package/ead/src/tinysrp/bn_div.c

   1 /* crypto/bn/bn_div.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 #define NO_ASM
  63
  64 /* The old slow way */
  65 #if 0
  66 int BN_div(BIGNUM *dv, BIGNUM *rem, const BIGNUM *m, const BIGNUM *d,
  67            BN_CTX *ctx)
  68         {
  69         int i,nm,nd;
  70         int ret = 0;
  71         BIGNUM *D;
  72
  73         bn_check_top(m);
  74         bn_check_top(d);
  75         if (BN_is_zero(d))
  76                 {
  77                 return(0);
  78                 }
  79
  80         if (BN_ucmp(m,d) < 0)
  81                 {
  82                 if (rem != NULL)
  83                         { if (BN_copy(rem,m) == NULL) return(0); }
  84                 if (dv != NULL) BN_zero(dv);
  85                 return(1);
  86                 }
  87
  88         BN_CTX_start(ctx);
  89         D = BN_CTX_get(ctx);
  90         if (dv == NULL) dv = BN_CTX_get(ctx);
  91         if (rem == NULL) rem = BN_CTX_get(ctx);
  92         if (D == NULL || dv == NULL || rem == NULL)
  93                 goto end;
  94
  95         nd=BN_num_bits(d);
  96         nm=BN_num_bits(m);
  97         if (BN_copy(D,d) == NULL) goto end;
  98         if (BN_copy(rem,m) == NULL) goto end;
  99
 100         /* The next 2 are needed so we can do a dv->d[0]|=1 later
 101          * since BN_lshift1 will only work once there is a value :-) */
 102         BN_zero(dv);
 103         bn_wexpand(dv,1);
 104         dv->top=1;
 105
 106         if (!BN_lshift(D,D,nm-nd)) goto end;
 107         for (i=nm-nd; i>=0; i--)
 108                 {
 109                 if (!BN_lshift1(dv,dv)) goto end;
 110                 if (BN_ucmp(rem,D) >= 0)
 111                         {
 112                         dv->d[0]|=1;
 113                         if (!BN_usub(rem,rem,D)) goto end;
 114                         }
 115 /* CAN IMPROVE (and have now :=) */
 116                 if (!BN_rshift1(D,D)) goto end;
 117                 }
 118         rem->neg=BN_is_zero(rem)?0:m->neg;
 119         dv->neg=m->neg^d->neg;
 120         ret = 1;
 121  end:
 122         BN_CTX_end(ctx);
 123         return(ret);
 124         }
 125
 126 #else
 127
 128 #if !defined(NO_ASM) && !defined(NO_INLINE_ASM) && !defined(PEDANTIC) && !defined(BN_DIV3W)
 129 # if defined(__GNUC__) && __GNUC__>=2
 130 #  if defined(__i386)
 131    /*
 132     * There were two reasons for implementing this template:
 133     * - GNU C generates a call to a function (__udivdi3 to be exact)
 134     *   in reply to ((((BN_ULLONG)n0)<<BN_BITS2)|n1)/d0 (I fail to
 135     *   understand why...);
 136     * - divl doesn't only calculate quotient, but also leaves
 137     *   remainder in %edx which we can definitely use here:-)
 138     *
 139     *                                   <appro@fy.chalmers.se>
 140     */
 141 #  define bn_div_words(n0,n1,d0)                \
 142         ({  asm volatile (                      \
 143                 "divl   %4"                     \
 144                 : "=a"(q), "=d"(rem)            \
 145                 : "a"(n1), "d"(n0), "g"(d0)     \
 146                 : "cc");                        \
 147             q;                                  \
 148         })
 149 #  define REMAINDER_IS_ALREADY_CALCULATED
 150 #  endif /* __<cpu> */
 151 # endif /* __GNUC__ */
 152 #endif /* NO_ASM */
 153
 154 int BN_div(BIGNUM *dv, BIGNUM *rm, const BIGNUM *num, const BIGNUM *divisor,
 155            BN_CTX *ctx)
 156         {
 157         int norm_shift,i,j,loop;
 158         BIGNUM *tmp,wnum,*snum,*sdiv,*res;
 159         BN_ULONG *resp,*wnump;
 160         BN_ULONG d0,d1;
 161         int num_n,div_n;
 162
 163         bn_check_top(num);
 164         bn_check_top(divisor);
 165
 166         if (BN_is_zero(divisor))
 167                 {
 168                 return(0);
 169                 }
 170
 171         if (BN_ucmp(num,divisor) < 0)
 172                 {
 173                 if (rm != NULL)
 174                         { if (BN_copy(rm,num) == NULL) return(0); }
 175                 if (dv != NULL) BN_zero(dv);
 176                 return(1);
 177                 }
 178
 179         BN_CTX_start(ctx);
 180         tmp=BN_CTX_get(ctx);
 181         tmp->neg=0;
 182         snum=BN_CTX_get(ctx);
 183         sdiv=BN_CTX_get(ctx);
 184         if (dv == NULL)
 185                 res=BN_CTX_get(ctx);
 186         else    res=dv;
 187         if (res == NULL) goto err;
 188
 189         /* First we normalise the numbers */
 190         norm_shift=BN_BITS2-((BN_num_bits(divisor))%BN_BITS2);
 191         BN_lshift(sdiv,divisor,norm_shift);
 192         sdiv->neg=0;
 193         norm_shift+=BN_BITS2;
 194         BN_lshift(snum,num,norm_shift);
 195         snum->neg=0;
 196         div_n=sdiv->top;
 197         num_n=snum->top;
 198         loop=num_n-div_n;
 199
 200         /* Lets setup a 'window' into snum
 201          * This is the part that corresponds to the current
 202          * 'area' being divided */
 203         BN_init(&wnum);
 204         wnum.d=  &(snum->d[loop]);
 205         wnum.top= div_n;
 206         wnum.dmax= snum->dmax+1; /* a bit of a lie */
 207
 208         /* Get the top 2 words of sdiv */
 209         /* i=sdiv->top; */
 210         d0=sdiv->d[div_n-1];
 211         d1=(div_n == 1)?0:sdiv->d[div_n-2];
 212
 213         /* pointer to the 'top' of snum */
 214         wnump= &(snum->d[num_n-1]);
 215
 216         /* Setup to 'res' */
 217         res->neg= (num->neg^divisor->neg);
 218         if (!bn_wexpand(res,(loop+1))) goto err;
 219         res->top=loop;
 220         resp= &(res->d[loop-1]);
 221
 222         /* space for temp */
 223         if (!bn_wexpand(tmp,(div_n+1))) goto err;
 224
 225         if (BN_ucmp(&wnum,sdiv) >= 0)
 226                 {
 227                 if (!BN_usub(&wnum,&wnum,sdiv)) goto err;
 228                 *resp=1;
 229                 res->d[res->top-1]=1;
 230                 }
 231         else
 232                 res->top--;
 233         resp--;
 234
 235         for (i=0; i<loop-1; i++)
 236                 {
 237                 BN_ULONG q,l0;
 238 #ifdef BN_DIV3W
 239                 q=bn_div_3_words(wnump,d1,d0);
 240 #else
 241                 BN_ULONG n0,n1,rem=0;
 242
 243                 n0=wnump[0];
 244                 n1=wnump[-1];
 245                 if (n0 == d0)
 246                         q=BN_MASK2;
 247                 else                    /* n0 < d0 */
 248                         {
 249 #ifdef BN_LLONG
 250                         BN_ULLONG t2;
 251
 252 #if defined(BN_LLONG) && defined(BN_DIV2W) && !defined(bn_div_words)
 253                         q=(BN_ULONG)(((((BN_ULLONG)n0)<<BN_BITS2)|n1)/d0);
 254 #else
 255                         q=bn_div_words(n0,n1,d0);
 256 #endif
 257
 258 #ifndef REMAINDER_IS_ALREADY_CALCULATED
 259                         /*
 260                          * rem doesn't have to be BN_ULLONG. The least we
 261                          * know it's less that d0, isn't it?
 262                          */
 263                         rem=(n1-q*d0)&BN_MASK2;
 264 #endif
 265                         t2=(BN_ULLONG)d1*q;
 266
 267                         for (;;)
 268                                 {
 269                                 if (t2 <= ((((BN_ULLONG)rem)<<BN_BITS2)|wnump[-2]))
 270                                         break;
 271                                 q--;
 272                                 rem += d0;
 273                                 if (rem < d0) break; /* don't let rem overflow */
 274                                 t2 -= d1;
 275                                 }
 276 #else /* !BN_LLONG */
 277                         BN_ULONG t2l,t2h,ql,qh;
 278
 279                         q=bn_div_words(n0,n1,d0);
 280 #ifndef REMAINDER_IS_ALREADY_CALCULATED
 281                         rem=(n1-q*d0)&BN_MASK2;
 282 #endif
 283
 284 #ifdef BN_UMULT_HIGH
 285                         t2l = d1 * q;
 286                         t2h = BN_UMULT_HIGH(d1,q);
 287 #else
 288                         t2l=LBITS(d1); t2h=HBITS(d1);
 289                         ql =LBITS(q);  qh =HBITS(q);
 290                         mul64(t2l,t2h,ql,qh); /* t2=(BN_ULLONG)d1*q; */
 291 #endif
 292
 293                         for (;;)
 294                                 {
 295                                 if ((t2h < rem) ||
 296                                         ((t2h == rem) && (t2l <= wnump[-2])))
 297                                         break;
 298                                 q--;
 299                                 rem += d0;
 300                                 if (rem < d0) break; /* don't let rem overflow */
 301                                 if (t2l < d1) t2h--; t2l -= d1;
 302                                 }
 303 #endif /* !BN_LLONG */
 304                         }
 305 #endif /* !BN_DIV3W */
 306
 307                 l0=bn_mul_words(tmp->d,sdiv->d,div_n,q);
 308                 wnum.d--; wnum.top++;
 309                 tmp->d[div_n]=l0;
 310                 for (j=div_n+1; j>0; j--)
 311                         if (tmp->d[j-1]) break;
 312                 tmp->top=j;
 313
 314                 j=wnum.top;
 315                 BN_sub(&wnum,&wnum,tmp);
 316
 317                 snum->top=snum->top+wnum.top-j;
 318
 319                 if (wnum.neg)
 320                         {
 321                         q--;
 322                         j=wnum.top;
 323                         BN_add(&wnum,&wnum,sdiv);
 324                         snum->top+=wnum.top-j;
 325                         }
 326                 *(resp--)=q;
 327                 wnump--;
 328                 }
 329         if (rm != NULL)
 330                 {
 331                 BN_rshift(rm,snum,norm_shift);
 332                 rm->neg=num->neg;
 333                 }
 334         BN_CTX_end(ctx);
 335         return(1);
 336 err:
 337         BN_CTX_end(ctx);
 338         return(0);
 339         }
 340
 341 #endif
 342
 343 /* rem != m */
 344 int BN_mod(BIGNUM *rem, const BIGNUM *m, const BIGNUM *d, BN_CTX *ctx)
 345         {
 346 #if 0 /* The old slow way */
 347         int i,nm,nd;
 348         BIGNUM *dv;
 349
 350         if (BN_ucmp(m,d) < 0)
 351                 return((BN_copy(rem,m) == NULL)?0:1);
 352
 353         BN_CTX_start(ctx);
 354         dv=BN_CTX_get(ctx);
 355
 356         if (!BN_copy(rem,m)) goto err;
 357
 358         nm=BN_num_bits(rem);
 359         nd=BN_num_bits(d);
 360         if (!BN_lshift(dv,d,nm-nd)) goto err;
 361         for (i=nm-nd; i>=0; i--)
 362                 {
 363                 if (BN_cmp(rem,dv) >= 0)
 364                         {
 365                         if (!BN_sub(rem,rem,dv)) goto err;
 366                         }
 367                 if (!BN_rshift1(dv,dv)) goto err;
 368                 }
 369         BN_CTX_end(ctx);
 370         return(1);
 371  err:
 372         BN_CTX_end(ctx);
 373         return(0);
 374 #else
 375         return(BN_div(NULL,rem,m,d,ctx));
 376 #endif
 377         }
 378