108 lines
2 KiB
C
108 lines
2 KiB
C
/*
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* ecvt.c - conversion routines for printing floating point numbers
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*/
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/* $Header$ */
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#ifndef NOFLOAT
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static char *cvt(long double value, int ndigit, int *decpt, int *sign, int ecvtflag);
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#define NDIGITS 128
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char *
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ecvt(long double value, int ndigit, int *decpt, int *sign)
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{
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return cvt(value, ndigit, decpt, sign, 1);
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}
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char *
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fcvt(long double value, int ndigit, int *decpt, int *sign)
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{
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return cvt(value, ndigit, decpt, sign, 0);
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}
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static struct powers_of_10 {
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long double pval;
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long double rpval;
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int exp;
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} p10[] = {
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1.0e32, 1.0e-32, 32,
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1.0e16, 1.0e-16, 16,
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1.0e8, 1.0e-8, 8,
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1.0e4, 1.0e-4, 4,
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1.0e2, 1.0e-2, 2,
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1.0e1, 1.0e-1, 1,
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1.0e0, 1.0e0, 0
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};
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static char *
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cvt(long double value, int ndigit, int *decpt, int *sign, int ecvtflag)
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{
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static char buf[NDIGITS+1];
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register char *p = buf;
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register char *pe;
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if (ndigit < 0) ndigit = 0;
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if (ndigit > NDIGITS) ndigit = NDIGITS;
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pe = &buf[ndigit];
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buf[0] = '\0';
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*sign = 0;
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if (value < 0) {
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*sign = 1;
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value = -value;
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}
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*decpt = 0;
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if (value != 0.0) {
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register struct powers_of_10 *pp = &p10[0];
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if (value >= 10.0) do {
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while (value >= pp->pval) {
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value *= pp->rpval;
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*decpt += pp->exp;
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}
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} while ((++pp)->exp > 0);
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pp = &p10[0];
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if (value < 1.0) do {
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while (value * pp->pval < 10.0) {
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value *= pp->pval;
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*decpt -= pp->exp;
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}
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} while ((++pp)->exp > 0);
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(*decpt)++; /* because now value in [1.0, 10.0) */
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}
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if (!ecvtflag) {
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/* for fcvt() we need ndigit digits behind the dot */
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pe += *decpt;
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if (pe > &buf[NDIGITS]) pe = &buf[NDIGITS];
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}
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while (p <= pe) {
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*p++ = (int)value + '0';
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value = 10.0 * (value - (int)value);
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}
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if (pe >= buf) {
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p = pe;
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*p += 5; /* round of at the end */
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while (*p > '9') {
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*p = '0';
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if (p > buf) ++*--p;
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else {
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*p = '1';
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++*decpt;
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if (!ecvtflag) {
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/* maybe add another digit at the end,
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because the point was shifted right
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*/
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if (pe > buf) *pe = '0';
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pe++;
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}
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}
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}
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*pe = '\0';
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}
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return buf;
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}
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#endif /* NOFLOAT */
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