82 lines
1.6 KiB
C
82 lines
1.6 KiB
C
#include <u.h>
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#include <libc.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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#define ADVANCE *s++ = c; if(s>=e) return NaN(); c = (*f)(vp)
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double
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charstod(int(*f)(void*), void *vp)
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{
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char str[400], *s, *e, *start;
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int c;
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s = str;
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e = str + sizeof str - 1;
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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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ADVANCE;
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}
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start = s;
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while(c >= '0' && c <= '9'){
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ADVANCE;
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}
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if(c == '.'){
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ADVANCE;
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while(c >= '0' && c <= '9'){
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ADVANCE;
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}
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}
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if(s > start && (c == 'e' || c == 'E')){
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ADVANCE;
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if(c == '-' || c == '+'){
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ADVANCE;
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}
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while(c >= '0' && c <= '9'){
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ADVANCE;
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}
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}else if(s == start && (c == 'i' || c == 'I')){
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ADVANCE;
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if(c != 'n' && c != 'N')
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return NaN();
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ADVANCE;
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if(c != 'f' && c != 'F')
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return NaN();
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ADVANCE;
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if(c != 'i' && c != 'I')
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return NaN();
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ADVANCE;
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if(c != 'n' && c != 'N')
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return NaN();
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ADVANCE;
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if(c != 'i' && c != 'I')
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return NaN();
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ADVANCE;
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if(c != 't' && c != 'T')
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return NaN();
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ADVANCE;
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if(c != 'y' && c != 'Y')
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return NaN();
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ADVANCE; /* so caller can back up uniformly */
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USED(c);
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}else if(s == str && (c == 'n' || c == 'N')){
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ADVANCE;
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if(c != 'a' && c != 'A')
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return NaN();
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ADVANCE;
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if(c != 'n' && c != 'N')
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return NaN();
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ADVANCE; /* so caller can back up uniformly */
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USED(c);
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}
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*s = 0;
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return strtod(str, &s);
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}
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