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4 office 1 /* crypto/bn/bn_add.c */
2 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
3 * All rights reserved.
4 *
5 * This package is an SSL implementation written
6 * by Eric Young (eay@cryptsoft.com).
7 * The implementation was written so as to conform with Netscapes SSL.
8 *
9 * This library is free for commercial and non-commercial use as long as
10 * the following conditions are aheared to. The following conditions
11 * apply to all code found in this distribution, be it the RC4, RSA,
12 * lhash, DES, etc., code; not just the SSL code. The SSL documentation
13 * included with this distribution is covered by the same copyright terms
14 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
15 *
16 * Copyright remains Eric Young's, and as such any Copyright notices in
17 * the code are not to be removed.
18 * If this package is used in a product, Eric Young should be given attribution
19 * as the author of the parts of the library used.
20 * This can be in the form of a textual message at program startup or
21 * in documentation (online or textual) provided with the package.
22 *
23 * Redistribution and use in source and binary forms, with or without
24 * modification, are permitted provided that the following conditions
25 * are met:
26 * 1. Redistributions of source code must retain the copyright
27 * notice, this list of conditions and the following disclaimer.
28 * 2. Redistributions in binary form must reproduce the above copyright
29 * notice, this list of conditions and the following disclaimer in the
30 * documentation and/or other materials provided with the distribution.
31 * 3. All advertising materials mentioning features or use of this software
32 * must display the following acknowledgement:
33 * "This product includes cryptographic software written by
34 * Eric Young (eay@cryptsoft.com)"
35 * The word 'cryptographic' can be left out if the rouines from the library
36 * being used are not cryptographic related :-).
37 * 4. If you include any Windows specific code (or a derivative thereof) from
38 * the apps directory (application code) you must include an acknowledgement:
39 * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
40 *
41 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
42 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
43 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
44 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
45 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
46 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
47 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
48 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
49 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
50 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
51 * SUCH DAMAGE.
52 *
53 * The licence and distribution terms for any publically available version or
54 * derivative of this code cannot be changed. i.e. this code cannot simply be
55 * copied and put under another distribution licence
56 * [including the GNU Public Licence.]
57 */
58  
59 #include <stdio.h>
60 #include "bn_lcl.h"
61  
62 /* r can == a or b */
63 int BN_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
64 {
65 const BIGNUM *tmp;
66  
67 bn_check_top(a);
68 bn_check_top(b);
69  
70 /* a + b a+b
71 * a + -b a-b
72 * -a + b b-a
73 * -a + -b -(a+b)
74 */
75 if (a->neg ^ b->neg)
76 {
77 /* only one is negative */
78 if (a->neg)
79 { tmp=a; a=b; b=tmp; }
80  
81 /* we are now a - b */
82  
83 if (BN_ucmp(a,b) < 0)
84 {
85 if (!BN_usub(r,b,a)) return(0);
86 r->neg=1;
87 }
88 else
89 {
90 if (!BN_usub(r,a,b)) return(0);
91 r->neg=0;
92 }
93 return(1);
94 }
95  
96 if (a->neg) /* both are neg */
97 r->neg=1;
98 else
99 r->neg=0;
100  
101 if (!BN_uadd(r,a,b)) return(0);
102 return(1);
103 }
104  
105 /* unsigned add of b to a, r must be large enough */
106 int BN_uadd(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
107 {
108 register int i;
109 int max,min;
110 BN_ULONG *ap,*bp,*rp,carry,t1;
111 const BIGNUM *tmp;
112  
113 bn_check_top(a);
114 bn_check_top(b);
115  
116 if (a->top < b->top)
117 { tmp=a; a=b; b=tmp; }
118 max=a->top;
119 min=b->top;
120  
121 if (bn_wexpand(r,max+1) == NULL)
122 return(0);
123  
124 r->top=max;
125  
126  
127 ap=a->d;
128 bp=b->d;
129 rp=r->d;
130 carry=0;
131  
132 carry=bn_add_words(rp,ap,bp,min);
133 rp+=min;
134 ap+=min;
135 bp+=min;
136 i=min;
137  
138 if (carry)
139 {
140 while (i < max)
141 {
142 i++;
143 t1= *(ap++);
144 if ((*(rp++)=(t1+1)&BN_MASK2) >= t1)
145 {
146 carry=0;
147 break;
148 }
149 }
150 if ((i >= max) && carry)
151 {
152 *(rp++)=1;
153 r->top++;
154 }
155 }
156 if (rp != ap)
157 {
158 for (; i<max; i++)
159 *(rp++)= *(ap++);
160 }
161 /* memcpy(rp,ap,sizeof(*ap)*(max-i));*/
162 return(1);
163 }
164  
165 /* unsigned subtraction of b from a, a must be larger than b. */
166 int BN_usub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
167 {
168 int max,min;
169 register BN_ULONG t1,t2,*ap,*bp,*rp;
170 int i,carry;
171 #if defined(IRIX_CC_BUG) && !defined(LINT)
172 int dummy;
173 #endif
174  
175 bn_check_top(a);
176 bn_check_top(b);
177  
178 if (a->top < b->top) /* hmm... should not be happening */
179 {
180 return(0);
181 }
182  
183 max=a->top;
184 min=b->top;
185 if (bn_wexpand(r,max) == NULL) return(0);
186  
187 ap=a->d;
188 bp=b->d;
189 rp=r->d;
190  
191 #if 1
192 carry=0;
193 for (i=0; i<min; i++)
194 {
195 t1= *(ap++);
196 t2= *(bp++);
197 if (carry)
198 {
199 carry=(t1 <= t2);
200 t1=(t1-t2-1)&BN_MASK2;
201 }
202 else
203 {
204 carry=(t1 < t2);
205 t1=(t1-t2)&BN_MASK2;
206 }
207 #if defined(IRIX_CC_BUG) && !defined(LINT)
208 dummy=t1;
209 #endif
210 *(rp++)=t1&BN_MASK2;
211 }
212 #else
213 carry=bn_sub_words(rp,ap,bp,min);
214 ap+=min;
215 bp+=min;
216 rp+=min;
217 i=min;
218 #endif
219 if (carry) /* subtracted */
220 {
221 while (i < max)
222 {
223 i++;
224 t1= *(ap++);
225 t2=(t1-1)&BN_MASK2;
226 *(rp++)=t2;
227 if (t1 > t2) break;
228 }
229 }
230 #if 0
231 memcpy(rp,ap,sizeof(*rp)*(max-i));
232 #else
233 if (rp != ap)
234 {
235 for (;;)
236 {
237 if (i++ >= max) break;
238 rp[0]=ap[0];
239 if (i++ >= max) break;
240 rp[1]=ap[1];
241 if (i++ >= max) break;
242 rp[2]=ap[2];
243 if (i++ >= max) break;
244 rp[3]=ap[3];
245 rp+=4;
246 ap+=4;
247 }
248 }
249 #endif
250  
251 r->top=max;
252 bn_fix_top(r);
253 return(1);
254 }
255  
256 int BN_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
257 {
258 int max;
259 int add=0,neg=0;
260 const BIGNUM *tmp;
261  
262 bn_check_top(a);
263 bn_check_top(b);
264  
265 /* a - b a-b
266 * a - -b a+b
267 * -a - b -(a+b)
268 * -a - -b b-a
269 */
270 if (a->neg)
271 {
272 if (b->neg)
273 { tmp=a; a=b; b=tmp; }
274 else
275 { add=1; neg=1; }
276 }
277 else
278 {
279 if (b->neg) { add=1; neg=0; }
280 }
281  
282 if (add)
283 {
284 if (!BN_uadd(r,a,b)) return(0);
285 r->neg=neg;
286 return(1);
287 }
288  
289 /* We are actually doing a - b :-) */
290  
291 max=(a->top > b->top)?a->top:b->top;
292 if (bn_wexpand(r,max) == NULL) return(0);
293 if (BN_ucmp(a,b) < 0)
294 {
295 if (!BN_usub(r,b,a)) return(0);
296 r->neg=1;
297 }
298 else
299 {
300 if (!BN_usub(r,a,b)) return(0);
301 r->neg=0;
302 }
303 return(1);
304 }
305