Replacing SkTDArray with SkAutoSTArray to reduce memory allocation overhead in SkTileGrid::search

BUG=https://code.google.com/p/skia/issues/detail?id=1735
R=tomhudson@chromium.org

Author: junov@chromium.org

Review URL: https://codereview.chromium.org/35633002

git-svn-id: http://skia.googlecode.com/svn/trunk@11936 2bbb7eff-a529-9590-31e7-b0007b416f81

2 files changed, 12 insertions, 9 deletions

diff --git a/src/core/SkTileGrid.cpp b/src/core/SkTileGrid.cpp
index c39e21b356..bbed00603d 100644
--- a/src/core/SkTileGrid.cpp
+++ b/src/core/SkTileGrid.cpp
@@ -91,13 +91,8 @@ void SkTileGrid::search(const SkIRect& query, SkTDArray<void*>* results) {
         *results = this->tile(tileStartX, tileStartY);
     } else {
         results->reset();
-        SkTDArray<int> curPositions;
-        curPositions.setCount(queryTileCount);
-        // Note: Reserving space for 1024 tile pointers on the stack. If the
-        // malloc becomes a bottleneck, we may consider increasing that number.
-        // Typical large web page, say 2k x 16k, would require 512 tiles of
-        // size 256 x 256 pixels.
-        SkAutoSTArray<1024, SkTDArray<void *>*> storage(queryTileCount);
+        SkAutoSTArray<kStackAllocationTileCount, int> curPositions(queryTileCount);
+        SkAutoSTArray<kStackAllocationTileCount, SkTDArray<void *>*> storage(queryTileCount);
         SkTDArray<void *>** tileRange = storage.get();
         int tile = 0;
         for (int x = tileStartX; x < tileEndX; ++x) {
diff --git a/src/core/SkTileGrid.h b/src/core/SkTileGrid.h
index e272673c63..77d972850f 100644
--- a/src/core/SkTileGrid.h
+++ b/src/core/SkTileGrid.h
@@ -25,7 +25,15 @@
  */
 class SkTileGrid : public SkBBoxHierarchy {
 public:
-    typedef void* (*SkTileGridNextDatumFunctionPtr)(SkTDArray<void*>** tileData, SkTDArray<int>& tileIndices);
+    enum {
+        // Number of tiles for which data is allocated on the stack in
+        // SkTileGrid::search. If malloc becomes a bottleneck, we may consider
+        // increasing this number. Typical large web page, say 2k x 16k, would
+        // require 512 tiles of size 256 x 256 pixels.
+        kStackAllocationTileCount = 1024
+    };
+
+    typedef void* (*SkTileGridNextDatumFunctionPtr)(SkTDArray<void*>** tileData, SkAutoSTArray<kStackAllocationTileCount, int>& tileIndices);
 
     SkTileGrid(int xTileCount, int yTileCount, const SkTileGridPicture::TileGridInfo& info,
         SkTileGridNextDatumFunctionPtr nextDatumFunction);
@@ -91,7 +99,7 @@ private:
  *     such that 'a < b' is true if 'a' was inserted into the tile grid before 'b'.
  */
 template <typename T>
-void* SkTileGridNextDatum(SkTDArray<void*>** tileData, SkTDArray<int>& tileIndices) {
+void* SkTileGridNextDatum(SkTDArray<void*>** tileData, SkAutoSTArray<SkTileGrid::kStackAllocationTileCount, int>& tileIndices) {
     T* minVal = NULL;
     int tileCount = tileIndices.count();
     int minIndex = tileCount;