c++11 雪花算法

以下是C++11实现的雪花算法代码示例：

#include <iostream>
#include <chrono>
#include <thread>

class Snowflake {
public:
    Snowflake(uint16_t worker_id, uint16_t data_center_id) :
        worker_id_(worker_id), data_center_id_(data_center_id) {}

    uint64_t NextId() {
        uint64_t timestamp = TimeGen();
        if (timestamp == last_timestamp_) {
            sequence_ = (sequence_ + 1) & kSequenceMask;
            if (sequence_ == 0) {
                timestamp = TilNextMillis(last_timestamp_);
            }
        } else {
            sequence_ = 0;
        }

        if (timestamp < last_timestamp_) {
            throw std::runtime_error("Clock moved backwards");
        }
        last_timestamp_ = timestamp;

        return ((timestamp - kEpoch) << kTimestampLeftShift) |
            (data_center_id_ << kDataCenterIdShift) |
            (worker_id_ << kWorkerIdShift) |
            sequence_;
    }

private:
    uint64_t TimeGen() {
        return std::chrono::duration_cast<std::chrono::milliseconds>(
            std::chrono::system_clock::now().time_since_epoch()).count();
    }

    uint64_t TilNextMillis(uint64_t last_timestamp) {
        uint64_t timestamp = TimeGen();
        while (timestamp <= last_timestamp) {
            std::this_thread::sleep_for(std::chrono::milliseconds(1));
            timestamp = TimeGen();
        }
        return timestamp;
    }

private:
    uint16_t worker_id_;
    uint16_t data_center_id_;
    uint64_t last_timestamp_ = 0;
    uint16_t sequence_ = 0;

    static constexpr uint64_t kEpoch = 1288834974657;
    static constexpr uint64_t kWorkerIdBits = 5;
    static constexpr uint64_t kDataCenterIdBits = 5;
    static constexpr uint64_t kMaxWorkerId = (1 << kWorkerIdBits) - 1;
    static constexpr uint64_t kMaxDataCenterId = (1 << kDataCenterIdBits) - 1;
    static constexpr uint64_t kSequenceBits = 12;
    static constexpr uint64_t kWorkerIdShift = kSequenceBits;
    static constexpr uint64_t kDataCenterIdShift = kSequenceBits + kWorkerIdBits;
    static constexpr uint64_t kTimestampLeftShift = kSequenceBits + kWorkerIdBits + kDataCenterIdBits;
    static constexpr uint64_t kSequenceMask = (1 << kSequenceBits) - 1;
};

int main() {
    Snowflake snowflake(1, 1);
    std::cout << snowflake.NextId() << std::endl;
    return 0;
}