Import of openssl-0.9.8, a feature release.
[dragonfly.git] / crypto / openssl-0.9 / crypto / bn / bn_div.c
CommitLineData
56276539
SS
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 bn_wexpand(dv,1);
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 computes dv := num / divisor, rounding towards zero, and sets up
173 * 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 */
179int BN_div(BIGNUM *dv, BIGNUM *rm, const BIGNUM *num, const BIGNUM *divisor,
180 BN_CTX *ctx)
181 {
182 int norm_shift,i,loop;
183 BIGNUM *tmp,wnum,*snum,*sdiv,*res;
184 BN_ULONG *resp,*wnump;
185 BN_ULONG d0,d1;
186 int num_n,div_n;
187
188 if (dv)
189 bn_check_top(dv);
190 if (rm)
191 bn_check_top(rm);
192 bn_check_top(num);
193 bn_check_top(divisor);
194
195 if (BN_is_zero(divisor))
196 {
197 BNerr(BN_F_BN_DIV,BN_R_DIV_BY_ZERO);
198 return(0);
199 }
200
201 if (BN_ucmp(num,divisor) < 0)
202 {
203 if (rm != NULL)
204 { if (BN_copy(rm,num) == NULL) return(0); }
205 if (dv != NULL) BN_zero(dv);
206 return(1);
207 }
208
209 BN_CTX_start(ctx);
210 tmp=BN_CTX_get(ctx);
211 snum=BN_CTX_get(ctx);
212 sdiv=BN_CTX_get(ctx);
213 if (dv == NULL)
214 res=BN_CTX_get(ctx);
215 else res=dv;
216 if (sdiv == NULL || res == NULL) goto err;
217
218 /* First we normalise the numbers */
219 norm_shift=BN_BITS2-((BN_num_bits(divisor))%BN_BITS2);
220 if (!(BN_lshift(sdiv,divisor,norm_shift))) goto err;
221 sdiv->neg=0;
222 norm_shift+=BN_BITS2;
223 if (!(BN_lshift(snum,num,norm_shift))) goto err;
224 snum->neg=0;
225 div_n=sdiv->top;
226 num_n=snum->top;
227 loop=num_n-div_n;
228 /* Lets setup a 'window' into snum
229 * This is the part that corresponds to the current
230 * 'area' being divided */
231 wnum.neg = 0;
232 wnum.d = &(snum->d[loop]);
233 wnum.top = div_n;
234 /* only needed when BN_ucmp messes up the values between top and max */
235 wnum.dmax = snum->dmax - loop; /* so we don't step out of bounds */
236
237 /* Get the top 2 words of sdiv */
238 /* div_n=sdiv->top; */
239 d0=sdiv->d[div_n-1];
240 d1=(div_n == 1)?0:sdiv->d[div_n-2];
241
242 /* pointer to the 'top' of snum */
243 wnump= &(snum->d[num_n-1]);
244
245 /* Setup to 'res' */
246 res->neg= (num->neg^divisor->neg);
247 if (!bn_wexpand(res,(loop+1))) goto err;
248 res->top=loop;
249 resp= &(res->d[loop-1]);
250
251 /* space for temp */
252 if (!bn_wexpand(tmp,(div_n+1))) goto err;
253
254 if (BN_ucmp(&wnum,sdiv) >= 0)
255 {
256 /* If BN_DEBUG_RAND is defined BN_ucmp changes (via
257 * bn_pollute) the const bignum arguments =>
258 * clean the values between top and max again */
259 bn_clear_top2max(&wnum);
260 bn_sub_words(wnum.d, wnum.d, sdiv->d, div_n);
261 *resp=1;
262 }
263 else
264 res->top--;
265 /* if res->top == 0 then clear the neg value otherwise decrease
266 * the resp pointer */
267 if (res->top == 0)
268 res->neg = 0;
269 else
270 resp--;
271
272 for (i=0; i<loop-1; i++, wnump--, resp--)
273 {
274 BN_ULONG q,l0;
275 /* the first part of the loop uses the top two words of
276 * snum and sdiv to calculate a BN_ULONG q such that
277 * | wnum - sdiv * q | < sdiv */
278#if defined(BN_DIV3W) && !defined(OPENSSL_NO_ASM)
279 BN_ULONG bn_div_3_words(BN_ULONG*,BN_ULONG,BN_ULONG);
280 q=bn_div_3_words(wnump,d1,d0);
281#else
282 BN_ULONG n0,n1,rem=0;
283
284 n0=wnump[0];
285 n1=wnump[-1];
286 if (n0 == d0)
287 q=BN_MASK2;
288 else /* n0 < d0 */
289 {
290#ifdef BN_LLONG
291 BN_ULLONG t2;
292
293#if defined(BN_LLONG) && defined(BN_DIV2W) && !defined(bn_div_words)
294 q=(BN_ULONG)(((((BN_ULLONG)n0)<<BN_BITS2)|n1)/d0);
295#else
296 q=bn_div_words(n0,n1,d0);
297#ifdef BN_DEBUG_LEVITTE
298 fprintf(stderr,"DEBUG: bn_div_words(0x%08X,0x%08X,0x%08\
299X) -> 0x%08X\n",
300 n0, n1, d0, q);
301#endif
302#endif
303
304#ifndef REMAINDER_IS_ALREADY_CALCULATED
305 /*
306 * rem doesn't have to be BN_ULLONG. The least we
307 * know it's less that d0, isn't it?
308 */
309 rem=(n1-q*d0)&BN_MASK2;
310#endif
311 t2=(BN_ULLONG)d1*q;
312
313 for (;;)
314 {
315 if (t2 <= ((((BN_ULLONG)rem)<<BN_BITS2)|wnump[-2]))
316 break;
317 q--;
318 rem += d0;
319 if (rem < d0) break; /* don't let rem overflow */
320 t2 -= d1;
321 }
322#else /* !BN_LLONG */
323 BN_ULONG t2l,t2h,ql,qh;
324
325 q=bn_div_words(n0,n1,d0);
326#ifdef BN_DEBUG_LEVITTE
327 fprintf(stderr,"DEBUG: bn_div_words(0x%08X,0x%08X,0x%08\
328X) -> 0x%08X\n",
329 n0, n1, d0, q);
330#endif
331#ifndef REMAINDER_IS_ALREADY_CALCULATED
332 rem=(n1-q*d0)&BN_MASK2;
333#endif
334
335#if defined(BN_UMULT_LOHI)
336 BN_UMULT_LOHI(t2l,t2h,d1,q);
337#elif defined(BN_UMULT_HIGH)
338 t2l = d1 * q;
339 t2h = BN_UMULT_HIGH(d1,q);
340#else
341 t2l=LBITS(d1); t2h=HBITS(d1);
342 ql =LBITS(q); qh =HBITS(q);
343 mul64(t2l,t2h,ql,qh); /* t2=(BN_ULLONG)d1*q; */
344#endif
345
346 for (;;)
347 {
348 if ((t2h < rem) ||
349 ((t2h == rem) && (t2l <= wnump[-2])))
350 break;
351 q--;
352 rem += d0;
353 if (rem < d0) break; /* don't let rem overflow */
354 if (t2l < d1) t2h--; t2l -= d1;
355 }
356#endif /* !BN_LLONG */
357 }
358#endif /* !BN_DIV3W */
359
360 l0=bn_mul_words(tmp->d,sdiv->d,div_n,q);
361 tmp->d[div_n]=l0;
362 wnum.d--;
363 /* ingore top values of the bignums just sub the two
364 * BN_ULONG arrays with bn_sub_words */
365 if (bn_sub_words(wnum.d, wnum.d, tmp->d, div_n+1))
366 {
367 /* Note: As we have considered only the leading
368 * two BN_ULONGs in the calculation of q, sdiv * q
369 * might be greater than wnum (but then (q-1) * sdiv
370 * is less or equal than wnum)
371 */
372 q--;
373 if (bn_add_words(wnum.d, wnum.d, sdiv->d, div_n))
374 /* we can't have an overflow here (assuming
375 * that q != 0, but if q == 0 then tmp is
376 * zero anyway) */
377 (*wnump)++;
378 }
379 /* store part of the result */
380 *resp = q;
381 }
382 bn_correct_top(snum);
383 if (rm != NULL)
384 {
385 /* Keep a copy of the neg flag in num because if rm==num
386 * BN_rshift() will overwrite it.
387 */
388 int neg = num->neg;
389 BN_rshift(rm,snum,norm_shift);
390 if (!BN_is_zero(rm))
391 rm->neg = neg;
392 bn_check_top(rm);
393 }
394 BN_CTX_end(ctx);
395 return(1);
396err:
397 if (rm)
398 bn_check_top(rm);
399 BN_CTX_end(ctx);
400 return(0);
401 }
402
403#endif