From 498d2ba71f7ee25ee8c3288e244e6fcc930ea557 Mon Sep 17 00:00:00 2001
From: Adam Gashlin <agashlin@gmail.com>
Date: Fri, 10 Apr 2015 23:58:28 -0400
Subject: [PATCH] Compute AccurateRip v2 checksum instead of v1.

---
 morituri/common/checksum.py | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/morituri/common/checksum.py b/morituri/common/checksum.py
index e45550af..473816dc 100644
--- a/morituri/common/checksum.py
+++ b/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
 
@@ -314,7 +316,9 @@ def do_checksum_buffer(self, buf, checksum):
         values = struct.unpack("<%dI" % (len(buf) / 4), buf)
         for i, value in enumerate(values):
             # self._bytes is updated after do_checksum_buffer
-            checksum += (self._bytes / 4 + i + 1) * value
+            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: