自己写的一个atoi

[root@localhost bishi]# cat itoa.c
#include <stdio.h>
#include <stdlib.h>

char* itoa(int value, char* str, int radix)
{
 static char dig[] ="0123456789"
                    "abcdefghijklmnopqrstuvwxyz";

int n = 0, neg = 0;
unsigned int v;
char* p;
char* q;
char c;

if (radix == 10 && value < 0) {
   value = -value;
   neg = 1;
}
v = value;
do {
 str[n++] = dig[v%radix];
 v /= radix;
} while (v);

if (neg)
 str[n++] = '-';
str[n] = '\0';

for (p = str, q = p+n-1; (p<q)&&(*q!='\0'); ++p, --q)
  {
   c = *p;
   *p = *q;
   *q = c;
  }
return str;
}

int main(int argc,char** argv)
{
 char str[32];
 if(argc != 3)
  {
   printf("Usage:%s num radix\n",argv[0]);
   return -1;
   }

 int i = atoi(argv[1]);
 int j = atoi(argv[2]);

 if(j>16)
  {
   printf("radix error\n");
   return -1;
  }

 itoa(i,str,j);
 printf("num:%d radix:%d str is %s\n",i,j,str);
 return 0;
}