341 lines
6.1 KiB
C
341 lines
6.1 KiB
C
/* crypto/bn/div.c */
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#include <stdio.h>
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#include "cryptlib.h"
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#include "bn.h"
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BN_ULONG bn_div_2word();
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int BN_div2(dv, rm, num, div,ctx)
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BIGNUM *dv;
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BIGNUM *rm;
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BIGNUM *num;
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BIGNUM *div;
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BN_CTX *ctx;
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{
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int norm_shift,i,j,nm,nd,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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#ifdef DEBUG
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BN_print(stdout,num); printf(" number\n");
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BN_print(stdout,div); printf(" divisor\n");
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#endif
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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_cmp(num,div) < 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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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(div))%BN_BITS2);
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BN_lshift(sdiv,div,norm_shift);
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norm_shift+=BN_BITS2;
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BN_lshift(snum,num,norm_shift);
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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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#ifdef DEBUG
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BN_print(stdout,snum); printf(" shifted num, forget last word\n");
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BN_print(stdout,sdiv); printf(" shifted div\n");
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#endif
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/* Lets setup a 'win'dow 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=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=0;
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res->top=loop;
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resp= &(res->d[loop-1]);
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bn_expand(res,(loop+1)*BN_BITS2);
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/* space for temp */
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bn_expand(tmp,(div_n+1)*BN_BITS2);
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#ifdef DEBUG
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printf("wnum="); BN_print(stdout,&wnum); printf(" initial sub check\n");
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printf("div ="); BN_print(stdout,sdiv); printf(" loop=%d\n",loop);
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#endif
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if (BN_cmp(&wnum,sdiv) >= 0)
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{
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BN_sub(&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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#ifdef DEBUG
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BN_print(stdout,res); printf(" initial result\n");
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BN_print(stdout,&wnum); printf(" wnum\n");
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#endif
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for (i=0; i<loop-1; i++)
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{
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BN_ULONG q,n0;
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BN_ULLONG t1,t2,t3;
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BN_ULONG l0;
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wnum.d--;
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wnum.top++;
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#ifdef DEBUG
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BN_print(stderr,&wnum); printf(" to divide\n");
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#endif
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q=0;
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n0=wnump[0];
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t1=((BN_ULLONG)n0<<BN_BITS2)|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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{
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t2=(t1/d0);
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q=(t2&BN_MASK2);
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#ifdef DEBUG
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printf("t1=%08X / d0=%08X = %X (%X)\n",t1,d0,q,t2);
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#endif
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}
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for (;;)
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{
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t2=(BN_ULLONG)d1*q;
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t3=t1-(BN_ULLONG)q*d0;
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#ifdef DEBUG
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printf("d1*q= %X n01-q*d0 = %X\n",t2,t3);
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#endif
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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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#ifdef DEBUG
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printf("reduce q\n");
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#endif
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q--;
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}
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l0=bn_mul_word(tmp->d,sdiv->d,div_n,q);
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if (l0)
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tmp->d[div_n]=l0;
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else
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tmp->d[div_n]=0;
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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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#ifdef DEBUG
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printf("q=%08X\n",q);
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BN_print(stdout,&wnum); printf(" number\n");
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BN_print(stdout,tmp); printf(" subtract\n");
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BN_print(stdout,snum); printf(" shifted number before\n");
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BN_print(stdout,&wnum); printf(" wnum before\n");
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#endif
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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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#ifdef DEBUG
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BN_print(stdout,&wnum); printf(" wnum after\n");
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BN_print(stdout,snum); printf(" shifted number after\n");
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#endif
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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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fprintf(stderr,"addback\n");
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#ifdef DEBUG
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BN_print(stdout,snum); printf("after addback************************:\n");
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#endif
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}
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*(resp--)=q;
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#ifdef DEBUG
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BN_print(stdout,res); printf(" result\n");
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#endif
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wnump--;
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}
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if (rm != NULL)
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BN_rshift(rm,snum,norm_shift);
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return(1);
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}
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main()
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{
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BIGNUM *a,*b,*c,*d;
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BIGNUM *cc,*dd;
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BN_CTX *ctx;
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int i,x;
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a=BN_new();
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b=BN_new();
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c=BN_new();
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d=BN_new();
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cc=BN_new();
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dd=BN_new();
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ctx=BN_CTX_new();
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for (i=0; i<10240; i++)
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{
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BN_rand(a,80,0,0);
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BN_rand(b,60,0,0);
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BN_div2(d,c,a,b,ctx);
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BN_div(dd,cc,a,b,ctx);
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if ((BN_cmp(d,dd) != 0) || (BN_cmp(c,cc) != 0))
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{
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BN_print(stderr,a); fprintf(stderr," / ");
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BN_print(stderr,b); fprintf(stderr," d=");
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BN_print(stderr,d); fprintf(stderr," r= ");
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BN_print(stderr,c); fprintf(stderr,"\nd=");
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BN_print(stderr,dd); fprintf(stderr," r= ");
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BN_print(stderr,cc); fprintf(stderr,"\n");
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}
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}
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#ifdef undef
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/*
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BN_rand(a,600,0,0);
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BN_rand(b,400,0,0);
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for (i=0; i<2000000; i++)
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{
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BN_div2(d,c,a,b,ctx);
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}
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*/
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/* for (i=0;;) */
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/* for (i=0; i<0xffffffff; i++)
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{
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BN_ULONG rr,r,a,b,c;
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BN_ULLONG l;
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a=rand()&BN_MASK2;
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b=rand()&BN_MASK2;
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for (;;)
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{
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c=rand()&BN_MASK2;
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if (c) break;
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}
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/* for (x=1; x<256*256; x++) */
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{
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c=x;
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a=i>>8;
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b=i&0xff;
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a&= ~(0xFFFFFF<<(BN_num_bits_word(c)));
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r=bn_div_2word(a,b,c);
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rr=(BN_ULONG)((((BN_ULLONG)a<<BN_BITS2)|b)/c);
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if ((i & 0xfffff) == 0) fprintf(stderr,"%d\n",i,r,rr);
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/*if (x == 255)
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fprintf(stderr,"%6d/%3d = %4d %4d\n",(a<<8)|b,c,r,rr); */
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if (rr != r)
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{
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fprintf(stderr,"%8d %02X%02X / %02X = %02X %02X\n",
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i,a,b,c,rr,r);
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abort();
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}
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}
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}
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#endif
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}
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/* Divide h-l by d and return the result. */
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BN_ULONG bn_div_2word(l,h,d)
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BN_ULONG l,h,d;
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{
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BN_ULONG dh,dl,q,ret=0,th,tl,t,top;
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int i,count=2;
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if (d == 0) return(-1);
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i=BN_num_bits_word(d);
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if ((i != BN_BITS2) && (h > 1<<i))
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{
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fprintf(stderr,"Division would overflow\n");
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abort();
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}
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i=BN_BITS2-i;
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if (h >= d) h-=d;
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if (i)
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{
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d<<=i;
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h=(h<<i)|(l>>(BN_BITS2-i));
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l<<=i;
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}
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dh=(d&BN_MASK2h)>>BN_BITS4;
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dl=(d&BN_MASK2l);
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for (;;)
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{
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if ((h>>BN_BITS4) == dh)
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q=BN_MASK2l;
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else
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q=h/dh;
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for (;;)
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{
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t=(h-q*dh);
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if ((t&BN_MASK2h) ||
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((dl*q) <= (
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(t<<BN_BITS4)+
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((l&BN_MASK2h)>>BN_BITS4))))
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break;
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q--;
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}
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th=q*dh;
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tl=q*dl;
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t=(tl>>BN_BITS4);
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tl=(tl<<BN_BITS4)&BN_MASK2h;
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th+=t;
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if (l < tl) th++;
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l-=tl;
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if (h < th)
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{
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fprintf(stderr,"add back\n");
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h+=d;
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q--;
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}
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h-=th;
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if (--count == 0) break;
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ret=q<<BN_BITS4;
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h=((h<<BN_BITS4)|(l>>BN_BITS4))&BN_MASK2;
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l=(l&BN_MASK2l)<<BN_BITS4;
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}
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ret|=q;
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return(ret);
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}
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