Integer to char in C (with long long support)

integer_to_char.c

void integer_to_char(long long value, char* str, int base) {
	static char num[] = "0123456789abcdefghijklmnopqrstuvwxyz";
	char *wstr = str;
	int sign;
	lldiv_t res;
	
	// 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 {
		res = lldiv(value, base);
		*wstr++ = num[res.rem];
	} while((value = res.quot));
	
	if(sign < 0) *wstr ++='-';
	
	*wstr='\0';
	
	// Reverse string
	reverse_string(str, wstr-1);	
}

/* 
* Return a string reverse 
*/
void reverse_string(char* begin, char* end) {
	char aux;	
	while(end > begin) aux=*end, *end--=*begin, *begin++=aux;
}