C++实现MurmurHash及性能解析

#include <cstdint>
#include <cstddef>
// 常量定义
static constexpr uint32_t MURMUR_SEED = 0xc70f6907; // 可自定义种子
static constexpr uint32_t c1 = 0xcc9e2d51;
static constexpr uint32_t c2 = 0x1b873593;
uint32_t murmur3_32(const uint8_t* key, size_t len) {
uint32_t h = MURMUR_SEED;
uint32_t k;
const uint8_t* tail;
const uint32_t* blocks = reinterpret_cast&lt;const uint32_t*&gt;(key);

// 处理完整的 4 字节块
for (size_t i = len / 4; i != 0; i--) {
    k = *blocks++;
    k *= c1;
    k = (k &lt;&lt; 15) | (k &gt;&gt; 17);
    k *= c2;

    h ^= k;
    h = (h &lt;&lt; 13) | (h &gt;&gt; 19);
    h = h * 5 + 0xe6546b64;
}

// 处理剩余字节（0~3 字节）
tail = reinterpret_cast&lt;const uint8_t*&gt;(blocks);
k = 0;
switch (len &amp; 3) {
    case 3: k ^= tail[2] &lt;&lt; 16;
    case 2: k ^= tail[1] &lt;&lt; 8;
    case 1: k ^= tail[0];
            k *= c1;
            k = (k &lt;&lt; 15) | (k &gt;&gt; 17);
            k *= c2;
            h ^= k;
};

// 终态混合
h ^= len;
h ^= h &gt;&gt; 16;
h *= 0x85ebca6b;
h ^= h &gt;&gt; 13;
h *= 0xc2b2ae35;
h ^= h &gt;&gt; 16;

return h;
}

#include <iostream>
#include <string>
int main() {
std::string str = "hello world";
uint32_t hash = murmur3_32(
reinterpret_cast<const uint8_t*>(str.data()),
str.size()
);
std::cout << "Hash: " << hash << "\n";
return 0;
}