Add SkCodec, including PNG implementation.

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
+
+#include "SkTypes.h"
+#include "SkColor.h"
+#include "SkImageInfo.h"
+
+class SkSwizzler : public SkNoncopyable {
+public:
+    /**
+     *  Enum describing the config of the source data.
+     */
+    enum SrcConfig {
+        kGray,  // 1 byte per pixel
+        kIndex, // 1 byte per pixel
+        kRGB,   // 3 bytes per pixel
+        kRGBX,  // 4 byes per pixel (ignore 4th)
+        kRGBA,  // 4 bytes per pixel
+        kRGB_565 // 2 bytes per pixel
+    };
+
+    static int BytesPerPixel(SrcConfig sc) {
+        switch (sc) {
+            case kGray:
+            case kIndex:
+                return 1;
+            case kRGB:
+                return 3;
+            case kRGBX:
+            case kRGBA:
+                return 4;
+            case kRGB_565:
+                return 2;
+        }
+    }
+
+    /**
+     *  Create a new SkSwizzler.
+     *  @param sc SrcConfig
+     *  @param info dimensions() describe both the src and the dst.
+     *              Other fields describe the dst.
+     *  @param dst Destination to write pixels. Must match info and dstRowBytes
+     *  @param dstRowBytes rowBytes for dst.
+     *  @param skipZeroes Whether to skip writing zeroes. Useful if dst is
+     *              zero-initialized. The implementation may or may not respect this.
+     *  @return A new SkSwizzler or NULL on failure.
+     */
+    static SkSwizzler* CreateSwizzler(SrcConfig sc, const SkPMColor* ctable,
+                                      const SkImageInfo& info, void* dst,
+                                      size_t dstRowBytes, bool skipZeroes);
+    /**
+     *  Swizzle the next line. Call height times, once for each row of source.
+     *  @param src The next row of the source data.
+     *  @return Whether the row had non-opaque alpha.
+     */
+    bool next(const uint8_t* SK_RESTRICT src);
+private:
+    /**
+     *  Method for converting raw data to Skia pixels.
+     *  @param dstRow Row in which to write the resulting pixels.
+     *  @param src Row of src data, in format specified by SrcConfig
+     *  @param width Width in pixels
+     *  @param bpp bytes per pixel of the source.
+     *  @param y Line of source.
+     *  @param ctable Colors (used for kIndex source).
+     */
+    typedef bool (*RowProc)(void* SK_RESTRICT dstRow,
+                            const uint8_t* SK_RESTRICT src,
+                            int width, int bpp, int y,
+                            const SkPMColor ctable[]);
+
+    const RowProc       fRowProc;
+    const SkPMColor*    fColorTable;    // Unowned pointer
+    const int           fSrcPixelSize;
+    const SkImageInfo   fDstInfo;
+    void*               fDstRow;
+    const size_t        fDstRowBytes;
+    int                 fCurrY;
+
+    SkSwizzler(RowProc proc, const SkPMColor* ctable, int srcBpp,
+               const SkImageInfo& info, void* dst, size_t rowBytes);
+
+};
+#endif // SkSwizzler_DEFINED
+