81 lines
1.1 KiB
C
81 lines
1.1 KiB
C
/* $Header$ */
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#ifndef NOFLOAT
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#include <ctype.h>
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extern double ldexp();
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double
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atof(p)
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register char *p;
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{
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register int c;
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int exp = 0, sign = 1, expsign = 0;
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double fl;
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double big = (double)(1L << 30) * (1L << 22);
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while (isspace(*p)) p++;
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c = *p;
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switch (c) {
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case '-':
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sign = -1;
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case '+':
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p++;
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}
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fl = 0.0;
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while (isdigit(c = *p++)) {
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if (fl < big)
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fl = 10.0 * fl + (double)(c - '0');
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else
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exp++;
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}
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if (c == '.') {
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while (isdigit(c = *p++)) {
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if (fl < big) {
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fl = 10.0 * fl + (double) (c - '0');
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exp--;
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}
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}
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}
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if (fl == 0) return 0;
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if (c == 'E' || c == 'e') {
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int exp1 = 0;
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int sign = 1;
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switch (*p) {
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case '-':
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sign = -1;
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case '+':
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p++;
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}
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while (isdigit(c = *p++)) {
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exp1 = 10 * exp1 + c - '0';
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}
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exp += sign * exp1;
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}
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if (exp < 0) {
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expsign = 1;
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exp = -exp;
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}
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if (exp != 0) {
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int oldexp = exp;
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double exp5 = 5;
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double correction = 1;
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while (exp) {
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if (exp % 2) correction *= exp5;
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exp /= 2;
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exp5 *= exp5;
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}
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if (expsign) fl = fl / correction;
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else fl = fl * correction;
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fl = ldexp(fl, expsign ? -oldexp : oldexp);
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}
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return sign * fl;
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}
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#endif
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