Make BRD take advantage of zero initialized memory

tools/codec/SkBitmapRegionCodec.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkAndroidCodec.h"
 #include "SkBitmapRegionCodec.h"
 #include "SkBitmapRegionDecoderPriv.h"
 #include "SkCodecPriv.h"
 #include "SkPixelRef.h"
 
 SkBitmapRegionCodec::SkBitmapRegionCodec(SkAndroidCodec* codec)
     : INHERITED(codec->getInfo().width(), codec->getInfo().height())
     , fCodec(codec)
 {}
 
-bool SkBitmapRegionCodec::decodeRegion(SkBitmap* bitmap, SkBitmap::Allocator* allocator,
+bool SkBitmapRegionCodec::decodeRegion(SkBitmap* bitmap, SkBRDAllocator* allocator,
         const SkIRect& desiredSubset, int sampleSize, SkColorType dstColorType,
         bool requireUnpremul) {
 
     // Fix the input sampleSize if necessary.
     if (sampleSize < 1) {
         sampleSize = 1;
     }
 
     // The size of the output bitmap is determined by the size of the
     // requested subset, not by the size of the intersection of the subset
@@ skipping 67 matching lines @@
     bitmap->setInfo(outInfo);
     if (!bitmap->tryAllocPixels(allocator, colorTable.get())) {
         SkCodecPrintf("Error: Could not allocate pixels.\n");
         return false;
     }
 
     // Zero the bitmap if the region is not completely within the image.
     // TODO (msarett): Can we make this faster by implementing it to only
     //                 zero parts of the image that we won't overwrite with
     //                 pixels?
-    // TODO (msarett): This could be skipped if memory is zero initialized.
-    //                 This would matter if this code is moved to Android and
-    //                 uses Android bitmaps.
-    if (SubsetType::kPartiallyInside_SubsetType == type) {
+    SkCodec::ZeroInitialized zeroInit = allocator ? allocator->zeroInit() :
+            SkCodec::kNo_ZeroInitialized;
+    if (SubsetType::kPartiallyInside_SubsetType == type &&
+            SkCodec::kNo_ZeroInitialized == zeroInit) {
         void* pixels = bitmap->getPixels();
         size_t bytes = outInfo.getSafeSize(bitmap->rowBytes());
         memset(pixels, 0, bytes);
     }
 
     // Decode into the destination bitmap
     SkAndroidCodec::AndroidOptions options;
     options.fSampleSize = sampleSize;
     options.fSubset = &subset;
     options.fColorPtr = colorPtr;
     options.fColorCount = colorCountPtr;
+    options.fZeroInitialized = zeroInit;
     void* dst = bitmap->getAddr(scaledOutX, scaledOutY);
 
     // FIXME: skbug.com/4538
     // It is important that we use the rowBytes on the pixelRef.  They may not be
     // set properly on the bitmap.
     SkPixelRef* pr = SkRef(bitmap->pixelRef());
     size_t rowBytes = pr->rowBytes();
     bitmap->setInfo(outInfo, rowBytes);
     bitmap->setPixelRef(pr)->unref();
     SkCodec::Result result = fCodec->getAndroidPixels(decodeInfo, dst, rowBytes, &options);
     if (SkCodec::kSuccess != result && SkCodec::kIncompleteInput != result) {
         SkCodecPrintf("Error: Could not get pixels.\n");
         return false;
     }
 
     return true;
 }
 
 bool SkBitmapRegionCodec::conversionSupported(SkColorType colorType) {
     // FIXME: Call virtual function when it lands.
     SkImageInfo info = SkImageInfo::Make(0, 0, colorType, fCodec->getInfo().alphaType(),
             fCodec->getInfo().profileType());
     return conversion_possible(info, fCodec->getInfo());
 }