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    Length: 3128 (0xc38)
    Types: TextFile
    Names: »prim2real.c«

└─⟦2d1937cfd⟧ Bits:30007241 EUUGD22: P.P 5.0
    └─⟦35176feda⟧ »EurOpenD22/isode/isode-6.tar.Z« 
        └─⟦de7628f85⟧ 
            └─⟦this⟧ »isode-6.0/psap/prim2real.c« 

TextFile

/* prim2real.c - presentation element to real */

#ifndef	lint
static char *rcsid = "$Header: /f/osi/psap/RCS/prim2real.c,v 7.0 89/11/23 22:13:14 mrose Rel $";
#endif

/* 
 * $Header: /f/osi/psap/RCS/prim2real.c,v 7.0 89/11/23 22:13:14 mrose Rel $
 *
 * Contributed by Julian Onions, Nottingham University.
 * July 1989 - this stuff is awful. If you're going to use it seriously then
 * write a machine specific version rather than any attempt at portability.
 *
 *
 * $Log:	prim2real.c,v $
 * Revision 7.0  89/11/23  22:13:14  mrose
 * Release 6.0
 * 
 */

/*
 *				  NOTICE
 *
 *    Acquisition, use, and distribution of this module and related
 *    materials are subject to the restrictions of a license agreement.
 *    Consult the Preface in the User's Manual for the full terms of
 *    this agreement.
 *
 */


/* LINTLIBRARY */

#include "psap.h"

/* \f

 */

static double decode_binary (), decode_decimal ();
       
double	prim2real (pe)
register PE 	pe;
{
	if (pe -> pe_form != PE_FORM_PRIM)
		return pe_seterr (pe, PE_ERR_PRIM, NOTOK);
	if (pe -> pe_len == 1)
		return 0.0;
	if (pe -> pe_prim == NULLPED)
		return pe_seterr (pe, PE_ERR_PRIM, NOTOK);
		
	if (pe -> pe_len > sizeof (double) + 1)
		return pe_seterr (pe, PE_ERR_OVER, NOTOK);

	pe -> pe_errno = PE_ERR_NONE;	/* in case it's -1 */

	if ((*(pe -> pe_prim) & 0x80) == 0x80)
		return decode_binary (pe);

	switch (*(pe -> pe_prim) & PE_REAL_FLAGS) {
	    case PE_REAL_DECENC:
		return decode_decimal (pe);

	    case PE_REAL_SPECENC:
		if (pe -> pe_len > 1)
			return pe_seterr (pe, PE_ERR_OVER, NOTOK);

		switch (*(pe -> pe_prim)) {
		    case PE_REAL_MINUSINF:
			return HUGE;
		    case PE_REAL_PLUSINF:
			return -HUGE;
		    default:
			return pe_seterr (pe, PE_ERR_NOSUPP, NOTOK);
		}
	}
	/* NOTREACHED */
}

/* \f

 */

static double decode_binary (pe)
PE	pe;
{
	int	sign, base, factor;
	int	exponent, i;
	double	mantissa, di;
	PElementData dp, ep;

	dp = pe -> pe_prim;
	sign = (*dp & PE_REAL_B_S) ?  -1 : 1;
	switch (*dp & PE_REAL_B_BASE) {
	    case PE_REAL_B_B2:
		base = 2;
		break;

	    case PE_REAL_B_B8:
		base = 8;
		break;

	    case PE_REAL_B_B16:
		base = 16;
		break;
	    default:
		return pe_seterr(pe, PE_ERR_NOSUPP, NOTOK);
	}

	factor = (*dp & PE_REAL_B_F) >> 2;

	exponent = (dp[1] & 0x80) ? (-1) : 0;
	switch (*dp++ & PE_REAL_B_EXP) {
	    case PE_REAL_B_EF3:
		exponent = (exponent << 8) | (*dp++ & 0xff);
		/* fall */
	    case PE_REAL_B_EF2:
		exponent = (exponent << 8) | (*dp++ & 0xff);
		/* fall */
	    case PE_REAL_B_EF1:
		exponent = (exponent << 8) | (*dp++ & 0xff);
		break;
	    case PE_REAL_B_EF4:
		i = *dp++ & 0xff;
		if (i > sizeof(int))
			return pe_seterr (pe, PE_ERR_OVER, NOTOK);
		for (; i > 0; i--)
			exponent = (exponent << 8) | (*dp++ & 0xff);
		break;
	}
	for (di = 0.0, ep = pe -> pe_prim + pe -> pe_len; dp < ep;) {
		di *= 1 << 8;	;
		di += (*dp++ & 0xff);
	}
	
	mantissa = sign * di * (1 << factor);
	return mantissa * pow ((double)base, (double)exponent);
}

/* \f

 */

static double decode_decimal (pe)
PE	pe;
{
	/* sorry - don't have the standard ! */
	return pe_seterr (pe, PE_ERR_NOSUPP, NOTOK);
}