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d02b48c6 | 1 | /* crypto/bn/bn_div.c */ |
58964a49 | 2 | /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com) |
d02b48c6 RE |
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> | |
84c15db5 | 60 | #include <openssl/bn.h> |
d02b48c6 RE |
61 | #include "cryptlib.h" |
62 | #include "bn_lcl.h" | |
63 | ||
64 | /* The old slow way */ | |
65 | #if 0 | |
0bde1089 UM |
66 | int BN_div(BIGNUM *dv, BIGNUM *rem, const BIGNUM *m, const BIGNUM *d, |
67 | BN_CTX *ctx) | |
d02b48c6 RE |
68 | { |
69 | int i,nm,nd; | |
70 | BIGNUM *D; | |
71 | ||
dfeab068 RE |
72 | bn_check_top(m); |
73 | bn_check_top(d); | |
d02b48c6 RE |
74 | if (BN_is_zero(d)) |
75 | { | |
76 | BNerr(BN_F_BN_DIV,BN_R_DIV_BY_ZERO); | |
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 | ||
dfeab068 RE |
88 | D= &(ctx->bn[ctx->tos]); |
89 | if (dv == NULL) dv= &(ctx->bn[ctx->tos+1]); | |
90 | if (rem == NULL) rem= &(ctx->bn[ctx->tos+2]); | |
d02b48c6 RE |
91 | |
92 | nd=BN_num_bits(d); | |
93 | nm=BN_num_bits(m); | |
94 | if (BN_copy(D,d) == NULL) return(0); | |
95 | if (BN_copy(rem,m) == NULL) return(0); | |
96 | ||
97 | /* The next 2 are needed so we can do a dv->d[0]|=1 later | |
98 | * since BN_lshift1 will only work once there is a value :-) */ | |
99 | BN_zero(dv); | |
dfeab068 | 100 | bn_wexpand(dv,1); |
d02b48c6 RE |
101 | dv->top=1; |
102 | ||
103 | if (!BN_lshift(D,D,nm-nd)) return(0); | |
104 | for (i=nm-nd; i>=0; i--) | |
105 | { | |
106 | if (!BN_lshift1(dv,dv)) return(0); | |
107 | if (BN_ucmp(rem,D) >= 0) | |
108 | { | |
109 | dv->d[0]|=1; | |
dfeab068 | 110 | if (!BN_usub(rem,rem,D)) return(0); |
d02b48c6 RE |
111 | } |
112 | /* CAN IMPROVE (and have now :=) */ | |
113 | if (!BN_rshift1(D,D)) return(0); | |
114 | } | |
115 | rem->neg=BN_is_zero(rem)?0:m->neg; | |
116 | dv->neg=m->neg^d->neg; | |
117 | return(1); | |
118 | } | |
119 | ||
120 | #else | |
121 | ||
84c15db5 BL |
122 | int BN_div(BIGNUM *dv, BIGNUM *rm, const BIGNUM *num, const BIGNUM *divisor, |
123 | BN_CTX *ctx) | |
d02b48c6 RE |
124 | { |
125 | int norm_shift,i,j,loop; | |
126 | BIGNUM *tmp,wnum,*snum,*sdiv,*res; | |
127 | BN_ULONG *resp,*wnump; | |
128 | BN_ULONG d0,d1; | |
129 | int num_n,div_n; | |
130 | ||
dfeab068 RE |
131 | bn_check_top(num); |
132 | bn_check_top(divisor); | |
133 | ||
58964a49 | 134 | if (BN_is_zero(divisor)) |
d02b48c6 RE |
135 | { |
136 | BNerr(BN_F_BN_DIV,BN_R_DIV_BY_ZERO); | |
137 | return(0); | |
138 | } | |
139 | ||
140 | if (BN_ucmp(num,divisor) < 0) | |
141 | { | |
142 | if (rm != NULL) | |
143 | { if (BN_copy(rm,num) == NULL) return(0); } | |
144 | if (dv != NULL) BN_zero(dv); | |
145 | return(1); | |
146 | } | |
147 | ||
dfeab068 | 148 | tmp= &(ctx->bn[ctx->tos]); |
d02b48c6 | 149 | tmp->neg=0; |
dfeab068 RE |
150 | snum= &(ctx->bn[ctx->tos+1]); |
151 | sdiv= &(ctx->bn[ctx->tos+2]); | |
d02b48c6 | 152 | if (dv == NULL) |
dfeab068 | 153 | res= &(ctx->bn[ctx->tos+3]); |
d02b48c6 RE |
154 | else res=dv; |
155 | ||
156 | /* First we normalise the numbers */ | |
157 | norm_shift=BN_BITS2-((BN_num_bits(divisor))%BN_BITS2); | |
158 | BN_lshift(sdiv,divisor,norm_shift); | |
159 | sdiv->neg=0; | |
160 | norm_shift+=BN_BITS2; | |
161 | BN_lshift(snum,num,norm_shift); | |
162 | snum->neg=0; | |
163 | div_n=sdiv->top; | |
164 | num_n=snum->top; | |
165 | loop=num_n-div_n; | |
166 | ||
167 | /* Lets setup a 'window' into snum | |
168 | * This is the part that corresponds to the current | |
169 | * 'area' being divided */ | |
dfeab068 | 170 | BN_init(&wnum); |
d02b48c6 RE |
171 | wnum.d= &(snum->d[loop]); |
172 | wnum.top= div_n; | |
dfeab068 | 173 | wnum.max= snum->max+1; /* a bit of a lie */ |
d02b48c6 RE |
174 | |
175 | /* Get the top 2 words of sdiv */ | |
176 | /* i=sdiv->top; */ | |
177 | d0=sdiv->d[div_n-1]; | |
178 | d1=(div_n == 1)?0:sdiv->d[div_n-2]; | |
179 | ||
180 | /* pointer to the 'top' of snum */ | |
181 | wnump= &(snum->d[num_n-1]); | |
182 | ||
183 | /* Setup to 'res' */ | |
184 | res->neg= (num->neg^divisor->neg); | |
58964a49 | 185 | if (!bn_wexpand(res,(loop+1))) goto err; |
dfeab068 | 186 | res->top=loop; |
d02b48c6 RE |
187 | resp= &(res->d[loop-1]); |
188 | ||
189 | /* space for temp */ | |
58964a49 | 190 | if (!bn_wexpand(tmp,(div_n+1))) goto err; |
d02b48c6 RE |
191 | |
192 | if (BN_ucmp(&wnum,sdiv) >= 0) | |
193 | { | |
dfeab068 | 194 | if (!BN_usub(&wnum,&wnum,sdiv)) goto err; |
d02b48c6 RE |
195 | *resp=1; |
196 | res->d[res->top-1]=1; | |
197 | } | |
198 | else | |
199 | res->top--; | |
200 | resp--; | |
201 | ||
202 | for (i=0; i<loop-1; i++) | |
203 | { | |
0dd25e36 AP |
204 | BN_ULONG q,l0; |
205 | #ifdef BN_DIV3W | |
0bbd0352 | 206 | q=bn_div_3_words(wnump,d1,d0); |
0dd25e36 | 207 | #else |
4c22909e | 208 | |
97e84e38 | 209 | #if !defined(NO_ASM) && !defined(PEDANTIC) |
4c22909e | 210 | # if defined(__GNUC__) && __GNUC__>=2 |
3b14cb71 | 211 | # if defined(__i386) |
4c22909e AP |
212 | /* |
213 | * There were two reasons for implementing this template: | |
214 | * - GNU C generates a call to a function (__udivdi3 to be exact) | |
215 | * in reply to ((((BN_ULLONG)n0)<<BN_BITS2)|n1)/d0 (I fail to | |
216 | * understand why...); | |
217 | * - divl doesn't only calculate quotient, but also leaves | |
218 | * remainder in %edx which we can definitely use here:-) | |
219 | * | |
220 | * <appro@fy.chalmers.se> | |
221 | */ | |
222 | # define bn_div_words(n0,n1,d0) \ | |
223 | ({ asm volatile ( \ | |
224 | "divl %4" \ | |
225 | : "=a"(q), "=d"(rem) \ | |
226 | : "a"(n1), "d"(n0), "g"(d0) \ | |
227 | : "cc"); \ | |
228 | q; \ | |
229 | }) | |
fe7cd164 | 230 | # define REMAINDER_IS_ALREADY_CALCULATED |
4c22909e AP |
231 | # endif /* __<cpu> */ |
232 | # endif /* __GNUC__ */ | |
233 | #endif /* NO_ASM */ | |
234 | BN_ULONG n0,n1,rem=0; | |
d02b48c6 | 235 | |
d02b48c6 RE |
236 | n0=wnump[0]; |
237 | n1=wnump[-1]; | |
238 | if (n0 == d0) | |
cb5b7850 | 239 | { |
d02b48c6 | 240 | q=BN_MASK2; |
cb5b7850 BM |
241 | #ifdef REMAINDER_IS_ALREADY_CALCULATED /* in this case it isn't */ |
242 | rem=(n1-q*d0)&BN_MASK2; | |
243 | #endif | |
244 | } | |
245 | else /* n0 < d0 */ | |
4c22909e | 246 | #if defined(BN_LLONG) && defined(BN_DIV2W) && !defined(bn_div_words) |
8e1589ec | 247 | q=(BN_ULONG)(((((BN_ULLONG)n0)<<BN_BITS2)|n1)/d0); |
0dd25e36 | 248 | #else |
dfeab068 | 249 | q=bn_div_words(n0,n1,d0); |
0dd25e36 | 250 | #endif |
d02b48c6 RE |
251 | { |
252 | #ifdef BN_LLONG | |
0dd25e36 AP |
253 | BN_ULLONG t2; |
254 | ||
fe7cd164 | 255 | #ifndef REMAINDER_IS_ALREADY_CALCULATED |
0dd25e36 AP |
256 | /* |
257 | * rem doesn't have to be BN_ULLONG. The least we | |
258 | * know it's less that d0, isn't it? | |
259 | */ | |
260 | rem=(n1-q*d0)&BN_MASK2; | |
4c22909e | 261 | #endif |
0dd25e36 | 262 | t2=(BN_ULLONG)d1*q; |
4c22909e | 263 | |
d02b48c6 RE |
264 | for (;;) |
265 | { | |
0dd25e36 | 266 | if (t2 <= ((((BN_ULLONG)rem)<<BN_BITS2)|wnump[-2])) |
d02b48c6 RE |
267 | break; |
268 | q--; | |
0dd25e36 AP |
269 | rem += d0; |
270 | if (rem < d0) break; /* don't let rem overflow */ | |
271 | t2 -= d1; | |
d02b48c6 RE |
272 | } |
273 | #else | |
0dd25e36 AP |
274 | BN_ULONG t2l,t2h,ql,qh; |
275 | ||
fe7cd164 | 276 | #ifndef REMAINDER_IS_ALREADY_CALCULATED |
0dd25e36 AP |
277 | /* |
278 | * It's more than enough with the only multiplication. | |
279 | * See the comment above in BN_LLONG section... | |
280 | */ | |
281 | rem=(n1-q*d0)&BN_MASK2; | |
4c22909e | 282 | #endif |
fb81ac5e AP |
283 | #ifdef BN_UMULT_HIGH |
284 | t2l = d1 * q; | |
285 | t2h = BN_UMULT_HIGH(d1,q); | |
286 | #else | |
0dd25e36 AP |
287 | t2l=LBITS(d1); t2h=HBITS(d1); |
288 | ql =LBITS(q); qh =HBITS(q); | |
289 | mul64(t2l,t2h,ql,qh); /* t2=(BN_ULLONG)d1*q; */ | |
fb81ac5e | 290 | #endif |
0dd25e36 | 291 | |
d02b48c6 RE |
292 | for (;;) |
293 | { | |
0dd25e36 AP |
294 | if ((t2h < rem) || |
295 | ((t2h == rem) && (t2l <= wnump[-2]))) | |
296 | break; | |
d02b48c6 | 297 | q--; |
0dd25e36 AP |
298 | rem += d0; |
299 | if (rem < d0) break; /* don't let rem overflow */ | |
300 | if (t2l < d1) t2h--; t2l -= d1; | |
d02b48c6 RE |
301 | } |
302 | #endif | |
303 | } | |
4c22909e | 304 | #endif /* !BN_DIV3W */ |
58964a49 | 305 | l0=bn_mul_words(tmp->d,sdiv->d,div_n,q); |
0bbd0352 | 306 | wnum.d--; wnum.top++; |
d02b48c6 RE |
307 | tmp->d[div_n]=l0; |
308 | for (j=div_n+1; j>0; j--) | |
309 | if (tmp->d[j-1]) break; | |
310 | tmp->top=j; | |
311 | ||
312 | j=wnum.top; | |
313 | BN_sub(&wnum,&wnum,tmp); | |
314 | ||
315 | snum->top=snum->top+wnum.top-j; | |
316 | ||
317 | if (wnum.neg) | |
318 | { | |
319 | q--; | |
320 | j=wnum.top; | |
321 | BN_add(&wnum,&wnum,sdiv); | |
322 | snum->top+=wnum.top-j; | |
323 | } | |
324 | *(resp--)=q; | |
325 | wnump--; | |
326 | } | |
327 | if (rm != NULL) | |
328 | { | |
329 | BN_rshift(rm,snum,norm_shift); | |
330 | rm->neg=num->neg; | |
331 | } | |
332 | return(1); | |
333 | err: | |
334 | return(0); | |
335 | } | |
336 | ||
337 | #endif | |
dfeab068 RE |
338 | |
339 | /* rem != m */ | |
84c15db5 | 340 | int BN_mod(BIGNUM *rem, const BIGNUM *m, const BIGNUM *d, BN_CTX *ctx) |
dfeab068 RE |
341 | { |
342 | #if 0 /* The old slow way */ | |
343 | int i,nm,nd; | |
344 | BIGNUM *dv; | |
345 | ||
346 | if (BN_ucmp(m,d) < 0) | |
347 | return((BN_copy(rem,m) == NULL)?0:1); | |
348 | ||
349 | dv= &(ctx->bn[ctx->tos]); | |
350 | ||
351 | if (!BN_copy(rem,m)) return(0); | |
352 | ||
353 | nm=BN_num_bits(rem); | |
354 | nd=BN_num_bits(d); | |
355 | if (!BN_lshift(dv,d,nm-nd)) return(0); | |
356 | for (i=nm-nd; i>=0; i--) | |
357 | { | |
358 | if (BN_cmp(rem,dv) >= 0) | |
359 | { | |
360 | if (!BN_sub(rem,rem,dv)) return(0); | |
361 | } | |
362 | if (!BN_rshift1(dv,dv)) return(0); | |
363 | } | |
364 | return(1); | |
365 | #else | |
366 | return(BN_div(NULL,rem,m,d,ctx)); | |
367 | #endif | |
368 | } | |
369 |