xref: /php-src/ext/bcmath/libbcmath/src/nearzero.c (revision e56ed6e1)
1 /* nearzero.c: bcmath library file. */
2 /*
3     Copyright (C) 1991, 1992, 1993, 1994, 1997 Free Software Foundation, Inc.
4     Copyright (C) 2000 Philip A. Nelson
5 
6     This library is free software; you can redistribute it and/or
7     modify it under the terms of the GNU Lesser General Public
8     License as published by the Free Software Foundation; either
9     version 2 of the License, or (at your option) any later version.
10 
11     This library is distributed in the hope that it will be useful,
12     but WITHOUT ANY WARRANTY; without even the implied warranty of
13     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
14     Lesser General Public License for more details.  (LICENSE)
15 
16     You should have received a copy of the GNU Lesser General Public
17     License along with this library; if not, write to:
18 
19       The Free Software Foundation, Inc.
20       59 Temple Place, Suite 330
21       Boston, MA 02111-1307 USA.
22 
23     You may contact the author by:
24        e-mail:  philnelson@acm.org
25       us-mail:  Philip A. Nelson
26                 Computer Science Department, 9062
27                 Western Washington University
28                 Bellingham, WA 98226-9062
29 
30 *************************************************************************/
31 
32 #include <stdbool.h>
33 #include "bcmath.h"
34 #include <stddef.h>
35 
36 /* In some places we need to check if the number NUM is almost zero.
37    Specifically, all but the last digit is 0 and the last digit is 1.
38    Last digit is defined by scale. */
39 
bc_is_near_zero(bc_num num,size_t scale)40 bool bc_is_near_zero(bc_num num, size_t scale)
41 {
42 	/* Error checking */
43 	if (scale > num->n_scale) {
44 		scale = num->n_scale;
45 	}
46 
47 	/* Initialize */
48 	size_t count = num->n_len + scale;
49 	const char *nptr = num->n_value;
50 
51 	/* The check */
52 	while ((count > 0) && (*nptr++ == 0)) {
53 		count--;
54 	}
55 
56 	return count == 0 || (count == 1 && *--nptr == 1);
57 }
58