bn_div.c revision 280297
1139825Simp/* crypto/bn/bn_div.c */ 294755Sbenno/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com) 3256901Snwhitehorn * All rights reserved. 4256901Snwhitehorn * 5256901Snwhitehorn * This package is an SSL implementation written 694755Sbenno * by Eric Young (eay@cryptsoft.com). 794755Sbenno * The implementation was written so as to conform with Netscapes SSL. 894755Sbenno * 994755Sbenno * This library is free for commercial and non-commercial use as long as 1094755Sbenno * the following conditions are aheared to. The following conditions 1194755Sbenno * apply to all code found in this distribution, be it the RC4, RSA, 1294755Sbenno * lhash, DES, etc., code; not just the SSL code. The SSL documentation 1394755Sbenno * included with this distribution is covered by the same copyright terms 1494755Sbenno * except that the holder is Tim Hudson (tjh@cryptsoft.com). 1594755Sbenno * 1694755Sbenno * Copyright remains Eric Young's, and as such any Copyright notices in 1794755Sbenno * the code are not to be removed. 18125702Sgrehan * If this package is used in a product, Eric Young should be given attribution 1994755Sbenno * as the author of the parts of the library used. 2094755Sbenno * This can be in the form of a textual message at program startup or 2194755Sbenno * in documentation (online or textual) provided with the package. 2294755Sbenno * 2394755Sbenno * Redistribution and use in source and binary forms, with or without 2494755Sbenno * modification, are permitted provided that the following conditions 2594755Sbenno * are met: 2694755Sbenno * 1. Redistributions of source code must retain the copyright 2794755Sbenno * notice, this list of conditions and the following disclaimer. 2894755Sbenno * 2. Redistributions in binary form must reproduce the above copyright 2994755Sbenno * notice, this list of conditions and the following disclaimer in the 3094755Sbenno * documentation and/or other materials provided with the distribution. 3194755Sbenno * 3. All advertising materials mentioning features or use of this software 3294755Sbenno * must display the following acknowledgement: 3394755Sbenno * "This product includes cryptographic software written by 3494755Sbenno * Eric Young (eay@cryptsoft.com)" 35227843Smarius * The word 'cryptographic' can be left out if the rouines from the library 36227843Smarius * being used are not cryptographic related :-). 37227843Smarius * 4. If you include any Windows specific code (or a derivative thereof) from 3894755Sbenno * the apps directory (application code) you must include an acknowledgement: 3994755Sbenno * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)" 4094755Sbenno * 4194755Sbenno * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND 4294755Sbenno * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 43256901Snwhitehorn * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 44256901Snwhitehorn * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 45256901Snwhitehorn * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 4694755Sbenno * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 47256901Snwhitehorn * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 48256901Snwhitehorn * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 49256901Snwhitehorn * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 50256855Snwhitehorn * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 51212239Smav * SUCH DAMAGE. 5294755Sbenno * 5394755Sbenno * The licence and distribution terms for any publically available version or 5494755Sbenno * derivative of this code cannot be changed. i.e. this code cannot simply be 5594755Sbenno * copied and put under another distribution licence 5694755Sbenno * [including the GNU Public Licence.] 5794755Sbenno */ 58261513Snwhitehorn 59256901Snwhitehorn#include <stdio.h> 60256901Snwhitehorn#include <openssl/bn.h> 61256901Snwhitehorn#include "cryptlib.h" 6294755Sbenno#include "bn_lcl.h" 6394755Sbenno 6494755Sbenno/* The old slow way */ 65261513Snwhitehorn#if 0 66256901Snwhitehornint BN_div(BIGNUM *dv, BIGNUM *rem, const BIGNUM *m, const BIGNUM *d, 67256901Snwhitehorn BN_CTX *ctx) 6894755Sbenno{ 6994755Sbenno int i, nm, nd; 70261513Snwhitehorn int ret = 0; 71261513Snwhitehorn BIGNUM *D; 72261513Snwhitehorn 73261513Snwhitehorn bn_check_top(m); 74261513Snwhitehorn bn_check_top(d); 7599652Sbenno if (BN_is_zero(d)) { 76261513Snwhitehorn BNerr(BN_F_BN_DIV, BN_R_DIV_BY_ZERO); 77261513Snwhitehorn return (0); 78261513Snwhitehorn } 79261513Snwhitehorn 80261513Snwhitehorn if (BN_ucmp(m, d) < 0) { 81261513Snwhitehorn if (rem != NULL) { 82261513Snwhitehorn if (BN_copy(rem, m) == NULL) 83261513Snwhitehorn return (0); 84261513Snwhitehorn } 85261513Snwhitehorn if (dv != NULL) 86261513Snwhitehorn BN_zero(dv); 8799652Sbenno return (1); 88261513Snwhitehorn } 89261513Snwhitehorn 90261513Snwhitehorn BN_CTX_start(ctx); 91261513Snwhitehorn D = BN_CTX_get(ctx); 92261513Snwhitehorn if (dv == NULL) 93261513Snwhitehorn dv = BN_CTX_get(ctx); 9494755Sbenno if (rem == NULL) 95261513Snwhitehorn rem = BN_CTX_get(ctx); 96261513Snwhitehorn if (D == NULL || dv == NULL || rem == NULL) 97261513Snwhitehorn goto end; 9894755Sbenno 9994755Sbenno nd = BN_num_bits(d); 10094755Sbenno nm = BN_num_bits(m); 10194755Sbenno if (BN_copy(D, d) == NULL) 10294755Sbenno goto end; 103256901Snwhitehorn if (BN_copy(rem, m) == NULL) 104261513Snwhitehorn goto end; 105261513Snwhitehorn 106256901Snwhitehorn /* 107256901Snwhitehorn * The next 2 are needed so we can do a dv->d[0]|=1 later since 108261513Snwhitehorn * BN_lshift1 will only work once there is a value :-) 109212239Smav */ 110261513Snwhitehorn BN_zero(dv); 111261513Snwhitehorn if (bn_wexpand(dv, 1) == NULL) 112261513Snwhitehorn goto end; 113256901Snwhitehorn dv->top = 1; 114256901Snwhitehorn 115261513Snwhitehorn if (!BN_lshift(D, D, nm - nd)) 116261513Snwhitehorn goto end; 117261513Snwhitehorn for (i = nm - nd; i >= 0; i--) { 118261513Snwhitehorn if (!BN_lshift1(dv, dv)) 119261513Snwhitehorn goto end; 120261513Snwhitehorn if (BN_ucmp(rem, D) >= 0) { 12194755Sbenno dv->d[0] |= 1; 122256901Snwhitehorn if (!BN_usub(rem, rem, D)) 123261513Snwhitehorn goto end; 124256855Snwhitehorn } 125256855Snwhitehorn/* CAN IMPROVE (and have now :=) */ 126256855Snwhitehorn if (!BN_rshift1(D, D)) 127256855Snwhitehorn goto end; 128256855Snwhitehorn } 129168885Sgrehan rem->neg = BN_is_zero(rem) ? 0 : m->neg; 130227843Smarius dv->neg = m->neg ^ d->neg; 13194755Sbenno ret = 1; 13294755Sbenno end: 133261513Snwhitehorn BN_CTX_end(ctx); 134261513Snwhitehorn return (ret); 135261513Snwhitehorn} 136261513Snwhitehorn 137261513Snwhitehorn#else 138261513Snwhitehorn 139269594Sian# if !defined(OPENSSL_NO_ASM) && !defined(OPENSSL_NO_INLINE_ASM) \ 140269594Sian && !defined(PEDANTIC) && !defined(BN_DIV3W) 141261513Snwhitehorn# if defined(__GNUC__) && __GNUC__>=2 14294755Sbenno# if defined(__i386) || defined (__i386__) 143261513Snwhitehorn /*- 144256901Snwhitehorn * There were two reasons for implementing this template: 145256901Snwhitehorn * - GNU C generates a call to a function (__udivdi3 to be exact) 146256901Snwhitehorn * in reply to ((((BN_ULLONG)n0)<<BN_BITS2)|n1)/d0 (I fail to 147256901Snwhitehorn * understand why...); 148256901Snwhitehorn * - divl doesn't only calculate quotient, but also leaves 149256901Snwhitehorn * remainder in %edx which we can definitely use here:-) 150256901Snwhitehorn * 151256901Snwhitehorn * <appro@fy.chalmers.se> 152256901Snwhitehorn */ 153256901Snwhitehorn# undef bn_div_words 154256901Snwhitehorn# define bn_div_words(n0,n1,d0) \ 155256901Snwhitehorn ({ asm volatile ( \ 156256901Snwhitehorn "divl %4" \ 157256901Snwhitehorn : "=a"(q), "=d"(rem) \ 158256901Snwhitehorn : "a"(n1), "d"(n0), "g"(d0) \ 159256901Snwhitehorn : "cc"); \ 160256901Snwhitehorn q; \ 161256901Snwhitehorn }) 162256901Snwhitehorn# define REMAINDER_IS_ALREADY_CALCULATED 163261513Snwhitehorn# elif defined(__x86_64) && defined(SIXTY_FOUR_BIT_LONG) 164256901Snwhitehorn /* 165256901Snwhitehorn * Same story here, but it's 128-bit by 64-bit division. Wow! 166256901Snwhitehorn * <appro@fy.chalmers.se> 167256901Snwhitehorn */ 168256901Snwhitehorn# undef bn_div_words 16994755Sbenno# define bn_div_words(n0,n1,d0) \ 170261513Snwhitehorn ({ asm volatile ( \ 171256901Snwhitehorn "divq %4" \ 172256901Snwhitehorn : "=a"(q), "=d"(rem) \ 173256901Snwhitehorn : "a"(n1), "d"(n0), "g"(d0) \ 174256901Snwhitehorn : "cc"); \ 175256901Snwhitehorn q; \ 176256901Snwhitehorn }) 177256901Snwhitehorn# define REMAINDER_IS_ALREADY_CALCULATED 178256901Snwhitehorn# endif /* __<cpu> */ 179256901Snwhitehorn# endif /* __GNUC__ */ 180256901Snwhitehorn# endif /* OPENSSL_NO_ASM */ 181256901Snwhitehorn 182261513Snwhitehorn/*- 183261513Snwhitehorn * BN_div computes dv := num / divisor, rounding towards 184261513Snwhitehorn * zero, and sets up rm such that dv*divisor + rm = num holds. 185256901Snwhitehorn * Thus: 186261513Snwhitehorn * dv->neg == num->neg ^ divisor->neg (unless the result is zero) 187261513Snwhitehorn * rm->neg == num->neg (unless the remainder is zero) 188261513Snwhitehorn * If 'dv' or 'rm' is NULL, the respective value is not returned. 189261513Snwhitehorn */ 190261513Snwhitehornint BN_div(BIGNUM *dv, BIGNUM *rm, const BIGNUM *num, const BIGNUM *divisor, 191265888Snwhitehorn BN_CTX *ctx) 192261513Snwhitehorn{ 193261513Snwhitehorn int norm_shift, i, loop; 194261513Snwhitehorn BIGNUM *tmp, wnum, *snum, *sdiv, *res; 195261513Snwhitehorn BN_ULONG *resp, *wnump; 196261513Snwhitehorn BN_ULONG d0, d1; 197261513Snwhitehorn int num_n, div_n; 198256901Snwhitehorn int no_branch = 0; 199261513Snwhitehorn 20094755Sbenno /* 201256901Snwhitehorn * Invalid zero-padding would have particularly bad consequences so don't 202261513Snwhitehorn * just rely on bn_check_top() here (bn_check_top() works only for 203261513Snwhitehorn * BN_DEBUG builds) 204178367Smarcel */ 205178367Smarcel if ((num->top > 0 && num->d[num->top - 1] == 0) || 206178367Smarcel (divisor->top > 0 && divisor->d[divisor->top - 1] == 0)) { 207261513Snwhitehorn BNerr(BN_F_BN_DIV, BN_R_NOT_INITIALIZED); 208178367Smarcel return 0; 209261513Snwhitehorn } 210261513Snwhitehorn 211256901Snwhitehorn bn_check_top(num); 212256901Snwhitehorn bn_check_top(divisor); 21394755Sbenno 21499652Sbenno if ((BN_get_flags(num, BN_FLG_CONSTTIME) != 0) 21599652Sbenno || (BN_get_flags(divisor, BN_FLG_CONSTTIME) != 0)) { 216257075Snwhitehorn no_branch = 1; 217171805Smarcel } 218261513Snwhitehorn 219261513Snwhitehorn bn_check_top(dv); 220261513Snwhitehorn bn_check_top(rm); 221261513Snwhitehorn /*- bn_check_top(num); *//* 222261513Snwhitehorn * 'num' has been checked already 223261513Snwhitehorn */ 224257075Snwhitehorn /*- bn_check_top(divisor); *//* 225257075Snwhitehorn * 'divisor' has been checked already 226257075Snwhitehorn */ 227257075Snwhitehorn 228257075Snwhitehorn if (BN_is_zero(divisor)) { 229257075Snwhitehorn BNerr(BN_F_BN_DIV, BN_R_DIV_BY_ZERO); 230257075Snwhitehorn return (0); 231257075Snwhitehorn } 232257075Snwhitehorn 233171805Smarcel if (!no_branch && BN_ucmp(num, divisor) < 0) { 234256901Snwhitehorn if (rm != NULL) { 235256901Snwhitehorn if (BN_copy(rm, num) == NULL) 236256901Snwhitehorn return (0); 237256901Snwhitehorn } 238256901Snwhitehorn if (dv != NULL) 239256901Snwhitehorn BN_zero(dv); 240256901Snwhitehorn return (1); 241124468Sgrehan } 242256901Snwhitehorn 243256969Snwhitehorn BN_CTX_start(ctx); 244256901Snwhitehorn tmp = BN_CTX_get(ctx); 245256969Snwhitehorn snum = BN_CTX_get(ctx); 24699652Sbenno sdiv = BN_CTX_get(ctx); 247256901Snwhitehorn if (dv == NULL) 248256901Snwhitehorn res = BN_CTX_get(ctx); 249256901Snwhitehorn else 250256901Snwhitehorn res = dv; 251261513Snwhitehorn if (sdiv == NULL || res == NULL || tmp == NULL || snum == NULL) 252256901Snwhitehorn goto err; 253256901Snwhitehorn 254256901Snwhitehorn /* First we normalise the numbers */ 255256901Snwhitehorn norm_shift = BN_BITS2 - ((BN_num_bits(divisor)) % BN_BITS2); 256256901Snwhitehorn if (!(BN_lshift(sdiv, divisor, norm_shift))) 257261513Snwhitehorn goto err; 258256901Snwhitehorn sdiv->neg = 0; 259256901Snwhitehorn norm_shift += BN_BITS2; 260256901Snwhitehorn if (!(BN_lshift(snum, num, norm_shift))) 26194755Sbenno goto err; 262178367Smarcel snum->neg = 0; 26394755Sbenno 26494755Sbenno if (no_branch) { 265256901Snwhitehorn /* 266261513Snwhitehorn * Since we don't know whether snum is larger than sdiv, we pad snum 26794755Sbenno * with enough zeroes without changing its value. 268256901Snwhitehorn */ 269261513Snwhitehorn if (snum->top <= sdiv->top + 1) { 27094755Sbenno if (bn_wexpand(snum, sdiv->top + 2) == NULL) 271256901Snwhitehorn goto err; 272256901Snwhitehorn for (i = snum->top; i < sdiv->top + 2; i++) 273256901Snwhitehorn snum->d[i] = 0; 27494755Sbenno snum->top = sdiv->top + 2; 275256901Snwhitehorn } else { 276256901Snwhitehorn if (bn_wexpand(snum, snum->top + 1) == NULL) 277256901Snwhitehorn goto err; 278256901Snwhitehorn snum->d[snum->top] = 0; 279124468Sgrehan snum->top++; 280256901Snwhitehorn } 28194755Sbenno } 28294755Sbenno 283256901Snwhitehorn div_n = sdiv->top; 284261513Snwhitehorn num_n = snum->top; 285124468Sgrehan loop = num_n - div_n; 286256901Snwhitehorn /* 287124468Sgrehan * Lets setup a 'window' into snum This is the part that corresponds to 288256901Snwhitehorn * the current 'area' being divided 289261513Snwhitehorn */ 290256901Snwhitehorn wnum.neg = 0; 291256901Snwhitehorn wnum.d = &(snum->d[loop]); 292256901Snwhitehorn wnum.top = div_n; 293125702Sgrehan /* 294256901Snwhitehorn * only needed when BN_ucmp messes up the values between top and max 295261513Snwhitehorn */ 296256901Snwhitehorn wnum.dmax = snum->dmax - loop; /* so we don't step out of bounds */ 297256901Snwhitehorn 298124468Sgrehan /* Get the top 2 words of sdiv */ 299256901Snwhitehorn /* div_n=sdiv->top; */ 300256901Snwhitehorn d0 = sdiv->d[div_n - 1]; 301256855Snwhitehorn d1 = (div_n == 1) ? 0 : sdiv->d[div_n - 2]; 302256901Snwhitehorn 303256901Snwhitehorn /* pointer to the 'top' of snum */ 304125702Sgrehan wnump = &(snum->d[num_n - 1]); 305256901Snwhitehorn 306256901Snwhitehorn /* Setup to 'res' */ 307261513Snwhitehorn res->neg = (num->neg ^ divisor->neg); 308256901Snwhitehorn if (!bn_wexpand(res, (loop + 1))) 309256901Snwhitehorn goto err; 310124468Sgrehan res->top = loop - no_branch; 311124468Sgrehan resp = &(res->d[loop - 1]); 31299652Sbenno 313261513Snwhitehorn /* space for temp */ 31499652Sbenno if (!bn_wexpand(tmp, (div_n + 1))) 31599652Sbenno goto err; 316261513Snwhitehorn 317256901Snwhitehorn if (!no_branch) { 318171805Smarcel if (BN_ucmp(&wnum, sdiv) >= 0) { 319256901Snwhitehorn /* 320256901Snwhitehorn * If BN_DEBUG_RAND is defined BN_ucmp changes (via bn_pollute) 32199652Sbenno * the const bignum arguments => clean the values between top and 322256901Snwhitehorn * max again 323256901Snwhitehorn */ 324257075Snwhitehorn bn_clear_top2max(&wnum); 325256901Snwhitehorn bn_sub_words(wnum.d, wnum.d, sdiv->d, div_n); 326256901Snwhitehorn *resp = 1; 327256901Snwhitehorn } else 328256901Snwhitehorn res->top--; 329256901Snwhitehorn } 330256901Snwhitehorn 331256901Snwhitehorn /* 332256901Snwhitehorn * if res->top == 0 then clear the neg value otherwise decrease the resp 333256901Snwhitehorn * pointer 334256901Snwhitehorn */ 335256901Snwhitehorn if (res->top == 0) 336256901Snwhitehorn res->neg = 0; 337256901Snwhitehorn else 338256901Snwhitehorn resp--; 339256901Snwhitehorn 340256901Snwhitehorn for (i = 0; i < loop - 1; i++, wnump--, resp--) { 341256901Snwhitehorn BN_ULONG q, l0; 342256901Snwhitehorn /* 343256901Snwhitehorn * the first part of the loop uses the top two words of snum and sdiv 344256901Snwhitehorn * to calculate a BN_ULONG q such that | wnum - sdiv * q | < sdiv 345256901Snwhitehorn */ 346256901Snwhitehorn# if defined(BN_DIV3W) && !defined(OPENSSL_NO_ASM) 34799652Sbenno BN_ULONG bn_div_3_words(BN_ULONG *, BN_ULONG, BN_ULONG); 34899652Sbenno q = bn_div_3_words(wnump, d1, d0); 34999652Sbenno# else 350256901Snwhitehorn BN_ULONG n0, n1, rem = 0; 351256901Snwhitehorn 352256901Snwhitehorn n0 = wnump[0]; 353171805Smarcel n1 = wnump[-1]; 354256901Snwhitehorn if (n0 == d0) 355256901Snwhitehorn q = BN_MASK2; 356256901Snwhitehorn else { /* n0 < d0 */ 357256901Snwhitehorn 358256901Snwhitehorn# ifdef BN_LLONG 359256901Snwhitehorn BN_ULLONG t2; 360171805Smarcel 36199652Sbenno# if defined(BN_LLONG) && defined(BN_DIV2W) && !defined(bn_div_words) 362256901Snwhitehorn q = (BN_ULONG)(((((BN_ULLONG) n0) << BN_BITS2) | n1) / d0); 363256901Snwhitehorn# else 364256901Snwhitehorn q = bn_div_words(n0, n1, d0); 365256901Snwhitehorn# ifdef BN_DEBUG_LEVITTE 366256901Snwhitehorn fprintf(stderr, "DEBUG: bn_div_words(0x%08X,0x%08X,0x%08\ 367256901SnwhitehornX) -> 0x%08X\n", n0, n1, d0, q); 36899652Sbenno# endif 36999652Sbenno# endif 37099652Sbenno 37199652Sbenno# ifndef REMAINDER_IS_ALREADY_CALCULATED 37299652Sbenno /* 373261513Snwhitehorn * rem doesn't have to be BN_ULLONG. The least we 374256901Snwhitehorn * know it's less that d0, isn't it? 37599652Sbenno */ 376261513Snwhitehorn rem = (n1 - q * d0) & BN_MASK2; 377256901Snwhitehorn# endif 378261513Snwhitehorn t2 = (BN_ULLONG) d1 *q; 37999652Sbenno 380261513Snwhitehorn for (;;) { 381261513Snwhitehorn if (t2 <= ((((BN_ULLONG) rem) << BN_BITS2) | wnump[-2])) 382261513Snwhitehorn break; 383261513Snwhitehorn q--; 384256901Snwhitehorn rem += d0; 385256901Snwhitehorn if (rem < d0) 386256901Snwhitehorn break; /* don't let rem overflow */ 387256901Snwhitehorn t2 -= d1; 388256901Snwhitehorn } 389256901Snwhitehorn# else /* !BN_LLONG */ 390256901Snwhitehorn BN_ULONG t2l, t2h; 391256901Snwhitehorn 392124468Sgrehan q = bn_div_words(n0, n1, d0); 39399652Sbenno# ifdef BN_DEBUG_LEVITTE 394256901Snwhitehorn fprintf(stderr, "DEBUG: bn_div_words(0x%08X,0x%08X,0x%08\ 395256901SnwhitehornX) -> 0x%08X\n", n0, n1, d0, q); 396256901Snwhitehorn# endif 397256901Snwhitehorn# ifndef REMAINDER_IS_ALREADY_CALCULATED 398256901Snwhitehorn rem = (n1 - q * d0) & BN_MASK2; 39999652Sbenno# endif 40099652Sbenno 401256901Snwhitehorn# if defined(BN_UMULT_LOHI) 402261513Snwhitehorn BN_UMULT_LOHI(t2l, t2h, d1, q); 403256901Snwhitehorn# elif defined(BN_UMULT_HIGH) 40499652Sbenno t2l = d1 * q; 405256901Snwhitehorn t2h = BN_UMULT_HIGH(d1, q); 40699652Sbenno# else 407256901Snwhitehorn { 408256901Snwhitehorn BN_ULONG ql, qh; 409256901Snwhitehorn t2l = LBITS(d1); 410256901Snwhitehorn t2h = HBITS(d1); 411256855Snwhitehorn ql = LBITS(q); 412256901Snwhitehorn qh = HBITS(q); 413256901Snwhitehorn mul64(t2l, t2h, ql, qh); /* t2=(BN_ULLONG)d1*q; */ 41499652Sbenno } 415256901Snwhitehorn# endif 416261513Snwhitehorn 417256901Snwhitehorn for (;;) { 418261513Snwhitehorn if ((t2h < rem) || ((t2h == rem) && (t2l <= wnump[-2]))) 419256901Snwhitehorn break; 420256901Snwhitehorn q--; 421256901Snwhitehorn rem += d0; 42299652Sbenno if (rem < d0) 423124468Sgrehan break; /* don't let rem overflow */ 424256855Snwhitehorn if (t2l < d1) 425261513Snwhitehorn t2h--; 426168885Sgrehan t2l -= d1; 427261513Snwhitehorn } 428168885Sgrehan# endif /* !BN_LLONG */ 429256901Snwhitehorn } 430256901Snwhitehorn# endif /* !BN_DIV3W */ 431168885Sgrehan 432168885Sgrehan l0 = bn_mul_words(tmp->d, sdiv->d, div_n, q); 433261513Snwhitehorn tmp->d[div_n] = l0; 434261513Snwhitehorn wnum.d--; 435256901Snwhitehorn /* 436261513Snwhitehorn * ingore top values of the bignums just sub the two BN_ULONG arrays 437261513Snwhitehorn * with bn_sub_words 438256901Snwhitehorn */ 439256901Snwhitehorn if (bn_sub_words(wnum.d, wnum.d, tmp->d, div_n + 1)) { 440256901Snwhitehorn /* 441256901Snwhitehorn * Note: As we have considered only the leading two BN_ULONGs in 442256901Snwhitehorn * the calculation of q, sdiv * q might be greater than wnum (but 443256901Snwhitehorn * then (q-1) * sdiv is less or equal than wnum) 444256901Snwhitehorn */ 445256901Snwhitehorn q--; 446256901Snwhitehorn if (bn_add_words(wnum.d, wnum.d, sdiv->d, div_n)) 447256901Snwhitehorn /* 448256901Snwhitehorn * we can't have an overflow here (assuming that q != 0, but 449256901Snwhitehorn * if q == 0 then tmp is zero anyway) 450256901Snwhitehorn */ 451256901Snwhitehorn (*wnump)++; 452261513Snwhitehorn } 453256901Snwhitehorn /* store part of the result */ 454256901Snwhitehorn *resp = q; 455256901Snwhitehorn } 456256901Snwhitehorn bn_correct_top(snum); 457256901Snwhitehorn if (rm != NULL) { 458256901Snwhitehorn /* 459256901Snwhitehorn * Keep a copy of the neg flag in num because if rm==num BN_rshift() 460256969Snwhitehorn * will overwrite it. 461256901Snwhitehorn */ 462256901Snwhitehorn int neg = num->neg; 463256914Snwhitehorn BN_rshift(rm, snum, norm_shift); 464256914Snwhitehorn if (!BN_is_zero(rm)) 465256914Snwhitehorn rm->neg = neg; 466256914Snwhitehorn bn_check_top(rm); 467256914Snwhitehorn } 468256914Snwhitehorn if (no_branch) 469256901Snwhitehorn bn_correct_top(res); 470256901Snwhitehorn BN_CTX_end(ctx); 471256901Snwhitehorn return (1); 472256901Snwhitehorn err: 473256901Snwhitehorn bn_check_top(rm); 474256901Snwhitehorn BN_CTX_end(ctx); 475256901Snwhitehorn return (0); 476256901Snwhitehorn} 477256901Snwhitehorn#endif 478256901Snwhitehorn