(decompressor.decompress(current_data, CHUNK_SIZE))
current_data = decompressor.unconsumed_tail
# Make sure we allow the scheduler to do other work if we get stuck in this tight loop.
if len(current_data) > 0:
time.sleep(0)
return size_info, fn
