Some usability ideas around SkTHash.

src/core/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
 
+#include "SkString.h"
+#include "SkTLogic.h"
 #include "SkTypes.h"
 
 /**
  *  Computes a 32bit checksum from a blob of 32bit aligned data. This is meant
  *  to be very very fast, as it is used internally by the font cache, in
  *  conjuction with the entire raw key. This algorithm does not generate
  *  unique values as well as others (e.g. MD5) but it performs much faster.
  *  Skia's use cases can survive non-unique values (since the entire key is
  *  always available). Clients should only be used in circumstances where speed
  *  over uniqueness is at a premium.
@@ skipping 41 matching lines @@
         hash *= 0x85ebca6b;
         hash ^= hash >> 16;
         return hash;
     }
 
     /**
      * Calculate 32-bit Murmur hash (murmur3).
      * This should take 2-3x longer than SkChecksum::Compute, but is a considerably better hash.
      * See en.wikipedia.org/wiki/MurmurHash.
      *
-     *  @param data Memory address of the data block to be processed. Must be 32-bit aligned.
-     *  @param size Size of the data block in bytes. Must be a multiple of 4.
+     *  @param data Memory address of the data block to be processed.
+     *  @param size Size of the data block in bytes.
      *  @param seed Initial hash seed. (optional)
      *  @return hash result
      */
-    static uint32_t Murmur3(const uint32_t* data, size_t bytes, uint32_t seed=0) {
+    static uint32_t Murmur3(const void* data, size_t bytes, uint32_t seed=0) {
         // Use may_alias to remind the compiler we're intentionally violating strict aliasing,
         // and so not to apply strict-aliasing-based optimizations.
         typedef uint32_t SK_ATTRIBUTE(may_alias) aliased_uint32_t;
+        typedef uint8_t SK_ATTRIBUTE(may_alias) aliased_uint8_t;
+
+        // Handle 4 bytes at a time while possible.
         const aliased_uint32_t* safe_data = (const aliased_uint32_t*)data;
-
-        SkASSERTF(SkIsAlign4(bytes), "Expected 4-byte multiple, got %zu", bytes);
         const size_t words = bytes/4;
-
-
         uint32_t hash = seed;
         for (size_t i = 0; i < words; i++) {
             uint32_t k = safe_data[i];
             k *= 0xcc9e2d51;
             k = (k << 15) | (k >> 17);
             k *= 0x1b873593;
 
             hash ^= k;
             hash = (hash << 13) | (hash >> 19);
             hash *= 5;
             hash += 0xe6546b64;
         }
+
+        // Handle last 0-3 bytes.
+        const aliased_uint8_t* safe_tail = (const uint8_t*)(safe_data + words);
+        uint32_t k = 0;
+        switch (bytes & 3) {
+            case 3: k ^= safe_tail[2] << 16;
+            case 2: k ^= safe_tail[1] <<  8;
+            case 1: k ^= safe_tail[0] <<  0;
+                    k *= 0xcc9e2d51;
+                    k = (k << 15) | (k >> 17);
+                    k *= 0x1b873593;
+                    hash ^= k;
+        }
+
         hash ^= bytes;
         return Mix(hash);
     }
 
     /**
      *  Compute a 32-bit checksum for a given data block
      *
      *  WARNING: this algorithm is tuned for efficiency, not backward/forward
      *  compatibility.  It may change at any time, so a checksum generated with
      *  one version of the Skia code may not match a checksum generated with
@@ skipping 49 matching lines @@
          *  since >>32 is undefined for 32bit ints, hence the wacky HALFBITS
          *  define.
          */
         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) {
+        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());
+}
+
 #endif