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 <openssl/local/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; 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 { 359 BN_ULONG ql, qh; 360 t2l=LBITS(d1); t2h=HBITS(d1); 361 ql =LBITS(q); qh =HBITS(q); 362 mul64(t2l,t2h,ql,qh); /* t2=(BN_ULLONG)d1*q; */ 363 } 364#endif 365 366 for (;;) 367 { 368 if ((t2h < rem) || 369 ((t2h == rem) && (t2l <= wnump[-2]))) 370 break; 371 q--; 372 rem += d0; 373 if (rem < d0) break; /* don't let rem overflow */ 374 if (t2l < d1) t2h--; t2l -= d1; 375 } 376#endif /* !BN_LLONG */ 377 } 378#endif /* !BN_DIV3W */ 379 380 l0=bn_mul_words(tmp->d,sdiv->d,div_n,q); 381 tmp->d[div_n]=l0; 382 wnum.d--; 383 /* ingore top values of the bignums just sub the two 384 * BN_ULONG arrays with bn_sub_words */ 385 if (bn_sub_words(wnum.d, wnum.d, tmp->d, div_n+1)) 386 { 387 /* Note: As we have considered only the leading 388 * two BN_ULONGs in the calculation of q, sdiv * q 389 * might be greater than wnum (but then (q-1) * sdiv 390 * is less or equal than wnum) 391 */ 392 q--; 393 if (bn_add_words(wnum.d, wnum.d, sdiv->d, div_n)) 394 /* we can't have an overflow here (assuming 395 * that q != 0, but if q == 0 then tmp is 396 * zero anyway) */ 397 (*wnump)++; 398 } 399 /* store part of the result */ 400 *resp = q; 401 } 402 bn_correct_top(snum); 403 if (rm != NULL) 404 { 405 /* Keep a copy of the neg flag in num because if rm==num 406 * BN_rshift() will overwrite it. 407 */ 408 int neg = num->neg; 409 BN_rshift(rm,snum,norm_shift); 410 if (!BN_is_zero(rm)) 411 rm->neg = neg; 412 bn_check_top(rm); 413 } 414 BN_CTX_end(ctx); 415 return(1); 416err: 417 bn_check_top(rm); 418 BN_CTX_end(ctx); 419 return(0); 420 } 421 422 423/* BN_div_no_branch is a special version of BN_div. It does not contain 424 * branches that may leak sensitive information. 425 */ 426static int BN_div_no_branch(BIGNUM *dv, BIGNUM *rm, const BIGNUM *num, 427 const BIGNUM *divisor, BN_CTX *ctx) 428 { 429 int norm_shift,i,loop; 430 BIGNUM *tmp,wnum,*snum,*sdiv,*res; 431 BN_ULONG *resp,*wnump; 432 BN_ULONG d0,d1; 433 int num_n,div_n; 434 435 bn_check_top(dv); 436 bn_check_top(rm); 437 /* bn_check_top(num); */ /* 'num' has been checked in BN_div() */ 438 bn_check_top(divisor); 439 440 if (BN_is_zero(divisor)) 441 { 442 BNerr(BN_F_BN_DIV_NO_BRANCH,BN_R_DIV_BY_ZERO); 443 return(0); 444 } 445 446 BN_CTX_start(ctx); 447 tmp=BN_CTX_get(ctx); 448 snum=BN_CTX_get(ctx); 449 sdiv=BN_CTX_get(ctx); 450 if (dv == NULL) 451 res=BN_CTX_get(ctx); 452 else res=dv; 453 if (sdiv == NULL || res == NULL) goto err; 454 455 /* First we normalise the numbers */ 456 norm_shift=BN_BITS2-((BN_num_bits(divisor))%BN_BITS2); 457 if (!(BN_lshift(sdiv,divisor,norm_shift))) goto err; 458 sdiv->neg=0; 459 norm_shift+=BN_BITS2; 460 if (!(BN_lshift(snum,num,norm_shift))) goto err; 461 snum->neg=0; 462 463 /* Since we don't know whether snum is larger than sdiv, 464 * we pad snum with enough zeroes without changing its 465 * value. 466 */ 467 if (snum->top <= sdiv->top+1) 468 { 469 if (bn_wexpand(snum, sdiv->top + 2) == NULL) goto err; 470 for (i = snum->top; i < sdiv->top + 2; i++) snum->d[i] = 0; 471 snum->top = sdiv->top + 2; 472 } 473 else 474 { 475 if (bn_wexpand(snum, snum->top + 1) == NULL) goto err; 476 snum->d[snum->top] = 0; 477 snum->top ++; 478 } 479 480 div_n=sdiv->top; 481 num_n=snum->top; 482 loop=num_n-div_n; 483 /* Lets setup a 'window' into snum 484 * This is the part that corresponds to the current 485 * 'area' being divided */ 486 wnum.neg = 0; 487 wnum.d = &(snum->d[loop]); 488 wnum.top = div_n; 489 /* only needed when BN_ucmp messes up the values between top and max */ 490 wnum.dmax = snum->dmax - loop; /* so we don't step out of bounds */ 491 492 /* Get the top 2 words of sdiv */ 493 /* div_n=sdiv->top; */ 494 d0=sdiv->d[div_n-1]; 495 d1=(div_n == 1)?0:sdiv->d[div_n-2]; 496 497 /* pointer to the 'top' of snum */ 498 wnump= &(snum->d[num_n-1]); 499 500 /* Setup to 'res' */ 501 res->neg= (num->neg^divisor->neg); 502 if (!bn_wexpand(res,(loop+1))) goto err; 503 res->top=loop-1; 504 resp= &(res->d[loop-1]); 505 506 /* space for temp */ 507 if (!bn_wexpand(tmp,(div_n+1))) goto err; 508 509 /* if res->top == 0 then clear the neg value otherwise decrease 510 * the resp pointer */ 511 if (res->top == 0) 512 res->neg = 0; 513 else 514 resp--; 515 516 for (i=0; i<loop-1; i++, wnump--, resp--) 517 { 518 BN_ULONG q,l0; 519 /* the first part of the loop uses the top two words of 520 * snum and sdiv to calculate a BN_ULONG q such that 521 * | wnum - sdiv * q | < sdiv */ 522#if defined(BN_DIV3W) && !defined(OPENSSL_NO_ASM) 523 BN_ULONG bn_div_3_words(BN_ULONG*,BN_ULONG,BN_ULONG); 524 q=bn_div_3_words(wnump,d1,d0); 525#else 526 BN_ULONG n0,n1,rem=0; 527 528 n0=wnump[0]; 529 n1=wnump[-1]; 530 if (n0 == d0) 531 q=BN_MASK2; 532 else /* n0 < d0 */ 533 { 534#ifdef BN_LLONG 535 BN_ULLONG t2; 536 537#if defined(BN_LLONG) && defined(BN_DIV2W) && !defined(bn_div_words) 538 q=(BN_ULONG)(((((BN_ULLONG)n0)<<BN_BITS2)|n1)/d0); 539#else 540 q=bn_div_words(n0,n1,d0); 541#ifdef BN_DEBUG_LEVITTE 542 fprintf(stderr,"DEBUG: bn_div_words(0x%08X,0x%08X,0x%08\ 543X) -> 0x%08X\n", 544 n0, n1, d0, q); 545#endif 546#endif 547 548#ifndef REMAINDER_IS_ALREADY_CALCULATED 549 /* 550 * rem doesn't have to be BN_ULLONG. The least we 551 * know it's less that d0, isn't it? 552 */ 553 rem=(n1-q*d0)&BN_MASK2; 554#endif 555 t2=(BN_ULLONG)d1*q; 556 557 for (;;) 558 { 559 if (t2 <= ((((BN_ULLONG)rem)<<BN_BITS2)|wnump[-2])) 560 break; 561 q--; 562 rem += d0; 563 if (rem < d0) break; /* don't let rem overflow */ 564 t2 -= d1; 565 } 566#else /* !BN_LLONG */ 567 BN_ULONG t2l,t2h; 568 569 q=bn_div_words(n0,n1,d0); 570#ifdef BN_DEBUG_LEVITTE 571 fprintf(stderr,"DEBUG: bn_div_words(0x%08X,0x%08X,0x%08\ 572X) -> 0x%08X\n", 573 n0, n1, d0, q); 574#endif 575#ifndef REMAINDER_IS_ALREADY_CALCULATED 576 rem=(n1-q*d0)&BN_MASK2; 577#endif 578 579#if defined(BN_UMULT_LOHI) 580 BN_UMULT_LOHI(t2l,t2h,d1,q); 581#elif defined(BN_UMULT_HIGH) 582 t2l = d1 * q; 583 t2h = BN_UMULT_HIGH(d1,q); 584#else 585 { 586 BN_ULONG ql, qh; 587 t2l=LBITS(d1); t2h=HBITS(d1); 588 ql =LBITS(q); qh =HBITS(q); 589 mul64(t2l,t2h,ql,qh); /* t2=(BN_ULLONG)d1*q; */ 590 } 591#endif 592 593 for (;;) 594 { 595 if ((t2h < rem) || 596 ((t2h == rem) && (t2l <= wnump[-2]))) 597 break; 598 q--; 599 rem += d0; 600 if (rem < d0) break; /* don't let rem overflow */ 601 if (t2l < d1) t2h--; t2l -= d1; 602 } 603#endif /* !BN_LLONG */ 604 } 605#endif /* !BN_DIV3W */ 606 607 l0=bn_mul_words(tmp->d,sdiv->d,div_n,q); 608 tmp->d[div_n]=l0; 609 wnum.d--; 610 /* ingore top values of the bignums just sub the two 611 * BN_ULONG arrays with bn_sub_words */ 612 if (bn_sub_words(wnum.d, wnum.d, tmp->d, div_n+1)) 613 { 614 /* Note: As we have considered only the leading 615 * two BN_ULONGs in the calculation of q, sdiv * q 616 * might be greater than wnum (but then (q-1) * sdiv 617 * is less or equal than wnum) 618 */ 619 q--; 620 if (bn_add_words(wnum.d, wnum.d, sdiv->d, div_n)) 621 /* we can't have an overflow here (assuming 622 * that q != 0, but if q == 0 then tmp is 623 * zero anyway) */ 624 (*wnump)++; 625 } 626 /* store part of the result */ 627 *resp = q; 628 } 629 bn_correct_top(snum); 630 if (rm != NULL) 631 { 632 /* Keep a copy of the neg flag in num because if rm==num 633 * BN_rshift() will overwrite it. 634 */ 635 int neg = num->neg; 636 BN_rshift(rm,snum,norm_shift); 637 if (!BN_is_zero(rm)) 638 rm->neg = neg; 639 bn_check_top(rm); 640 } 641 bn_correct_top(res); 642 BN_CTX_end(ctx); 643 return(1); 644err: 645 bn_check_top(rm); 646 BN_CTX_end(ctx); 647 return(0); 648 } 649 650#endif 651