GPSTracker/utils.c at master · erwincas/GPSTracker · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
#include "utils.h"

char * ftoa(double f, char * buf, int precision)
{
	char * ptr = buf;
	char * p = ptr;
	char * p1;
	char c;
	long intPart;

	// check precision bounds
	if (precision > MAX_PRECISION)
		precision = MAX_PRECISION;

	// sign stuff
	if (f < 0)
	{
		f = -f;
		*ptr++ = '-';
	}

	if (precision < 0)  // negative precision == automatic precision guess
	{
		if (f < 1.0) precision = 6;
		else if (f < 10.0) precision = 5;
		else if (f < 100.0) precision = 4;
		else if (f < 1000.0) precision = 3;
		else if (f < 10000.0) precision = 2;
		else if (f < 100000.0) precision = 1;
		else precision = 0;
	}

	// round value according the precision
	if (precision)
		f += rounders[precision];

	// integer part...
	intPart = f;
	f -= intPart;

	if (!intPart)
		*ptr++ = '0';
	else
	{
		// save start pointer
		p = ptr;

		// convert (reverse order)
		while (intPart)
		{
			*p++ = '0' + intPart % 10;
			intPart /= 10;
		}

		// save end pos
		p1 = p;

		// reverse result
		while (p > ptr)
		{
			c = *--p;
			*p = *ptr;
			*ptr++ = c;
		}

		// restore end pos
		ptr = p1;
	}

	// decimal part
	if (precision)
	{
		// place decimal point
		*ptr++ = '.';

		// convert
		while (precision--)
		{
			f *= 10.0;
			c = f;
			*ptr++ = '0' + c;
			f -= c;
		}
	}

	// terminating zero
	*ptr = 0;

	return buf;
}