Simplified linear pipeline.

src/core/SkLinearBitmapPipeline.h

+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkLinearBitmapPipeline_DEFINED
+#define SkLinearBitmapPipeline_DEFINED
+
+#include <algorithm>
+#include <cmath>
+#include <limits>
+#include <cstdio>
+#include "SkColor.h"
+#include "SkImageInfo.h"
+#include "SkMatrix.h"
+#include "SkShader.h"
+#include "SkSize.h"
+#include "SkNx.h"
+
+using Sk4fArg = const Sk4f&;
+
+class PointProcessorInterface {
+public:
+    virtual ~PointProcessorInterface() { }
+    virtual void pointListFew(int n, Sk4fArg xs, Sk4fArg ys) = 0;
+    virtual void pointList4(Sk4fArg xs, Sk4fArg ys) = 0;
+};
+
+class PixelPlacerInterface {
+public:
+    virtual ~PixelPlacerInterface() { }
+    virtual void setDestination(SkPM4f* dst) = 0;
+    virtual void placePixel(Sk4fArg pixel0) = 0;
+    virtual void place4Pixels(Sk4fArg p0, Sk4fArg p1, Sk4fArg p2, Sk4fArg p3) = 0;
+};
+
+class SkLinearBitmapPipeline {
+public:
+    SkLinearBitmapPipeline(
+        const SkMatrix& inverse,
+        SkShader::TileMode xTile, SkShader::TileMode yTile,
+        const SkImageInfo& srcImageInfo,
+        const void* srcImageData);
+
+    void shadeSpan4f(int x, int y, SkPM4f* dst, int count);
+
+    template<typename Base, size_t kSize>
+    class PolymorphicUnion {
+    public:
+        PolymorphicUnion() {}
+
+        ~PolymorphicUnion() { get()->~Base(); }
+
+        template<typename Variant, typename... Args>
+        void Initialize(Args&&... args) {
+            SkASSERTF(sizeof(Variant) <= sizeof(fSpace),
+                      "Size Variant: %d, Space: %d", sizeof(Variant), sizeof(fSpace));
+
+            new(&fSpace) Variant(std::forward<Args>(args)...);
+        };
+
+        Base* get() const { return reinterpret_cast<Base*>(&fSpace); }
+        Base* operator->() const { return get(); }
+        Base& operator*() const { return *get(); }
+
+    private:
+        struct SK_STRUCT_ALIGN(16) Space {
+            char space[kSize];
+        };
+        mutable Space fSpace;
+    };
+
+    using MatrixStage = PolymorphicUnion<PointProcessorInterface, 112>;
+    using TileStage   = PolymorphicUnion<PointProcessorInterface,  96>;
+    using SampleStage = PolymorphicUnion<PointProcessorInterface,  80>;
+    using PixelStage  = PolymorphicUnion<PixelPlacerInterface,     80>;
+
+private:
+    PointProcessorInterface* fFirstStage;
+    MatrixStage fMatrixStage;
+    TileStage   fTileXOrBothStage;
+    TileStage   fTileYStage;
+    SampleStage fSampleStage;
+    PixelStage  fPixelStage;
+};
+
+#endif  // SkLinearBitmapPipeline_DEFINED