NEON Optimized RGBA->PMColor sampling in SkSwizzler

src/codec/SkSwizzler.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkSwizzler_DEFINED
 #define SkSwizzler_DEFINED
 
@@ skipping 150 matching lines @@
     template <RowProc Proc>
     static void SkipLeading8888ZerosThen(void* SK_RESTRICT dstRow,
                                          const uint8_t* SK_RESTRICT src,
                                          int dstWidth, int bpp, int deltaSrc, int offset,
                                          const SkPMColor ctable[]);
 
     template <RowProc Proc>
     static void SkipLeadingGrayAlphaZerosThen(void* dst, const uint8_t* src, int width, int bpp,
                                               int deltaSrc, int offset, const SkPMColor ctable[]);
 
-    // May be NULL.  We have not implemented optimized functions for all supported transforms.
-    const RowProc       fFastProc;
-    // Always non-NULL.  Supports sampling.
+    // Always non-NULL.  Supports all sample sizes.
     const RowProc       fSlowProc;
-    // The actual RowProc we are using.  This depends on if fFastProc is non-NULL and
-    // whether or not we are sampling.
+
+    // Optimized functions are supported for some conversions at various sample sizes.
+    // If a RowProc is NULL, it indicates that the particular conversion at the
+    // particular sample size does not have a fast version.
+    struct FastProcs {
+        FastProcs()
+            : fSampleSize1(nullptr)
+            , fSampleSize2(nullptr)
+            , fSampleSize4(nullptr)
+            , fSampleSize8(nullptr)
+        {}
+
+        RowProc fSampleSize1;
+        RowProc fSampleSize2;
+        RowProc fSampleSize4;
+        RowProc fSampleSize8;
+    };
+    const FastProcs     fFastProcs;
+
+    // The actual RowProc we are using.  This will be equal to one of the fFastProcs
+    // if the appropriate proc is non-NULL.  Otherwise, this will be fSlowProc.
     RowProc             fActualProc;
 
     const SkPMColor*    fColorTable;      // Unowned pointer
 
     // Subset Swizzles
     // There are two types of subset swizzles that we support.  We do not
     // support both at the same time.
     // TODO: If we want to support partial scanlines for gifs (which may
     //       use frame subsets), we will need to support both subsetting
     //       modes at the same time.
@@ skipping 68 matching lines @@
     int                 fAllocatedWidth;
 
     int                 fSampleX;         // Step between X samples
     const int           fSrcBPP;          // Bits/bytes per pixel for the SrcConfig
                                           // if bitsPerPixel % 8 == 0
                                           //     fBPP is bytesPerPixel
                                           // else
                                           //     fBPP is bitsPerPixel
     const int           fDstBPP;          // Bytes per pixel for the destination color type
 
-    SkSwizzler(RowProc fastProc, RowProc proc, const SkPMColor* ctable, int srcOffset,
+    SkSwizzler(RowProc proc, const FastProcs& fastProcs, const SkPMColor* ctable, int srcOffset,
             int srcWidth, int dstOffset, int dstWidth, int srcBPP, int dstBPP);
 
     int onSetSampleX(int) override;
 
 };
 #endif // SkSwizzler_DEFINED