First pass at a blitter for R11 EAC alpha masks. This shaves 10ms off

src/utils/SkTextureCompressor.h

Index: src/utils/SkTextureCompressor.h
diff --git a/src/utils/SkTextureCompressor.h b/src/utils/SkTextureCompressor.h
index ec6153ace9d945c38544633335dde8f9f3f85ce0..1242ed90771a51f5a12ca2a095327e798d177837 100644
--- a/src/utils/SkTextureCompressor.h
+++ b/src/utils/SkTextureCompressor.h
@@ -9,6 +9,7 @@
 #define SkTextureCompressor_DEFINED
 
 #include "SkImageInfo.h"
+#include "SkBlitter.h"
 
 class SkBitmap;
 class SkData;
@@ -42,6 +43,112 @@ namespace SkTextureCompressor {
     // allows SIMD optimized compression functions to be implemented.
     typedef bool (*CompressionProc)(uint8_t* dst, const uint8_t* src,
                                     int width, int height, int rowBytes);
+

[robertphillips, 2014/07/21 14:28:06]

// This class ... ?

[krajcevski, 2014/07/21 17:35:27]

Done.

+    class R11_EACBlitter : public SkBlitter {
+    public:
+        R11_EACBlitter(int width, int height, void *latcBuffer);
+        virtual ~R11_EACBlitter() { this->flushRuns(); }
+

[robertphillips, 2014/07/21 14:28:06]

/// -> // ?

[krajcevski, 2014/07/21 17:35:27]

Done.

+        /// Blit a horizontal run of one or more pixels.
+        virtual void blitH(int x, int y, int width) SK_OVERRIDE {

[robertphillips, 2014/07/21 14:28:06]

Is this allowed in the SkBlitter contract or a TODO ?

[krajcevski, 2014/07/21 17:35:27]

All of the not implemented functions are more of a TODO. I think that they are
all required by the contract, but it really depends how you're going to use the
blitter. I.e. if this blitter gets used for a RGB bitmap, then it probably
should fail because this function isn't implemented.

I've added a comment to each fail to reflect this.

+            SkFAIL("Not implemented!");
+        }
+
+        /// Blit a horizontal run of antialiased pixels; runs[] is a *sparse*
+        /// zero-terminated run-length encoding of spans of constant alpha values.
+        virtual void blitAntiH(int x, int y,
+                               const SkAlpha* antialias,
+                               const int16_t* runs) SK_OVERRIDE;
+
+        /// Blit a vertical run of pixels with a constant alpha value.
+        virtual void blitV(int x, int y, int height, SkAlpha alpha) SK_OVERRIDE {

[robertphillips, 2014/07/21 14:28:06]

Again - can we do without this?

[krajcevski, 2014/07/21 17:35:26]

Done.

+            SkFAIL("Not implemented!");
+        }
+
+        /// Blit a solid rectangle one or more pixels wide.
+        virtual void blitRect(int x, int y, int width, int height) SK_OVERRIDE {

[robertphillips, 2014/07/21 14:28:06]

Here too?

[krajcevski, 2014/07/21 17:35:27]

Done.

+            SkFAIL("Not implemented!");
+        }
+
+        /** Blit a rectangle with one alpha-blended column on the left,
+            width (zero or more) opaque pixels, and one alpha-blended column
+            on the right.
+            The result will always be at least two pixels wide.    */
+        virtual void blitAntiRect(int x, int y, int width, int height,
+                                  SkAlpha leftAlpha, SkAlpha rightAlpha) SK_OVERRIDE {

[robertphillips, 2014/07/21 14:28:06]

?

[krajcevski, 2014/07/21 17:35:27]

Done.

+            SkFAIL("Not implemented!");
+        }
+        /// Blit a pattern of pixels defined by a rectangle-clipped mask;
+        /// typically used for text.
+        virtual void blitMask(const SkMask&, const SkIRect& clip) SK_OVERRIDE {

[robertphillips, 2014/07/21 14:28:06]

?

[krajcevski, 2014/07/21 17:35:27]

Done.

+            SkFAIL("Not implemented!");
+        }
+
+        /** If the blitter just sets a single value for each pixel, return the
+            bitmap it draws into, and assign value. If not, return NULL and ignore
+            the value parameter.
+        */
+        virtual const SkBitmap* justAnOpaqueColor(uint32_t* value) SK_OVERRIDE {
+            return NULL;
+        }
+
+        /**
+         * Compressed texture blitters only really work correctly if they get
+         * four blocks at a time. That being said, this blitter tries it's best
+         * to preserve semantics if blitAntiH doesn't get called in too many
+         * weird ways...
+         */
+        virtual int requestRowsPreserved() const { return kR11_EACBlockSz; }
+
+    protected:
+        virtual void onNotifyFinished() { this->flushRuns(); }
+
+    private:
+        static const int kR11_EACBlockSz = 4;
+        static const int kPixelsPerBlock = kR11_EACBlockSz * kR11_EACBlockSz;
+
+        // Various utility functions
+        int blocksWide() const { return fWidth / kR11_EACBlockSz; }
+        int blocksTall() const { return fHeight / kR11_EACBlockSz; }
+        int totalBlocks() const { return (fWidth * fHeight) / kPixelsPerBlock; }
+
+        // Returns the block index for the block containing pixel (x, y). Block
+        // indices start at zero and proceed in raster order.
+        int getBlockOffset(int x, int y) const {
+            SkASSERT(x < fWidth);
+            SkASSERT(y < fHeight);
+            const int blockCol = x / kR11_EACBlockSz;
+            const int blockRow = y / kR11_EACBlockSz;
+            return blockRow * this->blocksWide() + blockCol;
+        }
+
+        // Returns a pointer to the block containing pixel (x, y)
+        uint64_t *getBlock(int x, int y) const {
+            return fBuffer + getBlockOffset(x, y);
+        }
+

[robertphillips, 2014/07/21 14:28:06]

order is supposed to be member variables then methods.

[krajcevski, 2014/07/21 17:35:27]

Done.

+        const int16_t kLongestRun;
+        const SkAlpha kZeroAlpha;
+        struct BufferedRun {
+            const SkAlpha* fAlphas;
+            const int16_t* fRuns;
+            int fX, fY;
+        } fBufferedRuns[kR11_EACBlockSz];
+        int fNextRun;
+
+        // The following function writes the buffered runs to compressed blocks.
+        // If fNextRun < 4, then we fill the runs that we haven't buffered with
+        // the constant zero buffer.
+        void flushRuns();
+
+        // The width and height of the image that we're blitting
+        const int fWidth;
+        const int fHeight;
+
+        // The R11 EAC buffer that we're blitting into. It is assumed that the buffer
+        // is large enough to store a compressed image of size fWidth*fHeight.
+        uint64_t*const fBuffer;
+    };
 }
 
 #endif