Make SkSHA1 and SkM5 use common SkDigestHash result type

src/utils/SkBitmapHasher.h

 
 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkBitmapHasher_DEFINED
 #define SkBitmapHasher_DEFINED
 
 #include "SkBitmap.h"
 #include "SkBitmapTransformer.h"
+#include "SkHashDigest.h"
 
-// TODO(epoger): Soon, SkHashDigest will become a real class of its own,
-// and callers won't be able to assume it converts to/from a uint64_t.
-typedef uint64_t SkHashDigest;
+// TODO(epoger): Once we figure out which bitmap hash algorithm to use
+// long-term, pick one BITMAP_HASH_TYPE setting and delete the unused code.
+//
+// For now, disable this to keep the old uint64_t bitmap hash.
+//#define BITMAP_HASH_TYPE_SkHashDigest

[epoger, 2013/04/18 16:39:34]

Patchset 3 adds code (turned off by default by preprocessor directives) to pass
around the cityhash-generated bitmap hash as an SkHashDigest instead of as a
uint64_t.

If we switch to MD5 or SHA1 instead of cityhash, we'll need to use something
bigger than a uint64_t (e.g. an SkHashDigest or SkData object) to pass the
digest around.  So, using that larger object for cityhash also will make it
easier to switch later.

+
+// Set automatically using the above.
+#ifdef BITMAP_HASH_TYPE_SkHashDigest
+  #define BITMAP_HASH_TYPE SkHashDigest
+#else
+  #define BITMAP_HASH_TYPE uint64_t
+#endif
 
 /**
  * Static class that can generate an SkHashDigest from an SkBitmap.
  */
 class SkBitmapHasher {
 public:
     /**
      * Fills in "result" with a hash of the pixels in this bitmap.
      *
      * If this is unable to compute the hash for some reason,
      * it returns false.
      *
      * Note: depending on the bitmap config, we may need to create an
      * intermediate SkBitmap and copy the pixels over to it... so in some
      * cases, performance and memory usage can suffer.
      */
-    static bool ComputeDigest(const SkBitmap& bitmap, SkHashDigest *result);
+    static bool ComputeDigest(const SkBitmap& bitmap, BITMAP_HASH_TYPE *result);
 
 private:
     static bool ComputeDigestInternal(const SkBitmap& bitmap,
                                       const SkBitmapTransformer& transformer,
-                                      SkHashDigest *result);
+                                      BITMAP_HASH_TYPE *result);
 };
 
 #endif