任意进制的转换函数

//
//  main.c
//  baseconv
//
//  Created by Cheney Shen on 11-4-16.
//  Copyright 2011年 __MyCompanyName__. All rights reserved.
//

#include <stdio.h>
#include <limits.h>
#include <string.h>

char* baseconv(unsigned long long, int);

int main (int argc, const char * argv[])
{
    printf("the result is %s", baseconv(3942095803582093809, 2));
    return 0;
}

char* baseconv(unsigned long long num, int base) {
    static char retbuf[sizeof(int)*CHAR_BIT + 1];
    char *p;
    
    if(base < 2 || base > 16)
        return NULL;
    
    p = &retbuf[sizeof(retbuf) - 1];
    *p = '\0';
    
    do{
        *--p = "0123456789abcdef"[num % base];
        num /= base;
    } while(num != 0);
    return p;
}

the result is 11011010110101001000110011111101001011000100011001100111110001