1 /* compare.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 "private.h"
35 #include <stddef.h>
36
37
38 /* Compare two bc numbers. Return value is 0 if equal, -1 if N1 is less
39 than N2 and +1 if N1 is greater than N2. If USE_SIGN is false, just
40 compare the magnitudes. */
41
_bc_do_compare(bc_num n1,bc_num n2,size_t scale,bool use_sign)42 bcmath_compare_result _bc_do_compare(bc_num n1, bc_num n2, size_t scale, bool use_sign)
43 {
44 char *n1ptr, *n2ptr;
45
46 /* First, compare signs. */
47 if (use_sign && n1->n_sign != n2->n_sign) {
48 if (n1->n_sign == PLUS) {
49 /* Positive N1 > Negative N2 */
50 return BCMATH_LEFT_GREATER;
51 } else {
52 /* Negative N1 < Positive N1 */
53 return BCMATH_RIGHT_GREATER;
54 }
55 }
56
57 /* Now compare the magnitude. */
58 if (n1->n_len != n2->n_len) {
59 if (n1->n_len > n2->n_len) {
60 /* Magnitude of n1 > n2. */
61 if (!use_sign || n1->n_sign == PLUS) {
62 return BCMATH_LEFT_GREATER;
63 } else {
64 return BCMATH_RIGHT_GREATER;
65 }
66 } else {
67 /* Magnitude of n1 < n2. */
68 if (!use_sign || n1->n_sign == PLUS) {
69 return BCMATH_RIGHT_GREATER;
70 } else {
71 return BCMATH_LEFT_GREATER;
72 }
73 }
74 }
75
76 size_t n1_scale = MIN(n1->n_scale, scale);
77 size_t n2_scale = MIN(n2->n_scale, scale);
78
79 /* If we get here, they have the same number of integer digits.
80 check the integer part and the equal length part of the fraction. */
81 size_t count = n1->n_len + MIN (n1_scale, n2_scale);
82 n1ptr = n1->n_value;
83 n2ptr = n2->n_value;
84
85 while ((count > 0) && (*n1ptr == *n2ptr)) {
86 n1ptr++;
87 n2ptr++;
88 count--;
89 }
90
91 if (count != 0) {
92 if (*n1ptr > *n2ptr) {
93 /* Magnitude of n1 > n2. */
94 if (!use_sign || n1->n_sign == PLUS) {
95 return BCMATH_LEFT_GREATER;
96 } else {
97 return BCMATH_RIGHT_GREATER;
98 }
99 } else {
100 /* Magnitude of n1 < n2. */
101 if (!use_sign || n1->n_sign == PLUS) {
102 return BCMATH_RIGHT_GREATER;
103 } else {
104 return BCMATH_LEFT_GREATER;
105 }
106 }
107 }
108
109 /* They are equal up to the last part of the equal part of the fraction. */
110 if (n1_scale != n2_scale) {
111 if (n1_scale > n2_scale) {
112 for (count = n1_scale - n2_scale; count > 0; count--) {
113 if (*n1ptr++ != 0) {
114 /* Magnitude of n1 > n2. */
115 if (!use_sign || n1->n_sign == PLUS) {
116 return BCMATH_LEFT_GREATER;
117 } else {
118 return BCMATH_RIGHT_GREATER;
119 }
120 }
121 }
122 } else {
123 for (count = n2_scale - n1_scale; count > 0; count--) {
124 if (*n2ptr++ != 0) {
125 /* Magnitude of n1 < n2. */
126 if (!use_sign || n1->n_sign == PLUS) {
127 return BCMATH_RIGHT_GREATER;
128 } else {
129 return BCMATH_LEFT_GREATER;
130 }
131 }
132 }
133 }
134 }
135
136 /* They must be equal! */
137 return BCMATH_EQUAL;
138 }
139
140
141 /* This is the "user callable" routine to compare numbers N1 and N2. */
bc_compare(bc_num n1,bc_num n2,size_t scale)142 bcmath_compare_result bc_compare(bc_num n1, bc_num n2, size_t scale)
143 {
144 return _bc_do_compare(n1, n2, scale, true);
145 }
146
