C code 字符串与整数的相互转化

 #include<stdio.h>
 int str_to_int(const char *str,int *num);
 void int_to_str(char str[],const int strLen,const int num);

 int main(int argc,char *argv[])
 {
     char str[];
     int ret = ,n = ;
     while()
     {
         scanf("%s",str);
         ret = str_to_int(str,&n);
         if(ret == )
         {
             printf("%d\n",n);
             int_to_str(str,,n);
             printf("%s\n",str);
         }
         else
         {
             printf("error\n");
         }
     }
     return ;
 }

 int str_to_int(const char *str,int *num)
 {
     int sign = ;
     *num = ;
     const char *p = str;
     while(*p != '\0')
     {
         if( *p >= '' && *p <= '' )
         {
             *num = *num *  + *p - '';
             p++;
         }
         else if( *p == '-' && *num == )
         {
             sign = -;
             p++;
         }
         else
         {
             return -;
         }
     }
     *num *= sign;
     return ;
 }

 void int_to_str(char str[],const int strLen,const int num)
 {
     int tmp = ,n = ,i = ;
     if(num < )
     {
         n = -num;
         i = ;
     }
     while(n != )
     {
         tmp = tmp *  + n%;
         n /= ;
     }
     while(i<strLen && tmp != )
     {
         str[i++] = tmp %  + '';
         tmp /= ;
     }
 }