1 /* Copyright (c) 2002-2006 Lucent Technologies; see LICENSE */
2 #include <stdarg.h>
3 #include <string.h>
4 #include "plan9.h"
5 #include "fmt.h"
6 #include "fmtdef.h"
7 
8 /*
9  * Reads a floating-point number by interpreting successive characters
10  * returned by (*f)(vp).  The last call it makes to f terminates the
11  * scan, so is not a character in the number.  It may therefore be
12  * necessary to back up the input stream up one byte after calling charstod.
13  */
14 
15 double
16 fmtcharstod(int(*f)(void*), void *vp)
17 {
18 	double num, dem;
19 	int neg, eneg, dig, exp, c;
20 
21 	num = 0;
22 	neg = 0;
23 	dig = 0;
24 	exp = 0;
25 	eneg = 0;
26 
27 	c = (*f)(vp);
28 	while(c == ' ' || c == '\t')
29 		c = (*f)(vp);
30 	if(c == '-' || c == '+'){
31 		if(c == '-')
32 			neg = 1;
33 		c = (*f)(vp);
34 	}
35 	while(c >= '0' && c <= '9'){
36 		num = num*10 + c-'0';
37 		c = (*f)(vp);
38 	}
39 	if(c == '.')
40 		c = (*f)(vp);
41 	while(c >= '0' && c <= '9'){
42 		num = num*10 + c-'0';
43 		dig++;
44 		c = (*f)(vp);
45 	}
46 	if(c == 'e' || c == 'E'){
47 		c = (*f)(vp);
48 		if(c == '-' || c == '+'){
49 			if(c == '-'){
50 				dig = -dig;
51 				eneg = 1;
52 			}
53 			c = (*f)(vp);
54 		}
55 		while(c >= '0' && c <= '9'){
56 			exp = exp*10 + c-'0';
57 			c = (*f)(vp);
58 		}
59 	}
60 	exp -= dig;
61 	if(exp < 0){
62 		exp = -exp;
63 		eneg = !eneg;
64 	}
65 	dem = __fmtpow10(exp);
66 	if(eneg)
67 		num /= dem;
68 	else
69 		num *= dem;
70 	if(neg)
71 		return -num;
72 	return num;
73 }