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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> | |
60 | #include "cryptlib.h" | |
61 | #include "bn_lcl.h" | |
62 | ||
63 | /* The old slow way */ | |
64 | #if 0 | |
65 | int BN_div(dv, rem, m, d,ctx) | |
66 | BIGNUM *dv; | |
67 | BIGNUM *rem; | |
68 | BIGNUM *m; | |
69 | BIGNUM *d; | |
70 | BN_CTX *ctx; | |
71 | { | |
72 | int i,nm,nd; | |
73 | BIGNUM *D; | |
74 | ||
75 | if (BN_is_zero(d)) | |
76 | { | |
77 | BNerr(BN_F_BN_DIV,BN_R_DIV_BY_ZERO); | |
78 | return(0); | |
79 | } | |
80 | ||
81 | if (BN_ucmp(m,d) < 0) | |
82 | { | |
83 | if (rem != NULL) | |
84 | { if (BN_copy(rem,m) == NULL) return(0); } | |
85 | if (dv != NULL) BN_zero(dv); | |
86 | return(1); | |
87 | } | |
88 | ||
89 | D=ctx->bn[ctx->tos]; | |
90 | if (dv == NULL) dv=ctx->bn[ctx->tos+1]; | |
91 | if (rem == NULL) rem=ctx->bn[ctx->tos+2]; | |
92 | ||
93 | nd=BN_num_bits(d); | |
94 | nm=BN_num_bits(m); | |
95 | if (BN_copy(D,d) == NULL) return(0); | |
96 | if (BN_copy(rem,m) == NULL) return(0); | |
97 | ||
98 | /* The next 2 are needed so we can do a dv->d[0]|=1 later | |
99 | * since BN_lshift1 will only work once there is a value :-) */ | |
100 | BN_zero(dv); | |
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; | |
110 | bn_qsub(rem,rem,D); | |
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 | ||
122 | int BN_div(dv, rm, num, divisor,ctx) | |
123 | BIGNUM *dv; | |
124 | BIGNUM *rm; | |
125 | BIGNUM *num; | |
126 | BIGNUM *divisor; | |
127 | BN_CTX *ctx; | |
128 | { | |
129 | int norm_shift,i,j,loop; | |
130 | BIGNUM *tmp,wnum,*snum,*sdiv,*res; | |
131 | BN_ULONG *resp,*wnump; | |
132 | BN_ULONG d0,d1; | |
133 | int num_n,div_n; | |
134 | ||
58964a49 | 135 | if (BN_is_zero(divisor)) |
d02b48c6 RE |
136 | { |
137 | BNerr(BN_F_BN_DIV,BN_R_DIV_BY_ZERO); | |
138 | return(0); | |
139 | } | |
140 | ||
141 | if (BN_ucmp(num,divisor) < 0) | |
142 | { | |
143 | if (rm != NULL) | |
144 | { if (BN_copy(rm,num) == NULL) return(0); } | |
145 | if (dv != NULL) BN_zero(dv); | |
146 | return(1); | |
147 | } | |
148 | ||
149 | tmp=ctx->bn[ctx->tos]; | |
150 | tmp->neg=0; | |
151 | snum=ctx->bn[ctx->tos+1]; | |
152 | sdiv=ctx->bn[ctx->tos+2]; | |
153 | if (dv == NULL) | |
154 | res=ctx->bn[ctx->tos+3]; | |
155 | else res=dv; | |
156 | ||
157 | /* First we normalise the numbers */ | |
158 | norm_shift=BN_BITS2-((BN_num_bits(divisor))%BN_BITS2); | |
159 | BN_lshift(sdiv,divisor,norm_shift); | |
160 | sdiv->neg=0; | |
161 | norm_shift+=BN_BITS2; | |
162 | BN_lshift(snum,num,norm_shift); | |
163 | snum->neg=0; | |
164 | div_n=sdiv->top; | |
165 | num_n=snum->top; | |
166 | loop=num_n-div_n; | |
167 | ||
168 | /* Lets setup a 'window' into snum | |
169 | * This is the part that corresponds to the current | |
170 | * 'area' being divided */ | |
171 | wnum.d= &(snum->d[loop]); | |
172 | wnum.top= div_n; | |
173 | wnum.max= snum->max; /* a bit of a lie */ | |
174 | wnum.neg= 0; | |
175 | ||
176 | /* Get the top 2 words of sdiv */ | |
177 | /* i=sdiv->top; */ | |
178 | d0=sdiv->d[div_n-1]; | |
179 | d1=(div_n == 1)?0:sdiv->d[div_n-2]; | |
180 | ||
181 | /* pointer to the 'top' of snum */ | |
182 | wnump= &(snum->d[num_n-1]); | |
183 | ||
184 | /* Setup to 'res' */ | |
185 | res->neg= (num->neg^divisor->neg); | |
186 | res->top=loop; | |
58964a49 | 187 | if (!bn_wexpand(res,(loop+1))) goto err; |
d02b48c6 RE |
188 | resp= &(res->d[loop-1]); |
189 | ||
190 | /* space for temp */ | |
58964a49 | 191 | if (!bn_wexpand(tmp,(div_n+1))) goto err; |
d02b48c6 RE |
192 | |
193 | if (BN_ucmp(&wnum,sdiv) >= 0) | |
194 | { | |
195 | bn_qsub(&wnum,&wnum,sdiv); | |
196 | *resp=1; | |
197 | res->d[res->top-1]=1; | |
198 | } | |
199 | else | |
200 | res->top--; | |
201 | resp--; | |
202 | ||
203 | for (i=0; i<loop-1; i++) | |
204 | { | |
205 | BN_ULONG q,n0,n1; | |
206 | BN_ULONG l0; | |
207 | ||
208 | wnum.d--; wnum.top++; | |
209 | n0=wnump[0]; | |
210 | n1=wnump[-1]; | |
211 | if (n0 == d0) | |
212 | q=BN_MASK2; | |
213 | else | |
214 | q=bn_div64(n0,n1,d0); | |
215 | { | |
216 | #ifdef BN_LLONG | |
217 | BN_ULLONG t1,t2,rem; | |
218 | t1=((BN_ULLONG)n0<<BN_BITS2)|n1; | |
219 | for (;;) | |
220 | { | |
221 | t2=(BN_ULLONG)d1*q; | |
222 | rem=t1-(BN_ULLONG)q*d0; | |
223 | if ((rem>>BN_BITS2) || | |
224 | (t2 <= ((BN_ULLONG)(rem<<BN_BITS2)+wnump[-2]))) | |
225 | break; | |
226 | q--; | |
227 | } | |
228 | #else | |
229 | BN_ULONG t1l,t1h,t2l,t2h,t3l,t3h,ql,qh,t3t; | |
230 | t1h=n0; | |
231 | t1l=n1; | |
232 | for (;;) | |
233 | { | |
234 | t2l=LBITS(d1); t2h=HBITS(d1); | |
235 | ql =LBITS(q); qh =HBITS(q); | |
236 | mul64(t2l,t2h,ql,qh); /* t2=(BN_ULLONG)d1*q; */ | |
237 | ||
238 | t3t=LBITS(d0); t3h=HBITS(d0); | |
239 | mul64(t3t,t3h,ql,qh); /* t3=t1-(BN_ULLONG)q*d0; */ | |
58964a49 | 240 | t3l=(t1l-t3t)&BN_MASK2; |
d02b48c6 | 241 | if (t3l > t1l) t3h++; |
58964a49 | 242 | t3h=(t1h-t3h)&BN_MASK2; |
d02b48c6 RE |
243 | |
244 | /*if ((t3>>BN_BITS2) || | |
245 | (t2 <= ((t3<<BN_BITS2)+wnump[-2]))) | |
246 | break; */ | |
247 | if (t3h) break; | |
248 | if (t2h < t3l) break; | |
249 | if ((t2h == t3l) && (t2l <= wnump[-2])) break; | |
250 | ||
251 | q--; | |
252 | } | |
253 | #endif | |
254 | } | |
58964a49 | 255 | l0=bn_mul_words(tmp->d,sdiv->d,div_n,q); |
d02b48c6 RE |
256 | tmp->d[div_n]=l0; |
257 | for (j=div_n+1; j>0; j--) | |
258 | if (tmp->d[j-1]) break; | |
259 | tmp->top=j; | |
260 | ||
261 | j=wnum.top; | |
262 | BN_sub(&wnum,&wnum,tmp); | |
263 | ||
264 | snum->top=snum->top+wnum.top-j; | |
265 | ||
266 | if (wnum.neg) | |
267 | { | |
268 | q--; | |
269 | j=wnum.top; | |
270 | BN_add(&wnum,&wnum,sdiv); | |
271 | snum->top+=wnum.top-j; | |
272 | } | |
273 | *(resp--)=q; | |
274 | wnump--; | |
275 | } | |
276 | if (rm != NULL) | |
277 | { | |
278 | BN_rshift(rm,snum,norm_shift); | |
279 | rm->neg=num->neg; | |
280 | } | |
281 | return(1); | |
282 | err: | |
283 | return(0); | |
284 | } | |
285 | ||
286 | #endif |