/* crypto/bn/bn_sqr.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 "cryptlib.h"

#include "bn_lcl.h"

/* r must not be a */

/* I've just gone over this and it is now %20 faster on x86 - eay - 27 Jun 96 */

EXPORT_C int BN_sqr(BIGNUM *r, const BIGNUM *a, BN_CTX *ctx)

	{

	int max,al;

	int ret = 0;

	BIGNUM *tmp,*rr;

#ifdef BN_COUNT

	fprintf(stderr,"BN_sqr %d * %d\n",a->top,a->top);

#endif

	bn_check_top(a);

	al=a->top;

	if (al <= 0)

		{

		r->top=0;

		return 1;

		}

	BN_CTX_start(ctx);

	rr=(a != r) ? r : BN_CTX_get(ctx);

	tmp=BN_CTX_get(ctx);

	if (!rr || !tmp) goto err;

	max = 2 * al; /* Non-zero (from above) */

	if (bn_wexpand(rr,max) == NULL) goto err;

	if (al == 4)

		{

#ifndef BN_SQR_COMBA

		BN_ULONG t[8];

		bn_sqr_normal(rr->d,a->d,4,t);

#else

		bn_sqr_comba4(rr->d,a->d);

#endif

		}

	else if (al == 8)

		{

#ifndef BN_SQR_COMBA

		BN_ULONG t[16];

		bn_sqr_normal(rr->d,a->d,8,t);

#else

		bn_sqr_comba8(rr->d,a->d);

#endif

		}

	else 

		{

#if defined(BN_RECURSION)

		if (al < BN_SQR_RECURSIVE_SIZE_NORMAL)

			{

			BN_ULONG t[BN_SQR_RECURSIVE_SIZE_NORMAL*2];

			bn_sqr_normal(rr->d,a->d,al,t);

			}

		else

			{

			int j,k;

			j=BN_num_bits_word((BN_ULONG)al);

			j=1<<(j-1);

			k=j+j;

			if (al == j)

				{

				if (bn_wexpand(tmp,k*2) == NULL) goto err;

				bn_sqr_recursive(rr->d,a->d,al,tmp->d);

				}

			else

				{

				if (bn_wexpand(tmp,max) == NULL) goto err;

				bn_sqr_normal(rr->d,a->d,al,tmp->d);

				}

			}

#else

		if (bn_wexpand(tmp,max) == NULL) goto err;

		bn_sqr_normal(rr->d,a->d,al,tmp->d);

#endif

		}

	rr->neg=0;

	/* If the most-significant half of the top word of 'a' is zero, then

	 * the square of 'a' will max-1 words. */

	if(a->d[al - 1] == (a->d[al - 1] & BN_MASK2l))

		rr->top = max - 1;

	else

		rr->top = max;

	if (rr != r) BN_copy(r,rr);

	ret = 1;

 err:

	bn_check_top(rr);

	bn_check_top(tmp);

	BN_CTX_end(ctx);

	return(ret);

	}

/* tmp must have 2*n words */

EXPORT_C void bn_sqr_normal(BN_ULONG *r, const BN_ULONG *a, int n, BN_ULONG *tmp)

	{

	int i,j,max;

	const BN_ULONG *ap;

	BN_ULONG *rp;

	max=n*2;

	ap=a;

	rp=r;

	rp[0]=rp[max-1]=0;

	rp++;

	j=n;

	if (--j > 0)

		{

		ap++;

		rp[j]=bn_mul_words(rp,ap,j,ap[-1]);

		rp+=2;

		}

	for (i=n-2; i>0; i--)

		{

		j--;

		ap++;

		rp[j]=bn_mul_add_words(rp,ap,j,ap[-1]);

		rp+=2;

		}

	bn_add_words(r,r,r,max);

	/* There will not be a carry */

	bn_sqr_words(tmp,a,n);

	bn_add_words(r,r,tmp,max);

	}

#ifdef BN_RECURSION

/* r is 2*n words in size,

 * a and b are both n words in size.    (There's not actually a 'b' here ...)

 * n must be a power of 2.

 * We multiply and return the result.

 * t must be 2*n words in size

 * We calculate

 * a[0]*b[0]

 * a[0]*b[0]+a[1]*b[1]+(a[0]-a[1])*(b[1]-b[0])

 * a[1]*b[1]

 */

EXPORT_C void bn_sqr_recursive(BN_ULONG *r, const BN_ULONG *a, int n2, BN_ULONG *t)

	{

	int n=n2/2;

	int zero,c1;

	BN_ULONG ln,lo,*p;

#ifdef BN_COUNT

	fprintf(stderr," bn_sqr_recursive %d * %d\n",n2,n2);

#endif

	if (n2 == 4)

		{

#ifndef BN_SQR_COMBA

		bn_sqr_normal(r,a,4,t);

#else

		bn_sqr_comba4(r,a);

#endif

		return;

		}

	else if (n2 == 8)

		{

#ifndef BN_SQR_COMBA

		bn_sqr_normal(r,a,8,t);

#else

		bn_sqr_comba8(r,a);

#endif

		return;

		}

	if (n2 < BN_SQR_RECURSIVE_SIZE_NORMAL)

		{

		bn_sqr_normal(r,a,n2,t);

		return;

		}

	/* r=(a[0]-a[1])*(a[1]-a[0]) */

	c1=bn_cmp_words(a,&(a[n]),n);

	zero=0;

	if (c1 > 0)

		bn_sub_words(t,a,&(a[n]),n);

	else if (c1 < 0)

		bn_sub_words(t,&(a[n]),a,n);

	else

		zero=1;

	/* The result will always be negative unless it is zero */

	p= &(t[n2*2]);

	if (!zero)

		bn_sqr_recursive(&(t[n2]),t,n,p);

	else

		memset(&(t[n2]),0,n2*sizeof(BN_ULONG));

	bn_sqr_recursive(r,a,n,p);

	bn_sqr_recursive(&(r[n2]),&(a[n]),n,p);

	/* t[32] holds (a[0]-a[1])*(a[1]-a[0]), it is negative or zero

	 * r[10] holds (a[0]*b[0])

	 * r[32] holds (b[1]*b[1])

	 */

	c1=(int)(bn_add_words(t,r,&(r[n2]),n2));

	/* t[32] is negative */

	c1-=(int)(bn_sub_words(&(t[n2]),t,&(t[n2]),n2));

	/* t[32] holds (a[0]-a[1])*(a[1]-a[0])+(a[0]*a[0])+(a[1]*a[1])

	 * r[10] holds (a[0]*a[0])

	 * r[32] holds (a[1]*a[1])

	 * c1 holds the carry bits

	 */

	c1+=(int)(bn_add_words(&(r[n]),&(r[n]),&(t[n2]),n2));

	if (c1)

		{

		p= &(r[n+n2]);

		lo= *p;

		ln=(lo+c1)&BN_MASK2;

		*p=ln;

		/* The overflow will stop before we over write

		 * words we should not overwrite */

		if (ln < (BN_ULONG)c1)

			{

			do	{

				p++;

				lo= *p;

				ln=(lo+1)&BN_MASK2;

				*p=ln;

				} while (ln == 0);

			}

		}

	}

#endif