source: trunk/cscrypt/bn_div.c@ 3181

Last change on this file since 3181 was 3181, checked in by dingo35, 10 years ago

Adding threadsafety FIXMEs, feel free to join checking..

File size: 9.6 KB
Line 
1//FIXME Not checked on threadsafety yet; after checking please remove this line
2/* crypto/bn/bn_div.c */
3/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
4 * All rights reserved.
5 *
6 * This package is an SSL implementation written
7 * by Eric Young (eay@cryptsoft.com).
8 * The implementation was written so as to conform with Netscapes SSL.
9 *
10 * This library is free for commercial and non-commercial use as long as
11 * the following conditions are aheared to. The following conditions
12 * apply to all code found in this distribution, be it the RC4, RSA,
13 * lhash, DES, etc., code; not just the SSL code. The SSL documentation
14 * included with this distribution is covered by the same copyright terms
15 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
16 *
17 * Copyright remains Eric Young's, and as such any Copyright notices in
18 * the code are not to be removed.
19 * If this package is used in a product, Eric Young should be given attribution
20 * as the author of the parts of the library used.
21 * This can be in the form of a textual message at program startup or
22 * in documentation (online or textual) provided with the package.
23 *
24 * Redistribution and use in source and binary forms, with or without
25 * modification, are permitted provided that the following conditions
26 * are met:
27 * 1. Redistributions of source code must retain the copyright
28 * notice, this list of conditions and the following disclaimer.
29 * 2. Redistributions in binary form must reproduce the above copyright
30 * notice, this list of conditions and the following disclaimer in the
31 * documentation and/or other materials provided with the distribution.
32 * 3. All advertising materials mentioning features or use of this software
33 * must display the following acknowledgement:
34 * "This product includes cryptographic software written by
35 * Eric Young (eay@cryptsoft.com)"
36 * The word 'cryptographic' can be left out if the rouines from the library
37 * being used are not cryptographic related :-).
38 * 4. If you include any Windows specific code (or a derivative thereof) from
39 * the apps directory (application code) you must include an acknowledgement:
40 * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
41 *
42 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
43 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
44 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
45 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
46 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
47 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
48 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
49 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
50 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
51 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
52 * SUCH DAMAGE.
53 *
54 * The licence and distribution terms for any publically available version or
55 * derivative of this code cannot be changed. i.e. this code cannot simply be
56 * copied and put under another distribution licence
57 * [including the GNU Public Licence.]
58 */
59
60#include <stdio.h>
61#include "openssl_mods.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 {
77 return(0);
78 }
79
80 if (BN_ucmp(m,d) < 0)
81 {
82 if (rem != NULL)
83 { if (BN_copy(rem,m) == NULL) return(0); }
84 if (dv != NULL) BN_zero(dv);
85 return(1);
86 }
87
88 BN_CTX_start(ctx);
89 D = BN_CTX_get(ctx);
90 if (dv == NULL) dv = BN_CTX_get(ctx);
91 if (rem == NULL) rem = BN_CTX_get(ctx);
92 if (D == NULL || dv == NULL || rem == NULL)
93 goto end;
94
95 nd=BN_num_bits(d);
96 nm=BN_num_bits(m);
97 if (BN_copy(D,d) == NULL) goto end;
98 if (BN_copy(rem,m) == NULL) goto end;
99
100 /* The next 2 are needed so we can do a dv->d[0]|=1 later
101 * since BN_lshift1 will only work once there is a value :-) */
102 BN_zero(dv);
103 bn_wexpand(dv,1);
104 dv->top=1;
105
106 if (!BN_lshift(D,D,nm-nd)) goto end;
107 for (i=nm-nd; i>=0; i--)
108 {
109 if (!BN_lshift1(dv,dv)) goto end;
110 if (BN_ucmp(rem,D) >= 0)
111 {
112 dv->d[0]|=1;
113 if (!BN_usub(rem,rem,D)) goto end;
114 }
115/* CAN IMPROVE (and have now :=) */
116 if (!BN_rshift1(D,D)) goto end;
117 }
118 rem->neg=BN_is_zero(rem)?0:m->neg;
119 dv->neg=m->neg^d->neg;
120 ret = 1;
121 end:
122 BN_CTX_end(ctx);
123 return(ret);
124 }
125
126#else
127
128#if !defined(NO_ASM) && !defined(NO_INLINE_ASM) && !defined(PEDANTIC) && !defined(BN_DIV3W)
129# if defined(__GNUC__) && __GNUC__>=2
130# if defined(__i386) || defined (__i386__)
131 /*
132 * There were two reasons for implementing this template:
133 * - GNU C generates a call to a function (__udivdi3 to be exact)
134 * in reply to ((((BN_ULLONG)n0)<<BN_BITS2)|n1)/d0 (I fail to
135 * understand why...);
136 * - divl doesn't only calculate quotient, but also leaves
137 * remainder in %edx which we can definitely use here:-)
138 *
139 * <appro@fy.chalmers.se>
140 */
141# define bn_div_words(n0,n1,d0) \
142 ({ asm volatile ( \
143 "divl %4" \
144 : "=a"(q), "=d"(rem) \
145 : "a"(n1), "d"(n0), "g"(d0) \
146 : "cc"); \
147 q; \
148 })
149# define REMAINDER_IS_ALREADY_CALCULATED
150# endif /* __<cpu> */
151# endif /* __GNUC__ */
152#endif /* NO_ASM */
153
154int BN_div(BIGNUM *dv, BIGNUM *rm, const BIGNUM *num, const BIGNUM *divisor,
155 BN_CTX *ctx)
156 {
157 int norm_shift,i,j,loop;
158 BIGNUM *tmp,wnum,*snum,*sdiv,*res;
159 BN_ULONG *resp,*wnump;
160 BN_ULONG d0,d1;
161 int num_n,div_n;
162
163 bn_check_top(num);
164 bn_check_top(divisor);
165
166 if (BN_is_zero(divisor))
167 {
168 return(0);
169 }
170
171 if (BN_ucmp(num,divisor) < 0)
172 {
173 if (rm != NULL)
174 { if (BN_copy(rm,num) == NULL) return(0); }
175 if (dv != NULL) BN_zero(dv);
176 return(1);
177 }
178
179 BN_CTX_start(ctx);
180 tmp=BN_CTX_get(ctx);
181 snum=BN_CTX_get(ctx);
182 sdiv=BN_CTX_get(ctx);
183 if (dv == NULL)
184 res=BN_CTX_get(ctx);
185 else res=dv;
186 if (sdiv==NULL || res == NULL) goto err;
187 tmp->neg=0;
188
189 /* First we normalise the numbers */
190 norm_shift=BN_BITS2-((BN_num_bits(divisor))%BN_BITS2);
191 BN_lshift(sdiv,divisor,norm_shift);
192 sdiv->neg=0;
193 norm_shift+=BN_BITS2;
194 BN_lshift(snum,num,norm_shift);
195 snum->neg=0;
196 div_n=sdiv->top;
197 num_n=snum->top;
198 loop=num_n-div_n;
199
200 /* Lets setup a 'window' into snum
201 * This is the part that corresponds to the current
202 * 'area' being divided */
203 BN_init(&wnum);
204 wnum.d= &(snum->d[loop]);
205 wnum.top= div_n;
206 wnum.dmax= snum->dmax+1; /* a bit of a lie */
207
208 /* Get the top 2 words of sdiv */
209 /* i=sdiv->top; */
210 d0=sdiv->d[div_n-1];
211 d1=(div_n == 1)?0:sdiv->d[div_n-2];
212
213 /* pointer to the 'top' of snum */
214 wnump= &(snum->d[num_n-1]);
215
216 /* Setup to 'res' */
217 res->neg= (num->neg^divisor->neg);
218 if (!bn_wexpand(res,(loop+1))) goto err;
219 res->top=loop;
220 resp= &(res->d[loop-1]);
221
222 /* space for temp */
223 if (!bn_wexpand(tmp,(div_n+1))) goto err;
224
225 if (BN_ucmp(&wnum,sdiv) >= 0)
226 {
227 if (!BN_usub(&wnum,&wnum,sdiv)) goto err;
228 *resp=1;
229 res->d[res->top-1]=1;
230 }
231 else
232 res->top--;
233 resp--;
234
235 for (i=0; i<loop-1; i++)
236 {
237 BN_ULONG q,l0;
238#if defined(BN_DIV3W) && !defined(NO_ASM)
239 BN_ULONG bn_div_3_words(BN_ULONG*,BN_ULONG,BN_ULONG);
240 q=bn_div_3_words(wnump,d1,d0);
241#else
242 BN_ULONG n0,n1,rem=0;
243
244 n0=wnump[0];
245 n1=wnump[-1];
246 if (n0 == d0)
247 q=BN_MASK2;
248 else /* n0 < d0 */
249 {
250#ifdef BN_LLONG
251 BN_ULLONG t2;
252
253#if defined(BN_LLONG) && defined(BN_DIV2W) && !defined(bn_div_words)
254 q=(BN_ULONG)(((((BN_ULLONG)n0)<<BN_BITS2)|n1)/d0);
255#else
256 q=bn_div_words(n0,n1,d0);
257#endif
258
259#ifndef REMAINDER_IS_ALREADY_CALCULATED
260 /*
261 * rem doesn't have to be BN_ULLONG. The least we
262 * know it's less that d0, isn't it?
263 */
264 rem=(n1-q*d0)&BN_MASK2;
265#endif
266 t2=(BN_ULLONG)d1*q;
267
268 for (;;)
269 {
270 if (t2 <= ((((BN_ULLONG)rem)<<BN_BITS2)|wnump[-2]))
271 break;
272 q--;
273 rem += d0;
274 if (rem < d0) break; /* don't let rem overflow */
275 t2 -= d1;
276 }
277#else /* !BN_LLONG */
278 BN_ULONG t2l,t2h,ql,qh;
279
280 q=bn_div_words(n0,n1,d0);
281#ifndef REMAINDER_IS_ALREADY_CALCULATED
282 rem=(n1-q*d0)&BN_MASK2;
283#endif
284
285#ifdef BN_UMULT_HIGH
286 t2l = d1 * q;
287 t2h = BN_UMULT_HIGH(d1,q);
288#else
289 t2l=LBITS(d1); t2h=HBITS(d1);
290 ql =LBITS(q); qh =HBITS(q);
291 mul64(t2l,t2h,ql,qh); /* t2=(BN_ULLONG)d1*q; */
292#endif
293
294 for (;;)
295 {
296 if ((t2h < rem) ||
297 ((t2h == rem) && (t2l <= wnump[-2])))
298 break;
299 q--;
300 rem += d0;
301 if (rem < d0) break; /* don't let rem overflow */
302 if (t2l < d1) t2h--; t2l -= d1;
303 }
304#endif /* !BN_LLONG */
305 }
306#endif /* !BN_DIV3W */
307
308 l0=bn_mul_words(tmp->d,sdiv->d,div_n,q);
309 wnum.d--; wnum.top++;
310 tmp->d[div_n]=l0;
311 for (j=div_n+1; j>0; j--)
312 if (tmp->d[j-1]) break;
313 tmp->top=j;
314
315 j=wnum.top;
316 BN_sub(&wnum,&wnum,tmp);
317
318 snum->top=snum->top+wnum.top-j;
319
320 if (wnum.neg)
321 {
322 q--;
323 j=wnum.top;
324 BN_add(&wnum,&wnum,sdiv);
325 snum->top+=wnum.top-j;
326 }
327 *(resp--)=q;
328 wnump--;
329 }
330 if (rm != NULL)
331 {
332 BN_rshift(rm,snum,norm_shift);
333 rm->neg=num->neg;
334 }
335 BN_CTX_end(ctx);
336 return(1);
337err:
338 BN_CTX_end(ctx);
339 return(0);
340 }
341
342#endif
343
344/* rem != m */
345int BN_mod(BIGNUM *rem, const BIGNUM *m, const BIGNUM *d, BN_CTX *ctx)
346 {
347#if 0 /* The old slow way */
348 int i,nm,nd;
349 BIGNUM *dv;
350
351 if (BN_ucmp(m,d) < 0)
352 return((BN_copy(rem,m) == NULL)?0:1);
353
354 BN_CTX_start(ctx);
355 dv=BN_CTX_get(ctx);
356
357 if (!BN_copy(rem,m)) goto err;
358
359 nm=BN_num_bits(rem);
360 nd=BN_num_bits(d);
361 if (!BN_lshift(dv,d,nm-nd)) goto err;
362 for (i=nm-nd; i>=0; i--)
363 {
364 if (BN_cmp(rem,dv) >= 0)
365 {
366 if (!BN_sub(rem,rem,dv)) goto err;
367 }
368 if (!BN_rshift1(dv,dv)) goto err;
369 }
370 BN_CTX_end(ctx);
371 return(1);
372 err:
373 BN_CTX_end(ctx);
374 return(0);
375#else
376 return(BN_div(NULL,rem,m,d,ctx));
377#endif
378 }
379
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