YUV software decode path stride fixes.

base/bits.h

 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file defines some bit utilities.
 
 #ifndef BASE_BITS_H_
 #define BASE_BITS_H_
 
 #include "base/basictypes.h"
@@ skipping 23 matching lines @@
 // Returns the integer i such as 2^(i-1) < n <= 2^i
 inline int Log2Ceiling(uint32 n) {
   if (n == 0) {
     return -1;
   } else {
     // Log2Floor returns -1 for 0, so the following works correctly for n=1.
     return 1 + Log2Floor(n - 1);
   }
 }
 
+// Returns the largest i such as i <= n and i == k * mul for some integer k
+inline uint32 RoundDown(uint32 n, uint32 mul) {
+  return (n / mul) * mul;
+}
+
+// Returns the smallest i such as i >= n and i == k * mul for some integer k
+inline uint32 RoundUp(uint32 n, uint32 mul) {
+  return (n + (mul - 1)) / mul * mul;

[jar (doing other things), 2012/11/20 22:54:35]

Does this do what you want when:
n + mul - 1 > UINT_MAX?

[sheu, 2012/11/20 23:13:50]

It doesn't but I don't really have other suggestions for this, besides
increasing the width of the intermediate.  O don't believe we'll be rounding to
anything excessive -- maybe DCHECK this?

+}
+
 }  // namespace bits
 }  // namespace base
 
 #endif  // BASE_BITS_H_