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