Add SkCodec, including PNG implementation.

src/codec/SkSwizzler.cpp

Index: src/codec/SkSwizzler.cpp
diff --git a/src/codec/SkSwizzler.cpp b/src/codec/SkSwizzler.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..563933f13a03c16e880c2b8132c7df3657fc4868
--- /dev/null
+++ b/src/codec/SkSwizzler.cpp
@@ -0,0 +1,221 @@
+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkColorPriv.h"
+#include "SkSwizzler.h"
+#include "SkTemplates.h"
+
+// index
+
+#define A32_MASK_IN_PLACE   (SkPMColor)(SK_A32_MASK << SK_A32_SHIFT)
+
+static bool swizzle_index_to_n32(void* SK_RESTRICT dstRow,
+                                 const uint8_t* SK_RESTRICT src,
+                                 int width, int deltaSrc, int, const SkPMColor ctable[]) {
+
+    SkPMColor* SK_RESTRICT dst = (SkPMColor*)dstRow;
+    SkPMColor cc = A32_MASK_IN_PLACE;
+    for (int x = 0; x < width; x++) {
+        SkPMColor c = ctable[*src];
+        cc &= c;
+        dst[x] = c;
+        src += deltaSrc;
+    }
+    return cc != A32_MASK_IN_PLACE;
+}
+
+static bool swizzle_index_to_n32_skipZ(void* SK_RESTRICT dstRow,
+                                      const uint8_t* SK_RESTRICT src,
+                                      int width, int deltaSrc, int,
+                                      const SkPMColor ctable[]) {
+
+    SkPMColor* SK_RESTRICT dst = (SkPMColor*)dstRow;
+    SkPMColor cc = A32_MASK_IN_PLACE;
+    for (int x = 0; x < width; x++) {
+        SkPMColor c = ctable[*src];
+        cc &= c;
+        if (c != 0) {
+            dst[x] = c;
+        }
+        src += deltaSrc;
+    }
+    return cc != A32_MASK_IN_PLACE;
+}
+
+#undef A32_MASK_IN_PLACE
+
+// n32
+static bool swizzle_rgbx_to_n32(void* SK_RESTRICT dstRow,
+                                const uint8_t* SK_RESTRICT src,
+                                int width, int deltaSrc, int, const SkPMColor[]) {
+    SkPMColor* SK_RESTRICT dst = (SkPMColor*)dstRow;
+    for (int x = 0; x < width; x++) {
+        dst[x] = SkPackARGB32(0xFF, src[0], src[1], src[2]);
+        src += deltaSrc;
+    }
+    return false;
+}
+
+static bool swizzle_rgba_to_n32_premul(void* SK_RESTRICT dstRow,
+                                       const uint8_t* SK_RESTRICT src,
+                                       int width, int deltaSrc, int, const SkPMColor[]) {
+    SkPMColor* SK_RESTRICT dst = (SkPMColor*)dstRow;
+    unsigned alphaMask = 0xFF;
+    for (int x = 0; x < width; x++) {
+        unsigned alpha = src[3];
+        dst[x] = SkPreMultiplyARGB(alpha, src[0], src[1], src[2]);
+        src += deltaSrc;
+        alphaMask &= alpha;
+    }
+    return alphaMask != 0xFF;
+}
+
+static bool swizzle_rgba_to_n32_unpremul(void* SK_RESTRICT dstRow,
+                                         const uint8_t* SK_RESTRICT src,
+                                         int width, int deltaSrc, int,
+                                         const SkPMColor[]) {
+    uint32_t* SK_RESTRICT dst = reinterpret_cast<uint32_t*>(dstRow);
+    unsigned alphaMask = 0xFF;
+    for (int x = 0; x < width; x++) {
+        unsigned alpha = src[3];
+        dst[x] = SkPackARGB32NoCheck(alpha, src[0], src[1], src[2]);
+        src += deltaSrc;
+        alphaMask &= alpha;
+    }
+    return alphaMask != 0xFF;
+}
+
+static bool swizzle_rgba_to_n32_premul_skipZ(void* SK_RESTRICT dstRow,
+                                             const uint8_t* SK_RESTRICT src,
+                                             int width, int deltaSrc, int,
+                                             const SkPMColor[]) {
+    SkPMColor* SK_RESTRICT dst = (SkPMColor*)dstRow;
+    unsigned alphaMask = 0xFF;
+    for (int x = 0; x < width; x++) {
+        unsigned alpha = src[3];
+        if (0 != alpha) {
+            dst[x] = SkPreMultiplyARGB(alpha, src[0], src[1], src[2]);
+        }
+        src += deltaSrc;
+        alphaMask &= alpha;
+    }
+    return alphaMask != 0xFF;
+}
+
+/**
+    FIXME: This was my idea to cheat in order to continue taking advantage of skipping zeroes.
+    This would be fine for drawing normally, but not for drawing with transfer modes. Being
+    honest means we can draw correctly with transfer modes, with the cost of not being able
+    to take advantage of Android's free unwritten pages. Something to keep in mind when we
+    decide whether to switch to unpremul default.
+static bool swizzle_rgba_to_n32_unpremul_skipZ(void* SK_RESTRICT dstRow,
+                                               const uint8_t* SK_RESTRICT src,
+                                               int width, int deltaSrc, int,
+                                               const SkPMColor[]) {
+    SkPMColor* SK_RESTRICT dst = (SkPMColor*)dstRow;
+    unsigned alphaMask = 0xFF;
+    for (int x = 0; x < width; x++) {
+        unsigned alpha = src[3];
+        // NOTE: We cheat here. The caller requested unpremul and skip zeroes. It's possible
+        // the color components are not zero, but we skip them anyway, meaning they'll remain
+        // zero (implied by the request to skip zeroes).
+        if (0 != alpha) {
+            dst[x] = SkPackARGB32NoCheck(alpha, src[0], src[1], src[2]);
+        }
+        src += deltaSrc;
+        alphaMask &= alpha;
+    }
+    return alphaMask != 0xFF;
+}
+*/
+
+SkSwizzler* SkSwizzler::CreateSwizzler(SkSwizzler::SrcConfig sc, const SkPMColor* ctable,
+                                       const SkImageInfo& info, void* dst,
+                                       size_t dstRowBytes, bool skipZeroes) {
+    if (info.colorType() == kUnknown_SkColorType) {
+        return NULL;
+    }
+    if (info.minRowBytes() > dstRowBytes) {
+        return  NULL;
+    }
+    if (kIndex == sc && NULL == ctable) {
+        return NULL;
+    }
+    RowProc proc = NULL;
+    switch (sc) {
+        case kIndex:
+            switch (info.colorType()) {
+                case kN32_SkColorType:
+                    // We assume the color premultiplied ctable (or not) as desired.
+                    if (skipZeroes) {
+                        proc = &swizzle_index_to_n32_skipZ;
+                    } else {
+                        proc = &swizzle_index_to_n32;
+                    }
+                    break;
+                    
+                default:
+                    break;
+            }
+            break;
+        case kRGBX:
+            // TODO: Support other swizzles.
+            switch (info.colorType()) {
+                case kN32_SkColorType:
+                    proc = &swizzle_rgbx_to_n32;
+                    break;
+                default:
+                    break;
+            }
+            break;
+        case kRGBA:
+            switch (info.colorType()) {
+                case kN32_SkColorType:
+                    if (info.alphaType() == kUnpremul_SkAlphaType) {
+                        // Respect skipZeroes?
+                        proc = &swizzle_rgba_to_n32_unpremul;
+                    } else {
+                        if (skipZeroes) {
+                            proc = &swizzle_rgba_to_n32_premul_skipZ;
+                        } else {
+                            proc = &swizzle_rgba_to_n32_premul;
+                        }
+                    }
+                    break;
+                default:
+                    break;
+            }
+            break;
+        default:
+            break;
+    }
+    if (NULL == proc) {
+        return NULL;
+    }
+    return SkNEW_ARGS(SkSwizzler, (proc, ctable, BytesPerPixel(sc), info, dst, dstRowBytes));
+}
+
+SkSwizzler::SkSwizzler(RowProc proc, const SkPMColor* ctable, int srcBpp,
+                       const SkImageInfo& info, void* dst, size_t rowBytes)
+    : fRowProc(proc)
+    , fColorTable(ctable)
+    , fSrcPixelSize(srcBpp)
+    , fDstInfo(info)
+    , fDstRow(dst)
+    , fDstRowBytes(rowBytes)
+    , fCurrY(0)
+{
+}
+
+bool SkSwizzler::next(const uint8_t* SK_RESTRICT src) {
+    SkASSERT(fCurrY < fDstInfo.height());
+    const bool hadAlpha = fRowProc(fDstRow, src, fDstInfo.width(), fSrcPixelSize,
+                                   fCurrY, fColorTable);
+    fCurrY++;
+    fDstRow = SkTAddOffset<void>(fDstRow, fDstRowBytes);
+    return hadAlpha;
+}