286 lines
7.3 KiB
C
286 lines
7.3 KiB
C
/* crypto/bn/bn_div.c */
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/* Copyright (C) 1995-1997 Eric Young (eay@cryptsoft.com)
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* All rights reserved.
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*
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* This package is an SSL implementation written
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* by Eric Young (eay@cryptsoft.com).
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* The implementation was written so as to conform with Netscapes SSL.
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*
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* This library is free for commercial and non-commercial use as long as
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* the following conditions are aheared to. The following conditions
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* apply to all code found in this distribution, be it the RC4, RSA,
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* lhash, DES, etc., code; not just the SSL code. The SSL documentation
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* included with this distribution is covered by the same copyright terms
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* except that the holder is Tim Hudson (tjh@cryptsoft.com).
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*
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* Copyright remains Eric Young's, and as such any Copyright notices in
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* the code are not to be removed.
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* If this package is used in a product, Eric Young should be given attribution
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* as the author of the parts of the library used.
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* This can be in the form of a textual message at program startup or
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* in documentation (online or textual) provided with the package.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* "This product includes cryptographic software written by
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* Eric Young (eay@cryptsoft.com)"
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* The word 'cryptographic' can be left out if the rouines from the library
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* being used are not cryptographic related :-).
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* 4. If you include any Windows specific code (or a derivative thereof) from
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* the apps directory (application code) you must include an acknowledgement:
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* "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
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*
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* THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* The licence and distribution terms for any publically available version or
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* derivative of this code cannot be changed. i.e. this code cannot simply be
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* copied and put under another distribution licence
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* [including the GNU Public Licence.]
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*/
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#include <stdio.h>
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#include "cryptlib.h"
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#include "bn_lcl.h"
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/* The old slow way */
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#if 0
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int BN_div(dv, rem, m, d,ctx)
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BIGNUM *dv;
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BIGNUM *rem;
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BIGNUM *m;
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BIGNUM *d;
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BN_CTX *ctx;
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{
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int i,nm,nd;
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BIGNUM *D;
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if (BN_is_zero(d))
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{
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BNerr(BN_F_BN_DIV,BN_R_DIV_BY_ZERO);
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return(0);
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}
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if (BN_ucmp(m,d) < 0)
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{
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if (rem != NULL)
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{ if (BN_copy(rem,m) == NULL) return(0); }
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if (dv != NULL) BN_zero(dv);
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return(1);
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}
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D=ctx->bn[ctx->tos];
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if (dv == NULL) dv=ctx->bn[ctx->tos+1];
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if (rem == NULL) rem=ctx->bn[ctx->tos+2];
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nd=BN_num_bits(d);
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nm=BN_num_bits(m);
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if (BN_copy(D,d) == NULL) return(0);
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if (BN_copy(rem,m) == NULL) return(0);
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/* The next 2 are needed so we can do a dv->d[0]|=1 later
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* since BN_lshift1 will only work once there is a value :-) */
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BN_zero(dv);
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dv->top=1;
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if (!BN_lshift(D,D,nm-nd)) return(0);
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for (i=nm-nd; i>=0; i--)
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{
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if (!BN_lshift1(dv,dv)) return(0);
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if (BN_ucmp(rem,D) >= 0)
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{
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dv->d[0]|=1;
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bn_qsub(rem,rem,D);
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}
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/* CAN IMPROVE (and have now :=) */
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if (!BN_rshift1(D,D)) return(0);
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}
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rem->neg=BN_is_zero(rem)?0:m->neg;
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dv->neg=m->neg^d->neg;
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return(1);
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}
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#else
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int BN_div(dv, rm, num, divisor,ctx)
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BIGNUM *dv;
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BIGNUM *rm;
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BIGNUM *num;
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BIGNUM *divisor;
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BN_CTX *ctx;
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{
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int norm_shift,i,j,loop;
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BIGNUM *tmp,wnum,*snum,*sdiv,*res;
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BN_ULONG *resp,*wnump;
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BN_ULONG d0,d1;
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int num_n,div_n;
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if (BN_is_zero(num))
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{
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BNerr(BN_F_BN_DIV,BN_R_DIV_BY_ZERO);
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return(0);
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}
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if (BN_ucmp(num,divisor) < 0)
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{
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if (rm != NULL)
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{ if (BN_copy(rm,num) == NULL) return(0); }
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if (dv != NULL) BN_zero(dv);
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return(1);
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}
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tmp=ctx->bn[ctx->tos];
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tmp->neg=0;
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snum=ctx->bn[ctx->tos+1];
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sdiv=ctx->bn[ctx->tos+2];
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if (dv == NULL)
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res=ctx->bn[ctx->tos+3];
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else res=dv;
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/* First we normalise the numbers */
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norm_shift=BN_BITS2-((BN_num_bits(divisor))%BN_BITS2);
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BN_lshift(sdiv,divisor,norm_shift);
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sdiv->neg=0;
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norm_shift+=BN_BITS2;
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BN_lshift(snum,num,norm_shift);
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snum->neg=0;
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div_n=sdiv->top;
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num_n=snum->top;
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loop=num_n-div_n;
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/* Lets setup a 'window' into snum
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* This is the part that corresponds to the current
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* 'area' being divided */
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wnum.d= &(snum->d[loop]);
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wnum.top= div_n;
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wnum.max= snum->max; /* a bit of a lie */
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wnum.neg= 0;
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/* Get the top 2 words of sdiv */
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/* i=sdiv->top; */
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d0=sdiv->d[div_n-1];
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d1=(div_n == 1)?0:sdiv->d[div_n-2];
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/* pointer to the 'top' of snum */
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wnump= &(snum->d[num_n-1]);
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/* Setup to 'res' */
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res->neg= (num->neg^divisor->neg);
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res->top=loop;
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if (!bn_expand(res,(loop+1)*BN_BITS2)) goto err;
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resp= &(res->d[loop-1]);
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/* space for temp */
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if (!bn_expand(tmp,(div_n+1)*BN_BITS2)) goto err;
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if (BN_ucmp(&wnum,sdiv) >= 0)
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{
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bn_qsub(&wnum,&wnum,sdiv);
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*resp=1;
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res->d[res->top-1]=1;
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}
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else
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res->top--;
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resp--;
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for (i=0; i<loop-1; i++)
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{
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BN_ULONG q,n0,n1;
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BN_ULONG l0;
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wnum.d--; wnum.top++;
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n0=wnump[0];
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n1=wnump[-1];
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if (n0 == d0)
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q=BN_MASK2;
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else
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q=bn_div64(n0,n1,d0);
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{
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#ifdef BN_LLONG
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BN_ULLONG t1,t2,rem;
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t1=((BN_ULLONG)n0<<BN_BITS2)|n1;
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for (;;)
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{
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t2=(BN_ULLONG)d1*q;
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rem=t1-(BN_ULLONG)q*d0;
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if ((rem>>BN_BITS2) ||
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(t2 <= ((BN_ULLONG)(rem<<BN_BITS2)+wnump[-2])))
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break;
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q--;
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}
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#else
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BN_ULONG t1l,t1h,t2l,t2h,t3l,t3h,ql,qh,t3t;
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t1h=n0;
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t1l=n1;
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for (;;)
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{
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t2l=LBITS(d1); t2h=HBITS(d1);
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ql =LBITS(q); qh =HBITS(q);
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mul64(t2l,t2h,ql,qh); /* t2=(BN_ULLONG)d1*q; */
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t3t=LBITS(d0); t3h=HBITS(d0);
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mul64(t3t,t3h,ql,qh); /* t3=t1-(BN_ULLONG)q*d0; */
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t3l=(t1l-t3t);
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if (t3l > t1l) t3h++;
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t3h=(t1h-t3h);
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/*if ((t3>>BN_BITS2) ||
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(t2 <= ((t3<<BN_BITS2)+wnump[-2])))
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break; */
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if (t3h) break;
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if (t2h < t3l) break;
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if ((t2h == t3l) && (t2l <= wnump[-2])) break;
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q--;
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}
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#endif
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}
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l0=bn_mul_word(tmp->d,sdiv->d,div_n,q);
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tmp->d[div_n]=l0;
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for (j=div_n+1; j>0; j--)
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if (tmp->d[j-1]) break;
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tmp->top=j;
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j=wnum.top;
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BN_sub(&wnum,&wnum,tmp);
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snum->top=snum->top+wnum.top-j;
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if (wnum.neg)
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{
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q--;
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j=wnum.top;
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BN_add(&wnum,&wnum,sdiv);
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snum->top+=wnum.top-j;
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}
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*(resp--)=q;
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wnump--;
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}
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if (rm != NULL)
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{
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BN_rshift(rm,snum,norm_shift);
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rm->neg=num->neg;
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}
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return(1);
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err:
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return(0);
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}
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#endif
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