#include <stdio.h>
 
void dump_hex(char* ptr, size_t length)
{
    size_t i;
    for(i = 0; i < length; ++i)
    {
        printf("%01x%01x", (ptr[i] >> 4) & 0x0F, ptr[i] & 0x0F);
    }
}
 
int main(void) {
	char hoge[] = { 0xde, 0xad, 0xbe, 0xef };
	dump_hex(hoge, 4);
	return 0;
}