bn_div.c revision 98d58bb80c64b02a33662f0ea80351d4a1535267
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 <openssl/bn.h> 61#include "cryptlib.h" 62#include "bn_lcl.h" 63 64 65/* The old slow way */ 66#if 0 67int BN_div(BIGNUM *dv, BIGNUM *rem, const BIGNUM *m, const BIGNUM *d, 68 BN_CTX *ctx) 69 { 70 int i,nm,nd; 71 int ret = 0; 72 BIGNUM *D; 73 74 bn_check_top(m); 75 bn_check_top(d); 76 if (BN_is_zero(d)) 77 { 78 BNerr(BN_F_BN_DIV,BN_R_DIV_BY_ZERO); 79 return(0); 80 } 81 82 if (BN_ucmp(m,d) < 0) 83 { 84 if (rem != NULL) 85 { if (BN_copy(rem,m) == NULL) return(0); } 86 if (dv != NULL) BN_zero(dv); 87 return(1); 88 } 89 90 BN_CTX_start(ctx); 91 D = BN_CTX_get(ctx); 92 if (dv == NULL) dv = BN_CTX_get(ctx); 93 if (rem == NULL) rem = BN_CTX_get(ctx); 94 if (D == NULL || dv == NULL || rem == NULL) 95 goto end; 96 97 nd=BN_num_bits(d); 98 nm=BN_num_bits(m); 99 if (BN_copy(D,d) == NULL) goto end; 100 if (BN_copy(rem,m) == NULL) goto end; 101 102 /* The next 2 are needed so we can do a dv->d[0]|=1 later 103 * since BN_lshift1 will only work once there is a value :-) */ 104 BN_zero(dv); 105 if(bn_wexpand(dv,1) == NULL) goto end; 106 dv->top=1; 107 108 if (!BN_lshift(D,D,nm-nd)) goto end; 109 for (i=nm-nd; i>=0; i--) 110 { 111 if (!BN_lshift1(dv,dv)) goto end; 112 if (BN_ucmp(rem,D) >= 0) 113 { 114 dv->d[0]|=1; 115 if (!BN_usub(rem,rem,D)) goto end; 116 } 117/* CAN IMPROVE (and have now :=) */ 118 if (!BN_rshift1(D,D)) goto end; 119 } 120 rem->neg=BN_is_zero(rem)?0:m->neg; 121 dv->neg=m->neg^d->neg; 122 ret = 1; 123 end: 124 BN_CTX_end(ctx); 125 return(ret); 126 } 127 128#else 129 130#if !defined(OPENSSL_NO_ASM) && !defined(OPENSSL_NO_INLINE_ASM) \ 131 && !defined(PEDANTIC) && !defined(BN_DIV3W) 132# if defined(__GNUC__) && __GNUC__>=2 133# if defined(__i386) || defined (__i386__) 134 /* 135 * There were two reasons for implementing this template: 136 * - GNU C generates a call to a function (__udivdi3 to be exact) 137 * in reply to ((((BN_ULLONG)n0)<<BN_BITS2)|n1)/d0 (I fail to 138 * understand why...); 139 * - divl doesn't only calculate quotient, but also leaves 140 * remainder in %edx which we can definitely use here:-) 141 * 142 * <appro@fy.chalmers.se> 143 */ 144# define bn_div_words(n0,n1,d0) \ 145 ({ asm volatile ( \ 146 "divl %4" \ 147 : "=a"(q), "=d"(rem) \ 148 : "a"(n1), "d"(n0), "g"(d0) \ 149 : "cc"); \ 150 q; \ 151 }) 152# define REMAINDER_IS_ALREADY_CALCULATED 153# elif defined(__x86_64) && defined(SIXTY_FOUR_BIT_LONG) 154 /* 155 * Same story here, but it's 128-bit by 64-bit division. Wow! 156 * <appro@fy.chalmers.se> 157 */ 158# define bn_div_words(n0,n1,d0) \ 159 ({ asm volatile ( \ 160 "divq %4" \ 161 : "=a"(q), "=d"(rem) \ 162 : "a"(n1), "d"(n0), "g"(d0) \ 163 : "cc"); \ 164 q; \ 165 }) 166# define REMAINDER_IS_ALREADY_CALCULATED 167# endif /* __<cpu> */ 168# endif /* __GNUC__ */ 169#endif /* OPENSSL_NO_ASM */ 170 171 172/* BN_div[_no_branch] computes dv := num / divisor, rounding towards 173 * zero, and sets up rm such that dv*divisor + rm = num holds. 174 * Thus: 175 * dv->neg == num->neg ^ divisor->neg (unless the result is zero) 176 * rm->neg == num->neg (unless the remainder is zero) 177 * If 'dv' or 'rm' is NULL, the respective value is not returned. 178 */ 179static int BN_div_no_branch(BIGNUM *dv, BIGNUM *rm, const BIGNUM *num, 180 const BIGNUM *divisor, BN_CTX *ctx); 181int BN_div(BIGNUM *dv, BIGNUM *rm, const BIGNUM *num, const BIGNUM *divisor, 182 BN_CTX *ctx) 183 { 184 int norm_shift,i,loop; 185 BIGNUM *tmp,wnum,*snum,*sdiv,*res; 186 BN_ULONG *resp,*wnump; 187 BN_ULONG d0,d1; 188 int num_n,div_n; 189 190 /* Invalid zero-padding would have particularly bad consequences 191 * in the case of 'num', so don't just rely on bn_check_top() for this one 192 * (bn_check_top() works only for BN_DEBUG builds) */ 193 if (num->top > 0 && num->d[num->top - 1] == 0) 194 { 195 BNerr(BN_F_BN_DIV,BN_R_NOT_INITIALIZED); 196 return 0; 197 } 198 199 bn_check_top(num); 200 201 if ((BN_get_flags(num, BN_FLG_CONSTTIME) != 0) || (BN_get_flags(divisor, BN_FLG_CONSTTIME) != 0)) 202 { 203 return BN_div_no_branch(dv, rm, num, divisor, ctx); 204 } 205 206 bn_check_top(dv); 207 bn_check_top(rm); 208 /* bn_check_top(num); */ /* 'num' has been checked already */ 209 bn_check_top(divisor); 210 211 if (BN_is_zero(divisor)) 212 { 213 BNerr(BN_F_BN_DIV,BN_R_DIV_BY_ZERO); 214 return(0); 215 } 216 217 if (BN_ucmp(num,divisor) < 0) 218 { 219 if (rm != NULL) 220 { if (BN_copy(rm,num) == NULL) return(0); } 221 if (dv != NULL) BN_zero(dv); 222 return(1); 223 } 224 225 BN_CTX_start(ctx); 226 tmp=BN_CTX_get(ctx); 227 snum=BN_CTX_get(ctx); 228 sdiv=BN_CTX_get(ctx); 229 if (dv == NULL) 230 res=BN_CTX_get(ctx); 231 else res=dv; 232 if (sdiv == NULL || res == NULL || tmp == NULL || snum == NULL) 233 goto err; 234 235 /* First we normalise the numbers */ 236 norm_shift=BN_BITS2-((BN_num_bits(divisor))%BN_BITS2); 237 if (!(BN_lshift(sdiv,divisor,norm_shift))) goto err; 238 sdiv->neg=0; 239 norm_shift+=BN_BITS2; 240 if (!(BN_lshift(snum,num,norm_shift))) goto err; 241 snum->neg=0; 242 div_n=sdiv->top; 243 num_n=snum->top; 244 loop=num_n-div_n; 245 /* Lets setup a 'window' into snum 246 * This is the part that corresponds to the current 247 * 'area' being divided */ 248 wnum.neg = 0; 249 wnum.d = &(snum->d[loop]); 250 wnum.top = div_n; 251 /* only needed when BN_ucmp messes up the values between top and max */ 252 wnum.dmax = snum->dmax - loop; /* so we don't step out of bounds */ 253 254 /* Get the top 2 words of sdiv */ 255 /* div_n=sdiv->top; */ 256 d0=sdiv->d[div_n-1]; 257 d1=(div_n == 1)?0:sdiv->d[div_n-2]; 258 259 /* pointer to the 'top' of snum */ 260 wnump= &(snum->d[num_n-1]); 261 262 /* Setup to 'res' */ 263 res->neg= (num->neg^divisor->neg); 264 if (!bn_wexpand(res,(loop+1))) goto err; 265 res->top=loop; 266 resp= &(res->d[loop-1]); 267 268 /* space for temp */ 269 if (!bn_wexpand(tmp,(div_n+1))) goto err; 270 271 if (BN_ucmp(&wnum,sdiv) >= 0) 272 { 273 /* If BN_DEBUG_RAND is defined BN_ucmp changes (via 274 * bn_pollute) the const bignum arguments => 275 * clean the values between top and max again */ 276 bn_clear_top2max(&wnum); 277 bn_sub_words(wnum.d, wnum.d, sdiv->d, div_n); 278 *resp=1; 279 } 280 else 281 res->top--; 282 /* if res->top == 0 then clear the neg value otherwise decrease 283 * the resp pointer */ 284 if (res->top == 0) 285 res->neg = 0; 286 else 287 resp--; 288 289 for (i=0; i<loop-1; i++, wnump--, resp--) 290 { 291 BN_ULONG q,l0; 292 /* the first part of the loop uses the top two words of 293 * snum and sdiv to calculate a BN_ULONG q such that 294 * | wnum - sdiv * q | < sdiv */ 295#if defined(BN_DIV3W) && !defined(OPENSSL_NO_ASM) 296 BN_ULONG bn_div_3_words(BN_ULONG*,BN_ULONG,BN_ULONG); 297 q=bn_div_3_words(wnump,d1,d0); 298#else 299 BN_ULONG n0,n1,rem=0; 300 301 n0=wnump[0]; 302 n1=wnump[-1]; 303 if (n0 == d0) 304 q=BN_MASK2; 305 else /* n0 < d0 */ 306 { 307#ifdef BN_LLONG 308 BN_ULLONG t2; 309 310#if defined(BN_LLONG) && defined(BN_DIV2W) && !defined(bn_div_words) 311 q=(BN_ULONG)(((((BN_ULLONG)n0)<<BN_BITS2)|n1)/d0); 312#else 313 q=bn_div_words(n0,n1,d0); 314#ifdef BN_DEBUG_LEVITTE 315 fprintf(stderr,"DEBUG: bn_div_words(0x%08X,0x%08X,0x%08\ 316X) -> 0x%08X\n", 317 n0, n1, d0, q); 318#endif 319#endif 320 321#ifndef REMAINDER_IS_ALREADY_CALCULATED 322 /* 323 * rem doesn't have to be BN_ULLONG. The least we 324 * know it's less that d0, isn't it? 325 */ 326 rem=(n1-q*d0)&BN_MASK2; 327#endif 328 t2=(BN_ULLONG)d1*q; 329 330 for (;;) 331 { 332 if (t2 <= ((((BN_ULLONG)rem)<<BN_BITS2)|wnump[-2])) 333 break; 334 q--; 335 rem += d0; 336 if (rem < d0) break; /* don't let rem overflow */ 337 t2 -= d1; 338 } 339#else /* !BN_LLONG */ 340 BN_ULONG t2l,t2h,ql,qh; 341 342 q=bn_div_words(n0,n1,d0); 343#ifdef BN_DEBUG_LEVITTE 344 fprintf(stderr,"DEBUG: bn_div_words(0x%08X,0x%08X,0x%08\ 345X) -> 0x%08X\n", 346 n0, n1, d0, q); 347#endif 348#ifndef REMAINDER_IS_ALREADY_CALCULATED 349 rem=(n1-q*d0)&BN_MASK2; 350#endif 351 352#if defined(BN_UMULT_LOHI) 353 BN_UMULT_LOHI(t2l,t2h,d1,q); 354#elif defined(BN_UMULT_HIGH) 355 t2l = d1 * q; 356 t2h = BN_UMULT_HIGH(d1,q); 357#else 358 t2l=LBITS(d1); t2h=HBITS(d1); 359 ql =LBITS(q); qh =HBITS(q); 360 mul64(t2l,t2h,ql,qh); /* t2=(BN_ULLONG)d1*q; */ 361#endif 362 363 for (;;) 364 { 365 if ((t2h < rem) || 366 ((t2h == rem) && (t2l <= wnump[-2]))) 367 break; 368 q--; 369 rem += d0; 370 if (rem < d0) break; /* don't let rem overflow */ 371 if (t2l < d1) t2h--; t2l -= d1; 372 } 373#endif /* !BN_LLONG */ 374 } 375#endif /* !BN_DIV3W */ 376 377 l0=bn_mul_words(tmp->d,sdiv->d,div_n,q); 378 tmp->d[div_n]=l0; 379 wnum.d--; 380 /* ingore top values of the bignums just sub the two 381 * BN_ULONG arrays with bn_sub_words */ 382 if (bn_sub_words(wnum.d, wnum.d, tmp->d, div_n+1)) 383 { 384 /* Note: As we have considered only the leading 385 * two BN_ULONGs in the calculation of q, sdiv * q 386 * might be greater than wnum (but then (q-1) * sdiv 387 * is less or equal than wnum) 388 */ 389 q--; 390 if (bn_add_words(wnum.d, wnum.d, sdiv->d, div_n)) 391 /* we can't have an overflow here (assuming 392 * that q != 0, but if q == 0 then tmp is 393 * zero anyway) */ 394 (*wnump)++; 395 } 396 /* store part of the result */ 397 *resp = q; 398 } 399 bn_correct_top(snum); 400 if (rm != NULL) 401 { 402 /* Keep a copy of the neg flag in num because if rm==num 403 * BN_rshift() will overwrite it. 404 */ 405 int neg = num->neg; 406 BN_rshift(rm,snum,norm_shift); 407 if (!BN_is_zero(rm)) 408 rm->neg = neg; 409 bn_check_top(rm); 410 } 411 BN_CTX_end(ctx); 412 return(1); 413err: 414 bn_check_top(rm); 415 BN_CTX_end(ctx); 416 return(0); 417 } 418 419 420/* BN_div_no_branch is a special version of BN_div. It does not contain 421 * branches that may leak sensitive information. 422 */ 423static int BN_div_no_branch(BIGNUM *dv, BIGNUM *rm, const BIGNUM *num, 424 const BIGNUM *divisor, BN_CTX *ctx) 425 { 426 int norm_shift,i,loop; 427 BIGNUM *tmp,wnum,*snum,*sdiv,*res; 428 BN_ULONG *resp,*wnump; 429 BN_ULONG d0,d1; 430 int num_n,div_n; 431 432 bn_check_top(dv); 433 bn_check_top(rm); 434 /* bn_check_top(num); */ /* 'num' has been checked in BN_div() */ 435 bn_check_top(divisor); 436 437 if (BN_is_zero(divisor)) 438 { 439 BNerr(BN_F_BN_DIV_NO_BRANCH,BN_R_DIV_BY_ZERO); 440 return(0); 441 } 442 443 BN_CTX_start(ctx); 444 tmp=BN_CTX_get(ctx); 445 snum=BN_CTX_get(ctx); 446 sdiv=BN_CTX_get(ctx); 447 if (dv == NULL) 448 res=BN_CTX_get(ctx); 449 else res=dv; 450 if (sdiv == NULL || res == NULL) goto err; 451 452 /* First we normalise the numbers */ 453 norm_shift=BN_BITS2-((BN_num_bits(divisor))%BN_BITS2); 454 if (!(BN_lshift(sdiv,divisor,norm_shift))) goto err; 455 sdiv->neg=0; 456 norm_shift+=BN_BITS2; 457 if (!(BN_lshift(snum,num,norm_shift))) goto err; 458 snum->neg=0; 459 460 /* Since we don't know whether snum is larger than sdiv, 461 * we pad snum with enough zeroes without changing its 462 * value. 463 */ 464 if (snum->top <= sdiv->top+1) 465 { 466 if (bn_wexpand(snum, sdiv->top + 2) == NULL) goto err; 467 for (i = snum->top; i < sdiv->top + 2; i++) snum->d[i] = 0; 468 snum->top = sdiv->top + 2; 469 } 470 else 471 { 472 if (bn_wexpand(snum, snum->top + 1) == NULL) goto err; 473 snum->d[snum->top] = 0; 474 snum->top ++; 475 } 476 477 div_n=sdiv->top; 478 num_n=snum->top; 479 loop=num_n-div_n; 480 /* Lets setup a 'window' into snum 481 * This is the part that corresponds to the current 482 * 'area' being divided */ 483 wnum.neg = 0; 484 wnum.d = &(snum->d[loop]); 485 wnum.top = div_n; 486 /* only needed when BN_ucmp messes up the values between top and max */ 487 wnum.dmax = snum->dmax - loop; /* so we don't step out of bounds */ 488 489 /* Get the top 2 words of sdiv */ 490 /* div_n=sdiv->top; */ 491 d0=sdiv->d[div_n-1]; 492 d1=(div_n == 1)?0:sdiv->d[div_n-2]; 493 494 /* pointer to the 'top' of snum */ 495 wnump= &(snum->d[num_n-1]); 496 497 /* Setup to 'res' */ 498 res->neg= (num->neg^divisor->neg); 499 if (!bn_wexpand(res,(loop+1))) goto err; 500 res->top=loop-1; 501 resp= &(res->d[loop-1]); 502 503 /* space for temp */ 504 if (!bn_wexpand(tmp,(div_n+1))) goto err; 505 506 /* if res->top == 0 then clear the neg value otherwise decrease 507 * the resp pointer */ 508 if (res->top == 0) 509 res->neg = 0; 510 else 511 resp--; 512 513 for (i=0; i<loop-1; i++, wnump--, resp--) 514 { 515 BN_ULONG q,l0; 516 /* the first part of the loop uses the top two words of 517 * snum and sdiv to calculate a BN_ULONG q such that 518 * | wnum - sdiv * q | < sdiv */ 519#if defined(BN_DIV3W) && !defined(OPENSSL_NO_ASM) 520 BN_ULONG bn_div_3_words(BN_ULONG*,BN_ULONG,BN_ULONG); 521 q=bn_div_3_words(wnump,d1,d0); 522#else 523 BN_ULONG n0,n1,rem=0; 524 525 n0=wnump[0]; 526 n1=wnump[-1]; 527 if (n0 == d0) 528 q=BN_MASK2; 529 else /* n0 < d0 */ 530 { 531#ifdef BN_LLONG 532 BN_ULLONG t2; 533 534#if defined(BN_LLONG) && defined(BN_DIV2W) && !defined(bn_div_words) 535 q=(BN_ULONG)(((((BN_ULLONG)n0)<<BN_BITS2)|n1)/d0); 536#else 537 q=bn_div_words(n0,n1,d0); 538#ifdef BN_DEBUG_LEVITTE 539 fprintf(stderr,"DEBUG: bn_div_words(0x%08X,0x%08X,0x%08\ 540X) -> 0x%08X\n", 541 n0, n1, d0, q); 542#endif 543#endif 544 545#ifndef REMAINDER_IS_ALREADY_CALCULATED 546 /* 547 * rem doesn't have to be BN_ULLONG. The least we 548 * know it's less that d0, isn't it? 549 */ 550 rem=(n1-q*d0)&BN_MASK2; 551#endif 552 t2=(BN_ULLONG)d1*q; 553 554 for (;;) 555 { 556 if (t2 <= ((((BN_ULLONG)rem)<<BN_BITS2)|wnump[-2])) 557 break; 558 q--; 559 rem += d0; 560 if (rem < d0) break; /* don't let rem overflow */ 561 t2 -= d1; 562 } 563#else /* !BN_LLONG */ 564 BN_ULONG t2l,t2h,ql,qh; 565 566 q=bn_div_words(n0,n1,d0); 567#ifdef BN_DEBUG_LEVITTE 568 fprintf(stderr,"DEBUG: bn_div_words(0x%08X,0x%08X,0x%08\ 569X) -> 0x%08X\n", 570 n0, n1, d0, q); 571#endif 572#ifndef REMAINDER_IS_ALREADY_CALCULATED 573 rem=(n1-q*d0)&BN_MASK2; 574#endif 575 576#if defined(BN_UMULT_LOHI) 577 BN_UMULT_LOHI(t2l,t2h,d1,q); 578#elif defined(BN_UMULT_HIGH) 579 t2l = d1 * q; 580 t2h = BN_UMULT_HIGH(d1,q); 581#else 582 t2l=LBITS(d1); t2h=HBITS(d1); 583 ql =LBITS(q); qh =HBITS(q); 584 mul64(t2l,t2h,ql,qh); /* t2=(BN_ULLONG)d1*q; */ 585#endif 586 587 for (;;) 588 { 589 if ((t2h < rem) || 590 ((t2h == rem) && (t2l <= wnump[-2]))) 591 break; 592 q--; 593 rem += d0; 594 if (rem < d0) break; /* don't let rem overflow */ 595 if (t2l < d1) t2h--; t2l -= d1; 596 } 597#endif /* !BN_LLONG */ 598 } 599#endif /* !BN_DIV3W */ 600 601 l0=bn_mul_words(tmp->d,sdiv->d,div_n,q); 602 tmp->d[div_n]=l0; 603 wnum.d--; 604 /* ingore top values of the bignums just sub the two 605 * BN_ULONG arrays with bn_sub_words */ 606 if (bn_sub_words(wnum.d, wnum.d, tmp->d, div_n+1)) 607 { 608 /* Note: As we have considered only the leading 609 * two BN_ULONGs in the calculation of q, sdiv * q 610 * might be greater than wnum (but then (q-1) * sdiv 611 * is less or equal than wnum) 612 */ 613 q--; 614 if (bn_add_words(wnum.d, wnum.d, sdiv->d, div_n)) 615 /* we can't have an overflow here (assuming 616 * that q != 0, but if q == 0 then tmp is 617 * zero anyway) */ 618 (*wnump)++; 619 } 620 /* store part of the result */ 621 *resp = q; 622 } 623 bn_correct_top(snum); 624 if (rm != NULL) 625 { 626 /* Keep a copy of the neg flag in num because if rm==num 627 * BN_rshift() will overwrite it. 628 */ 629 int neg = num->neg; 630 BN_rshift(rm,snum,norm_shift); 631 if (!BN_is_zero(rm)) 632 rm->neg = neg; 633 bn_check_top(rm); 634 } 635 bn_correct_top(res); 636 BN_CTX_end(ctx); 637 return(1); 638err: 639 bn_check_top(rm); 640 BN_CTX_end(ctx); 641 return(0); 642 } 643 644#endif 645