package/ead/src/tinysrp/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 "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