rename SkBitmapChecksummer as SkBitmapHasher, and prepare for it to possibly use

src/utils/SkBitmapChecksummer.cpp

-
-/*
- * Copyright 2012 Google Inc.
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
-
-#include "SkBitmap.h"
-#include "SkBitmapChecksummer.h"
-#include "SkBitmapTransformer.h"
-#include "SkCityHash.h"
-#include "SkEndian.h"
-
-/**
- * Write an integer value into a bytebuffer in little-endian order.
- */
-static void write_int_to_buffer(int val, char* buf) {
-    val = SkEndian_SwapLE32(val);
-    for (int byte=0; byte<4; byte++) {
-        *buf++ = (char)(val & 0xff);
-        val = val >> 8;
-    }
-}
-
-/*static*/ uint64_t SkBitmapChecksummer::Compute64Internal(
-        const SkBitmap& bitmap, const SkBitmapTransformer& transformer) {
-    size_t pixelBufferSize = transformer.bytesNeededTotal();
-    size_t totalBufferSize = pixelBufferSize + 8; // leave room for x/y dimensions
-
-    SkAutoMalloc bufferManager(totalBufferSize);
-    char *bufferStart = static_cast<char *>(bufferManager.get());
-    char *bufPtr = bufferStart;
-    // start with the x/y dimensions
-    write_int_to_buffer(bitmap.width(), bufPtr);
-    bufPtr += 4;
-    write_int_to_buffer(bitmap.height(), bufPtr);
-    bufPtr += 4;
-
-    // add all the pixel data
-    if (!transformer.copyBitmapToPixelBuffer(bufPtr, pixelBufferSize)) {
-        return 0;
-    }
-    return SkCityHash::Compute64(bufferStart, totalBufferSize);
-}
-
-/*static*/ uint64_t SkBitmapChecksummer::Compute64(const SkBitmap& bitmap) {
-    const SkBitmapTransformer::PixelFormat kPixelFormat =
-        SkBitmapTransformer::kARGB_8888_Premul_PixelFormat;
-
-    // First, try to transform the existing bitmap.
-    const SkBitmapTransformer transformer =
-        SkBitmapTransformer(bitmap, kPixelFormat);
-    if (transformer.isValid(false)) {
-        return Compute64Internal(bitmap, transformer);
-    }
-
-    // Hmm, that didn't work. Maybe if we create a new
-    // kARGB_8888_Config version of the bitmap it will work better?
-    SkBitmap copyBitmap;
-    bitmap.copyTo(&copyBitmap, SkBitmap::kARGB_8888_Config);
-    const SkBitmapTransformer copyTransformer =
-        SkBitmapTransformer(copyBitmap, kPixelFormat);
-    if (copyTransformer.isValid(true)) {
-        return Compute64Internal(copyBitmap, copyTransformer);
-    } else {
-        return 0;
-    }
-}