/* 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);

	}