/*
* The authors of this software are Rob Pike and Ken Thompson,
* with contributions from Mike Burrows and Sean Dorward.
*
* Copyright (c) 2002-2006 by Lucent Technologies.
* Portions Copyright (c) 2004 Google Inc.
*
* Permission to use, copy, modify, and distribute this software for any
* purpose without fee is hereby granted, provided that this entire notice
* is included in all copies of any software which is or includes a copy
* or modification of this software and in all copies of the supporting
* documentation for such software.
* THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR IMPLIED
* WARRANTY. IN PARTICULAR, NEITHER THE AUTHORS NOR LUCENT TECHNOLOGIES
* NOR GOOGLE INC MAKE ANY REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING
* THE MERCHANTABILITY OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE.
*/
#include <u.h>
#include <libc.h>
#include "fmtdef.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.
*/
double
fmtcharstod(int(*f)(void*), void *vp)
{
double num, dem;
int neg, eneg, dig, exp, c;
num = 0;
neg = 0;
dig = 0;
exp = 0;
eneg = 0;
c = (*f)(vp);
while(c == ' ' || c == '\t')
c = (*f)(vp);
if(c == '-' || c == '+'){
if(c == '-')
neg = 1;
c = (*f)(vp);
}
while(c >= '0' && c <= '9'){
num = num*10 + c-'0';
c = (*f)(vp);
}
if(c == '.')
c = (*f)(vp);
while(c >= '0' && c <= '9'){
num = num*10 + c-'0';
dig++;
c = (*f)(vp);
}
if(c == 'e' || c == 'E'){
c = (*f)(vp);
if(c == '-' || c == '+'){
if(c == '-'){
dig = -dig;
eneg = 1;
}
c = (*f)(vp);
}
while(c >= '0' && c <= '9'){
exp = exp*10 + c-'0';
c = (*f)(vp);
}
}
exp -= dig;
if(exp < 0){
exp = -exp;
eneg = !eneg;
}
dem = __fmtpow10(exp);
if(eneg)
num /= dem;
else
num *= dem;
if(neg)
return -num;
return num;
}