xref: /PHP-8.3/ext/bcmath/libbcmath/src/sub.c (revision e56ed6e1)
1 /* sub.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 "bcmath.h"
33 #include "private.h"
34 #include <stddef.h>
35 #include <stdbool.h>
36 #include <string.h>
37 
38 /* Here is the full subtract routine that takes care of negative numbers.
39    N2 is subtracted from N1 and the result placed in RESULT.  SCALE_MIN
40    is the minimum scale for the result. */
41 
bc_sub(bc_num n1,bc_num n2,bc_num * result,size_t scale_min)42 void bc_sub(bc_num n1, bc_num n2, bc_num *result, size_t scale_min)
43 {
44 	bc_num diff = NULL;
45 
46 	if (n1->n_sign != n2->n_sign) {
47 		diff = _bc_do_add(n1, n2, scale_min);
48 		diff->n_sign = n1->n_sign;
49 	} else {
50 		/* subtraction must be done. */
51 		/* Compare magnitudes. */
52 		switch (_bc_do_compare(n1, n2, false, false)) {
53 			case -1:
54 				/* n1 is less than n2, subtract n1 from n2. */
55 				diff = _bc_do_sub(n2, n1, scale_min);
56 				diff->n_sign = (n2->n_sign == PLUS ? MINUS : PLUS);
57 				break;
58 			case 0: {
59 				/* They are equal! return zero! */
60 				size_t res_scale = MAX (scale_min, MAX(n1->n_scale, n2->n_scale));
61 				diff = bc_new_num (1, res_scale);
62 				memset(diff->n_value, 0, res_scale + 1);
63 				break;
64 			}
65 			case 1:
66 				/* n2 is less than n1, subtract n2 from n1. */
67 				diff = _bc_do_sub(n1, n2, scale_min);
68 				diff->n_sign = n1->n_sign;
69 				break;
70 		}
71 	}
72 
73 	/* Clean up and return. */
74 	bc_free_num (result);
75 	*result = diff;
76 }
77