Revert of implement readPixels and writePixels natively, w/o using the (deprecated)

src/core/SkConfig8888.cpp

 #include "SkConfig8888.h"
-#include "SkColorPriv.h"
 #include "SkMathPriv.h"
 #include "SkUnPreMultiply.h"
 
-enum AlphaVerb {
-    kNothing_AlphaVerb,
-    kPremul_AlphaVerb,
-    kUnpremul_AlphaVerb,
-};
-
-template <bool doSwapRB, AlphaVerb doAlpha> uint32_t convert32(uint32_t c) {
-    if (doSwapRB) {
-        c = SkSwizzle_RB(c);
-    }
-
-    // Lucky for us, in both RGBA and BGRA, the alpha component is always in the same place, so
-    // we can perform premul or unpremul the same way without knowing the swizzles for RGB.
-    switch (doAlpha) {
-        case kNothing_AlphaVerb:
-            // no change
-            break;
-        case kPremul_AlphaVerb:
-            c = SkPreMultiplyARGB(SkGetPackedA32(c), SkGetPackedR32(c),
-                                  SkGetPackedG32(c), SkGetPackedB32(c));
-            break;
-        case kUnpremul_AlphaVerb:
-            c = SkUnPreMultiply::UnPreMultiplyPreservingByteOrder(c);
-            break;
-    }
-    return c;
-}
-
-template <bool doSwapRB, AlphaVerb doAlpha>
-void convert32_row(uint32_t* dst, const uint32_t* src, int count) {
-    // This has to be correct if src == dst (but not partial overlap)
-    for (int i = 0; i < count; ++i) {
-        dst[i] = convert32<doSwapRB, doAlpha>(src[i]);
-    }
-}
-
-static bool is_32bit_colortype(SkColorType ct) {
-    return kRGBA_8888_SkColorType == ct || kBGRA_8888_SkColorType == ct;
-}
-
-static AlphaVerb compute_AlphaVerb(SkAlphaType src, SkAlphaType dst) {
-    SkASSERT(kIgnore_SkAlphaType != src);
-    SkASSERT(kIgnore_SkAlphaType != dst);
-
-    if (kOpaque_SkAlphaType == src || kOpaque_SkAlphaType == dst || src == dst) {
-        return kNothing_AlphaVerb;
-    }
-    if (kPremul_SkAlphaType == dst) {
-        SkASSERT(kUnpremul_SkAlphaType == src);
-        return kPremul_AlphaVerb;
-    } else {
-        SkASSERT(kPremul_SkAlphaType == src);
-        SkASSERT(kUnpremul_SkAlphaType == dst);
-        return kUnpremul_AlphaVerb;
-    }
-}
-
-static void memcpy32_row(uint32_t* dst, const uint32_t* src, int count) {
-    memcpy(dst, src, count * 4);
-}
-
-bool SkSrcPixelInfo::convertPixelsTo(SkDstPixelInfo* dst, int width, int height) const {
-    if (width <= 0 || height <= 0) {
-        return false;
-    }
-
-    if (!is_32bit_colortype(fColorType) || !is_32bit_colortype(dst->fColorType)) {
-        return false;
-    }
-
-    void (*proc)(uint32_t* dst, const uint32_t* src, int count);
-    AlphaVerb doAlpha = compute_AlphaVerb(fAlphaType, dst->fAlphaType);
-    bool doSwapRB = fColorType != dst->fColorType;
-
-    switch (doAlpha) {
-        case kNothing_AlphaVerb:
-            if (doSwapRB) {
-                proc = convert32_row<true, kNothing_AlphaVerb>;
-            } else {
-                if (fPixels == dst->fPixels) {
-                    return true;
-                }
-                proc = memcpy32_row;
+namespace {
+
+template <int A_IDX, int R_IDX, int G_IDX, int B_IDX>
+inline uint32_t pack_config8888(uint32_t a, uint32_t r,
+                                uint32_t g, uint32_t b) {
+#ifdef SK_CPU_LENDIAN
+    return (a << (A_IDX * 8)) | (r << (R_IDX * 8)) |
+           (g << (G_IDX * 8)) | (b << (B_IDX * 8));
+#else
+    return (a << ((3-A_IDX) * 8)) | (r << ((3-R_IDX) * 8)) |
+           (g << ((3-G_IDX) * 8)) | (b << ((3-B_IDX) * 8));
+#endif
+}
+
+template <int A_IDX, int R_IDX, int G_IDX, int B_IDX>
+inline void unpack_config8888(uint32_t color,
+                              uint32_t* a, uint32_t* r,
+                              uint32_t* g, uint32_t* b) {
+#ifdef SK_CPU_LENDIAN
+    *a = (color >> (A_IDX * 8)) & 0xff;
+    *r = (color >> (R_IDX * 8)) & 0xff;
+    *g = (color >> (G_IDX * 8)) & 0xff;
+    *b = (color >> (B_IDX * 8)) & 0xff;
+#else
+    *a = (color >> ((3 - A_IDX) * 8)) & 0xff;
+    *r = (color >> ((3 - R_IDX) * 8)) & 0xff;
+    *g = (color >> ((3 - G_IDX) * 8)) & 0xff;
+    *b = (color >> ((3 - B_IDX) * 8)) & 0xff;
+#endif
+}
+
+#ifdef SK_CPU_LENDIAN
+    static const int SK_NATIVE_A_IDX = SK_A32_SHIFT / 8;
+    static const int SK_NATIVE_R_IDX = SK_R32_SHIFT / 8;
+    static const int SK_NATIVE_G_IDX = SK_G32_SHIFT / 8;
+    static const int SK_NATIVE_B_IDX = SK_B32_SHIFT / 8;
+#else
+    static const int SK_NATIVE_A_IDX = 3 - (SK_A32_SHIFT / 8);
+    static const int SK_NATIVE_R_IDX = 3 - (SK_R32_SHIFT / 8);
+    static const int SK_NATIVE_G_IDX = 3 - (SK_G32_SHIFT / 8);
+    static const int SK_NATIVE_B_IDX = 3 - (SK_B32_SHIFT / 8);
+#endif
+
+/**
+ * convert_pixel<OUT_CFG, IN_CFG converts a pixel value from one Config8888 to
+ * another. It is implemented by first expanding OUT_CFG to r, g, b, a indices
+ * and an is_premul bool as params to another template function. Then IN_CFG is
+ * expanded via another function call.
+ */
+
+template <bool OUT_PM, int OUT_A_IDX, int OUT_R_IDX, int OUT_G_IDX, int OUT_B_IDX,
+          bool IN_PM,  int IN_A_IDX,  int IN_R_IDX,  int IN_G_IDX,  int IN_B_IDX>
+inline uint32_t convert_pixel(uint32_t pixel) {
+    uint32_t a, r, g, b;
+    unpack_config8888<IN_A_IDX, IN_R_IDX, IN_G_IDX, IN_B_IDX>(pixel, &a, &r, &g, &b);
+    if (IN_PM && !OUT_PM) {
+        // Using SkUnPreMultiply::ApplyScale is faster than (value * 0xff) / a.
+        if (a) {
+            SkUnPreMultiply::Scale scale = SkUnPreMultiply::GetScale(a);
+            r = SkUnPreMultiply::ApplyScale(scale, r);
+            g = SkUnPreMultiply::ApplyScale(scale, g);
+            b = SkUnPreMultiply::ApplyScale(scale, b);
+        } else {
+            return 0;
+        }
+    } else if (!IN_PM && OUT_PM) {
+        // This matches SkUnPreMultiply conversion which we are replacing.
+        r = SkMulDiv255Round(r, a);
+        g = SkMulDiv255Round(g, a);
+        b = SkMulDiv255Round(b, a);
+    }
+    return pack_config8888<OUT_A_IDX, OUT_R_IDX, OUT_G_IDX, OUT_B_IDX>(a, r, g, b);
+}
+
+template <bool OUT_PM, int OUT_A_IDX, int OUT_R_IDX, int OUT_G_IDX, int OUT_B_IDX, SkCanvas::Config8888 IN_CFG>
+inline uint32_t convert_pixel(uint32_t pixel) {
+    switch(IN_CFG) {
+        case SkCanvas::kNative_Premul_Config8888:
+            return convert_pixel<OUT_PM, OUT_A_IDX,       OUT_R_IDX,       OUT_G_IDX,       OUT_B_IDX,
+                                 true,  SK_NATIVE_A_IDX,  SK_NATIVE_R_IDX, SK_NATIVE_G_IDX, SK_NATIVE_B_IDX>(pixel);
+            break;
+        case SkCanvas::kNative_Unpremul_Config8888:
+            return convert_pixel<OUT_PM, OUT_A_IDX,       OUT_R_IDX,       OUT_G_IDX,       OUT_B_IDX,
+                                 false,  SK_NATIVE_A_IDX, SK_NATIVE_R_IDX, SK_NATIVE_G_IDX, SK_NATIVE_B_IDX>(pixel);
+            break;
+        case SkCanvas::kBGRA_Premul_Config8888:
+            return convert_pixel<OUT_PM, OUT_A_IDX, OUT_R_IDX, OUT_G_IDX, OUT_B_IDX,
+                                 true,  3,         2,         1,         0>(pixel);
+            break;
+        case SkCanvas::kBGRA_Unpremul_Config8888:
+            return convert_pixel<OUT_PM, OUT_A_IDX, OUT_R_IDX, OUT_G_IDX, OUT_B_IDX,
+                                 false,  3,         2,         1,         0>(pixel);
+            break;
+        case SkCanvas::kRGBA_Premul_Config8888:
+            return convert_pixel<OUT_PM, OUT_A_IDX, OUT_R_IDX, OUT_G_IDX, OUT_B_IDX,
+                                 true,  3,         0,         1,         2>(pixel);
+            break;
+        case SkCanvas::kRGBA_Unpremul_Config8888:
+            return convert_pixel<OUT_PM, OUT_A_IDX, OUT_R_IDX, OUT_G_IDX, OUT_B_IDX,
+                                 false,  3,         0,         1,         2>(pixel);
+            break;
+        default:
+            SkDEBUGFAIL("Unexpected config8888");
+            return 0;
+            break;
+    }
+}
+
+template <SkCanvas::Config8888 OUT_CFG, SkCanvas::Config8888 IN_CFG>
+inline uint32_t convert_pixel(uint32_t pixel) {
+    switch(OUT_CFG) {
+        case SkCanvas::kNative_Premul_Config8888:
+            return convert_pixel<true,  SK_NATIVE_A_IDX,  SK_NATIVE_R_IDX, SK_NATIVE_G_IDX, SK_NATIVE_B_IDX, IN_CFG>(pixel);
+            break;
+        case SkCanvas::kNative_Unpremul_Config8888:
+            return convert_pixel<false,  SK_NATIVE_A_IDX,  SK_NATIVE_R_IDX, SK_NATIVE_G_IDX, SK_NATIVE_B_IDX, IN_CFG>(pixel);
+            break;
+        case SkCanvas::kBGRA_Premul_Config8888:
+            return convert_pixel<true, 3, 2, 1, 0, IN_CFG>(pixel);
+            break;
+        case SkCanvas::kBGRA_Unpremul_Config8888:
+            return convert_pixel<false, 3, 2, 1, 0, IN_CFG>(pixel);
+            break;
+        case SkCanvas::kRGBA_Premul_Config8888:
+            return convert_pixel<true, 3, 0, 1, 2, IN_CFG>(pixel);
+            break;
+        case SkCanvas::kRGBA_Unpremul_Config8888:
+            return convert_pixel<false, 3, 0, 1, 2, IN_CFG>(pixel);
+            break;
+        default:
+            SkDEBUGFAIL("Unexpected config8888");
+            return 0;
+            break;
+    }
+}
+
+/**
+ * SkConvertConfig8888Pixels has 6 * 6 possible combinations of src and dst
+ * configs. Each is implemented as an instantiation templated function. Two
+ * levels of switch statements are used to select the correct instantiation, one
+ * for the src config and one for the dst config.
+ */
+
+template <SkCanvas::Config8888 DST_CFG, SkCanvas::Config8888 SRC_CFG>
+inline void convert_config8888(uint32_t* dstPixels,
+                               size_t dstRowBytes,
+                               const uint32_t* srcPixels,
+                               size_t srcRowBytes,
+                               int width,
+                               int height) {
+    intptr_t dstPix = reinterpret_cast<intptr_t>(dstPixels);
+    intptr_t srcPix = reinterpret_cast<intptr_t>(srcPixels);
+
+    for (int y = 0; y < height; ++y) {
+        srcPixels = reinterpret_cast<const uint32_t*>(srcPix);
+        dstPixels = reinterpret_cast<uint32_t*>(dstPix);
+        for (int x = 0; x < width; ++x) {
+            dstPixels[x] = convert_pixel<DST_CFG, SRC_CFG>(srcPixels[x]);
+        }
+        dstPix += dstRowBytes;
+        srcPix += srcRowBytes;
+    }
+}
+
+template <SkCanvas::Config8888 SRC_CFG>
+inline void convert_config8888(uint32_t* dstPixels,
+                               size_t dstRowBytes,
+                               SkCanvas::Config8888 dstConfig,
+                               const uint32_t* srcPixels,
+                               size_t srcRowBytes,
+                               int width,
+                               int height) {
+    switch(dstConfig) {
+        case SkCanvas::kNative_Premul_Config8888:
+            convert_config8888<SkCanvas::kNative_Premul_Config8888, SRC_CFG>(dstPixels, dstRowBytes, srcPixels, srcRowBytes, width, height);
+            break;
+        case SkCanvas::kNative_Unpremul_Config8888:
+            convert_config8888<SkCanvas::kNative_Unpremul_Config8888, SRC_CFG>(dstPixels, dstRowBytes, srcPixels, srcRowBytes, width, height);
+            break;
+        case SkCanvas::kBGRA_Premul_Config8888:
+            convert_config8888<SkCanvas::kBGRA_Premul_Config8888, SRC_CFG>(dstPixels, dstRowBytes, srcPixels, srcRowBytes, width, height);
+            break;
+        case SkCanvas::kBGRA_Unpremul_Config8888:
+            convert_config8888<SkCanvas::kBGRA_Unpremul_Config8888, SRC_CFG>(dstPixels, dstRowBytes, srcPixels, srcRowBytes, width, height);
+            break;
+        case SkCanvas::kRGBA_Premul_Config8888:
+            convert_config8888<SkCanvas::kRGBA_Premul_Config8888, SRC_CFG>(dstPixels, dstRowBytes, srcPixels, srcRowBytes, width, height);
+            break;
+        case SkCanvas::kRGBA_Unpremul_Config8888:
+            convert_config8888<SkCanvas::kRGBA_Unpremul_Config8888, SRC_CFG>(dstPixels, dstRowBytes, srcPixels, srcRowBytes, width, height);
+            break;
+        default:
+            SkDEBUGFAIL("Unexpected config8888");
+            break;
+    }
+}
+
+}
+
+void SkConvertConfig8888Pixels(uint32_t* dstPixels,
+                               size_t dstRowBytes,
+                               SkCanvas::Config8888 dstConfig,
+                               const uint32_t* srcPixels,
+                               size_t srcRowBytes,
+                               SkCanvas::Config8888 srcConfig,
+                               int width,
+                               int height) {
+    if (srcConfig == dstConfig) {
+        if (srcPixels == dstPixels) {
+            return;
+        }
+        if (dstRowBytes == srcRowBytes &&
+            4U * width == srcRowBytes) {
+            memcpy(dstPixels, srcPixels, srcRowBytes * height);
+            return;
+        } else {
+            intptr_t srcPix = reinterpret_cast<intptr_t>(srcPixels);
+            intptr_t dstPix = reinterpret_cast<intptr_t>(dstPixels);
+            for (int y = 0; y < height; ++y) {
+                srcPixels = reinterpret_cast<const uint32_t*>(srcPix);
+                dstPixels = reinterpret_cast<uint32_t*>(dstPix);
+                memcpy(dstPixels, srcPixels, 4 * width);
+                srcPix += srcRowBytes;
+                dstPix += dstRowBytes;
             }
-            break;
-        case kPremul_AlphaVerb:
-            if (doSwapRB) {
-                proc = convert32_row<true, kPremul_AlphaVerb>;
-            } else {
-                proc = convert32_row<false, kPremul_AlphaVerb>;
-            }
-            break;
-        case kUnpremul_AlphaVerb:
-            if (doSwapRB) {
-                proc = convert32_row<true, kUnpremul_AlphaVerb>;
-            } else {
-                proc = convert32_row<false, kUnpremul_AlphaVerb>;
-            }
-            break;
-    }
-
-    uint32_t* dstP = static_cast<uint32_t*>(dst->fPixels);
-    const uint32_t* srcP = static_cast<const uint32_t*>(fPixels);
-    size_t srcInc = fRowBytes >> 2;
-    size_t dstInc = dst->fRowBytes >> 2;
-    for (int y = 0; y < height; ++y) {
-        proc(dstP, srcP, width);
-        dstP += dstInc;
-        srcP += srcInc;
-    }
-    return true;
-}
+            return;
+        }
+    }
+    switch(srcConfig) {
+        case SkCanvas::kNative_Premul_Config8888:
+            convert_config8888<SkCanvas::kNative_Premul_Config8888>(dstPixels, dstRowBytes, dstConfig, srcPixels, srcRowBytes, width, height);
+            break;
+        case SkCanvas::kNative_Unpremul_Config8888:
+            convert_config8888<SkCanvas::kNative_Unpremul_Config8888>(dstPixels, dstRowBytes, dstConfig, srcPixels, srcRowBytes, width, height);
+            break;
+        case SkCanvas::kBGRA_Premul_Config8888:
+            convert_config8888<SkCanvas::kBGRA_Premul_Config8888>(dstPixels, dstRowBytes, dstConfig, srcPixels, srcRowBytes, width, height);
+            break;
+        case SkCanvas::kBGRA_Unpremul_Config8888:
+            convert_config8888<SkCanvas::kBGRA_Unpremul_Config8888>(dstPixels, dstRowBytes, dstConfig, srcPixels, srcRowBytes, width, height);
+            break;
+        case SkCanvas::kRGBA_Premul_Config8888:
+            convert_config8888<SkCanvas::kRGBA_Premul_Config8888>(dstPixels, dstRowBytes, dstConfig, srcPixels, srcRowBytes, width, height);
+            break;
+        case SkCanvas::kRGBA_Unpremul_Config8888:
+            convert_config8888<SkCanvas::kRGBA_Unpremul_Config8888>(dstPixels, dstRowBytes, dstConfig, srcPixels, srcRowBytes, width, height);
+            break;
+        default:
+            SkDEBUGFAIL("Unexpected config8888");
+            break;
+    }
+}
+
+uint32_t SkPackConfig8888(SkCanvas::Config8888 config,
+                          uint32_t a,
+                          uint32_t r,
+                          uint32_t g,
+                          uint32_t b) {
+    switch (config) {
+        case SkCanvas::kNative_Premul_Config8888:
+        case SkCanvas::kNative_Unpremul_Config8888:
+            return pack_config8888<SK_NATIVE_A_IDX,
+                                   SK_NATIVE_R_IDX,
+                                   SK_NATIVE_G_IDX,
+                                   SK_NATIVE_B_IDX>(a, r, g, b);
+        case SkCanvas::kBGRA_Premul_Config8888:
+        case SkCanvas::kBGRA_Unpremul_Config8888:
+            return pack_config8888<3, 2, 1, 0>(a, r, g, b);
+        case SkCanvas::kRGBA_Premul_Config8888:
+        case SkCanvas::kRGBA_Unpremul_Config8888:
+            return pack_config8888<3, 0, 1, 2>(a, r, g, b);
+        default:
+            SkDEBUGFAIL("Unexpected config8888");
+            return 0;
+    }
+}