cscrypt/bn_add.c

   1 #include "bn.h"
   2
   3 #ifndef WITH_LIBCRYPTO
   4 //FIXME Not checked on threadsafety yet; after checking please remove this line
   5 /* crypto/bn/bn_add.c */
   6 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
   7  * All rights reserved.
   8  *
   9  * This package is an SSL implementation written
  10  * by Eric Young (eay@cryptsoft.com).
  11  * The implementation was written so as to conform with Netscapes SSL.
  12  *
  13  * This library is free for commercial and non-commercial use as long as
  14  * the following conditions are aheared to.  The following conditions
  15  * apply to all code found in this distribution, be it the RC4, RSA,
  16  * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
  17  * included with this distribution is covered by the same copyright terms
  18  * except that the holder is Tim Hudson (tjh@cryptsoft.com).
  19  *
  20  * Copyright remains Eric Young's, and as such any Copyright notices in
  21  * the code are not to be removed.
  22  * If this package is used in a product, Eric Young should be given attribution
  23  * as the author of the parts of the library used.
  24  * This can be in the form of a textual message at program startup or
  25  * in documentation (online or textual) provided with the package.
  26  *
  27  * Redistribution and use in source and binary forms, with or without
  28  * modification, are permitted provided that the following conditions
  29  * are met:
  30  * 1. Redistributions of source code must retain the copyright
  31  *    notice, this list of conditions and the following disclaimer.
  32  * 2. Redistributions in binary form must reproduce the above copyright
  33  *    notice, this list of conditions and the following disclaimer in the
  34  *    documentation and/or other materials provided with the distribution.
  35  * 3. All advertising materials mentioning features or use of this software
  36  *    must display the following acknowledgement:
  37  *    "This product includes cryptographic software written by
  38  *     Eric Young (eay@cryptsoft.com)"
  39  *    The word 'cryptographic' can be left out if the rouines from the library
  40  *    being used are not cryptographic related :-).
  41  * 4. If you include any Windows specific code (or a derivative thereof) from
  42  *    the apps directory (application code) you must include an acknowledgement:
  43  *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
  44  *
  45  * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
  46  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  47  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  48  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  49  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  50  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  51  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  52  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  53  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  54  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  55  * SUCH DAMAGE.
  56  *
  57  * The license and distribution terms for any publically available version or
  58  * derivative of this code cannot be changed.  i.e. this code cannot simply be
  59  * copied and put under another distribution license
  60  * [including the GNU Public License.]
  61  */
  62
  63 #include <stdio.h>
  64 #include "openssl_mods.h"
  65 #include "bn_lcl.h"
  66
  67 /* r can == a or b */
  68 int BN_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
  69 {
  70         const BIGNUM *tmp;
  71
  72         bn_check_top(a);
  73         bn_check_top(b);
  74
  75         /*  a +  b  a+b
  76          *  a + -b  a-b
  77          * -a +  b  b-a
  78          * -a + -b  -(a+b)
  79          */
  80         if(a->neg ^ b->neg)
  81         {
  82                 /* only one is negative */
  83                 if(a->neg)
  84                 {
  85                         tmp = a;
  86                         a = b;
  87                         b = tmp;
  88                 }
  89
  90                 /* we are now a - b */
  91
  92                 if(BN_ucmp(a, b) < 0)
  93                 {
  94                         if(!BN_usub(r, b, a)) { return (0); }
  95                         r->neg = 1;
  96                 }
  97                 else
  98                 {
  99                         if(!BN_usub(r, a, b)) { return (0); }
 100                         r->neg = 0;
 101                 }
 102                 return (1);
 103         }
 104
 105         if(a->neg)  /* both are neg */
 106                 { r->neg = 1; }
 107         else
 108                 { r->neg = 0; }
 109
 110         if(!BN_uadd(r, a, b)) { return (0); }
 111         return (1);
 112 }
 113
 114 /* unsigned add of b to a, r must be large enough */
 115 int BN_uadd(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
 116 {
 117         register int i;
 118         int max, min;
 119         BN_ULONG *ap, *bp, *rp, carry, t1;
 120         const BIGNUM *tmp;
 121
 122         bn_check_top(a);
 123         bn_check_top(b);
 124
 125         if(a->top < b->top)
 126         {
 127                 tmp = a;
 128                 a = b;
 129                 b = tmp;
 130         }
 131         max = a->top;
 132         min = b->top;
 133
 134         if(bn_wexpand(r, max + 1) == NULL)
 135                 { return (0); }
 136
 137         r->top = max;
 138
 139
 140         ap = a->d;
 141         bp = b->d;
 142         rp = r->d;
 143
 144         carry = bn_add_words(rp, ap, bp, min);
 145         rp += min;
 146         ap += min;
 147         i = min;
 148
 149         if(carry)
 150         {
 151                 while(i < max)
 152                 {
 153                         i++;
 154                         t1 = *(ap++);
 155                         if((*(rp++) = (t1 + 1)&BN_MASK2) >= t1)
 156                         {
 157                                 carry = 0;
 158                                 break;
 159                         }
 160                 }
 161                 if((i >= max) && carry)
 162                 {
 163                         *(rp++) = 1;
 164                         r->top++;
 165                 }
 166         }
 167         if(rp != ap)
 168         {
 169                 for(; i < max; i++)
 170                         { *(rp++) = *(ap++); }
 171         }
 172         /* memcpy(rp,ap,sizeof(*ap)*(max-i));*/
 173         return (1);
 174 }
 175
 176 /* unsigned subtraction of b from a, a must be larger than b. */
 177 int BN_usub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
 178 {
 179         int max, min;
 180         register BN_ULONG t1, t2, *ap, *bp, *rp;
 181         int i, carry;
 182
 183
 184         bn_check_top(a);
 185         bn_check_top(b);
 186
 187         if(a->top < b->top)  /* hmm... should not be happening */
 188         {
 189                 return (0);
 190         }
 191
 192         max = a->top;
 193         min = b->top;
 194         if(bn_wexpand(r, max) == NULL) { return (0); }
 195
 196         ap = a->d;
 197         bp = b->d;
 198         rp = r->d;
 199
 200 #if 1
 201         carry = 0;
 202         for(i = 0; i < min; i++)
 203         {
 204                 t1 = *(ap++);
 205                 t2 = *(bp++);
 206                 if(carry)
 207                 {
 208                         carry = (t1 <= t2);
 209                         t1 = (t1 - t2 - 1)&BN_MASK2;
 210                 }
 211                 else
 212                 {
 213                         carry = (t1 < t2);
 214                         t1 = (t1 - t2)&BN_MASK2;
 215                 }
 216 #if defined(IRIX_CC_BUG) && !defined(LINT)
 217                 int dummy;
 218                 dummy = t1;
 219 #endif
 220                 *(rp++) = t1 & BN_MASK2;
 221         }
 222 #else
 223         carry = bn_sub_words(rp, ap, bp, min);
 224         ap += min;
 225         bp += min;
 226         rp += min;
 227         i = min;
 228 #endif
 229         if(carry)  /* subtracted */
 230         {
 231                 while(i < max)
 232                 {
 233                         i++;
 234                         t1 = *(ap++);
 235                         t2 = (t1 - 1)&BN_MASK2;
 236                         *(rp++) = t2;
 237                         if(t1 > t2) { break; }
 238                 }
 239         }
 240 #if 0
 241         memcpy(rp, ap, sizeof(*rp) * (max - i));
 242 #else
 243         if(rp != ap)
 244         {
 245                 for(;;)
 246                 {
 247                         if(i++ >= max) { break; }
 248                         rp[0] = ap[0];
 249                         if(i++ >= max) { break; }
 250                         rp[1] = ap[1];
 251                         if(i++ >= max) { break; }
 252                         rp[2] = ap[2];
 253                         if(i++ >= max) { break; }
 254                         rp[3] = ap[3];
 255                         rp += 4;
 256                         ap += 4;
 257                 }
 258         }
 259 #endif
 260
 261         r->top = max;
 262         bn_fix_top(r);
 263         return (1);
 264 }
 265
 266 int BN_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
 267 {
 268         int max;
 269         int add = 0, neg = 0;
 270         const BIGNUM *tmp;
 271
 272         bn_check_top(a);
 273         bn_check_top(b);
 274
 275         /*  a -  b  a-b
 276          *  a - -b  a+b
 277          * -a -  b  -(a+b)
 278          * -a - -b  b-a
 279          */
 280         if(a->neg)
 281         {
 282                 if(b->neg)
 283                 {
 284                         tmp = a;
 285                         a = b;
 286                         b = tmp;
 287                 }
 288                 else
 289                 {
 290                         add = 1;
 291                         neg = 1;
 292                 }
 293         }
 294         else
 295         {
 296                 if(b->neg)
 297                 {
 298                         add = 1;
 299                         neg = 0;
 300                 }
 301         }
 302
 303         if(add)
 304         {
 305                 if(!BN_uadd(r, a, b)) { return (0); }
 306                 r->neg = neg;
 307                 return (1);
 308         }
 309
 310         /* We are actually doing a - b :-) */
 311
 312         max = (a->top > b->top) ? a->top : b->top;
 313         if(bn_wexpand(r, max) == NULL) { return (0); }
 314         if(BN_ucmp(a, b) < 0)
 315         {
 316                 if(!BN_usub(r, b, a)) { return (0); }
 317                 r->neg = 1;
 318         }
 319         else
 320         {
 321                 if(!BN_usub(r, a, b)) { return (0); }
 322                 r->neg = 0;
 323         }
 324         return (1);
 325 }
 326
 327 #endif