Compute AccurateRip v2 checksum instead of v1

Import hcs64/morituri@498d2ba.

Issue thomasvs/morituri#119.

Test branch in which AccurateRip v1 support is dropped in favor of
AccurateRip v2.

morituri/common/checksum.py

@@ -300,7 +300,9 @@ def do_checksum_buffer(self, buf, checksum):
             # ... on 5th frame, only use last value
             elif self._discFrameCounter == 5:
                 values = struct.unpack("<I", buf[-4:])
-                checksum += common.SAMPLES_PER_FRAME * 5 * values[0]
+                mvalue = common.SAMPLES_PER_FRAME * 5 * values[0]
+                (hi, lo) = divmod(mvalue, 2 ** 32)
+                checksum += lo + hi
                 checksum &= 0xFFFFFFFF
                 return checksum
 
@@ -311,18 +313,18 @@ def do_checksum_buffer(self, buf, checksum):
                 self.debug('skipping frame %d', self._discFrameCounter)
                 return checksum
 
-        # self._bytes is updated after do_checksum_buffer
-        factor = self._bytes / 4 + 1
         values = struct.unpack("<%dI" % (len(buf) / 4), buf)
-        for value in values:
-            checksum += factor * value
-            factor += 1
+        for i, value in enumerate(values):
+            # self._bytes is updated after do_checksum_buffer
+            mvalue = (self._bytes / 4 + i + 1) * value
+            (hi, lo) = divmod(mvalue, 2 ** 32)
+            checksum += lo + hi
+            checksum &= 0xFFFFFFFF
             # offset = self._bytes / 4 + i + 1
             # if offset % common.SAMPLES_PER_FRAME == 0:
             #   print 'frame %d, ends before %d, last value %08x, CRC %08x' % (
             #     offset / common.SAMPLES_PER_FRAME, offset, value, sum)
 
-        checksum &= 0xFFFFFFFF
         return checksum