zoom/firmware/util.c

#include "config.h"
#include "util.h"

/* Convert from ASCII hex.  Returns
   the value, or 16 if it was space/newline, or
   32 if some other character. */
uint8_t from_hex(uint8_t ch)
{
	if(ch==' ' || ch=='\r' || ch=='\n')
		return 16;

	if(ch < '0')
		goto bad;
	if(ch <= '9')
		return ch - '0';
	ch |= 0x20;
	if(ch < 'a')
		goto bad;
	if(ch <= 'f')
		return ch - 'a' + 10;
 bad:
	return 32;
}

const uint8_t hex[16]={'0','1','2','3','4','5','6','7',
		       '8','9','a','b','c','d','e','f'};

/* Convert 4 ASCII hex digits into a 16-bit unsigned number.
   Returns the number, or -1 if there's an error */
int32_t hex_to_u16(char x[4])
{
	uint16_t v = 0;
	uint8_t t;
	int i;

	for (i = 0; i < 4; i++) {
		t = from_hex(x[i]);
		if (t >= 16)
			return -1;
		v = (v << 4) | t;
	}
	return v;
}