124 lines
3.4 KiB
C
124 lines
3.4 KiB
C
/*****************************************************************************
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* RRDtool 1.4.9 Copyright by Tobi Oetiker, 1997-2014
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* This code is stolen from rateup (mrtg-2.x) by Dave Rand
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*****************************************************************************
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* diff calculate the difference between two very long integers available as
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* strings
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*****************************************************************************
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* $Id$
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* $Log$
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* Revision 1.4 2003/03/10 00:30:34 oetiker
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* handle cases with two negative numbers
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* -- Sasha Mikheev <sasha@avalon-net.co.il>
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*
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* Revision 1.3 2002/04/01 18:31:22 oetiker
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* "!" takes a higher preference than "||" this means rrd_update N:: would
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* segfault -- Oliver Cook <ollie@uk.clara.net>
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*
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* Revision 1.2 2002/02/01 20:34:49 oetiker
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* fixed version number and date/time
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*
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* Revision 1.1.1.1 2001/02/25 22:25:05 oetiker
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* checkin
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*
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* Revision 1.1 1998/10/08 18:21:45 oetiker
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* Initial revision
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*
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* Revision 1.3 1998/02/06 21:10:52 oetiker
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* removed max define .. it is now in rrd_tool.h
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*
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* Revision 1.2 1997/12/07 20:38:03 oetiker
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* ansified
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*
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* Revision 1.1 1997/11/28 23:31:59 oetiker
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* Initial revision
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*
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*****************************************************************************/
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#include <ctype.h>
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#include "rrd_tool.h"
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double rrd_diff(
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char *a,
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char *b)
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{
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char res[LAST_DS_LEN + 1], *a1, *b1, *r1, *fix;
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int c, x, m;
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char a_neg = 0, b_neg = 0;
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double result;
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while (!(isdigit((int) *a) || *a == 0)) {
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if (*a == '-')
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a_neg = 1;
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a++;
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}
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fix = a;
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while (isdigit((int) *fix))
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fix++;
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*fix = 0; /* maybe there is some non digit data in the string */
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while (!(isdigit((int) *b) || *b == 0)) {
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if (*b == '-')
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b_neg = 1;
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b++;
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}
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fix = b;
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while (isdigit((int) *fix))
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fix++;
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*fix = 0; /* maybe there is some non digit data in the string */
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if (!isdigit((int) *a) || !isdigit((int) *b))
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return DNAN;
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if (a_neg + b_neg == 1) /* can not handle numbers with different signs yet */
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return DNAN;
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a1 = &a[strlen(a) - 1];
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m = max(strlen(a), strlen(b));
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if (m > LAST_DS_LEN)
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return DNAN; /* result string too short */
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r1 = &res[m + 1];
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for (b1 = res; b1 <= r1; b1++)
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*b1 = ' ';
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b1 = &b[strlen(b) - 1];
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r1[1] = 0; /* Null terminate result */
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c = 0;
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for (x = 0; x < m; x++) {
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if (a1 >= a && b1 >= b) {
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*r1 = ((*a1 - c) - *b1) + '0';
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} else if (a1 >= a) {
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*r1 = (*a1 - c);
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} else {
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*r1 = ('0' - *b1 - c) + '0';
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}
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if (*r1 < '0') {
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*r1 += 10;
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c = 1;
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} else if (*r1 > '9') { /* 0 - 10 */
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*r1 -= 10;
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c = 1;
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} else {
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c = 0;
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}
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a1--;
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b1--;
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r1--;
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}
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if (c) {
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r1 = &res[m + 1];
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for (x = 0; isdigit((int) *r1) && x < m; x++, r1--) {
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*r1 = ('9' - *r1 + c) + '0';
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if (*r1 > '9') {
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*r1 -= 10;
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c = 1;
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} else {
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c = 0;
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}
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}
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result = -atof(res);
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} else
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result = atof(res);
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if (a_neg + b_neg == 2) /* both are negatives, reverse sign */
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result = -result;
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return result;
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}
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