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141 lines
3.4 KiB
C
141 lines
3.4 KiB
C
/*
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* Floating point conversion routines.
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* Devin Reade, 1997.
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*
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* $Id: cvt.c,v 1.2 1997/09/21 06:20:37 gdr Exp $
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*
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* This file is formatted with tab stops every 8 columns.
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*/
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#ifdef __ORCAC__
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segment "libc_stdlb";
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#endif
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#include <stdio.h>
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#include <string.h>
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#include <sane.h>
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#include <math.h>
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char *
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ecvt (double number, size_t ndigits, int *decpt, int *sign)
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{
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static DecForm convert;
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static Decimal d;
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convert.style = FLOATDECIMAL;
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if (ndigits > SIGDIGLEN) {
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ndigits = SIGDIGLEN;
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}
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convert.digits = ndigits;
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s_num2dec(&convert, number, &d);
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*decpt = (int)d.sig.length + d.exp;
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*sign = d.sgn;
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*(d.sig.text + (int)d.sig.length) = '\0'; /* depends on d.sig.unused */
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return d.sig.text;
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}
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char *
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fcvt (double number, size_t ndigits, int *decpt, int *sign)
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{
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static DecForm convert;
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static Decimal d;
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convert.style = FIXEDDECIMAL;
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if (ndigits > SIGDIGLEN) {
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ndigits = SIGDIGLEN;
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}
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convert.digits = ndigits;
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s_num2dec(&convert, number, &d);
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*decpt = (int)d.sig.length + d.exp;
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*sign = d.sgn;
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*(d.sig.text + (int)d.sig.length) = '\0'; /* depends on d.sig.unused */
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return d.sig.text;
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}
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/* __dtoa: These are the comments from the BSD implementation of
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this routine. Whether or not we have achieved compatibility
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remains to be seen.
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Arguments ndigits, decpt, sign are similar to those
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of ecvt and fcvt; trailing zeros are suppressed from
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the returned string. If not null, *rve is set to point
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to the end of the return value. If d is +-Infinity or NaN,
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then *decpt is set to 9999.
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mode:
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0 ==> shortest string that yields d when read in
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and rounded to nearest.
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1 ==> like 0, but with Steele & White stopping rule;
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e.g. with IEEE P754 arithmetic , mode 0 gives
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1e23 whereas mode 1 gives 9.999999999999999e22.
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2 ==> max(1,ndigits) significant digits. This gives a
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return value similar to that of ecvt, except
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that trailing zeros are suppressed.
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3 ==> through ndigits past the decimal point. This
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gives a return value similar to that from fcvt,
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except that trailing zeros are suppressed, and
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ndigits can be negative.
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4-9 should give the same return values as 2-3, i.e.,
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4 <= mode <= 9 ==> same return as mode
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2 + (mode & 1). These modes are mainly for
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debugging; often they run slower but sometimes
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faster than modes 2-3.
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4,5,8,9 ==> left-to-right digit generation.
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6-9 ==> don't try fast floating-point estimate
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(if applicable).
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Values of mode other than 0-9 are treated as mode 0.
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Sufficient space is allocated to the return value
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to hold the suppressed trailing zeros.
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*/
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#undef MAX
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#define MAX(a,b) (((a) > (b)) ? (a) : (b))
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char *
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__dtoa (double number, int mode, int ndigits, int *decpt, int *sign,
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char **rve)
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{
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char *result, *p;
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switch(mode) {
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case 2:
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case 4:
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case 6:
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case 8:
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mode0: /* this label doesn't belong here */
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result = ecvt(number, MAX(1, ndigits), decpt, sign);
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break;
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case 3:
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case 5:
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case 7:
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case 9:
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result = fcvt(number, ndigits, decpt, sign);
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break;
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case 0:
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case 1:
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default:
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goto mode0; /* TEMP KLUDGE */
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}
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/* truncate trailing zeros */
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p = result;
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while (*p) p++;
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p--;
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while ((p > result) && (*p == '0')) {
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*p-- = '\0';
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}
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if (rve != NULL) {
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*rve = p + 1;
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}
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/* set decimal point for NaNs and Infinities */
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if (isnan(number) || isinf(number)) {
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*decpt = 9999;
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}
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return result;
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}
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