1 /* crypto/bn/bn_add.c */
2 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
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.
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).
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.
23 * Redistribution and use in source and binary forms, with or without
24 * modification, are permitted provided that the following conditions
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)"
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
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.]
64 int BN_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
79 /* only one is negative */
81 { tmp=a; a=b; b=tmp; }
83 /* we are now a - b */
87 if (!BN_usub(r,b,a)) return(0);
92 if (!BN_usub(r,a,b)) return(0);
98 if (!BN_uadd(r,a,b)) return(0);
99 if (a_neg) /* both are neg */
106 /* unsigned add of b to a, r must be large enough */
107 int BN_uadd(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
111 BN_ULONG *ap,*bp,*rp,carry,t1;
118 { tmp=a; a=b; b=tmp; }
122 if (bn_wexpand(r,max+1) == NULL)
133 carry=bn_add_words(rp,ap,bp,min);
145 if ((*(rp++)=(t1+1)&BN_MASK2) >= t1)
151 if ((i >= max) && carry)
162 /* memcpy(rp,ap,sizeof(*ap)*(max-i));*/
167 /* unsigned subtraction of b from a, a must be larger than b. */
168 int BN_usub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
171 register BN_ULONG t1,t2,*ap,*bp,*rp;
173 #if defined(IRIX_CC_BUG) && !defined(LINT)
180 if (a->top < b->top) /* hmm... should not be happening */
182 BNerr(BN_F_BN_USUB,BN_R_ARG2_LT_ARG3);
188 if (bn_wexpand(r,max) == NULL) return(0);
196 for (i=0; i<min; i++)
203 t1=(t1-t2-1)&BN_MASK2;
210 #if defined(IRIX_CC_BUG) && !defined(LINT)
216 carry=bn_sub_words(rp,ap,bp,min);
222 if (carry) /* subtracted */
234 memcpy(rp,ap,sizeof(*rp)*(max-i));
240 if (i++ >= max) break;
242 if (i++ >= max) break;
244 if (i++ >= max) break;
246 if (i++ >= max) break;
260 int BN_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
277 { tmp=a; a=b; b=tmp; }
283 if (b->neg) { add=1; neg=0; }
288 if (!BN_uadd(r,a,b)) return(0);
293 /* We are actually doing a - b :-) */
295 max=(a->top > b->top)?a->top:b->top;
296 if (bn_wexpand(r,max) == NULL) return(0);
297 if (BN_ucmp(a,b) < 0)
299 if (!BN_usub(r,b,a)) return(0);
304 if (!BN_usub(r,a,b)) return(0);