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#include <u.h>
#include <libc.h>
/*
* Reads a floating-point number by interpreting successive characters
* returned by (*f)(vp). The last call it makes to f terminates the
* scan, so is not a character in the number. It may therefore be
* necessary to back up the input stream up one byte after calling charstod.
*/
#define ADVANCE *s++ = c; if(s>=e) return NaN(); c = (*f)(vp)
double
charstod(int(*f)(void*), void *vp)
{
char str[400], *s, *e, *start;
int c;
s = str;
e = str + sizeof str - 1;
c = (*f)(vp);
while(c == ' ' || c == '\t')
c = (*f)(vp);
if(c == '-' || c == '+'){
ADVANCE;
}
start = s;
while(c >= '0' && c <= '9'){
ADVANCE;
}
if(c == '.'){
ADVANCE;
while(c >= '0' && c <= '9'){
ADVANCE;
}
}
if(s > start && (c == 'e' || c == 'E')){
ADVANCE;
if(c == '-' || c == '+'){
ADVANCE;
}
while(c >= '0' && c <= '9'){
ADVANCE;
}
}else if(s == start && (c == 'i' || c == 'I')){
ADVANCE;
if(c != 'n' && c != 'N')
return NaN();
ADVANCE;
if(c != 'f' && c != 'F')
return NaN();
ADVANCE;
if(c != 'i' && c != 'I')
return NaN();
ADVANCE;
if(c != 'n' && c != 'N')
return NaN();
ADVANCE;
if(c != 'i' && c != 'I')
return NaN();
ADVANCE;
if(c != 't' && c != 'T')
return NaN();
ADVANCE;
if(c != 'y' && c != 'Y')
return NaN();
ADVANCE; /* so caller can back up uniformly */
USED(c);
}else if(s == str && (c == 'n' || c == 'N')){
ADVANCE;
if(c != 'a' && c != 'A')
return NaN();
ADVANCE;
if(c != 'n' && c != 'N')
return NaN();
ADVANCE; /* so caller can back up uniformly */
USED(c);
}
*s = 0;
return strtod(str, &s);
}
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