def read_varlen(data): NEXTBYTE = 1 value = 0 while NEXTBYTE: chr = next(data) # is the hi-bit set? if not (chr & 0x80): # no next BYTE NEXTBYTE = 0 # mask out the 8th bit chr = chr & 0x7f # shift last value up 7 bits value = value << 7 # add new value value += chr return value def write_varlen(value): b1 = value & 0x7F value >>= 7 if value: b2 = (value & 0x7F) | 0x80 value >>= 7 if value: b3 = (value & 0x7F) | 0x80 value >>= 7 if value: b4 = (value & 0x7F) | 0x80 res = bytes((b4,b3,b2,b1)) else: res = bytes((b3,b2,b1)) else: res = bytes((b2,b1)) else: res = bytes((b1,)) return res