83ca8831b62e152ecd4f1f3a137ca8a48138281a
1 /*****************************************************************************
2 * RRDtool 1.2.99907080300 Copyright by Tobi Oetiker, 1997-2007
3 * This code is stolen from rateup (mrtg-2.x) by Dave Rand
4 *****************************************************************************
5 * diff calculate the difference between two very long integers available as
6 * strings
7 *****************************************************************************
8 * $Id$
9 * $Log$
10 * Revision 1.4 2003/03/10 00:30:34 oetiker
11 * handle cases with two negative numbers
12 * -- Sasha Mikheev <sasha@avalon-net.co.il>
13 *
14 * Revision 1.3 2002/04/01 18:31:22 oetiker
15 * "!" takes a higher preference than "||" this means rrd_update N:: would
16 * segfault -- Oliver Cook <ollie@uk.clara.net>
17 *
18 * Revision 1.2 2002/02/01 20:34:49 oetiker
19 * fixed version number and date/time
20 *
21 * Revision 1.1.1.1 2001/02/25 22:25:05 oetiker
22 * checkin
23 *
24 * Revision 1.1 1998/10/08 18:21:45 oetiker
25 * Initial revision
26 *
27 * Revision 1.3 1998/02/06 21:10:52 oetiker
28 * removed max define .. it is now in rrd_tool.h
29 *
30 * Revision 1.2 1997/12/07 20:38:03 oetiker
31 * ansified
32 *
33 * Revision 1.1 1997/11/28 23:31:59 oetiker
34 * Initial revision
35 *
36 *****************************************************************************/
38 #include "rrd_tool.h"
40 double rrd_diff(
41 char *a,
42 char *b)
43 {
44 char res[LAST_DS_LEN + 1], *a1, *b1, *r1, *fix;
45 int c, x, m;
46 char a_neg = 0, b_neg = 0;
47 double result;
49 while (!(isdigit((int) *a) || *a == 0)) {
50 if (*a == '-')
51 a_neg = 1;
52 a++;
53 }
54 fix = a;
55 while (isdigit((int) *fix))
56 fix++;
57 *fix = 0; /* maybe there is some non digit data in the string */
58 while (!(isdigit((int) *b) || *b == 0)) {
59 if (*b == '-')
60 b_neg = 1;
61 b++;
62 }
63 fix = b;
64 while (isdigit((int) *fix))
65 fix++;
66 *fix = 0; /* maybe there is some non digit data in the string */
67 if (!isdigit((int) *a) || !isdigit((int) *b))
68 return DNAN;
69 if (a_neg + b_neg == 1) /* can not handle numbers with different signs yet */
70 return DNAN;
71 a1 = &a[strlen(a) - 1];
72 m = max(strlen(a), strlen(b));
73 if (m > LAST_DS_LEN)
74 return DNAN; /* result string too short */
76 r1 = &res[m + 1];
77 for (b1 = res; b1 <= r1; b1++)
78 *b1 = ' ';
79 b1 = &b[strlen(b) - 1];
80 r1[1] = 0; /* Null terminate result */
81 c = 0;
82 for (x = 0; x < m; x++) {
83 if (a1 >= a && b1 >= b) {
84 *r1 = ((*a1 - c) - *b1) + '0';
85 } else if (a1 >= a) {
86 *r1 = (*a1 - c);
87 } else {
88 *r1 = ('0' - *b1 - c) + '0';
89 }
90 if (*r1 < '0') {
91 *r1 += 10;
92 c = 1;
93 } else if (*r1 > '9') { /* 0 - 10 */
94 *r1 -= 10;
95 c = 1;
96 } else {
97 c = 0;
98 }
99 a1--;
100 b1--;
101 r1--;
102 }
103 if (c) {
104 r1 = &res[m + 1];
105 for (x = 0; isdigit((int) *r1) && x < m; x++, r1--) {
106 *r1 = ('9' - *r1 + c) + '0';
107 if (*r1 > '9') {
108 *r1 -= 10;
109 c = 1;
110 } else {
111 c = 0;
112 }
113 }
114 result = -atof(res);
115 } else
116 result = atof(res);
118 if (a_neg + b_neg == 2) /* both are negatives, reverse sign */
119 result = -result;
121 return result;
122 }