diff --git a/bench/FontCacheBench.cpp b/bench/FontCacheBench.cpp index 0e75c9cb17..697bde64f4 100644 --- a/bench/FontCacheBench.cpp +++ b/bench/FontCacheBench.cpp @@ -7,6 +7,7 @@ #include "Benchmark.h" #include "SkCanvas.h" +#include "SkChecksum.h" #include "SkFontHost.h" #include "SkPaint.h" #include "SkString.h" @@ -64,23 +65,12 @@ static uint32_t hasher0(uint32_t value) { return value ^ (value >> 8); } -static uint32_t hasher2(uint32_t h) { - h ^= h >> 16; - h *= 0x85ebca6b; - h ^= h >> 13; - h *= 0xc2b2ae35; - h ^= h >> 16; - - h ^= (h >> 8); - return h; -} - static const struct { const char* fName; HasherProc fHasher; } gRec[] = { { "hasher0", hasher0 }, - { "hasher2", hasher2 }, + { "hasher2", SkChecksum::Mix }, }; #define kMaxHashBits 12 diff --git a/src/core/SkChecksum.h b/src/core/SkChecksum.h index bf3228f91d..fe1e9584a2 100644 --- a/src/core/SkChecksum.h +++ b/src/core/SkChecksum.h @@ -36,6 +36,20 @@ private: } public: + /** + * uint32_t -> uint32_t hash, useful for when you're about to trucate this hash but you + * suspect its low bits aren't well mixed. + * + * This is the Murmur3 finalizer. + */ + static uint32_t Mix(uint32_t hash) { + hash ^= hash >> 16; + hash *= 0x85ebca6b; + hash ^= hash >> 13; + hash *= 0xc2b2ae35; + hash ^= hash >> 16; + return hash; + } /** * Calculate 32-bit Murmur hash (murmur3). @@ -48,7 +62,7 @@ public: * @return hash result */ static uint32_t Murmur3(const uint32_t* data, size_t bytes, uint32_t seed=0) { - SkASSERT(SkIsAlign4(bytes)); + SkASSERTF(SkIsAlign4(bytes), "Expected 4-byte multiple, got %zu", bytes); const size_t words = bytes/4; uint32_t hash = seed; @@ -64,12 +78,7 @@ public: hash += 0xe6546b64; } hash ^= bytes; - hash ^= hash >> 16; - hash *= 0x85ebca6b; - hash ^= hash >> 13; - hash *= 0xc2b2ae35; - hash ^= hash >> 16; - return hash; + return Mix(hash); } /** diff --git a/src/core/SkScaledImageCache.cpp b/src/core/SkScaledImageCache.cpp index eda4871711..1e7f51dd9e 100644 --- a/src/core/SkScaledImageCache.cpp +++ b/src/core/SkScaledImageCache.cpp @@ -5,6 +5,7 @@ * found in the LICENSE file. */ +#include "SkChecksum.h" #include "SkScaledImageCache.h" #include "SkMipMap.h" #include "SkPixelRef.h" @@ -29,32 +30,6 @@ static inline SkScaledImageCache::Rec* id_to_rec(SkScaledImageCache::ID* id) { return reinterpret_cast(id); } - // Implemented from en.wikipedia.org/wiki/MurmurHash. -static uint32_t compute_hash(const uint32_t data[], int count) { - uint32_t hash = 0; - - for (int i = 0; i < count; ++i) { - uint32_t k = data[i]; - k *= 0xcc9e2d51; - k = (k << 15) | (k >> 17); - k *= 0x1b873593; - - hash ^= k; - hash = (hash << 13) | (hash >> 19); - hash *= 5; - hash += 0xe6546b64; - } - - // hash ^= size; - hash ^= hash >> 16; - hash *= 0x85ebca6b; - hash ^= hash >> 13; - hash *= 0xc2b2ae35; - hash ^= hash >> 16; - - return hash; -} - struct SkScaledImageCache::Key { Key(uint32_t genID, SkScalar scaleX, @@ -64,7 +39,7 @@ struct SkScaledImageCache::Key { , fScaleX(scaleX) , fScaleY(scaleY) , fBounds(bounds) { - fHash = compute_hash(&fGenID, 7); + fHash = SkChecksum::Murmur3(&fGenID, 28); } bool operator<(const Key& other) const {