Implement canvas's globalCompositeOperation lighter properly....

skia/sgl/SkMask.cpp

 /* libs/graphics/sgl/SkMask.cpp
 **
 ** Copyright 2007, The Android Open Source Project
 **
 ** Licensed under the Apache License, Version 2.0 (the "License"); 
 ** you may not use this file except in compliance with the License. 
 ** You may obtain a copy of the License at 
 **
 **     http://www.apache.org/licenses/LICENSE-2.0 
 **
 ** Unless required by applicable law or agreed to in writing, software 
 ** distributed under the License is distributed on an "AS IS" BASIS, 
 ** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
 ** See the License for the specific language governing permissions and 
 ** limitations under the License.
 */
 
-#include <limits>
-
+#include "Sk64.h"
 #include "SkMask.h"
 
-size_t SkMask::computeImageSize() const
-{
-    // Prevent too large a number. There is a better fix for this in Skia
-    // trunk where it returns failure.
-    long long size = (long long)fBounds.height() * (long long)fRowBytes;
-    if (size >= std::numeric_limits<size_t>::max() / 2) {
-#ifdef WIN32
-        __debugbreak();
-#else
-        abort();
-#endif
+/** returns the product if it is positive and fits in 31 bits. Otherwise this
+    returns 0.
+ */
+static int32_t safeMul32(int32_t a, int32_t b) {
+    Sk64 size;
+    size.setMul(a, b);
+    if (size.is32() && size.isPos()) {
+        return size.get32();
     }
-
-    return size;
+    return 0;
 }
 
-size_t SkMask::computeTotalImageSize() const
-{
+size_t SkMask::computeImageSize() const {
+    return safeMul32(fBounds.height(), fRowBytes);
+}
+
+size_t SkMask::computeTotalImageSize() const {
     size_t size = this->computeImageSize();
-
     if (fFormat == SkMask::k3D_Format) {
-        // See computeImageSize for why we want to stop here.
-        if (size > std::numeric_limits<size_t>::max() / 3) {
-#ifdef WIN32
-            __debugbreak();
-#else
-        abort();
-#endif
-        }
-
-        size *= 3;
+        size = safeMul32(size, 3);
     }
     return size;
 }
 
 /** We explicitly use this allocator for SkBimap pixels, so that we can
     freely assign memory allocated by one class to the other.
 */
 uint8_t* SkMask::AllocImage(size_t size)
 {
     return (uint8_t*)sk_malloc_throw(SkAlign4(size));
 }
 
 /** We explicitly use this allocator for SkBimap pixels, so that we can
     freely assign memory allocated by one class to the other.
 */
 void SkMask::FreeImage(void* image)
 {
     sk_free(image);
 }