/* crypto/bn/bn_mul.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.]

 */

#ifndef BN_DEBUG

# undef NDEBUG /* avoid conflicting definitions */

# define NDEBUG

#endif

#include <stdio.h>

#include <assert.h>

#include "cryptlib.h"

#include "bn_lcl.h"

#if defined(OPENSSL_NO_ASM) || !defined(OPENSSL_BN_ASM_PART_WORDS)

/* Here follows specialised variants of bn_add_words() and

   bn_sub_words().  They have the property performing operations on

   arrays of different sizes.  The sizes of those arrays is expressed through

   cl, which is the common length ( basicall, min(len(a),len(b)) ), and dl,

   which is the delta between the two lengths, calculated as len(a)-len(b).

   All lengths are the number of BN_ULONGs...  For the operations that require

   a result array as parameter, it must have the length cl+abs(dl).

   These functions should probably end up in bn_asm.c as soon as there are

   assembler counterparts for the systems that use assembler files.  */

EXPORT_C BN_ULONG bn_sub_part_words(BN_ULONG *r,

	const BN_ULONG *a, const BN_ULONG *b,

	int cl, int dl)

	{

	BN_ULONG c, t;

	assert(cl >= 0);

	c = bn_sub_words(r, a, b, cl);

	if (dl == 0)

		return c;

	r += cl;

	a += cl;

	b += cl;

	if (dl < 0)

		{

#ifdef BN_COUNT

		fprintf(stderr, "  bn_sub_part_words %d + %d (dl < 0, c = %d)\n", cl, dl, c);

#endif

		for (;;)

			{

			t = b[0];

			r[0] = (0-t-c)&BN_MASK2;

			if (t != 0) c=1;

			if (++dl >= 0) break;

			t = b[1];

			r[1] = (0-t-c)&BN_MASK2;

			if (t != 0) c=1;

			if (++dl >= 0) break;

			t = b[2];

			r[2] = (0-t-c)&BN_MASK2;

			if (t != 0) c=1;

			if (++dl >= 0) break;

			t = b[3];

			r[3] = (0-t-c)&BN_MASK2;

			if (t != 0) c=1;

			if (++dl >= 0) break;

			b += 4;

			r += 4;

			}

		}

	else

		{

		int save_dl = dl;

#ifdef BN_COUNT

		fprintf(stderr, "  bn_sub_part_words %d + %d (dl > 0, c = %d)\n", cl, dl, c);

#endif

		while(c)

			{

			t = a[0];

			r[0] = (t-c)&BN_MASK2;

			if (t != 0) c=0;

			if (--dl <= 0) break;

			t = a[1];

			r[1] = (t-c)&BN_MASK2;

			if (t != 0) c=0;

			if (--dl <= 0) break;

			t = a[2];

			r[2] = (t-c)&BN_MASK2;

			if (t != 0) c=0;

			if (--dl <= 0) break;

			t = a[3];

			r[3] = (t-c)&BN_MASK2;

			if (t != 0) c=0;

			if (--dl <= 0) break;

			save_dl = dl;

			a += 4;

			r += 4;

			}

		if (dl > 0)

			{

#ifdef BN_COUNT

			fprintf(stderr, "  bn_sub_part_words %d + %d (dl > 0, c == 0)\n", cl, dl);

#endif

			if (save_dl > dl)

				{

				switch (save_dl - dl)

					{

				case 1:

					r[1] = a[1];

					if (--dl <= 0) break;

				case 2:

					r[2] = a[2];

					if (--dl <= 0) break;

				case 3:

					r[3] = a[3];

					if (--dl <= 0) break;

					}

				a += 4;

				r += 4;

				}

			}

		if (dl > 0)

			{

#ifdef BN_COUNT

			fprintf(stderr, "  bn_sub_part_words %d + %d (dl > 0, copy)\n", cl, dl);

#endif

			for(;;)

				{

				r[0] = a[0];

				if (--dl <= 0) break;

				r[1] = a[1];

				if (--dl <= 0) break;

				r[2] = a[2];

				if (--dl <= 0) break;

				r[3] = a[3];

				if (--dl <= 0) break;

				a += 4;

				r += 4;

				}

			}

		}

	return c;

	}

#endif

EXPORT_C BN_ULONG bn_add_part_words(BN_ULONG *r,

	const BN_ULONG *a, const BN_ULONG *b,

	int cl, int dl)

	{

	BN_ULONG c, l, t;

	assert(cl >= 0);

	c = bn_add_words(r, a, b, cl);

	if (dl == 0)

		return c;

	r += cl;

	a += cl;

	b += cl;

	if (dl < 0)

		{

		int save_dl = dl;

#ifdef BN_COUNT

		fprintf(stderr, "  bn_add_part_words %d + %d (dl < 0, c = %d)\n", cl, dl, c);

#endif

		while (c)

			{

			l=(c+b[0])&BN_MASK2;

			c=(l < c);

			r[0]=l;

			if (++dl >= 0) break;

			l=(c+b[1])&BN_MASK2;

			c=(l < c);

			r[1]=l;

			if (++dl >= 0) break;

			l=(c+b[2])&BN_MASK2;

			c=(l < c);

			r[2]=l;

			if (++dl >= 0) break;

			l=(c+b[3])&BN_MASK2;

			c=(l < c);

			r[3]=l;

			if (++dl >= 0) break;

			save_dl = dl;

			b+=4;

			r+=4;

			}

		if (dl < 0)

			{

#ifdef BN_COUNT

			fprintf(stderr, "  bn_add_part_words %d + %d (dl < 0, c == 0)\n", cl, dl);

#endif

			if (save_dl < dl)

				{

				switch (dl - save_dl)

					{

				case 1:

					r[1] = b[1];

					if (++dl >= 0) break;

				case 2:

					r[2] = b[2];

					if (++dl >= 0) break;

				case 3:

					r[3] = b[3];

					if (++dl >= 0) break;

					}

				b += 4;

				r += 4;

				}

			}

		if (dl < 0)

			{

#ifdef BN_COUNT

			fprintf(stderr, "  bn_add_part_words %d + %d (dl < 0, copy)\n", cl, dl);

#endif

			for(;;)

				{

				r[0] = b[0];

				if (++dl >= 0) break;

				r[1] = b[1];

				if (++dl >= 0) break;

				r[2] = b[2];

				if (++dl >= 0) break;

				r[3] = b[3];

				if (++dl >= 0) break;

				b += 4;

				r += 4;

				}

			}

		}

	else

		{

		int save_dl = dl;

#ifdef BN_COUNT

		fprintf(stderr, "  bn_add_part_words %d + %d (dl > 0)\n", cl, dl);

#endif

		while (c)

			{

			t=(a[0]+c)&BN_MASK2;

			c=(t < c);

			r[0]=t;

			if (--dl <= 0) break;

			t=(a[1]+c)&BN_MASK2;

			c=(t < c);

			r[1]=t;

			if (--dl <= 0) break;

			t=(a[2]+c)&BN_MASK2;

			c=(t < c);

			r[2]=t;

			if (--dl <= 0) break;

			t=(a[3]+c)&BN_MASK2;

			c=(t < c);

			r[3]=t;

			if (--dl <= 0) break;

			save_dl = dl;

			a+=4;

			r+=4;

			}

#ifdef BN_COUNT

		fprintf(stderr, "  bn_add_part_words %d + %d (dl > 0, c == 0)\n", cl, dl);

#endif

		if (dl > 0)

			{

			if (save_dl > dl)

				{

				switch (save_dl - dl)

					{

				case 1:

					r[1] = a[1];

					if (--dl <= 0) break;

				case 2:

					r[2] = a[2];

					if (--dl <= 0) break;

				case 3:

					r[3] = a[3];

					if (--dl <= 0) break;

					}

				a += 4;

				r += 4;

				}

			}

		if (dl > 0)

			{

#ifdef BN_COUNT

			fprintf(stderr, "  bn_add_part_words %d + %d (dl > 0, copy)\n", cl, dl);

#endif

			for(;;)

				{

				r[0] = a[0];

				if (--dl <= 0) break;

				r[1] = a[1];

				if (--dl <= 0) break;

				r[2] = a[2];

				if (--dl <= 0) break;

				r[3] = a[3];

				if (--dl <= 0) break;

				a += 4;

				r += 4;

				}

			}

		}

	return c;

	}

#ifdef BN_RECURSION

/* Karatsuba recursive multiplication algorithm

 * (cf. Knuth, The Art of Computer Programming, Vol. 2) */

/* r is 2*n2 words in size,

 * a and b are both n2 words in size.

 * n2 must be a power of 2.

 * We multiply and return the result.

 * t must be 2*n2 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_mul_recursive(BN_ULONG *r, BN_ULONG *a, BN_ULONG *b, int n2,

	int dna, int dnb, BN_ULONG *t)

	{

	int n=n2/2,c1,c2;

	int tna=n+dna, tnb=n+dnb;

	unsigned int neg,zero;

	BN_ULONG ln,lo,*p;

# ifdef BN_COUNT

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

# endif

# ifdef BN_MUL_COMBA

#  if 0

	if (n2 == 4)

		{

		bn_mul_comba4(r,a,b);

		return;

		}

#  endif

	/* Only call bn_mul_comba 8 if n2 == 8 and the

	 * two arrays are complete [steve]

	 */

	if (n2 == 8 && dna == 0 && dnb == 0)

		{

		bn_mul_comba8(r,a,b);

		return; 

		}

# endif /* BN_MUL_COMBA */

	/* Else do normal multiply */

	if (n2 < BN_MUL_RECURSIVE_SIZE_NORMAL)

		{

		bn_mul_normal(r,a,n2+dna,b,n2+dnb);

		if ((dna + dnb) < 0)

			memset(&r[2*n2 + dna + dnb], 0,

				sizeof(BN_ULONG) * -(dna + dnb));

		return;

		}

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

	c1=bn_cmp_part_words(a,&(a[n]),tna,n-tna);

	c2=bn_cmp_part_words(&(b[n]),b,tnb,tnb-n);

	zero=neg=0;

	switch (c1*3+c2)

		{

	case -4:

		bn_sub_part_words(t,      &(a[n]),a,      tna,tna-n); /* - */

		bn_sub_part_words(&(t[n]),b,      &(b[n]),tnb,n-tnb); /* - */

		break;

	case -3:

		zero=1;

		break;

	case -2:

		bn_sub_part_words(t,      &(a[n]),a,      tna,tna-n); /* - */

		bn_sub_part_words(&(t[n]),&(b[n]),b,      tnb,tnb-n); /* + */

		neg=1;

		break;

	case -1:

	case 0:

	case 1:

		zero=1;

		break;

	case 2:

		bn_sub_part_words(t,      a,      &(a[n]),tna,n-tna); /* + */

		bn_sub_part_words(&(t[n]),b,      &(b[n]),tnb,n-tnb); /* - */

		neg=1;

		break;

	case 3:

		zero=1;

		break;

	case 4:

		bn_sub_part_words(t,      a,      &(a[n]),tna,n-tna);

		bn_sub_part_words(&(t[n]),&(b[n]),b,      tnb,tnb-n);

		break;

		}

# ifdef BN_MUL_COMBA

	if (n == 4 && dna == 0 && dnb == 0) /* XXX: bn_mul_comba4 could take

					       extra args to do this well */

		{

		if (!zero)

			bn_mul_comba4(&(t[n2]),t,&(t[n]));

		else

			memset(&(t[n2]),0,8*sizeof(BN_ULONG));

		bn_mul_comba4(r,a,b);

		bn_mul_comba4(&(r[n2]),&(a[n]),&(b[n]));

		}

	else if (n == 8 && dna == 0 && dnb == 0) /* XXX: bn_mul_comba8 could

						    take extra args to do this

						    well */

		{

		if (!zero)

			bn_mul_comba8(&(t[n2]),t,&(t[n]));

		else

			memset(&(t[n2]),0,16*sizeof(BN_ULONG));

		bn_mul_comba8(r,a,b);

		bn_mul_comba8(&(r[n2]),&(a[n]),&(b[n]));

		}

	else

# endif /* BN_MUL_COMBA */

		{

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

		if (!zero)

			bn_mul_recursive(&(t[n2]),t,&(t[n]),n,0,0,p);

		else

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

		bn_mul_recursive(r,a,b,n,0,0,p);

		bn_mul_recursive(&(r[n2]),&(a[n]),&(b[n]),n,dna,dnb,p);

		}

	/* t[32] holds (a[0]-a[1])*(b[1]-b[0]), c1 is the sign

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

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

	 */

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

	if (neg) /* if t[32] is negative */

		{

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

		}

	else

		{

		/* Might have a carry */

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

		}

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

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

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

			}

		}

	}

/* n+tn is the word length

 * t needs to be n*4 is size, as does r */

EXPORT_C void bn_mul_part_recursive(BN_ULONG *r, BN_ULONG *a, BN_ULONG *b, int n,

	     int tna, int tnb, BN_ULONG *t)

	{

	int i,j,n2=n*2;

	int c1,c2,neg,zero;

	BN_ULONG ln,lo,*p;

# ifdef BN_COUNT

	fprintf(stderr," bn_mul_part_recursive (%d+%d) * (%d+%d)\n",

		tna, n, tnb, n);

# endif

	if (n < 8)

		{

		bn_mul_normal(r,a,n+tna,b,n+tnb);

		return;

		}

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

	c1=bn_cmp_part_words(a,&(a[n]),tna,n-tna);

	c2=bn_cmp_part_words(&(b[n]),b,tnb,tnb-n);

	zero=neg=0;

	switch (c1*3+c2)

		{

	case -4:

		bn_sub_part_words(t,      &(a[n]),a,      tna,tna-n); /* - */

		bn_sub_part_words(&(t[n]),b,      &(b[n]),tnb,n-tnb); /* - */

		break;

	case -3:

		zero=1;

		/* break; */

	case -2:

		bn_sub_part_words(t,      &(a[n]),a,      tna,tna-n); /* - */

		bn_sub_part_words(&(t[n]),&(b[n]),b,      tnb,tnb-n); /* + */

		neg=1;

		break;

	case -1:

	case 0:

	case 1:

		zero=1;

		/* break; */

	case 2:

		bn_sub_part_words(t,      a,      &(a[n]),tna,n-tna); /* + */

		bn_sub_part_words(&(t[n]),b,      &(b[n]),tnb,n-tnb); /* - */

		neg=1;

		break;

	case 3:

		zero=1;

		/* break; */

	case 4:

		bn_sub_part_words(t,      a,      &(a[n]),tna,n-tna);

		bn_sub_part_words(&(t[n]),&(b[n]),b,      tnb,tnb-n);

		break;

		}

		/* The zero case isn't yet implemented here. The speedup

		   would probably be negligible. */

# if 0

	if (n == 4)

		{

		bn_mul_comba4(&(t[n2]),t,&(t[n]));

		bn_mul_comba4(r,a,b);

		bn_mul_normal(&(r[n2]),&(a[n]),tn,&(b[n]),tn);

		memset(&(r[n2+tn*2]),0,sizeof(BN_ULONG)*(n2-tn*2));

		}

	else

# endif

	if (n == 8)

		{

		bn_mul_comba8(&(t[n2]),t,&(t[n]));

		bn_mul_comba8(r,a,b);

		bn_mul_normal(&(r[n2]),&(a[n]),tna,&(b[n]),tnb);

		memset(&(r[n2+tna+tnb]),0,sizeof(BN_ULONG)*(n2-tna-tnb));

		}

	else

		{

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

		bn_mul_recursive(&(t[n2]),t,&(t[n]),n,0,0,p);

		bn_mul_recursive(r,a,b,n,0,0,p);

		i=n/2;

		/* If there is only a bottom half to the number,

		 * just do it */

		if (tna > tnb)

			j = tna - i;

		else

			j = tnb - i;

		if (j == 0)

			{

			bn_mul_recursive(&(r[n2]),&(a[n]),&(b[n]),

				i,tna-i,tnb-i,p);

			memset(&(r[n2+i*2]),0,sizeof(BN_ULONG)*(n2-i*2));

			}

		else if (j > 0) /* eg, n == 16, i == 8 and tn == 11 */

				{

				bn_mul_part_recursive(&(r[n2]),&(a[n]),&(b[n]),

					i,tna-i,tnb-i,p);

				memset(&(r[n2+tna+tnb]),0,

					sizeof(BN_ULONG)*(n2-tna-tnb));

				}

		else /* (j < 0) eg, n == 16, i == 8 and tn == 5 */

			{

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

			if (tna < BN_MUL_RECURSIVE_SIZE_NORMAL

				&& tnb < BN_MUL_RECURSIVE_SIZE_NORMAL)

				{

				bn_mul_normal(&(r[n2]),&(a[n]),tna,&(b[n]),tnb);

				}

			else

				{

				for (;;)

					{

					i/=2;

					if (i <= tna && tna == tnb)

						{

						bn_mul_recursive(&(r[n2]),

							&(a[n]),&(b[n]),

							i,tna-i,tnb-i,p);

						break;

						}

					else if (i < tna || i < tnb)

						{

						bn_mul_part_recursive(&(r[n2]),

							&(a[n]),&(b[n]),

							i,tna-i,tnb-i,p);

						break;

						}

					}

				}

			}

		}

	/* t[32] holds (a[0]-a[1])*(b[1]-b[0]), c1 is the sign

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

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

	 */

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

	if (neg) /* if t[32] is negative */

		{

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

		}

	else

		{

		/* Might have a carry */

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

		}

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

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

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

			}

		}

	}

/* a and b must be the same size, which is n2.

 * r needs to be n2 words and t needs to be n2*2

 */

EXPORT_C void bn_mul_low_recursive(BN_ULONG *r, BN_ULONG *a, BN_ULONG *b, int n2,

	     BN_ULONG *t)

	{

	int n=n2/2;

# ifdef BN_COUNT

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

# endif

	bn_mul_recursive(r,a,b,n,0,0,&(t[0]));

	if (n >= BN_MUL_LOW_RECURSIVE_SIZE_NORMAL)

		{

		bn_mul_low_recursive(&(t[0]),&(a[0]),&(b[n]),n,&(t[n2]));

		bn_add_words(&(r[n]),&(r[n]),&(t[0]),n);

		bn_mul_low_recursive(&(t[0]),&(a[n]),&(b[0]),n,&(t[n2]));

		bn_add_words(&(r[n]),&(r[n]),&(t[0]),n);

		}

	else

		{

		bn_mul_low_normal(&(t[0]),&(a[0]),&(b[n]),n);

		bn_mul_low_normal(&(t[n]),&(a[n]),&(b[0]),n);

		bn_add_words(&(r[n]),&(r[n]),&(t[0]),n);

		bn_add_words(&(r[n]),&(r[n]),&(t[n]),n);

		}

	}

/* a and b must be the same size, which is n2.

 * r needs to be n2 words and t needs to be n2*2

 * l is the low words of the output.

 * t needs to be n2*3

 */

EXPORT_C void bn_mul_high(BN_ULONG *r, BN_ULONG *a, BN_ULONG *b, BN_ULONG *l, int n2,

	     BN_ULONG *t)

	{

	int i,n;

	int c1,c2;

	int neg,oneg,zero;

	BN_ULONG ll,lc,*lp,*mp;

# ifdef BN_COUNT

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

# endif

	n=n2/2;

	/* Calculate (al-ah)*(bh-bl) */

	neg=zero=0;

	c1=bn_cmp_words(&(a[0]),&(a[n]),n);

	c2=bn_cmp_words(&(b[n]),&(b[0]),n);

	switch (c1*3+c2)

		{

	case -4:

		bn_sub_words(&(r[0]),&(a[n]),&(a[0]),n);

		bn_sub_words(&(r[n]),&(b[0]),&(b[n]),n);

		break;

	case -3:

		zero=1;

		break;

	case -2:

		bn_sub_words(&(r[0]),&(a[n]),&(a[0]),n);

		bn_sub_words(&(r[n]),&(b[n]),&(b[0]),n);

		neg=1;

		break;

	case -1:

	case 0:

	case 1:

		zero=1;

		break;

	case 2:

		bn_sub_words(&(r[0]),&(a[0]),&(a[n]),n);

		bn_sub_words(&(r[n]),&(b[0]),&(b[n]),n);

		neg=1;

		break;

	case 3:

		zero=1;

		break;

	case 4:

		bn_sub_words(&(r[0]),&(a[0]),&(a[n]),n);

		bn_sub_words(&(r[n]),&(b[n]),&(b[0]),n);

		break;

		}

	oneg=neg;

	/* t[10] = (a[0]-a[1])*(b[1]-b[0]) */

	/* r[10] = (a[1]*b[1]) */

# ifdef BN_MUL_COMBA

	if (n == 8)

		{

		bn_mul_comba8(&(t[0]),&(r[0]),&(r[n]));

		bn_mul_comba8(r,&(a[n]),&(b[n]));

		}

	else

# endif

		{

		bn_mul_recursive(&(t[0]),&(r[0]),&(r[n]),n,0,0,&(t[n2]));

		bn_mul_recursive(r,&(a[n]),&(b[n]),n,0,0,&(t[n2]));

		}

	/* s0 == low(al*bl)

	 * s1 == low(ah*bh)+low((al-ah)*(bh-bl))+low(al*bl)+high(al*bl)

	 * We know s0 and s1 so the only unknown is high(al*bl)

	 * high(al*bl) == s1 - low(ah*bh+s0+(al-ah)*(bh-bl))

	 * high(al*bl) == s1 - (r[0]+l[0]+t[0])

	 */

	if (l != NULL)

		{

		lp= &(t[n2+n]);

		c1=(int)(bn_add_words(lp,&(r[0]),&(l[0]),n));

		}

	else

		{

		c1=0;

		lp= &(r[0]);

		}

	if (neg)

		neg=(int)(bn_sub_words(&(t[n2]),lp,&(t[0]),n));

	else

		{

		bn_add_words(&(t[n2]),lp,&(t[0]),n);

		neg=0;

		}

	if (l != NULL)

		{

		bn_sub_words(&(t[n2+n]),&(l[n]),&(t[n2]),n);

		}

	else

		{

		lp= &(t[n2+n]);

		mp= &(t[n2]);

		for (i=0; i<n; i++)

			lp[i]=((~mp[i])+1)&BN_MASK2;

		}

	/* s[0] = low(al*bl)

	 * t[3] = high(al*bl)

	 * t[10] = (a[0]-a[1])*(b[1]-b[0]) neg is the sign

	 * r[10] = (a[1]*b[1])

	 */

	/* R[10] = al*bl

	 * R[21] = al*bl + ah*bh + (a[0]-a[1])*(b[1]-b[0])

	 * R[32] = ah*bh

	 */

	/* R[1]=t[3]+l[0]+r[0](+-)t[0] (have carry/borrow)

	 * R[2]=r[0]+t[3]+r[1](+-)t[1] (have carry/borrow)

	 * R[3]=r[1]+(carry/borrow)

	 */

	if (l != NULL)

		{

		lp= &(t[n2]);

		c1= (int)(bn_add_words(lp,&(t[n2+n]),&(l[0]),n));

		}

	else

		{

		lp= &(t[n2+n]);

		c1=0;

		}

	c1+=(int)(bn_add_words(&(t[n2]),lp,  &(r[0]),n));

	if (oneg)

		c1-=(int)(bn_sub_words(&(t[n2]),&(t[n2]),&(t[0]),n));

	else

		c1+=(int)(bn_add_words(&(t[n2]),&(t[n2]),&(t[0]),n));

	c2 =(int)(bn_add_words(&(r[0]),&(r[0]),&(t[n2+n]),n));

	c2+=(int)(bn_add_words(&(r[0]),&(r[0]),&(r[n]),n));

	if (oneg)

		c2-=(int)(bn_sub_words(&(r[0]),&(r[0]),&(t[n]),n));

	else

		c2+=(int)(bn_add_words(&(r[0]),&(r[0]),&(t[n]),n));

	if (c1 != 0) /* Add starting at r[0], could be +ve or -ve */

		{

		i=0;

		if (c1 > 0)

			{

			lc=c1;

			do	{

				ll=(r[i]+lc)&BN_MASK2;

				r[i++]=ll;

				lc=(lc > ll);

				} while (lc);

			}

		else

			{

			lc= -c1;

			do	{

				ll=r[i];

				r[i++]=(ll-lc)&BN_MASK2;

				lc=(lc > ll);

				} while (lc);

			}

		}

	if (c2 != 0) /* Add starting at r[1] */

		{

		i=n;

		if (c2 > 0)

			{

			lc=c2;

			do	{

				ll=(r[i]+lc)&BN_MASK2;

				r[i++]=ll;

				lc=(lc > ll);

				} while (lc);

			}

		else

			{

			lc= -c2;

			do	{

				ll=r[i];

				r[i++]=(ll-lc)&BN_MASK2;

				lc=(lc > ll);

				} while (lc);

			}

		}

	}

#endif /* BN_RECURSION */

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

	{

	int ret=0;

	int top,al,bl;

	BIGNUM *rr;

#if defined(BN_MUL_COMBA) || defined(BN_RECURSION)

	int i;

#endif

#ifdef BN_RECURSION

	BIGNUM *t=NULL;

	int j=0,k;

#endif

#ifdef BN_COUNT

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

#endif

	bn_check_top(a);

	bn_check_top(b);

	bn_check_top(r);

	al=a->top;

	bl=b->top;

	if ((al == 0) || (bl == 0))

		{

		BN_zero(r);

		return(1);

		}

	top=al+bl;

	BN_CTX_start(ctx);

	if ((r == a) || (r == b))

		{

		if ((rr = BN_CTX_get(ctx)) == NULL) goto err;

		}

	else

		rr = r;

	rr->neg=a->neg^b->neg;

#if defined(BN_MUL_COMBA) || defined(BN_RECURSION)

	i = al-bl;

#endif

#ifdef BN_MUL_COMBA

	if (i == 0)

		{

# if 0

		if (al == 4)

			{

			if (bn_wexpand(rr,8) == NULL) goto err;

			rr->top=8;

			bn_mul_comba4(rr->d,a->d,b->d);

			goto end;

			}