stellar-stellar/src/snowflake/snowflake.cpp

#include <stdint.h>
#include <stdlib.h>

#include "log.h"
#include "snowflake.h"

#define SNOWFLAKE_LOG_ERROR(format, ...) LOG_ERROR("snowflake", format, ##__VA_ARGS__)

struct snowflake
{
    uint8_t worker_base_id;   //  5 bit [0, 31]
    uint8_t worker_offset_id; //  7 bit [0, 127]
    uint64_t thread_id;       //  limit 256
    uint64_t device_id;       // 12 bit [0, 4095] ( base << 7 | offset )
    uint64_t sequence;
};

struct snowflake *snowflake_new(uint16_t thread_id, uint8_t worker_base_id, uint8_t worker_offset_id)
{
    if (thread_id > 255)
    {
        SNOWFLAKE_LOG_ERROR("thread_id %u is invalid, range [0, 255]", thread_id);
        return NULL;
    }
    if (worker_base_id > 31)
    {
        SNOWFLAKE_LOG_ERROR("worker_base_id %u is invalid, range [0, 31]", worker_base_id);
        return NULL;
    }
    if (worker_offset_id > 127)
    {
        SNOWFLAKE_LOG_ERROR("worker_offset_id %u is invalid, range [0, 127]", worker_offset_id);
        return NULL;
    }

    struct snowflake *sf = (struct snowflake *)calloc(1, sizeof(struct snowflake));
    if (sf == NULL)
    {
        SNOWFLAKE_LOG_ERROR("calloc snowflake failed");
        return NULL;
    }

    sf->worker_base_id = worker_base_id;
    sf->worker_offset_id = worker_offset_id;
    sf->thread_id = thread_id;
    sf->device_id = ((worker_base_id << 7) | worker_offset_id) & 0xFFF;
    sf->sequence = 0;

    return sf;
}

void snowflake_free(struct snowflake *sf)
{
    if (sf != NULL)
    {
        free(sf);
        sf = NULL;
    }
}

/*
 * high -> low
 *
 * +------+------------------+----------------+------------------------+---------------------------+
 * | 1bit |  12bit device_id | 8bit thread_id | 28bit timestamp in sec | 15bit sequence per thread |
 * +------+------------------+----------------+------------------------+---------------------------+
 */

#define MAX_ID_PER_THREAD (32768)
#define MAX_ID_BASE_TIME (268435456L)

uint64_t snowflake_generate(struct snowflake *sf, uint64_t now_sec)
{
    if (sf == NULL)
    {
        SNOWFLAKE_LOG_ERROR("snowflake is NULL");
        return 0;
    }

    uint64_t id = 0;
    uint64_t id_per_thread = (sf->sequence++) % MAX_ID_PER_THREAD;
    uint64_t id_base_time = now_sec % MAX_ID_BASE_TIME;
    id = (sf->device_id << 51) |
         (sf->thread_id << 43) |
         (id_base_time << 15) |
         (id_per_thread);

    return id;
}

void snowflake_deserialize(uint64_t id, struct snowflake_meta *meta)
{
    if (meta == NULL)
    {
        return;
    }

    meta->sequence = id & 0x7FFF;
    meta->time_cycle = MAX_ID_BASE_TIME;
    meta->time_relative = (id >> 15) & 0xFFFFFFF;
    meta->thread_id = (id >> 43) & 0xFF;
    meta->device_id = (id >> 51) & 0xFFF;
    meta->worker_base_id = (meta->device_id >> 7) & 0x1F;
    meta->worker_offset_id = meta->device_id & 0x7F;
}