spriteblitter for memcpy case (for all configs)

src/core/SkBlitter_Sprite.cpp

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkSmallAllocator.h"
 #include "SkSpriteBlitter.h"
 
@@ skipping 20 matching lines @@
     SkDEBUGFAIL("how did we get here?");
 }
 
 void SkSpriteBlitter::blitMask(const SkMask&, const SkIRect& clip) {
     SkDEBUGFAIL("how did we get here?");
 }
 #endif
 
 ///////////////////////////////////////////////////////////////////////////////
 
+//  Only valid if...
+//      1. src == dst format
+//      2. paint has no modifiers (i.e. alpha, colorfilter, etc.)
+//      3. xfermode needs no blending: e.g. kSrc_Mode or kSrcOver_Mode + opaque src
+//
+class SkSpriteBlitter_memcpy : public SkSpriteBlitter {
+public:
+    static bool Supports(const SkPixmap& dst, const SkPixmap& src, const SkPaint& paint) {
+        if (dst.colorType() != src.colorType()) {
+            return false;
+        }
+        if (paint.getMaskFilter() || paint.getColorFilter() || paint.getImageFilter()) {
+            return false;
+        }
+        if (0xFF != paint.getAlpha()) {
+            return false;
+        }
+        SkXfermode::Mode mode;
+        if (!SkXfermode::AsMode(paint.getXfermode(), &mode)) {
+            return false;
+        }
+        if (SkXfermode::kSrc_Mode == mode) {
+            return true;
+        }
+        if (SkXfermode::kSrcOver_Mode == mode && src.isOpaque()) {
+            return true;
+        }
+        return false;
+    }
+
+    SkSpriteBlitter_memcpy(const SkPixmap& src)  : INHERITED(src) {}
+
+    void setup(const SkPixmap& dst, int left, int top, const SkPaint& paint) override {
+        SkASSERT(Supports(dst, fSource, paint));
+        this->INHERITED::setup(dst, left, top, paint);
+    }
+
+    void blitRect(int x, int y, int width, int height) override {
+        SkASSERT(fDst.colorType() == fSource.colorType());
+        SkASSERT(width > 0 && height > 0);
+
+        void* dst = fDst.writable_addr(x, y);

[mtklein, 2016/04/15 13:29:21]

It might be clearer to cast to char* early:

   auto dst = (      char*)fDst.writeable_addr(x,y);
   auto src = (const char*)fSource.addr(x-fLeft, y-fTop);

   size_t dstRB = ...;
   size_t srcRB = ...;
   size_t bytesToCopy = ...;

   while (height --> 0) {
       memcpy(dst, src, bytesToCopy);
       dst += dstRB;
       src += srcRB;
   }
   

[reed1, 2016/04/15 13:49:10]

Done.

+        const void* src = fSource.addr(x - fLeft, y - fTop);
+        size_t dstRB = fDst.rowBytes();
+        size_t srcRB = fSource.rowBytes();
+        size_t bytesToCopy = SkLeftShift(width, fSource.shiftPerPixel());

[mtklein, 2016/04/15 13:29:21]

Seems like it's not sensible for width to be negative here, so I am skeptical of
SkLeftShift.  We've asserted that width is positive, and if it were negative,
bytesToCopy would become impossibly large.  Might want to write this the old
usual way,

    width << fSource.shiftPerPixel()

which would let ubsan point out any negative values should that case ever come
up.  (The fix wouldn't be use SkLeftShift... it'd be to figure out how width got
negative.)

[reed1, 2016/04/15 13:49:10]

Done.

+
+        do {
+            memcpy(dst, src, bytesToCopy);
+            dst = (char*)dst + dstRB;
+            src = (const char*)src + srcRB;
+        } while (--height != 0);
+    }
+
+    typedef SkSpriteBlitter INHERITED;
+};
+
+
 // returning null means the caller will call SkBlitter::Choose() and
 // have wrapped the source bitmap inside a shader
 SkBlitter* SkBlitter::ChooseSprite(const SkPixmap& dst, const SkPaint& paint,
         const SkPixmap& source, int left, int top, SkTBlitterAllocator* allocator) {
     /*  We currently ignore antialiasing and filtertype, meaning we will take our
         special blitters regardless of these settings. Ignoring filtertype seems fine
         since by definition there is no scale in the matrix. Ignoring antialiasing is
         a bit of a hack, since we "could" pass in the fractional left/top for the bitmap,
         and respect that by blending the edges of the bitmap against the device. To support
         this we could either add more special blitters here, or detect antialiasing in the
         paint and return null if it is set, forcing the client to take the slow shader case
         (which does respect soft edges).
     */
     SkASSERT(allocator != nullptr);
 
     SkSpriteBlitter* blitter;
 
-    switch (dst.colorType()) {
-        case kRGB_565_SkColorType:
-            blitter = SkSpriteBlitter::ChooseD16(source, paint, allocator);
-            break;
-        case kN32_SkColorType:
-            if (dst.info().isSRGB()) {
-                blitter = SkSpriteBlitter::ChooseS32(source, paint, allocator);
-            } else {
-                blitter = SkSpriteBlitter::ChooseL32(source, paint, allocator);
-            }
-            break;
-        case kRGBA_F16_SkColorType:
-            blitter = SkSpriteBlitter::ChooseF16(source, paint, allocator);
-            break;
-        default:
-            blitter = nullptr;
-            break;
+    if (SkSpriteBlitter_memcpy::Supports(dst, source, paint)) {
+        blitter = allocator->createT<SkSpriteBlitter_memcpy>(source);
+    } else {
+        switch (dst.colorType()) {
+            case kRGB_565_SkColorType:
+                blitter = SkSpriteBlitter::ChooseD16(source, paint, allocator);
+                break;
+            case kN32_SkColorType:
+                if (dst.info().isSRGB()) {
+                    blitter = SkSpriteBlitter::ChooseS32(source, paint, allocator);
+                } else {
+                    blitter = SkSpriteBlitter::ChooseL32(source, paint, allocator);
+                }
+                break;
+            case kRGBA_F16_SkColorType:
+                blitter = SkSpriteBlitter::ChooseF16(source, paint, allocator);
+                break;
+            default:
+                blitter = nullptr;
+                break;
+        }
     }
 
     if (blitter) {
         blitter->setup(dst, left, top, paint);
     }
     return blitter;
 }