Add initial pipeline for decompressors

src/utils/SkTextureCompressor.h

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkTextureCompressor_DEFINED
 #define SkTextureCompressor_DEFINED
 
@@ skipping 26 matching lines @@
     // calling unref() on the returned data.
     SkData* CompressBitmapToFormat(const SkBitmap& bitmap, Format format);
 
     // Compresses the given src data into dst. The src data is assumed to be
     // large enough to hold width*height pixels. The dst data is expected to
     // be large enough to hold the compressed data according to the format.
     bool CompressBufferToFormat(uint8_t* dst, const uint8_t* src, SkColorType srcColorType,
                                 int width, int height, int rowBytes, Format format,
                                 bool opt = true /* Use optimization if available */);
 
+    // Decompresses the given src data from the format specified into the
+    // destination buffer. The width and height of the data passed corresponds
+    // to the width and height of the uncompressed image. The destination buffer (dst)
+    // is assumed to be large enough to hold the entire decompressed image. The
+    // decompressed image colors are determined based on the passed format:
+    //
+    // LATC -> Alpha 8
+    // R11_EAC -> Alpha 8
+    // ASTC -> RGBA
+    //
+    // Note, CompressBufferToFormat compresses A8 data into ASTC. However,
+    // general ASTC data encodes RGBA data, so that is what the decompressor
+    // operates on.
+    //
+    // Returns true if successfully decompresses the src data.
+    bool DecompressBufferFromFormat(uint8_t* dst, int dstRowBytes, const uint8_t* src,
+                                    int width, int height, Format format);
+
     // This typedef defines what the nominal aspects of a compression function
     // are. The typedef is not meant to be used by clients of the API, but rather
     // allows SIMD optimized compression functions to be implemented.
     typedef bool (*CompressionProc)(uint8_t* dst, const uint8_t* src,
                                     int width, int height, int rowBytes);
 
     // Returns the blitter for the given compression format. Note, the blitter
     // is intended to be used with the proper input. I.e. if you try to blit
     // RGB source data into an R11 EAC texture, you're gonna have a bad time.
     SkBlitter* CreateBlitterForFormat(int width, int height, void* compressedBuffer,
                                       Format format);
 
     // Returns the desired dimensions of the block size for the given format. These dimensions
-    // don't necessarily correspond to the hardware-specified dimensions, since there may
-    // be specialized algorithms that operate on multiple blocks at once. These dimensions
-    // reflect that optimization and return the appropriate operable dimensions.
-    void GetBlockDimensions(Format format, int* dimX, int* dimY);
+    // don't necessarily correspond to the specification's dimensions, since there may
+    // be specialized algorithms that operate on multiple blocks at once. If the
+    // flag 'matchSpec' is true, then the actual dimensions from the specification are
+    // returned. If the flag is false, then these dimensions reflect the appropriate operable
+    // dimensions of the compression functions.
+    void GetBlockDimensions(Format format, int* dimX, int* dimY, bool matchSpec = false);
 }
 
 #endif