itoa in C

itoa.c

/**
 *  Ansi C "itoa" based on Kernighan & Ritchie's "Ansi C"
 *
 */
void strreverse(char* begin, char* end) 
{
  char aux;
  
  while(end>begin)
    aux=*end, *end--=*begin, *begin++=aux;
}
  
void 
itoa(int value, char* str, int base) 
{
  static char num[] = "0123456789abcdefghijklmnopqrstuvwxyz";
  
  char* wstr = str;
  int sign;
  
  
  // Validate base
  if (base < 2 || base > 35) { 
    *wstr='\0'; 
    return; 
  }

  // Take care of sign
  if ((sign=value) < 0) 
    value = -value;

  // Conversion. Number is reversed.
  do {
    *wstr++ = num[value % base]; 
  } while (value /= base);
  
  if(sign<0) 
    *wstr++='-';

  *wstr='\0';
  // Reverse string
  strreverse(str,wstr-1);
}