SkTHash: hash from fnptr to functor type

include/private/SkChecksum.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 SkChecksum_DEFINED
 #define SkChecksum_DEFINED
 
@@ skipping 164 matching lines @@
          */
         if (8 == sizeof(result)) {
             result ^= result >> HALFBITS;
         }
         return static_cast<uint32_t>(result);
     }
 };
 
 // SkGoodHash should usually be your first choice in hashing data.
 // It should be both reasonably fast and high quality.
-
-template <typename K>
-uint32_t SkGoodHash(const K& k) {
-    if (sizeof(K) == 4) {
+struct SkGoodHash {
+    template <typename K>
+    SK_WHEN(sizeof(K) == 4, uint32_t) operator()(const K& k) const {
         return SkChecksum::Mix(*(const uint32_t*)&k);
     }
-    return SkChecksum::Murmur3(&k, sizeof(K));
-}
 
-inline uint32_t SkGoodHash(const SkString& k) {
-    return SkChecksum::Murmur3(k.c_str(), k.size());
-}
+    template <typename K>
+    SK_WHEN(sizeof(K) != 4, uint32_t) operator()(const K& k) const {
+        return SkChecksum::Murmur3(&k, sizeof(K));
+    }
+
+    uint32_t operator()(const SkString& k) const {
+        return SkChecksum::Murmur3(k.c_str(), k.size());
+    }
+};
 
 #endif