K2.6 patches and update.

[tomato.git] / release / src / router / openssl / crypto / bn / bn_div.c

/* crypto/bn/bn_div.c */
/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
 * All rights reserved.
 *
 * This package is an SSL implementation written
 * by Eric Young (eay@cryptsoft.com).
 * The implementation was written so as to conform with Netscapes SSL.
 * 
 * This library is free for commercial and non-commercial use as long as
 * the following conditions are aheared to.  The following conditions
 * apply to all code found in this distribution, be it the RC4, RSA,
 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
 * included with this distribution is covered by the same copyright terms
 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
 * 
 * Copyright remains Eric Young's, and as such any Copyright notices in
 * the code are not to be removed.
 * If this package is used in a product, Eric Young should be given attribution
 * as the author of the parts of the library used.
 * This can be in the form of a textual message at program startup or
 * in documentation (online or textual) provided with the package.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    "This product includes cryptographic software written by
 *     Eric Young (eay@cryptsoft.com)"
 *    The word 'cryptographic' can be left out if the rouines from the library
 *    being used are not cryptographic related :-).
 * 4. If you include any Windows specific code (or a derivative thereof) from 
 *    the apps directory (application code) you must include an acknowledgement:
 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
 * 
 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * 
 * The licence and distribution terms for any publically available version or
 * derivative of this code cannot be changed.  i.e. this code cannot simply be
 * copied and put under another distribution licence
 * [including the GNU Public Licence.]
 */

#include <stdio.h>
#include <openssl/bn.h>
#include "cryptlib.h"
#include "bn_lcl.h"


/* The old slow way */
#if 0
int BN_div(BIGNUM *dv, BIGNUM *rem, const BIGNUM *m, const BIGNUM *d,
           BN_CTX *ctx)
        {
        int i,nm,nd;
        int ret = 0;
        BIGNUM *D;

        bn_check_top(m);
        bn_check_top(d);
        if (BN_is_zero(d))
                {
                BNerr(BN_F_BN_DIV,BN_R_DIV_BY_ZERO);
                return(0);
                }

        if (BN_ucmp(m,d) < 0)
                {
                if (rem != NULL)
                        { if (BN_copy(rem,m) == NULL) return(0); }
                if (dv != NULL) BN_zero(dv);
                return(1);
                }

        BN_CTX_start(ctx);
        D = BN_CTX_get(ctx);
        if (dv == NULL) dv = BN_CTX_get(ctx);
        if (rem == NULL) rem = BN_CTX_get(ctx);
        if (D == NULL || dv == NULL || rem == NULL)
                goto end;

        nd=BN_num_bits(d);
        nm=BN_num_bits(m);
        if (BN_copy(D,d) == NULL) goto end;
        if (BN_copy(rem,m) == NULL) goto end;

        /* The next 2 are needed so we can do a dv->d[0]|=1 later
         * since BN_lshift1 will only work once there is a value :-) */
        BN_zero(dv);
        if(bn_wexpand(dv,1) == NULL) goto end;
        dv->top=1;

        if (!BN_lshift(D,D,nm-nd)) goto end;
        for (i=nm-nd; i>=0; i--)
                {
                if (!BN_lshift1(dv,dv)) goto end;
                if (BN_ucmp(rem,D) >= 0)
                        {
                        dv->d[0]|=1;
                        if (!BN_usub(rem,rem,D)) goto end;
                        }
/* CAN IMPROVE (and have now :=) */
                if (!BN_rshift1(D,D)) goto end;
                }
        rem->neg=BN_is_zero(rem)?0:m->neg;
        dv->neg=m->neg^d->neg;
        ret = 1;
 end:
        BN_CTX_end(ctx);
        return(ret);
        }

#else

#if !defined(OPENSSL_NO_ASM) && !defined(OPENSSL_NO_INLINE_ASM) \
    && !defined(PEDANTIC) && !defined(BN_DIV3W)
# if defined(__GNUC__) && __GNUC__>=2
#  if defined(__i386) || defined (__i386__)
   /*
    * There were two reasons for implementing this template:
    * - GNU C generates a call to a function (__udivdi3 to be exact)
    *   in reply to ((((BN_ULLONG)n0)<<BN_BITS2)|n1)/d0 (I fail to
    *   understand why...);
    * - divl doesn't only calculate quotient, but also leaves
    *   remainder in %edx which we can definitely use here:-)
    *
    *                                   <appro@fy.chalmers.se>
    */
#  define bn_div_words(n0,n1,d0)                \
        ({  asm volatile (                      \
                "divl   %4"                     \
                : "=a"(q), "=d"(rem)            \
                : "a"(n1), "d"(n0), "g"(d0)     \
                : "cc");                        \
            q;                                  \
        })
#  define REMAINDER_IS_ALREADY_CALCULATED
#  elif defined(__x86_64) && defined(SIXTY_FOUR_BIT_LONG)
   /*
    * Same story here, but it's 128-bit by 64-bit division. Wow!
    *                                   <appro@fy.chalmers.se>
    */
#  define bn_div_words(n0,n1,d0)                \
        ({  asm volatile (                      \
                "divq   %4"                     \
                : "=a"(q), "=d"(rem)            \
                : "a"(n1), "d"(n0), "g"(d0)     \
                : "cc");                        \
            q;                                  \
        })
#  define REMAINDER_IS_ALREADY_CALCULATED
#  endif /* __<cpu> */
# endif /* __GNUC__ */
#endif /* OPENSSL_NO_ASM */


/* BN_div computes  dv := num / divisor,  rounding towards
 * zero, and sets up rm  such that  dv*divisor + rm = num  holds.
 * Thus:
 *     dv->neg == num->neg ^ divisor->neg  (unless the result is zero)
 *     rm->neg == num->neg                 (unless the remainder is zero)
 * If 'dv' or 'rm' is NULL, the respective value is not returned.
 */
int BN_div(BIGNUM *dv, BIGNUM *rm, const BIGNUM *num, const BIGNUM *divisor,
           BN_CTX *ctx)
        {
        int norm_shift,i,loop;
        BIGNUM *tmp,wnum,*snum,*sdiv,*res;
        BN_ULONG *resp,*wnump;
        BN_ULONG d0,d1;
        int num_n,div_n;
        int no_branch=0;

        /* Invalid zero-padding would have particularly bad consequences
         * in the case of 'num', so don't just rely on bn_check_top() for this one
         * (bn_check_top() works only for BN_DEBUG builds) */
        if (num->top > 0 && num->d[num->top - 1] == 0)
                {
                BNerr(BN_F_BN_DIV,BN_R_NOT_INITIALIZED);
                return 0;
                }

        bn_check_top(num);

        if ((BN_get_flags(num, BN_FLG_CONSTTIME) != 0) || (BN_get_flags(divisor, BN_FLG_CONSTTIME) != 0))
                {
                no_branch=1;
                }

        bn_check_top(dv);
        bn_check_top(rm);
        /* bn_check_top(num); */ /* 'num' has been checked already */
        bn_check_top(divisor);

        if (BN_is_zero(divisor))
                {
                BNerr(BN_F_BN_DIV,BN_R_DIV_BY_ZERO);
                return(0);
                }

        if (!no_branch && BN_ucmp(num,divisor) < 0)
                {
                if (rm != NULL)
                        { if (BN_copy(rm,num) == NULL) return(0); }
                if (dv != NULL) BN_zero(dv);
                return(1);
                }

        BN_CTX_start(ctx);
        tmp=BN_CTX_get(ctx);
        snum=BN_CTX_get(ctx);
        sdiv=BN_CTX_get(ctx);
        if (dv == NULL)
                res=BN_CTX_get(ctx);
        else    res=dv;
        if (sdiv == NULL || res == NULL || tmp == NULL || snum == NULL)
                goto err;

        /* First we normalise the numbers */
        norm_shift=BN_BITS2-((BN_num_bits(divisor))%BN_BITS2);
        if (!(BN_lshift(sdiv,divisor,norm_shift))) goto err;
        sdiv->neg=0;
        norm_shift+=BN_BITS2;
        if (!(BN_lshift(snum,num,norm_shift))) goto err;
        snum->neg=0;

        if (no_branch)
                {
                /* Since we don't know whether snum is larger than sdiv,
                 * we pad snum with enough zeroes without changing its
                 * value. 
                 */
                if (snum->top <= sdiv->top+1) 
                        {
                        if (bn_wexpand(snum, sdiv->top + 2) == NULL) goto err;
                        for (i = snum->top; i < sdiv->top + 2; i++) snum->d[i] = 0;
                        snum->top = sdiv->top + 2;
                        }
                else
                        {
                        if (bn_wexpand(snum, snum->top + 1) == NULL) goto err;
                        snum->d[snum->top] = 0;
                        snum->top ++;
                        }
                }

        div_n=sdiv->top;
        num_n=snum->top;
        loop=num_n-div_n;
        /* Lets setup a 'window' into snum
         * This is the part that corresponds to the current
         * 'area' being divided */
        wnum.neg   = 0;
        wnum.d     = &(snum->d[loop]);
        wnum.top   = div_n;
        /* only needed when BN_ucmp messes up the values between top and max */
        wnum.dmax  = snum->dmax - loop; /* so we don't step out of bounds */

        /* Get the top 2 words of sdiv */
        /* div_n=sdiv->top; */
        d0=sdiv->d[div_n-1];
        d1=(div_n == 1)?0:sdiv->d[div_n-2];

        /* pointer to the 'top' of snum */
        wnump= &(snum->d[num_n-1]);

        /* Setup to 'res' */
        res->neg= (num->neg^divisor->neg);
        if (!bn_wexpand(res,(loop+1))) goto err;
        res->top=loop-no_branch;
        resp= &(res->d[loop-1]);

        /* space for temp */
        if (!bn_wexpand(tmp,(div_n+1))) goto err;

        if (!no_branch)
                {
                if (BN_ucmp(&wnum,sdiv) >= 0)
                        {
                        /* If BN_DEBUG_RAND is defined BN_ucmp changes (via
                         * bn_pollute) the const bignum arguments =>
                         * clean the values between top and max again */
                        bn_clear_top2max(&wnum);
                        bn_sub_words(wnum.d, wnum.d, sdiv->d, div_n);
                        *resp=1;
                        }
                else
                        res->top--;
                }

        /* if res->top == 0 then clear the neg value otherwise decrease
         * the resp pointer */
        if (res->top == 0)
                res->neg = 0;
        else
                resp--;

        for (i=0; i<loop-1; i++, wnump--, resp--)
                {
                BN_ULONG q,l0;
                /* the first part of the loop uses the top two words of
                 * snum and sdiv to calculate a BN_ULONG q such that
                 * | wnum - sdiv * q | < sdiv */
#if defined(BN_DIV3W) && !defined(OPENSSL_NO_ASM)
                BN_ULONG bn_div_3_words(BN_ULONG*,BN_ULONG,BN_ULONG);
                q=bn_div_3_words(wnump,d1,d0);
#else
                BN_ULONG n0,n1,rem=0;

                n0=wnump[0];
                n1=wnump[-1];
                if (n0 == d0)
                        q=BN_MASK2;
                else                    /* n0 < d0 */
                        {
#ifdef BN_LLONG
                        BN_ULLONG t2;

#if defined(BN_LLONG) && defined(BN_DIV2W) && !defined(bn_div_words)
                        q=(BN_ULONG)(((((BN_ULLONG)n0)<<BN_BITS2)|n1)/d0);
#else
                        q=bn_div_words(n0,n1,d0);
#ifdef BN_DEBUG_LEVITTE
                        fprintf(stderr,"DEBUG: bn_div_words(0x%08X,0x%08X,0x%08\
X) -> 0x%08X\n",
                                n0, n1, d0, q);
#endif
#endif

#ifndef REMAINDER_IS_ALREADY_CALCULATED
                        /*
                         * rem doesn't have to be BN_ULLONG. The least we
                         * know it's less that d0, isn't it?
                         */
                        rem=(n1-q*d0)&BN_MASK2;
#endif
                        t2=(BN_ULLONG)d1*q;

                        for (;;)
                                {
                                if (t2 <= ((((BN_ULLONG)rem)<<BN_BITS2)|wnump[-2]))
                                        break;
                                q--;
                                rem += d0;
                                if (rem < d0) break; /* don't let rem overflow */
                                t2 -= d1;
                                }
#else /* !BN_LLONG */
                        BN_ULONG t2l,t2h;

                        q=bn_div_words(n0,n1,d0);
#ifdef BN_DEBUG_LEVITTE
                        fprintf(stderr,"DEBUG: bn_div_words(0x%08X,0x%08X,0x%08\
X) -> 0x%08X\n",
                                n0, n1, d0, q);
#endif
#ifndef REMAINDER_IS_ALREADY_CALCULATED
                        rem=(n1-q*d0)&BN_MASK2;
#endif

#if defined(BN_UMULT_LOHI)
                        BN_UMULT_LOHI(t2l,t2h,d1,q);
#elif defined(BN_UMULT_HIGH)
                        t2l = d1 * q;
                        t2h = BN_UMULT_HIGH(d1,q);
#else
                        {
                        BN_ULONG ql, qh;
                        t2l=LBITS(d1); t2h=HBITS(d1);
                        ql =LBITS(q);  qh =HBITS(q);
                        mul64(t2l,t2h,ql,qh); /* t2=(BN_ULLONG)d1*q; */
                        }
#endif

                        for (;;)
                                {
                                if ((t2h < rem) ||
                                        ((t2h == rem) && (t2l <= wnump[-2])))
                                        break;
                                q--;
                                rem += d0;
                                if (rem < d0) break; /* don't let rem overflow */
                                if (t2l < d1) t2h--; t2l -= d1;
                                }
#endif /* !BN_LLONG */
                        }
#endif /* !BN_DIV3W */

                l0=bn_mul_words(tmp->d,sdiv->d,div_n,q);
                tmp->d[div_n]=l0;
                wnum.d--;
                /* ingore top values of the bignums just sub the two 
                 * BN_ULONG arrays with bn_sub_words */
                if (bn_sub_words(wnum.d, wnum.d, tmp->d, div_n+1))
                        {
                        /* Note: As we have considered only the leading
                         * two BN_ULONGs in the calculation of q, sdiv * q
                         * might be greater than wnum (but then (q-1) * sdiv
                         * is less or equal than wnum)
                         */
                        q--;
                        if (bn_add_words(wnum.d, wnum.d, sdiv->d, div_n))
                                /* we can't have an overflow here (assuming
                                 * that q != 0, but if q == 0 then tmp is
                                 * zero anyway) */
                                (*wnump)++;
                        }
                /* store part of the result */
                *resp = q;
                }
        bn_correct_top(snum);
        if (rm != NULL)
                {
                /* Keep a copy of the neg flag in num because if rm==num
                 * BN_rshift() will overwrite it.
                 */
                int neg = num->neg;
                BN_rshift(rm,snum,norm_shift);
                if (!BN_is_zero(rm))
                        rm->neg = neg;
                bn_check_top(rm);
                }
        if (no_branch)  bn_correct_top(res);
        BN_CTX_end(ctx);
        return(1);
err:
        bn_check_top(rm);
        BN_CTX_end(ctx);
        return(0);
        }
#endif