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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;
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
generated by cgit v1.2.3-55-g6feb (git 2.39.1) at 2025-03-21 08:18:41 +0000