/* crypto/bn/bn_word.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"

 EXPORT_C BN_ULONG BN_mod_word(const BIGNUM *a, BN_ULONG w)

 	{

 #ifndef BN_LLONG

 	BN_ULONG ret=0;

 #else

 	BN_ULLONG ret=0;

 #endif

 	int i;

 	if (w == 0)

 		return (BN_ULONG)-1;

 	bn_check_top(a);

 	w&=BN_MASK2;

 	for (i=a->top-1; i>=0; i--)

 		{

 #ifndef BN_LLONG

 		ret=((ret<<BN_BITS4)|((a->d[i]>>BN_BITS4)&BN_MASK2l))%w;

 		ret=((ret<<BN_BITS4)|(a->d[i]&BN_MASK2l))%w;

 #else

 		ret=(BN_ULLONG)(((ret<<(BN_ULLONG)BN_BITS2)|a->d[i])%

 			(BN_ULLONG)w);

 #endif

 		}

 	return((BN_ULONG)ret);

 	}

 EXPORT_C BN_ULONG BN_div_word(BIGNUM *a, BN_ULONG w)

 	{

 	BN_ULONG ret = 0;

 	int i, j;

 	bn_check_top(a);

 	w &= BN_MASK2;

 	if (!w)

 		/* actually this an error (division by zero) */

 		return (BN_ULONG)-1;

 	if (a->top == 0)

 		return 0;

 	/* normalize input (so bn_div_words doesn't complain) */

 	j = BN_BITS2 - BN_num_bits_word(w);

 	w <<= j;

 	if (!BN_lshift(a, a, j))

 		return (BN_ULONG)-1;

 	for (i=a->top-1; i>=0; i--)

 		{

 		BN_ULONG l,d;

 		l=a->d[i];

 		d=bn_div_words(ret,l,w);

 		ret=(l-((d*w)&BN_MASK2))&BN_MASK2;

 		a->d[i]=d;

 		}

 	if ((a->top > 0) && (a->d[a->top-1] == 0))

 		a->top--;

 	ret >>= j;

 	bn_check_top(a);

 	return(ret);

 	}

 EXPORT_C int BN_add_word(BIGNUM *a, BN_ULONG w)

 	{

 	BN_ULONG l;

 	int i;

 	bn_check_top(a);

 	w &= BN_MASK2;

 	/* degenerate case: w is zero */

 	if (!w) return 1;

 	/* degenerate case: a is zero */

 	if(BN_is_zero(a)) return BN_set_word(a, w);

 	/* handle 'a' when negative */

 	if (a->neg)

 		{

 		a->neg=0;

 		i=BN_sub_word(a,w);

 		if (!BN_is_zero(a))

 			a->neg=!(a->neg);

 		return(i);

 		}

 	/* Only expand (and risk failing) if it's possibly necessary */

 	if (((BN_ULONG)(a->d[a->top - 1] + 1) == 0) &&

 			(bn_wexpand(a,a->top+1) == NULL))

 		return(0);

 	i=0;

 	for (;;)

 		{

 		if (i >= a->top)

 			l=w;

 		else

 			l=(a->d[i]+w)&BN_MASK2;

 		a->d[i]=l;

 		if (w > l)

 			w=1;

 		else

 			break;

 		i++;

 		}

 	if (i >= a->top)

 		a->top++;

 	bn_check_top(a);

 	return(1);

 	}

 EXPORT_C int BN_sub_word(BIGNUM *a, BN_ULONG w)

 	{

 	int i;

 	bn_check_top(a);

 	w &= BN_MASK2;

 	/* degenerate case: w is zero */

 	if (!w) return 1;

 	/* degenerate case: a is zero */

 	if(BN_is_zero(a))

 		{

 		i = BN_set_word(a,w);

 		if (i != 0)

 			BN_set_negative(a, 1);

 		return i;

 		}

 	/* handle 'a' when negative */

 	if (a->neg)

 		{

 		a->neg=0;

 		i=BN_add_word(a,w);

 		a->neg=1;

 		return(i);

 		}

 	if ((a->top == 1) && (a->d[0] < w))

 		{

 		a->d[0]=w-a->d[0];

 		a->neg=1;

 		return(1);

 		}

 	i=0;

 	for (;;)

 		{

 		if (a->d[i] >= w)

 			{

 			a->d[i]-=w;

 			break;

 			}

 		else

 			{

 			a->d[i]=(a->d[i]-w)&BN_MASK2;

 			i++;

 			w=1;

 			}

 		}

 	if ((a->d[i] == 0) && (i == (a->top-1)))

 		a->top--;

 	bn_check_top(a);

 	return(1);

 	}

 EXPORT_C int BN_mul_word(BIGNUM *a, BN_ULONG w)

 	{

 	BN_ULONG ll;

 	bn_check_top(a);

 	w&=BN_MASK2;

 	if (a->top)

 		{

 		if (w == 0)

 			BN_zero(a);

 		else

 			{

 			ll=bn_mul_words(a->d,a->d,a->top,w);

 			if (ll)

 				{

 				if (bn_wexpand(a,a->top+1) == NULL) return(0);

 				a->d[a->top++]=ll;

 				}

 			}

 		}

 	bn_check_top(a);

 	return(1);

 	}