/* 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