1 /* crypto/bn/bn_div.c */
2 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
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.
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).
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.
23 * Redistribution and use in source and binary forms, with or without
24 * modification, are permitted provided that the following conditions
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)"
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
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.]
63 /* The old slow way */
65 int BN_div(dv, rem, m, d,ctx)
77 BNerr(BN_F_BN_DIV,BN_R_DIV_BY_ZERO);
84 { if (BN_copy(rem,m) == NULL) return(0); }
85 if (dv != NULL) BN_zero(dv);
90 if (dv == NULL) dv=ctx->bn[ctx->tos+1];
91 if (rem == NULL) rem=ctx->bn[ctx->tos+2];
95 if (BN_copy(D,d) == NULL) return(0);
96 if (BN_copy(rem,m) == NULL) return(0);
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 :-) */
103 if (!BN_lshift(D,D,nm-nd)) return(0);
104 for (i=nm-nd; i>=0; i--)
106 if (!BN_lshift1(dv,dv)) return(0);
107 if (BN_ucmp(rem,D) >= 0)
112 /* CAN IMPROVE (and have now :=) */
113 if (!BN_rshift1(D,D)) return(0);
115 rem->neg=BN_is_zero(rem)?0:m->neg;
116 dv->neg=m->neg^d->neg;
122 int BN_div(dv, rm, num, divisor,ctx)
129 int norm_shift,i,j,loop;
130 BIGNUM *tmp,wnum,*snum,*sdiv,*res;
131 BN_ULONG *resp,*wnump;
135 if (BN_is_zero(divisor))
137 BNerr(BN_F_BN_DIV,BN_R_DIV_BY_ZERO);
141 if (BN_ucmp(num,divisor) < 0)
144 { if (BN_copy(rm,num) == NULL) return(0); }
145 if (dv != NULL) BN_zero(dv);
149 tmp=ctx->bn[ctx->tos];
151 snum=ctx->bn[ctx->tos+1];
152 sdiv=ctx->bn[ctx->tos+2];
154 res=ctx->bn[ctx->tos+3];
157 /* First we normalise the numbers */
158 norm_shift=BN_BITS2-((BN_num_bits(divisor))%BN_BITS2);
159 BN_lshift(sdiv,divisor,norm_shift);
161 norm_shift+=BN_BITS2;
162 BN_lshift(snum,num,norm_shift);
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]);
173 wnum.max= snum->max; /* a bit of a lie */
176 /* Get the top 2 words of sdiv */
179 d1=(div_n == 1)?0:sdiv->d[div_n-2];
181 /* pointer to the 'top' of snum */
182 wnump= &(snum->d[num_n-1]);
185 res->neg= (num->neg^divisor->neg);
187 if (!bn_wexpand(res,(loop+1))) goto err;
188 resp= &(res->d[loop-1]);
191 if (!bn_wexpand(tmp,(div_n+1))) goto err;
193 if (BN_ucmp(&wnum,sdiv) >= 0)
195 bn_qsub(&wnum,&wnum,sdiv);
197 res->d[res->top-1]=1;
203 for (i=0; i<loop-1; i++)
208 wnum.d--; wnum.top++;
214 q=bn_div64(n0,n1,d0);
218 t1=((BN_ULLONG)n0<<BN_BITS2)|n1;
222 rem=t1-(BN_ULLONG)q*d0;
223 if ((rem>>BN_BITS2) ||
224 (t2 <= ((BN_ULLONG)(rem<<BN_BITS2)+wnump[-2])))
229 BN_ULONG t1l,t1h,t2l,t2h,t3l,t3h,ql,qh,t3t;
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; */
238 t3t=LBITS(d0); t3h=HBITS(d0);
239 mul64(t3t,t3h,ql,qh); /* t3=t1-(BN_ULLONG)q*d0; */
240 t3l=(t1l-t3t)&BN_MASK2;
241 if (t3l > t1l) t3h++;
242 t3h=(t1h-t3h)&BN_MASK2;
244 /*if ((t3>>BN_BITS2) ||
245 (t2 <= ((t3<<BN_BITS2)+wnump[-2])))
248 if (t2h < t3l) break;
249 if ((t2h == t3l) && (t2l <= wnump[-2])) break;
255 l0=bn_mul_words(tmp->d,sdiv->d,div_n,q);
257 for (j=div_n+1; j>0; j--)
258 if (tmp->d[j-1]) break;
262 BN_sub(&wnum,&wnum,tmp);
264 snum->top=snum->top+wnum.top-j;
270 BN_add(&wnum,&wnum,sdiv);
271 snum->top+=wnum.top-j;
278 BN_rshift(rm,snum,norm_shift);