63559a570c
This reverts commit e37d578796.
Change-Id: I7d979657d34e981998cd7c3ef3e05fd59e2721ab
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/293350
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Julia Lavrova <jlavrova@google.com>
67 lines
1.8 KiB
C++
67 lines
1.8 KiB
C++
/*
|
|
* 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 "include/core/SkString.h"
|
|
#include "include/core/SkTypes.h"
|
|
#include "include/private/SkNoncopyable.h"
|
|
#include "include/private/SkOpts_spi.h"
|
|
#include "include/private/SkTLogic.h"
|
|
|
|
class SkChecksum : SkNoncopyable {
|
|
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;
|
|
}
|
|
|
|
/**
|
|
* 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 version is 2-lines cheaper than Mix, but seems to be sufficient for the font cache.
|
|
*/
|
|
static uint32_t CheapMix(uint32_t hash) {
|
|
hash ^= hash >> 16;
|
|
hash *= 0x85ebca6b;
|
|
hash ^= hash >> 16;
|
|
return hash;
|
|
}
|
|
};
|
|
|
|
// SkGoodHash should usually be your first choice in hashing data.
|
|
// It should be both reasonably fast and high quality.
|
|
struct SkGoodHash {
|
|
template <typename K>
|
|
std::enable_if_t<sizeof(K) == 4, uint32_t> operator()(const K& k) const {
|
|
return SkChecksum::Mix(*(const uint32_t*)&k);
|
|
}
|
|
|
|
template <typename K>
|
|
std::enable_if_t<sizeof(K) != 4, uint32_t> operator()(const K& k) const {
|
|
return SkOpts::hash_fn(&k, sizeof(K), 0);
|
|
}
|
|
|
|
uint32_t operator()(const SkString& k) const {
|
|
return SkOpts::hash_fn(k.c_str(), k.size(), 0);
|
|
}
|
|
};
|
|
|
|
#endif
|