crypto/bn/bn_add.c

   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 "cryptlib.h"
  61 #include "bn_lcl.h"
  62
  63 /* r can == a or b */
  64 int BN_add(r, a, b)
  65 BIGNUM *r;
  66 BIGNUM *a;
  67 BIGNUM *b;
  68         {
  69         BIGNUM *tmp;
  70
  71         bn_check_top(a);
  72         bn_check_top(b);
  73
  74         /*  a +  b      a+b
  75          *  a + -b      a-b
  76          * -a +  b      b-a
  77          * -a + -b      -(a+b)
  78          */
  79         if (a->neg ^ b->neg)
  80                 {
  81                 /* only one is negative */
  82                 if (a->neg)
  83                         { tmp=a; a=b; b=tmp; }
  84
  85                 /* we are now a - b */
  86
  87                 if (BN_ucmp(a,b) < 0)
  88                         {
  89                         if (!BN_usub(r,b,a)) return(0);
  90                         r->neg=1;
  91                         }
  92                 else
  93                         {
  94                         if (!BN_usub(r,a,b)) return(0);
  95                         r->neg=0;
  96                         }
  97                 return(1);
  98                 }
  99
 100         if (a->neg) /* both are neg */
 101                 r->neg=1;
 102         else
 103                 r->neg=0;
 104
 105         if (!BN_uadd(r,a,b)) return(0);
 106         return(1);
 107         }
 108
 109 /* unsigned add of b to a, r must be large enough */
 110 int BN_uadd(r,a,b)
 111 BIGNUM *r;
 112 BIGNUM *a;
 113 BIGNUM *b;
 114         {
 115         register int i;
 116         int max,min;
 117         BN_ULONG *ap,*bp,*rp,carry,t1;
 118         BIGNUM *tmp;
 119
 120         bn_check_top(a);
 121         bn_check_top(b);
 122
 123         if (a->top < b->top)
 124                 { tmp=a; a=b; b=tmp; }
 125         max=a->top;
 126         min=b->top;
 127
 128         if (bn_wexpand(r,max+1) == NULL)
 129                 return(0);
 130
 131         r->top=max;
 132
 133
 134         ap=a->d;
 135         bp=b->d;
 136         rp=r->d;
 137         carry=0;
 138
 139         carry=bn_add_words(rp,ap,bp,min);
 140         rp+=min;
 141         ap+=min;
 142         bp+=min;
 143         i=min;
 144
 145         if (carry)
 146                 {
 147                 while (i < max)
 148                         {
 149                         i++;
 150                         t1= *(ap++);
 151                         if ((*(rp++)=(t1+1)&BN_MASK2) >= t1)
 152                                 {
 153                                 carry=0;
 154                                 break;
 155                                 }
 156                         }
 157                 if ((i >= max) && carry)
 158                         {
 159                         *(rp++)=1;
 160                         r->top++;
 161                         }
 162                 }
 163         if (rp != ap)
 164                 {
 165                 for (; i<max; i++)
 166                         *(rp++)= *(ap++);
 167                 }
 168         /* memcpy(rp,ap,sizeof(*ap)*(max-i));*/
 169         return(1);
 170         }
 171
 172 /* unsigned subtraction of b from a, a must be larger than b. */
 173 int BN_usub(r, a, b)
 174 BIGNUM *r;
 175 BIGNUM *a;
 176 BIGNUM *b;
 177         {
 178         int max,min,ret=1;
 179         register BN_ULONG t1,t2,*ap,*bp,*rp;
 180         int i,carry;
 181 #if defined(IRIX_CC_BUG) && !defined(LINT)
 182         int dummy;
 183 #endif
 184
 185         bn_check_top(a);
 186         bn_check_top(b);
 187
 188         if (a->top < b->top) /* hmm... should not be happening */
 189                 {
 190                 BNerr(BN_F_BN_USUB,BN_R_ARG2_LT_ARG3);
 191                 return(0);
 192                 }
 193
 194         max=a->top;
 195         min=b->top;
 196         if (bn_wexpand(r,max) == NULL) return(0);
 197
 198         ap=a->d;
 199         bp=b->d;
 200         rp=r->d;
 201
 202 #if 1
 203         carry=0;
 204         for (i=0; i<min; i++)
 205                 {
 206                 t1= *(ap++);
 207                 t2= *(bp++);
 208                 if (carry)
 209                         {
 210                         carry=(t1 <= t2);
 211                         t1=(t1-t2-1)&BN_MASK2;
 212                         }
 213                 else
 214                         {
 215                         carry=(t1 < t2);
 216                         t1=(t1-t2)&BN_MASK2;
 217                         }
 218 #if defined(IRIX_CC_BUG) && !defined(LINT)
 219                 dummy=t1;
 220 #endif
 221                 *(rp++)=t1&BN_MASK2;
 222                 }
 223 #else
 224         carry=bn_sub_words(rp,ap,bp,min);
 225         ap+=min;
 226         bp+=min;
 227         rp+=min;
 228         i=min;
 229 #endif
 230         if (carry) /* subtracted */
 231                 {
 232                 while (i < max)
 233                         {
 234                         i++;
 235                         t1= *(ap++);
 236                         t2=(t1-1)&BN_MASK2;
 237                         *(rp++)=t2;
 238                         if (t1 > t2) break;
 239                         }
 240                 }
 241 #if 0
 242         memcpy(rp,ap,sizeof(*rp)*(max-i));
 243 #else
 244         if (rp != ap)
 245                 {
 246                 for (;;)
 247                         {
 248                         if (i++ >= max) break;
 249                         rp[0]=ap[0];
 250                         if (i++ >= max) break;
 251                         rp[1]=ap[1];
 252                         if (i++ >= max) break;
 253                         rp[2]=ap[2];
 254                         if (i++ >= max) break;
 255                         rp[3]=ap[3];
 256                         rp+=4;
 257                         ap+=4;
 258                         }
 259                 }
 260 #endif
 261
 262         r->top=max;
 263         bn_fix_top(r);
 264         return(1);
 265         }
 266
 267 int BN_sub(r, a, b)
 268 BIGNUM *r;
 269 BIGNUM *a;
 270 BIGNUM *b;
 271         {
 272         int max;
 273         int add=0,neg=0;
 274         BIGNUM *tmp;
 275
 276         bn_check_top(a);
 277         bn_check_top(b);
 278
 279         /*  a -  b      a-b
 280          *  a - -b      a+b
 281          * -a -  b      -(a+b)
 282          * -a - -b      b-a
 283          */
 284         if (a->neg)
 285                 {
 286                 if (b->neg)
 287                         { tmp=a; a=b; b=tmp; }
 288                 else
 289                         { add=1; neg=1; }
 290                 }
 291         else
 292                 {
 293                 if (b->neg) { add=1; neg=0; }
 294                 }
 295
 296         if (add)
 297                 {
 298                 if (!BN_uadd(r,a,b)) return(0);
 299                 r->neg=neg;
 300                 return(1);
 301                 }
 302
 303         /* We are actually doing a - b :-) */
 304
 305         max=(a->top > b->top)?a->top:b->top;
 306         if (bn_wexpand(r,max) == NULL) return(0);
 307         if (BN_ucmp(a,b) < 0)
 308                 {
 309                 if (!BN_usub(r,b,a)) return(0);
 310                 r->neg=1;
 311                 }
 312         else
 313                 {
 314                 if (!BN_usub(r,a,b)) return(0);
 315                 r->neg=0;
 316                 }
 317         return(1);
 318         }
 319