charstod.c (1357B) download
1/* Copyright (c) 2002-2006 Lucent Technologies; see LICENSE */
2#include "fmt.h"
3#include "fmtdef.h"
4#include "plan9.h"
5
6#include <stdarg.h>
7#include <string.h>
8
9/*
10 * Reads a floating-point number by interpreting successive characters
11 * returned by (*f)(vp). The last call it makes to f terminates the
12 * scan, so is not a character in the number. It may therefore be
13 * necessary to back up the input stream up one byte after calling charstod.
14 */
15
16double
17fmtcharstod(int (*f)(void*), void* vp) {
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}