#include <ctype.h>
#include <errno.h>
#include <getopt.h>
#include <stdio.h>

#define ASCII 0
#define DECIMAL 10
#define HEX 16

void usage (char* name) {
    fprintf(stderr,
        "usage: %s [opts] <CONVERTME>\n"
		"Prints the ASCII character, decimal, and hex equivalents of its\n"
		"arguments.  Each option changes how subsequent arguments are\n"
		"interpreted until another option is given.\n"
        "Options:\n"
        "    -a <S>   print values for the ascii string S. (default)\n"
        "    -d <N>   print values for the decimal number N\n"
        "    -x <H>   print values for the hexidecimal number H\n"
        "    -h       print this help and exit\n"
        , name);
}

void decode(unsigned char c) {
    if (isprint(c)) {
        printf("%1$c  %1$3d  0x%1$x\n",c);
    } else { 
        printf("** %1$3d  0x%1$x\n",c);
    }
}

void decode_str(char* str) {
    int i;
    for (i = 0; i < strlen(str); i++) {
        decode(str[i]);
    }
}   

int main (int argc, char ** argv) {
    unsigned char c;
    unsigned char hexarg[3];
    int i,j;
    int intarg = 0;
    int type = ASCII;

    char opt = 0;
	if (1 == argc) {
		usage(argv[0]);
	}

	for (i = 1; i < argc; i++) {
		if ('-' == argv[i][0]) {
			switch (argv[i][1]) {
				case 'a':
				case 'A':
					type = ASCII;
					break;
				case 'd':
				case 'D':
					type = DECIMAL;
					break;
				case 'x':
				case 'X':
					type = HEX;
					break;
				default:
					fprintf(stderr,"Unknown option %c\n",argv[i][1]);
					break;
			}
		} else {
			switch (type) {
				case ASCII:
				default:
					decode_str(argv[i]);
					break;
				case DECIMAL:
					intarg = strtol(argv[i], NULL, DECIMAL);
					decode((unsigned char) (intarg & 0xFF));
					break;
				case HEX:
					// take arguments as two hex digits
					for (j = 0; j+1 < strlen(argv[i]); j+=2) {
						hexarg[0] = argv[i][j];
						hexarg[1] = argv[i][j+1];
						hexarg[2] = 0;
						intarg = strtol(hexarg, NULL, HEX);
						decode((unsigned char) (intarg & 0xFF));
					}
					// odd number of digits, so take care of the last one
					if (0 != argv[i][j]) {
						hexarg[0] = argv[i][j];
						hexarg[1] = 0;
						intarg = strtol(hexarg, NULL, HEX);
						decode((unsigned char) (intarg & 0xFF));
					}
					break;
			}
		}
	}
}