71 lines
1.2 KiB
C
71 lines
1.2 KiB
C
#include <u.h>
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#include <libc.h>
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#include "fmtdef.h"
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/*
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* Reads a floating-point number by interpreting successive characters
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* returned by (*f)(vp). The last call it makes to f terminates the
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* scan, so is not a character in the number. It may therefore be
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* necessary to back up the input stream up one byte after calling charstod.
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*/
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double
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fmtcharstod(int(*f)(void*), void *vp)
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{
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double num, dem;
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int neg, eneg, dig, exp, c;
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num = 0;
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neg = 0;
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dig = 0;
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exp = 0;
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eneg = 0;
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c = (*f)(vp);
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while(c == ' ' || c == '\t')
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c = (*f)(vp);
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if(c == '-' || c == '+'){
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if(c == '-')
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neg = 1;
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c = (*f)(vp);
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}
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while(c >= '0' && c <= '9'){
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num = num*10 + c-'0';
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c = (*f)(vp);
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}
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if(c == '.')
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c = (*f)(vp);
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while(c >= '0' && c <= '9'){
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num = num*10 + c-'0';
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dig++;
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c = (*f)(vp);
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}
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if(c == 'e' || c == 'E'){
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c = (*f)(vp);
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if(c == '-' || c == '+'){
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if(c == '-'){
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dig = -dig;
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eneg = 1;
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}
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c = (*f)(vp);
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}
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while(c >= '0' && c <= '9'){
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exp = exp*10 + c-'0';
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c = (*f)(vp);
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}
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}
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exp -= dig;
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if(exp < 0){
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exp = -exp;
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eneg = !eneg;
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}
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dem = __fmtpow10(exp);
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if(eneg)
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num /= dem;
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else
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num *= dem;
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if(neg)
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return -num;
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return num;
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}
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