/*
   =============================================================================
	dec2fr.c -- Buchla 700 fractional 2's complement conversion functions
	Version 10 -- 1987-12-06 -- D.N. Lynx Crowe
   =============================================================================
*/

#define	TESTER	0

#include "stddefs.h"
#include "stdio.h"

#define	SFACT	1000L		/* scale factor */

static int32_t d2f[][10] = {	/* decimal to fraction table */

	{0x00000000L, 0x000019A0L, 0x00003336L, 0x00004CD0L, 0x00006668L,
	 0x00008000L, 0x000099A0L, 0x0000B336L, 0x0000CCCEL, 0x0000E668L},

	{0x00000000L, 0x00000290L, 0x00000520L, 0x000007B0L, 0x00000A40L,
	 0x00000CD0L, 0x00000F60L, 0x000011F0L, 0x00001480L, 0x00001710L}
};

static int32_t f2d[] = {		/* fraction to decimal table */

	50000L, 25000L, 12500L,  6250L,
	 3125L,	 1562L,   781L,   390L,
	  195L,    97L,    48L,    24L,
	   12L,     6L,     3L,     1L
};

/* 
*/

/*
   =============================================================================
	dec2fr() -- convert an ASCII decimal string to fractional binary

	The input string is 4 characters in the range 100- to 100+ inclusive.
	The result is a 2's complement binary fractional value.
   =============================================================================
*/

int16_t dec2fr(int8_t *s)
{
	register int16_t i;

	if (s[0] EQ '1') {

		if (s[1] EQ '0') {

			if (s[2] EQ '0') {

				if (s[3] EQ '-')
					return(0x8000);  /* -100 */
				else
					return(0x7FFF);  /* +100 */

			} else {

				return(0xFFFF);	/* ERROR */
			}

		} else {

			return(0xFFFF);	/* ERROR */

		}

/* 
*/

	} else if (s[0] EQ '0') {

		i = (d2f[0][s[1] - '0'] + d2f[1][s[2] - '0']) >> 1;

		if (s[3] EQ '-') {

			if (i)
				return(~i);	/* negative number */
			else
				return(0);	/* zero is always 0 */

		} else {

			return(i);	/* positive number */
		}
	}

	return(0xFFFF);	/* ERROR */
}

/* 
*/

/*
   =============================================================================
	fr2dec() -- convert a 2's complement fraction to decimal ASCII notation

	The input is a 2's complement binary fractional value.
	The result string is 4 characters in the range 100- to 100+ inclusive.
   =============================================================================
*/

int8_t *fr2dec(int16_t v, int8_t *s)
{
	register int32_t acc, sc;
	register int16_t i, p;

	if (v EQ 0x7FFF) {	/* +100 */

		sprintf(s, "100+");
		return(s);
	}

	if (v EQ 0x8000) {	/* -100 */

		sprintf(s, "100-");
		return(s);
	}

	if (v & 0x8000) {

		v = ~v;		/* negative number */
		p = '-';

	} else {

		p = '+';	/* positive number */
	}

	acc = 0;

	for (i = 0; i LT 15; i++)
		if (v & (1 << (14 - i)))
			acc += f2d[i];

	sc = SFACT;
	acc /= sc;
	sprintf(s, "%03d%c", (int16_t)acc, p);
	return(s);
}

/* 
*/

#if TESTER

#include "stdio.h"

#include "stdio.h"

extern	int	memcmp();

char t[8], v[8];

/*
   =============================================================================
	test program for fractional two's complement conversion functions
   =============================================================================
*/

main()
{
	register short i;
	register short u;

	for (i = 0; i < 101; i++) {

		if (i EQ 50)
			printf("\f");

		sprintf(t, "%03d+", i);
		u = dec2fr(t);

		if (u EQ 0xFFFF) {

			printf("[%s] = ERROR  = ??????    ", t);

		} else {

			fr2dec(u, v);
			printf("[%s] = 0x%04x = [%s]", t, u, v);
		}

		printf(" %s    ", memcmp(t, v, 4) ? "<--" : "   ");

		sprintf(t, "%03d-", i);
		u = dec2fr(t);

		if (u EQ 0xFFFF) {

			printf("    [%s] = ERROR  = ??????\n", t);

		} else {

			fr2dec(u, v);
			printf("    [%s] = 0x%04x = [%s]", t, u, v);
		}

		printf(" %s\n", memcmp(t, v, 4) ? "<--" : "");

	}
}

#endif