#include <stdlib.h> // malloc
#include <stdio.h> // sprintf

char * atohex(unsigned char * a, size_t len, unsigned int * aalen){
	char *aa;
	//two bytes of output per byte of input, plus newline
	(*aalen) = 2 * len * sizeof *aa + 1;
	aa = (char*)malloc((*aalen));
	
	for(int i = 0; i < len; i++){
		sprintf(aa + (2 * i), "%02x", a[i]);
	}
	aa[(*aalen)-1] = '\n';
	return aa;
}