/*
 * This module implements functions for decoding phone numbers.
 */

#include <sys/types.h>

static char gsm_address_digits[16] =
	{'0','1','2','3','4','5','6','7','8','9','*','#','a','b','c','?'};

decode_phone_number(data, nbytes, out)
	u_char *data;
	unsigned nbytes;
	char *out;
{
	u_char *dp, *endp;
	int c;

	dp = data;
	endp = data + nbytes;
	while (dp < endp) {
		c = *dp & 0xF;
		if (c == 0xF)
			return(-1);
		*out++ = gsm_address_digits[c];
		c = *dp >> 4;
		if (c == 0xF) {
			if (dp + 1 == endp)
				break;
			else
				return(-1);
		}
		*out++ = gsm_address_digits[c];
		dp++;
	}
	*out = '\0';
	return(0);
}