bn_div.c revision 296465
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/* The old slow way */ 65#if 0 66int 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 BNerr(BN_F_BN_DIV, BN_R_DIV_BY_ZERO); 77 return (0); 78 } 79 80 if (BN_ucmp(m, d) < 0) { 81 if (rem != NULL) { 82 if (BN_copy(rem, m) == NULL) 83 return (0); 84 } 85 if (dv != NULL) 86 BN_zero(dv); 87 return (1); 88 } 89 90 BN_CTX_start(ctx); 91 D = BN_CTX_get(ctx); 92 if (dv == NULL) 93 dv = BN_CTX_get(ctx); 94 if (rem == NULL) 95 rem = BN_CTX_get(ctx); 96 if (D == NULL || dv == NULL || rem == NULL) 97 goto end; 98 99 nd = BN_num_bits(d); 100 nm = BN_num_bits(m); 101 if (BN_copy(D, d) == NULL) 102 goto end; 103 if (BN_copy(rem, m) == NULL) 104 goto end; 105 106 /* 107 * The next 2 are needed so we can do a dv->d[0]|=1 later since 108 * BN_lshift1 will only work once there is a value :-) 109 */ 110 BN_zero(dv); 111 if (bn_wexpand(dv, 1) == NULL) 112 goto end; 113 dv->top = 1; 114 115 if (!BN_lshift(D, D, nm - nd)) 116 goto end; 117 for (i = nm - nd; i >= 0; i--) { 118 if (!BN_lshift1(dv, dv)) 119 goto end; 120 if (BN_ucmp(rem, D) >= 0) { 121 dv->d[0] |= 1; 122 if (!BN_usub(rem, rem, D)) 123 goto end; 124 } 125/* CAN IMPROVE (and have now :=) */ 126 if (!BN_rshift1(D, D)) 127 goto end; 128 } 129 rem->neg = BN_is_zero(rem) ? 0 : m->neg; 130 dv->neg = m->neg ^ d->neg; 131 ret = 1; 132 end: 133 BN_CTX_end(ctx); 134 return (ret); 135} 136 137#else 138 139# if !defined(OPENSSL_NO_ASM) && !defined(OPENSSL_NO_INLINE_ASM) \ 140 && !defined(PEDANTIC) && !defined(BN_DIV3W) 141# if defined(__GNUC__) && __GNUC__>=2 142# if defined(__i386) || defined (__i386__) 143 /*- 144 * There were two reasons for implementing this template: 145 * - GNU C generates a call to a function (__udivdi3 to be exact) 146 * in reply to ((((BN_ULLONG)n0)<<BN_BITS2)|n1)/d0 (I fail to 147 * understand why...); 148 * - divl doesn't only calculate quotient, but also leaves 149 * remainder in %edx which we can definitely use here:-) 150 * 151 * <appro@fy.chalmers.se> 152 */ 153# define bn_div_words(n0,n1,d0) \ 154 ({ asm volatile ( \ 155 "divl %4" \ 156 : "=a"(q), "=d"(rem) \ 157 : "a"(n1), "d"(n0), "g"(d0) \ 158 : "cc"); \ 159 q; \ 160 }) 161# define REMAINDER_IS_ALREADY_CALCULATED 162# elif defined(__x86_64) && defined(SIXTY_FOUR_BIT_LONG) 163 /* 164 * Same story here, but it's 128-bit by 64-bit division. Wow! 165 * <appro@fy.chalmers.se> 166 */ 167# define bn_div_words(n0,n1,d0) \ 168 ({ asm volatile ( \ 169 "divq %4" \ 170 : "=a"(q), "=d"(rem) \ 171 : "a"(n1), "d"(n0), "g"(d0) \ 172 : "cc"); \ 173 q; \ 174 }) 175# define REMAINDER_IS_ALREADY_CALCULATED 176# endif /* __<cpu> */ 177# endif /* __GNUC__ */ 178# endif /* OPENSSL_NO_ASM */ 179 180/*- 181 * BN_div[_no_branch] computes dv := num / divisor, rounding towards 182 * zero, and sets up rm such that dv*divisor + rm = num holds. 183 * Thus: 184 * dv->neg == num->neg ^ divisor->neg (unless the result is zero) 185 * rm->neg == num->neg (unless the remainder is zero) 186 * If 'dv' or 'rm' is NULL, the respective value is not returned. 187 */ 188static int BN_div_no_branch(BIGNUM *dv, BIGNUM *rm, const BIGNUM *num, 189 const BIGNUM *divisor, BN_CTX *ctx); 190int BN_div(BIGNUM *dv, BIGNUM *rm, const BIGNUM *num, const BIGNUM *divisor, 191 BN_CTX *ctx) 192{ 193 int norm_shift, i, loop; 194 BIGNUM *tmp, wnum, *snum, *sdiv, *res; 195 BN_ULONG *resp, *wnump; 196 BN_ULONG d0, d1; 197 int num_n, div_n; 198 199 /* 200 * Invalid zero-padding would have particularly bad consequences in the 201 * case of 'num', so don't just rely on bn_check_top() for this one 202 * (bn_check_top() works only for BN_DEBUG builds) 203 */ 204 if (num->top > 0 && num->d[num->top - 1] == 0) { 205 BNerr(BN_F_BN_DIV, BN_R_NOT_INITIALIZED); 206 return 0; 207 } 208 209 bn_check_top(num); 210 211 if ((BN_get_flags(num, BN_FLG_CONSTTIME) != 0) 212 || (BN_get_flags(divisor, BN_FLG_CONSTTIME) != 0)) { 213 return BN_div_no_branch(dv, rm, num, divisor, ctx); 214 } 215 216 bn_check_top(dv); 217 bn_check_top(rm); 218 /*- bn_check_top(num); *//* 219 * 'num' has been checked already 220 */ 221 bn_check_top(divisor); 222 223 if (BN_is_zero(divisor)) { 224 BNerr(BN_F_BN_DIV, BN_R_DIV_BY_ZERO); 225 return (0); 226 } 227 228 if (BN_ucmp(num, divisor) < 0) { 229 if (rm != NULL) { 230 if (BN_copy(rm, num) == NULL) 231 return (0); 232 } 233 if (dv != NULL) 234 BN_zero(dv); 235 return (1); 236 } 237 238 BN_CTX_start(ctx); 239 tmp = BN_CTX_get(ctx); 240 snum = BN_CTX_get(ctx); 241 sdiv = BN_CTX_get(ctx); 242 if (dv == NULL) 243 res = BN_CTX_get(ctx); 244 else 245 res = dv; 246 if (sdiv == NULL || res == NULL || tmp == NULL || snum == NULL) 247 goto err; 248 249 /* First we normalise the numbers */ 250 norm_shift = BN_BITS2 - ((BN_num_bits(divisor)) % BN_BITS2); 251 if (!(BN_lshift(sdiv, divisor, norm_shift))) 252 goto err; 253 sdiv->neg = 0; 254 norm_shift += BN_BITS2; 255 if (!(BN_lshift(snum, num, norm_shift))) 256 goto err; 257 snum->neg = 0; 258 div_n = sdiv->top; 259 num_n = snum->top; 260 loop = num_n - div_n; 261 /* 262 * Lets setup a 'window' into snum This is the part that corresponds to 263 * the current 'area' being divided 264 */ 265 wnum.neg = 0; 266 wnum.d = &(snum->d[loop]); 267 wnum.top = div_n; 268 /* 269 * only needed when BN_ucmp messes up the values between top and max 270 */ 271 wnum.dmax = snum->dmax - loop; /* so we don't step out of bounds */ 272 273 /* Get the top 2 words of sdiv */ 274 /* div_n=sdiv->top; */ 275 d0 = sdiv->d[div_n - 1]; 276 d1 = (div_n == 1) ? 0 : sdiv->d[div_n - 2]; 277 278 /* pointer to the 'top' of snum */ 279 wnump = &(snum->d[num_n - 1]); 280 281 /* Setup to 'res' */ 282 res->neg = (num->neg ^ divisor->neg); 283 if (!bn_wexpand(res, (loop + 1))) 284 goto err; 285 res->top = loop; 286 resp = &(res->d[loop - 1]); 287 288 /* space for temp */ 289 if (!bn_wexpand(tmp, (div_n + 1))) 290 goto err; 291 292 if (BN_ucmp(&wnum, sdiv) >= 0) { 293 /* 294 * If BN_DEBUG_RAND is defined BN_ucmp changes (via bn_pollute) the 295 * const bignum arguments => clean the values between top and max 296 * again 297 */ 298 bn_clear_top2max(&wnum); 299 bn_sub_words(wnum.d, wnum.d, sdiv->d, div_n); 300 *resp = 1; 301 } else 302 res->top--; 303 /* 304 * if res->top == 0 then clear the neg value otherwise decrease the resp 305 * pointer 306 */ 307 if (res->top == 0) 308 res->neg = 0; 309 else 310 resp--; 311 312 for (i = 0; i < loop - 1; i++, wnump--, resp--) { 313 BN_ULONG q, l0; 314 /* 315 * the first part of the loop uses the top two words of snum and sdiv 316 * to calculate a BN_ULONG q such that | wnum - sdiv * q | < sdiv 317 */ 318# if defined(BN_DIV3W) && !defined(OPENSSL_NO_ASM) 319 BN_ULONG bn_div_3_words(BN_ULONG *, BN_ULONG, BN_ULONG); 320 q = bn_div_3_words(wnump, d1, d0); 321# else 322 BN_ULONG n0, n1, rem = 0; 323 324 n0 = wnump[0]; 325 n1 = wnump[-1]; 326 if (n0 == d0) 327 q = BN_MASK2; 328 else { /* n0 < d0 */ 329 330# ifdef BN_LLONG 331 BN_ULLONG t2; 332 333# if defined(BN_LLONG) && defined(BN_DIV2W) && !defined(bn_div_words) 334 q = (BN_ULONG)(((((BN_ULLONG) n0) << BN_BITS2) | n1) / d0); 335# else 336 q = bn_div_words(n0, n1, d0); 337# ifdef BN_DEBUG_LEVITTE 338 fprintf(stderr, "DEBUG: bn_div_words(0x%08X,0x%08X,0x%08\ 339X) -> 0x%08X\n", n0, n1, d0, q); 340# endif 341# endif 342 343# ifndef REMAINDER_IS_ALREADY_CALCULATED 344 /* 345 * rem doesn't have to be BN_ULLONG. The least we 346 * know it's less that d0, isn't it? 347 */ 348 rem = (n1 - q * d0) & BN_MASK2; 349# endif 350 t2 = (BN_ULLONG) d1 *q; 351 352 for (;;) { 353 if (t2 <= ((((BN_ULLONG) rem) << BN_BITS2) | wnump[-2])) 354 break; 355 q--; 356 rem += d0; 357 if (rem < d0) 358 break; /* don't let rem overflow */ 359 t2 -= d1; 360 } 361# else /* !BN_LLONG */ 362 BN_ULONG t2l, t2h; 363# if !defined(BN_UMULT_LOHI) && !defined(BN_UMULT_HIGH) 364 BN_ULONG ql, qh; 365# endif 366 367 q = bn_div_words(n0, n1, d0); 368# ifdef BN_DEBUG_LEVITTE 369 fprintf(stderr, "DEBUG: bn_div_words(0x%08X,0x%08X,0x%08\ 370X) -> 0x%08X\n", n0, n1, d0, q); 371# endif 372# ifndef REMAINDER_IS_ALREADY_CALCULATED 373 rem = (n1 - q * d0) & BN_MASK2; 374# endif 375 376# if defined(BN_UMULT_LOHI) 377 BN_UMULT_LOHI(t2l, t2h, d1, q); 378# elif defined(BN_UMULT_HIGH) 379 t2l = d1 * q; 380 t2h = BN_UMULT_HIGH(d1, q); 381# else 382 t2l = LBITS(d1); 383 t2h = HBITS(d1); 384 ql = LBITS(q); 385 qh = HBITS(q); 386 mul64(t2l, t2h, ql, qh); /* t2=(BN_ULLONG)d1*q; */ 387# endif 388 389 for (;;) { 390 if ((t2h < rem) || ((t2h == rem) && (t2l <= wnump[-2]))) 391 break; 392 q--; 393 rem += d0; 394 if (rem < d0) 395 break; /* don't let rem overflow */ 396 if (t2l < d1) 397 t2h--; 398 t2l -= d1; 399 } 400# endif /* !BN_LLONG */ 401 } 402# endif /* !BN_DIV3W */ 403 404 l0 = bn_mul_words(tmp->d, sdiv->d, div_n, q); 405 tmp->d[div_n] = l0; 406 wnum.d--; 407 /* 408 * ingore top values of the bignums just sub the two BN_ULONG arrays 409 * with bn_sub_words 410 */ 411 if (bn_sub_words(wnum.d, wnum.d, tmp->d, div_n + 1)) { 412 /* 413 * Note: As we have considered only the leading two BN_ULONGs in 414 * the calculation of q, sdiv * q might be greater than wnum (but 415 * then (q-1) * sdiv is less or equal than wnum) 416 */ 417 q--; 418 if (bn_add_words(wnum.d, wnum.d, sdiv->d, div_n)) 419 /* 420 * we can't have an overflow here (assuming that q != 0, but 421 * if q == 0 then tmp is zero anyway) 422 */ 423 (*wnump)++; 424 } 425 /* store part of the result */ 426 *resp = q; 427 } 428 bn_correct_top(snum); 429 if (rm != NULL) { 430 /* 431 * Keep a copy of the neg flag in num because if rm==num BN_rshift() 432 * will overwrite it. 433 */ 434 int neg = num->neg; 435 BN_rshift(rm, snum, norm_shift); 436 if (!BN_is_zero(rm)) 437 rm->neg = neg; 438 bn_check_top(rm); 439 } 440 BN_CTX_end(ctx); 441 return (1); 442 err: 443 bn_check_top(rm); 444 BN_CTX_end(ctx); 445 return (0); 446} 447 448/* 449 * BN_div_no_branch is a special version of BN_div. It does not contain 450 * branches that may leak sensitive information. 451 */ 452static int BN_div_no_branch(BIGNUM *dv, BIGNUM *rm, const BIGNUM *num, 453 const BIGNUM *divisor, BN_CTX *ctx) 454{ 455 int norm_shift, i, loop; 456 BIGNUM *tmp, wnum, *snum, *sdiv, *res; 457 BN_ULONG *resp, *wnump; 458 BN_ULONG d0, d1; 459 int num_n, div_n; 460 461 bn_check_top(dv); 462 bn_check_top(rm); 463 /*- bn_check_top(num); *//* 464 * 'num' has been checked in BN_div() 465 */ 466 bn_check_top(divisor); 467 468 if (BN_is_zero(divisor)) { 469 BNerr(BN_F_BN_DIV_NO_BRANCH, BN_R_DIV_BY_ZERO); 470 return (0); 471 } 472 473 BN_CTX_start(ctx); 474 tmp = BN_CTX_get(ctx); 475 snum = BN_CTX_get(ctx); 476 sdiv = BN_CTX_get(ctx); 477 if (dv == NULL) 478 res = BN_CTX_get(ctx); 479 else 480 res = dv; 481 if (sdiv == NULL || res == NULL) 482 goto err; 483 484 /* First we normalise the numbers */ 485 norm_shift = BN_BITS2 - ((BN_num_bits(divisor)) % BN_BITS2); 486 if (!(BN_lshift(sdiv, divisor, norm_shift))) 487 goto err; 488 sdiv->neg = 0; 489 norm_shift += BN_BITS2; 490 if (!(BN_lshift(snum, num, norm_shift))) 491 goto err; 492 snum->neg = 0; 493 494 /* 495 * Since we don't know whether snum is larger than sdiv, we pad snum with 496 * enough zeroes without changing its value. 497 */ 498 if (snum->top <= sdiv->top + 1) { 499 if (bn_wexpand(snum, sdiv->top + 2) == NULL) 500 goto err; 501 for (i = snum->top; i < sdiv->top + 2; i++) 502 snum->d[i] = 0; 503 snum->top = sdiv->top + 2; 504 } else { 505 if (bn_wexpand(snum, snum->top + 1) == NULL) 506 goto err; 507 snum->d[snum->top] = 0; 508 snum->top++; 509 } 510 511 div_n = sdiv->top; 512 num_n = snum->top; 513 loop = num_n - div_n; 514 /* 515 * Lets setup a 'window' into snum This is the part that corresponds to 516 * the current 'area' being divided 517 */ 518 wnum.neg = 0; 519 wnum.d = &(snum->d[loop]); 520 wnum.top = div_n; 521 /* 522 * only needed when BN_ucmp messes up the values between top and max 523 */ 524 wnum.dmax = snum->dmax - loop; /* so we don't step out of bounds */ 525 526 /* Get the top 2 words of sdiv */ 527 /* div_n=sdiv->top; */ 528 d0 = sdiv->d[div_n - 1]; 529 d1 = (div_n == 1) ? 0 : sdiv->d[div_n - 2]; 530 531 /* pointer to the 'top' of snum */ 532 wnump = &(snum->d[num_n - 1]); 533 534 /* Setup to 'res' */ 535 res->neg = (num->neg ^ divisor->neg); 536 if (!bn_wexpand(res, (loop + 1))) 537 goto err; 538 res->top = loop - 1; 539 resp = &(res->d[loop - 1]); 540 541 /* space for temp */ 542 if (!bn_wexpand(tmp, (div_n + 1))) 543 goto err; 544 545 /* 546 * if res->top == 0 then clear the neg value otherwise decrease the resp 547 * pointer 548 */ 549 if (res->top == 0) 550 res->neg = 0; 551 else 552 resp--; 553 554 for (i = 0; i < loop - 1; i++, wnump--, resp--) { 555 BN_ULONG q, l0; 556 /* 557 * the first part of the loop uses the top two words of snum and sdiv 558 * to calculate a BN_ULONG q such that | wnum - sdiv * q | < sdiv 559 */ 560# if defined(BN_DIV3W) && !defined(OPENSSL_NO_ASM) 561 BN_ULONG bn_div_3_words(BN_ULONG *, BN_ULONG, BN_ULONG); 562 q = bn_div_3_words(wnump, d1, d0); 563# else 564 BN_ULONG n0, n1, rem = 0; 565 566 n0 = wnump[0]; 567 n1 = wnump[-1]; 568 if (n0 == d0) 569 q = BN_MASK2; 570 else { /* n0 < d0 */ 571 572# ifdef BN_LLONG 573 BN_ULLONG t2; 574 575# if defined(BN_LLONG) && defined(BN_DIV2W) && !defined(bn_div_words) 576 q = (BN_ULONG)(((((BN_ULLONG) n0) << BN_BITS2) | n1) / d0); 577# else 578 q = bn_div_words(n0, n1, d0); 579# ifdef BN_DEBUG_LEVITTE 580 fprintf(stderr, "DEBUG: bn_div_words(0x%08X,0x%08X,0x%08\ 581X) -> 0x%08X\n", n0, n1, d0, q); 582# endif 583# endif 584 585# ifndef REMAINDER_IS_ALREADY_CALCULATED 586 /* 587 * rem doesn't have to be BN_ULLONG. The least we 588 * know it's less that d0, isn't it? 589 */ 590 rem = (n1 - q * d0) & BN_MASK2; 591# endif 592 t2 = (BN_ULLONG) d1 *q; 593 594 for (;;) { 595 if (t2 <= ((((BN_ULLONG) rem) << BN_BITS2) | wnump[-2])) 596 break; 597 q--; 598 rem += d0; 599 if (rem < d0) 600 break; /* don't let rem overflow */ 601 t2 -= d1; 602 } 603# else /* !BN_LLONG */ 604 BN_ULONG t2l, t2h; 605# if !defined(BN_UMULT_LOHI) && !defined(BN_UMULT_HIGH) 606 BN_ULONG ql, qh; 607# endif 608 609 q = bn_div_words(n0, n1, d0); 610# ifdef BN_DEBUG_LEVITTE 611 fprintf(stderr, "DEBUG: bn_div_words(0x%08X,0x%08X,0x%08\ 612X) -> 0x%08X\n", n0, n1, d0, q); 613# endif 614# ifndef REMAINDER_IS_ALREADY_CALCULATED 615 rem = (n1 - q * d0) & BN_MASK2; 616# endif 617 618# if defined(BN_UMULT_LOHI) 619 BN_UMULT_LOHI(t2l, t2h, d1, q); 620# elif defined(BN_UMULT_HIGH) 621 t2l = d1 * q; 622 t2h = BN_UMULT_HIGH(d1, q); 623# else 624 t2l = LBITS(d1); 625 t2h = HBITS(d1); 626 ql = LBITS(q); 627 qh = HBITS(q); 628 mul64(t2l, t2h, ql, qh); /* t2=(BN_ULLONG)d1*q; */ 629# endif 630 631 for (;;) { 632 if ((t2h < rem) || ((t2h == rem) && (t2l <= wnump[-2]))) 633 break; 634 q--; 635 rem += d0; 636 if (rem < d0) 637 break; /* don't let rem overflow */ 638 if (t2l < d1) 639 t2h--; 640 t2l -= d1; 641 } 642# endif /* !BN_LLONG */ 643 } 644# endif /* !BN_DIV3W */ 645 646 l0 = bn_mul_words(tmp->d, sdiv->d, div_n, q); 647 tmp->d[div_n] = l0; 648 wnum.d--; 649 /* 650 * ingore top values of the bignums just sub the two BN_ULONG arrays 651 * with bn_sub_words 652 */ 653 if (bn_sub_words(wnum.d, wnum.d, tmp->d, div_n + 1)) { 654 /* 655 * Note: As we have considered only the leading two BN_ULONGs in 656 * the calculation of q, sdiv * q might be greater than wnum (but 657 * then (q-1) * sdiv is less or equal than wnum) 658 */ 659 q--; 660 if (bn_add_words(wnum.d, wnum.d, sdiv->d, div_n)) 661 /* 662 * we can't have an overflow here (assuming that q != 0, but 663 * if q == 0 then tmp is zero anyway) 664 */ 665 (*wnump)++; 666 } 667 /* store part of the result */ 668 *resp = q; 669 } 670 bn_correct_top(snum); 671 if (rm != NULL) { 672 /* 673 * Keep a copy of the neg flag in num because if rm==num BN_rshift() 674 * will overwrite it. 675 */ 676 int neg = num->neg; 677 BN_rshift(rm, snum, norm_shift); 678 if (!BN_is_zero(rm)) 679 rm->neg = neg; 680 bn_check_top(rm); 681 } 682 bn_correct_top(res); 683 BN_CTX_end(ctx); 684 return (1); 685 err: 686 bn_check_top(rm); 687 BN_CTX_end(ctx); 688 return (0); 689} 690 691#endif 692