rename SkBitmapChecksummer as SkBitmapHasher, and prepare for it to possibly use
some algorithm other than CityHash
Review URL: https://codereview.chromium.org/14170010

git-svn-id: http://skia.googlecode.com/svn/trunk@8639 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/tests/BitmapHasherTest.cpp b/tests/BitmapHasherTest.cpp
new file mode 100644
index 0000000..6aa464d
--- /dev/null
+++ b/tests/BitmapHasherTest.cpp
@@ -0,0 +1,64 @@
+
+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+#include "Test.h"
+
+#include "SkBitmap.h"
+#include "SkBitmapHasher.h"
+#include "SkColor.h"
+
+// Word size that is large enough to hold results of any checksum type.
+typedef uint64_t checksum_result;
+
+namespace skiatest {
+    class BitmapHasherTestClass : public Test {
+    public:
+        static Test* Factory(void*) {return SkNEW(BitmapHasherTestClass); }
+    protected:
+        virtual void onGetName(SkString* name) { name->set("BitmapHasher"); }
+        virtual void onRun(Reporter* reporter) {
+            this->fReporter = reporter;
+            RunTest();
+        }
+    private:
+
+        // Fill in bitmap with test data.
+        void CreateTestBitmap(SkBitmap &bitmap, SkBitmap::Config config, int width, int height,
+                              SkColor color) {
+            bitmap.setConfig(config, width, height);
+            REPORTER_ASSERT(fReporter, bitmap.allocPixels());
+            bitmap.setIsOpaque(true);
+            bitmap.eraseColor(color);
+        }
+
+        void RunTest() {
+            // Test SkBitmapHasher
+            SkBitmap bitmap;
+            SkHashDigest digest;
+            // initial test case
+            CreateTestBitmap(bitmap, SkBitmap::kARGB_8888_Config, 333, 555, SK_ColorBLUE);
+            REPORTER_ASSERT(fReporter, SkBitmapHasher::ComputeDigest(bitmap, &digest));
+            REPORTER_ASSERT(fReporter, digest == 0x18f9df68b1b02f38ULL);
+            // same pixel data but different dimensions should yield a different checksum
+            CreateTestBitmap(bitmap, SkBitmap::kARGB_8888_Config, 555, 333, SK_ColorBLUE);
+            REPORTER_ASSERT(fReporter, SkBitmapHasher::ComputeDigest(bitmap, &digest));
+            REPORTER_ASSERT(fReporter, digest == 0x6b0298183f786c8eULL);
+            // same dimensions but different color should yield a different checksum
+            CreateTestBitmap(bitmap, SkBitmap::kARGB_8888_Config, 555, 333, SK_ColorGREEN);
+            REPORTER_ASSERT(fReporter, SkBitmapHasher::ComputeDigest(bitmap, &digest));
+            REPORTER_ASSERT(fReporter, digest == 0xc6b4b3f6fadaaf37ULL);
+            // same pixel colors in a different config should yield the same checksum
+            CreateTestBitmap(bitmap, SkBitmap::kARGB_4444_Config, 555, 333, SK_ColorGREEN);
+            REPORTER_ASSERT(fReporter, SkBitmapHasher::ComputeDigest(bitmap, &digest));
+            REPORTER_ASSERT(fReporter, digest == 0xc6b4b3f6fadaaf37ULL);
+        }
+
+        Reporter* fReporter;
+    };
+
+    static TestRegistry gReg(BitmapHasherTestClass::Factory);
+}