Code-C++-Snowflake

Code-C++-Snowflake

#include <iostream>
#include <chrono>
#include <cstdint>
#include <stdexcept>
 
using std::int64_t;

class Snowflake {
private:
    // 雪花算法的各个参数
    static constexpr int64_t workerIdBits = 5;
    static constexpr int64_t datacenterIdBits = 5;
    static constexpr int64_t sequenceBits = 12;
 
    static constexpr int64_t maxWorkerId = -1 ^ (-1 << workerIdBits);
    static constexpr int64_t maxDatacenterId = -1 ^ (-1 << datacenterIdBits);
    static constexpr int64_t sequenceMask = -1 ^ (-1 << sequenceBits);
 // sequenceMask =0b111111111111
    int64_t workerId;
    int64_t datacenterId;
    int64_t sequence = 0;
    int64_t lastTimestamp = -1;
 
public:
    Snowflake(int64_t workerId, int64_t datacenterId)
            : workerId(workerId), datacenterId(datacenterId) {}
 
    int64_t generateId() {
        // 获取当前时间戳（毫秒级）
        auto timestamp = std::chrono::duration_cast<std::chrono::milliseconds>(
                std::chrono::system_clock::now().time_since_epoch()).count();
 
        if (timestamp < lastTimestamp) {
            throw std::runtime_error("Invalid system clock!");
        }
 
        if (timestamp == lastTimestamp) {
            sequence = (sequence + 1) & sequenceMask;
            if (sequence == 0) {
                timestamp = waitNextMillis(lastTimestamp);
            }
        } else {
            sequence = 0;
        }
 
        lastTimestamp = timestamp;
 
        // 生成最终的唯一ID
        int64_t uniqueId = (timestamp << (workerIdBits + datacenterIdBits + sequenceBits)) |
                           (datacenterId << (workerIdBits + sequenceBits)) |
                           (workerId << sequenceBits) |
                           sequence;
        return uniqueId;
    }
 
private:
    int64_t waitNextMillis(int64_t lastTimestamp) {
        auto timestamp = std::chrono::duration_cast<std::chrono::milliseconds>(
                std::chrono::system_clock::now().time_since_epoch()).count();
        while (timestamp <= lastTimestamp) {
            timestamp = std::chrono::duration_cast<std::chrono::milliseconds>(
                    std::chrono::system_clock::now().time_since_epoch()).count();
        }
        return timestamp;
    }
};
 
int main() {
    Snowflake snowflake(1, 1);
    for (int i = 0; i < 10; i++) {
        int64_t uniqueId = snowflake.generateId();
        std::cout << uniqueId << std::endl;
    }
 
    return 0;
}

本文修订依据：C++11 工作草案 N3337 §18.4.1 cstdint.syn。该头文件在 std 命名空间中提供 int64_t；本文补充 <cstdint> 和 using std::int64_t;，不改变 Snowflake 位布局、时间戳或唯一性假设。

AI 修改声明： 本文由 LLM 协助修订，最近修改时间：2026-09-25 10:42（UTC+08:00）。修订仅补充 C++11 int64_t 所需的 <cstdint> 和命名空间引入。