Slim Skia down to just one murmur3 implementation.
BUG=skia: Committed: https://skia.googlesource.com/skia/+/6ac0037b70410ff7d5ce5788bc89314223e1a587 R=reed@google.com, mtklein@google.com Author: mtklein@chromium.org Review URL: https://codereview.chromium.org/376183004
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@ -7,6 +7,7 @@
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#include "Benchmark.h"
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#include "SkCanvas.h"
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#include "SkChecksum.h"
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#include "SkFontHost.h"
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#include "SkPaint.h"
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#include "SkString.h"
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@ -64,23 +65,12 @@ static uint32_t hasher0(uint32_t value) {
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return value ^ (value >> 8);
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}
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static uint32_t hasher2(uint32_t h) {
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h ^= h >> 16;
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h *= 0x85ebca6b;
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h ^= h >> 13;
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h *= 0xc2b2ae35;
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h ^= h >> 16;
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h ^= (h >> 8);
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return h;
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}
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static const struct {
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const char* fName;
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HasherProc fHasher;
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} gRec[] = {
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{ "hasher0", hasher0 },
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{ "hasher2", hasher2 },
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{ "hasher2", SkChecksum::Mix },
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};
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#define kMaxHashBits 12
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@ -36,6 +36,20 @@ private:
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}
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public:
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/**
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* uint32_t -> uint32_t hash, useful for when you're about to trucate this hash but you
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* suspect its low bits aren't well mixed.
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*
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* This is the Murmur3 finalizer.
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*/
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static uint32_t Mix(uint32_t hash) {
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hash ^= hash >> 16;
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hash *= 0x85ebca6b;
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hash ^= hash >> 13;
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hash *= 0xc2b2ae35;
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hash ^= hash >> 16;
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return hash;
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}
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/**
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* Calculate 32-bit Murmur hash (murmur3).
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@ -48,7 +62,7 @@ public:
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* @return hash result
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*/
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static uint32_t Murmur3(const uint32_t* data, size_t bytes, uint32_t seed=0) {
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SkASSERT(SkIsAlign4(bytes));
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SkASSERTF(SkIsAlign4(bytes), "Expected 4-byte multiple, got %zu", bytes);
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const size_t words = bytes/4;
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uint32_t hash = seed;
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@ -64,12 +78,7 @@ public:
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hash += 0xe6546b64;
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}
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hash ^= bytes;
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hash ^= hash >> 16;
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hash *= 0x85ebca6b;
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hash ^= hash >> 13;
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hash *= 0xc2b2ae35;
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hash ^= hash >> 16;
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return hash;
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return Mix(hash);
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}
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/**
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@ -5,6 +5,7 @@
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* found in the LICENSE file.
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*/
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#include "SkChecksum.h"
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#include "SkScaledImageCache.h"
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#include "SkMipMap.h"
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#include "SkPixelRef.h"
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@ -29,32 +30,6 @@ static inline SkScaledImageCache::Rec* id_to_rec(SkScaledImageCache::ID* id) {
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return reinterpret_cast<SkScaledImageCache::Rec*>(id);
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}
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// Implemented from en.wikipedia.org/wiki/MurmurHash.
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static uint32_t compute_hash(const uint32_t data[], int count) {
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uint32_t hash = 0;
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for (int i = 0; i < count; ++i) {
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uint32_t k = data[i];
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k *= 0xcc9e2d51;
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k = (k << 15) | (k >> 17);
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k *= 0x1b873593;
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hash ^= k;
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hash = (hash << 13) | (hash >> 19);
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hash *= 5;
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hash += 0xe6546b64;
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}
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// hash ^= size;
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hash ^= hash >> 16;
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hash *= 0x85ebca6b;
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hash ^= hash >> 13;
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hash *= 0xc2b2ae35;
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hash ^= hash >> 16;
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return hash;
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}
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struct SkScaledImageCache::Key {
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Key(uint32_t genID,
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SkScalar scaleX,
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@ -64,7 +39,7 @@ struct SkScaledImageCache::Key {
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, fScaleX(scaleX)
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, fScaleY(scaleY)
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, fBounds(bounds) {
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fHash = compute_hash(&fGenID, 7);
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fHash = SkChecksum::Murmur3(&fGenID, 28);
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}
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bool operator<(const Key& other) const {
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