C语言生成随机uuid编码

#include <stdio.h>
#include <stdlib.h>
  
/**
 * Create random UUID
 *
 * @param buf - buffer to be filled with the uuid string
 */
char *random_uuid( char buf[37] )
{
    const char *c = "89ab";
    char *p = buf;
    int n;
  
    for( n = 0; n < 16; ++n )
    {
        int b = rand()%255;
  
        switch( n )
        {
            case 6:
                sprintf(
                    p,
                    "4%x",
                    b%15 );
                break;
            case 8:
                sprintf(
                    p,
                    "%c%x",
                    c[rand()%strlen( c )],
                    b%15 );
                break;
            default:
                sprintf(
                    p,
                    "%02x",
                    b );
                break;
        }
  
        p += 2;
  
        switch( n )
        {
            case 3:
            case 5:
            case 7:
            case 9:
                *p++ = '-';
                break;
        }
    }
  
    *p = 0;
  
    return buf;
}