crypto/openssl-0.9.7d/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;
  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         if (!BN_uadd(r,a,b)) return(0);
  99         if (a_neg) /* both are neg */
 100                 r->neg=1;
 101         else
 102                 r->neg=0;
 103         return(1);
 104         }
 105
 106 /* unsigned add of b to a, r must be large enough */
 107 int BN_uadd(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
 108         {
 109         register int i;
 110         int max,min;
 111         BN_ULONG *ap,*bp,*rp,carry,t1;
 112         const BIGNUM *tmp;
 113
 114         bn_check_top(a);
 115         bn_check_top(b);
 116
 117         if (a->top < b->top)
 118                 { tmp=a; a=b; b=tmp; }
 119         max=a->top;
 120         min=b->top;
 121
 122         if (bn_wexpand(r,max+1) == NULL)
 123                 return(0);
 124
 125         r->top=max;
 126
 127
 128         ap=a->d;
 129         bp=b->d;
 130         rp=r->d;
 131         carry=0;
 132
 133         carry=bn_add_words(rp,ap,bp,min);
 134         rp+=min;
 135         ap+=min;
 136         bp+=min;
 137         i=min;
 138
 139         if (carry)
 140                 {
 141                 while (i < max)
 142                         {
 143                         i++;
 144                         t1= *(ap++);
 145                         if ((*(rp++)=(t1+1)&BN_MASK2) >= t1)
 146                                 {
 147                                 carry=0;
 148                                 break;
 149                                 }
 150                         }
 151                 if ((i >= max) && carry)
 152                         {
 153                         *(rp++)=1;
 154                         r->top++;
 155                         }
 156                 }
 157         if (rp != ap)
 158                 {
 159                 for (; i<max; i++)
 160                         *(rp++)= *(ap++);
 161                 }
 162         /* memcpy(rp,ap,sizeof(*ap)*(max-i));*/
 163         r->neg = 0;
 164         return(1);
 165         }
 166
 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)
 169         {
 170         int max,min;
 171         register BN_ULONG t1,t2,*ap,*bp,*rp;
 172         int i,carry;
 173 #if defined(IRIX_CC_BUG) && !defined(LINT)
 174         int dummy;
 175 #endif
 176
 177         bn_check_top(a);
 178         bn_check_top(b);
 179
 180         if (a->top < b->top) /* hmm... should not be happening */
 181                 {
 182                 BNerr(BN_F_BN_USUB,BN_R_ARG2_LT_ARG3);
 183                 return(0);
 184                 }
 185
 186         max=a->top;
 187         min=b->top;
 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=0; i<min; 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         i=min;
 221 #endif
 222         if (carry) /* subtracted */
 223                 {
 224                 while (i < max)
 225                         {
 226                         i++;
 227                         t1= *(ap++);
 228                         t2=(t1-1)&BN_MASK2;
 229                         *(rp++)=t2;
 230                         if (t1 > t2) break;
 231                         }
 232                 }
 233 #if 0
 234         memcpy(rp,ap,sizeof(*rp)*(max-i));
 235 #else
 236         if (rp != ap)
 237                 {
 238                 for (;;)
 239                         {
 240                         if (i++ >= max) break;
 241                         rp[0]=ap[0];
 242                         if (i++ >= max) break;
 243                         rp[1]=ap[1];
 244                         if (i++ >= max) break;
 245                         rp[2]=ap[2];
 246                         if (i++ >= max) break;
 247                         rp[3]=ap[3];
 248                         rp+=4;
 249                         ap+=4;
 250                         }
 251                 }
 252 #endif
 253
 254         r->top=max;
 255         r->neg=0;
 256         bn_fix_top(r);
 257         return(1);
 258         }
 259
 260 int BN_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
 261         {
 262         int max;
 263         int add=0,neg=0;
 264         const BIGNUM *tmp;
 265
 266         bn_check_top(a);
 267         bn_check_top(b);
 268
 269         /*  a -  b      a-b
 270          *  a - -b      a+b
 271          * -a -  b      -(a+b)
 272          * -a - -b      b-a
 273          */
 274         if (a->neg)
 275                 {
 276                 if (b->neg)
 277                         { tmp=a; a=b; b=tmp; }
 278                 else
 279                         { add=1; neg=1; }
 280                 }
 281         else
 282                 {
 283                 if (b->neg) { add=1; neg=0; }
 284                 }
 285
 286         if (add)
 287                 {
 288                 if (!BN_uadd(r,a,b)) return(0);
 289                 r->neg=neg;
 290                 return(1);
 291                 }
 292
 293         /* We are actually doing a - b :-) */
 294
 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)
 298                 {
 299                 if (!BN_usub(r,b,a)) return(0);
 300                 r->neg=1;
 301                 }
 302         else
 303                 {
 304                 if (!BN_usub(r,a,b)) return(0);
 305                 r->neg=0;
 306                 }
 307         return(1);
 308         }
 309