1 /*
2  * The authors of this software are Rob Pike and Ken Thompson.
3  *              Copyright (c) 2002 by Lucent Technologies.
4  * Permission to use, copy, modify, and distribute this software for any
5  * purpose without fee is hereby granted, provided that this entire notice
6  * is included in all copies of any software which is or includes a copy
7  * or modification of this software and in all copies of the supporting
8  * documentation for such software.
9  * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR IMPLIED
10  * WARRANTY.  IN PARTICULAR, NEITHER THE AUTHORS NOR LUCENT TECHNOLOGIES MAKE
11  * ANY REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE MERCHANTABILITY
12  * OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE.
13  */
14 #include <stdarg.h>
15 #include <string.h>
16 #include "plan9.h"
17 #include "fmt.h"
18 #include "fmtdef.h"
19 
20 /*
21  * Reads a floating-point number by interpreting successive characters
22  * returned by (*f)(vp).  The last call it makes to f terminates the
23  * scan, so is not a character in the number.  It may therefore be
24  * necessary to back up the input stream up one byte after calling charstod.
25  */
26 
27 double
28 fmtcharstod(int(*f)(void*), void *vp)
29 {
30 	double num, dem;
31 	int neg, eneg, dig, exp, c;
32 
33 	num = 0;
34 	neg = 0;
35 	dig = 0;
36 	exp = 0;
37 	eneg = 0;
38 
39 	c = (*f)(vp);
40 	while(c == ' ' || c == '\t')
41 		c = (*f)(vp);
42 	if(c == '-' || c == '+'){
43 		if(c == '-')
44 			neg = 1;
45 		c = (*f)(vp);
46 	}
47 	while(c >= '0' && c <= '9'){
48 		num = num*10 + c-'0';
49 		c = (*f)(vp);
50 	}
51 	if(c == '.')
52 		c = (*f)(vp);
53 	while(c >= '0' && c <= '9'){
54 		num = num*10 + c-'0';
55 		dig++;
56 		c = (*f)(vp);
57 	}
58 	if(c == 'e' || c == 'E'){
59 		c = (*f)(vp);
60 		if(c == '-' || c == '+'){
61 			if(c == '-'){
62 				dig = -dig;
63 				eneg = 1;
64 			}
65 			c = (*f)(vp);
66 		}
67 		while(c >= '0' && c <= '9'){
68 			exp = exp*10 + c-'0';
69 			c = (*f)(vp);
70 		}
71 	}
72 	exp -= dig;
73 	if(exp < 0){
74 		exp = -exp;
75 		eneg = !eneg;
76 	}
77 	dem = __fmtpow10(exp);
78 	if(eneg)
79 		num /= dem;
80 	else
81 		num *= dem;
82 	if(neg)
83 		return -num;
84 	return num;
85 }