sfputd.c   [plain text]

#include	"sfhdr.h"

/*	Write out a floating point value in a portable format
**
**	Written by Kiem-Phong Vo.
*/

#if __STD_C
int _sfputd(Sfio_t* f, Sfdouble_t v)
#else
int _sfputd(f,v)
Sfio_t*		f;
Sfdouble_t	v;
#endif
{
#define N_ARRAY		(16*sizeof(Sfdouble_t))
	reg ssize_t	n, w;
	reg uchar	*s, *ends;
	int		exp;
	uchar		c[N_ARRAY];
	double		x;

	SFMTXSTART(f,-1);

	if(f->mode != SF_WRITE && _sfmode(f,SF_WRITE,0) < 0)
		SFMTXRETURN(f, -1);
	SFLOCK(f,0);

	/* get the sign of v */
	if(v < 0.)
	{	v = -v;
		n = 1;
	}
	else	n = 0;

#if !_ast_fltmax_double /* don't know how to do these yet */
	if(v > SF_MAXDOUBLE && !_has_expfuncs)
	{	SFOPEN(f,0);
		SFMTXRETURN(f, -1);
	}
#endif

	/* make the magnitude of v < 1 */
	if(v != 0.)
		v = frexp(v,&exp);
	else	exp = 0;

	/* code the sign of v and exp */
	if((w = exp) < 0)
	{	n |= 02;
		w = -w;
	}

	/* write out the signs and the exp */
	SFOPEN(f,0);
	if(sfputc(f,n) < 0 || (w = sfputu(f,w)) < 0)
		SFMTXRETURN(f, -1);
	SFLOCK(f,0);
	w += 1;

	s = (ends = &c[0])+sizeof(c);
	while(s > ends)
	{	/* get 2^SF_PRECIS precision at a time */
		n = (int)(x = ldexp(v,SF_PRECIS));
		*--s = n|SF_MORE;
		v = x-n;
		if(v <= 0.)
			break;
	}

	/* last byte is not SF_MORE */
	ends = &c[0] + sizeof(c) -1;
	*ends &= ~SF_MORE;

	/* write out coded bytes */
	n = ends - s + 1;
	w = SFWRITE(f,(Void_t*)s,n) == n ? w+n : -1;

	SFOPEN(f,0);
	SFMTXRETURN(f,w);
}