1d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.orgimport struct 2d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.orgimport sys 3d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org 4d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.orgdef readU32(contents, offset): 5d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org wordBytes = contents[offset:offset + 4] 6d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org return struct.unpack('>I', wordBytes)[0] 7d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org 8d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.orgdef readU16(contents, offset): 9d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org wordBytes = contents[offset:offset + 2] 10d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org return struct.unpack('>H', wordBytes)[0] 11d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org 12d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.orgdef checkChecksum(infile): 13d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org contents = infile.read() 14d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org if len(contents) % 4: 15d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org print 'File length is not a multiple of 4' 16d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org 17d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org sum = 0 18d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org for offset in range(0, len(contents), 4): 19d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org sum += readU32(contents, offset) 20d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org while sum >= 2**32: 21d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org sum -= 2**32 22d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org print 'Sum of whole file: %x' % sum 23d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org 24d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org numTables = readU16(contents, 4) 25d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org 26d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org for offset in range(12, 12 + numTables * 16, 16): 27d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org tag = contents[offset:offset + 4] 28d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org chksum = readU32(contents, offset + 4) 29d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org toffset = readU32(contents, offset + 8) 30d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org tlength = readU32(contents, offset + 12) 31d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org 32d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org sum = 0 33d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org for offset2 in range(toffset, toffset + tlength, 4): 34d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org sum += readU32(contents, offset2) 35d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org while sum >= 2**32: 36d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org sum -= 2**32 37d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org if sum != chksum: 38d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org print 'Bad chksum: %s' % tag 39d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org 40d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.orgif __name__ == '__main__': 41d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org if len(sys.argv) != 2: 42d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org print 'Usage: %s <ttf filename>' % sys.argv[0] 43d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org else: 44d257d186ae2a08042a412824678f98241a1a4f3cyusukes@chromium.org checkChecksum(file(sys.argv[1], 'r')) 45