#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) doublecharstod(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);}