sl@0: /* crypto/bn/bn_word.c */
sl@0: /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
sl@0:  * All rights reserved.
sl@0:  *
sl@0:  * This package is an SSL implementation written
sl@0:  * by Eric Young (eay@cryptsoft.com).
sl@0:  * The implementation was written so as to conform with Netscapes SSL.
sl@0:  * 
sl@0:  * This library is free for commercial and non-commercial use as long as
sl@0:  * the following conditions are aheared to.  The following conditions
sl@0:  * apply to all code found in this distribution, be it the RC4, RSA,
sl@0:  * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
sl@0:  * included with this distribution is covered by the same copyright terms
sl@0:  * except that the holder is Tim Hudson (tjh@cryptsoft.com).
sl@0:  * 
sl@0:  * Copyright remains Eric Young's, and as such any Copyright notices in
sl@0:  * the code are not to be removed.
sl@0:  * If this package is used in a product, Eric Young should be given attribution
sl@0:  * as the author of the parts of the library used.
sl@0:  * This can be in the form of a textual message at program startup or
sl@0:  * in documentation (online or textual) provided with the package.
sl@0:  * 
sl@0:  * Redistribution and use in source and binary forms, with or without
sl@0:  * modification, are permitted provided that the following conditions
sl@0:  * are met:
sl@0:  * 1. Redistributions of source code must retain the copyright
sl@0:  *    notice, this list of conditions and the following disclaimer.
sl@0:  * 2. Redistributions in binary form must reproduce the above copyright
sl@0:  *    notice, this list of conditions and the following disclaimer in the
sl@0:  *    documentation and/or other materials provided with the distribution.
sl@0:  * 3. All advertising materials mentioning features or use of this software
sl@0:  *    must display the following acknowledgement:
sl@0:  *    "This product includes cryptographic software written by
sl@0:  *     Eric Young (eay@cryptsoft.com)"
sl@0:  *    The word 'cryptographic' can be left out if the rouines from the library
sl@0:  *    being used are not cryptographic related :-).
sl@0:  * 4. If you include any Windows specific code (or a derivative thereof) from 
sl@0:  *    the apps directory (application code) you must include an acknowledgement:
sl@0:  *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
sl@0:  * 
sl@0:  * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
sl@0:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
sl@0:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
sl@0:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
sl@0:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
sl@0:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
sl@0:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
sl@0:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
sl@0:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
sl@0:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
sl@0:  * SUCH DAMAGE.
sl@0:  * 
sl@0:  * The licence and distribution terms for any publically available version or
sl@0:  * derivative of this code cannot be changed.  i.e. this code cannot simply be
sl@0:  * copied and put under another distribution licence
sl@0:  * [including the GNU Public Licence.]
sl@0:  */
sl@0: 
sl@0: #include <stdio.h>
sl@0: #include "cryptlib.h"
sl@0: #include "bn_lcl.h"
sl@0: 
sl@0: EXPORT_C BN_ULONG BN_mod_word(const BIGNUM *a, BN_ULONG w)
sl@0: 	{
sl@0: #ifndef BN_LLONG
sl@0: 	BN_ULONG ret=0;
sl@0: #else
sl@0: 	BN_ULLONG ret=0;
sl@0: #endif
sl@0: 	int i;
sl@0: 
sl@0: 	if (w == 0)
sl@0: 		return (BN_ULONG)-1;
sl@0: 
sl@0: 	bn_check_top(a);
sl@0: 	w&=BN_MASK2;
sl@0: 	for (i=a->top-1; i>=0; i--)
sl@0: 		{
sl@0: #ifndef BN_LLONG
sl@0: 		ret=((ret<<BN_BITS4)|((a->d[i]>>BN_BITS4)&BN_MASK2l))%w;
sl@0: 		ret=((ret<<BN_BITS4)|(a->d[i]&BN_MASK2l))%w;
sl@0: #else
sl@0: 		ret=(BN_ULLONG)(((ret<<(BN_ULLONG)BN_BITS2)|a->d[i])%
sl@0: 			(BN_ULLONG)w);
sl@0: #endif
sl@0: 		}
sl@0: 	return((BN_ULONG)ret);
sl@0: 	}
sl@0: 
sl@0: EXPORT_C BN_ULONG BN_div_word(BIGNUM *a, BN_ULONG w)
sl@0: 	{
sl@0: 	BN_ULONG ret = 0;
sl@0: 	int i, j;
sl@0: 
sl@0: 	bn_check_top(a);
sl@0: 	w &= BN_MASK2;
sl@0: 
sl@0: 	if (!w)
sl@0: 		/* actually this an error (division by zero) */
sl@0: 		return (BN_ULONG)-1;
sl@0: 	if (a->top == 0)
sl@0: 		return 0;
sl@0: 
sl@0: 	/* normalize input (so bn_div_words doesn't complain) */
sl@0: 	j = BN_BITS2 - BN_num_bits_word(w);
sl@0: 	w <<= j;
sl@0: 	if (!BN_lshift(a, a, j))
sl@0: 		return (BN_ULONG)-1;
sl@0: 
sl@0: 	for (i=a->top-1; i>=0; i--)
sl@0: 		{
sl@0: 		BN_ULONG l,d;
sl@0: 		
sl@0: 		l=a->d[i];
sl@0: 		d=bn_div_words(ret,l,w);
sl@0: 		ret=(l-((d*w)&BN_MASK2))&BN_MASK2;
sl@0: 		a->d[i]=d;
sl@0: 		}
sl@0: 	if ((a->top > 0) && (a->d[a->top-1] == 0))
sl@0: 		a->top--;
sl@0: 	ret >>= j;
sl@0: 	bn_check_top(a);
sl@0: 	return(ret);
sl@0: 	}
sl@0: 
sl@0: EXPORT_C int BN_add_word(BIGNUM *a, BN_ULONG w)
sl@0: 	{
sl@0: 	BN_ULONG l;
sl@0: 	int i;
sl@0: 
sl@0: 	bn_check_top(a);
sl@0: 	w &= BN_MASK2;
sl@0: 
sl@0: 	/* degenerate case: w is zero */
sl@0: 	if (!w) return 1;
sl@0: 	/* degenerate case: a is zero */
sl@0: 	if(BN_is_zero(a)) return BN_set_word(a, w);
sl@0: 	/* handle 'a' when negative */
sl@0: 	if (a->neg)
sl@0: 		{
sl@0: 		a->neg=0;
sl@0: 		i=BN_sub_word(a,w);
sl@0: 		if (!BN_is_zero(a))
sl@0: 			a->neg=!(a->neg);
sl@0: 		return(i);
sl@0: 		}
sl@0: 	/* Only expand (and risk failing) if it's possibly necessary */
sl@0: 	if (((BN_ULONG)(a->d[a->top - 1] + 1) == 0) &&
sl@0: 			(bn_wexpand(a,a->top+1) == NULL))
sl@0: 		return(0);
sl@0: 	i=0;
sl@0: 	for (;;)
sl@0: 		{
sl@0: 		if (i >= a->top)
sl@0: 			l=w;
sl@0: 		else
sl@0: 			l=(a->d[i]+w)&BN_MASK2;
sl@0: 		a->d[i]=l;
sl@0: 		if (w > l)
sl@0: 			w=1;
sl@0: 		else
sl@0: 			break;
sl@0: 		i++;
sl@0: 		}
sl@0: 	if (i >= a->top)
sl@0: 		a->top++;
sl@0: 	bn_check_top(a);
sl@0: 	return(1);
sl@0: 	}
sl@0: 
sl@0: EXPORT_C int BN_sub_word(BIGNUM *a, BN_ULONG w)
sl@0: 	{
sl@0: 	int i;
sl@0: 
sl@0: 	bn_check_top(a);
sl@0: 	w &= BN_MASK2;
sl@0: 
sl@0: 	/* degenerate case: w is zero */
sl@0: 	if (!w) return 1;
sl@0: 	/* degenerate case: a is zero */
sl@0: 	if(BN_is_zero(a))
sl@0: 		{
sl@0: 		i = BN_set_word(a,w);
sl@0: 		if (i != 0)
sl@0: 			BN_set_negative(a, 1);
sl@0: 		return i;
sl@0: 		}
sl@0: 	/* handle 'a' when negative */
sl@0: 	if (a->neg)
sl@0: 		{
sl@0: 		a->neg=0;
sl@0: 		i=BN_add_word(a,w);
sl@0: 		a->neg=1;
sl@0: 		return(i);
sl@0: 		}
sl@0: 
sl@0: 	if ((a->top == 1) && (a->d[0] < w))
sl@0: 		{
sl@0: 		a->d[0]=w-a->d[0];
sl@0: 		a->neg=1;
sl@0: 		return(1);
sl@0: 		}
sl@0: 	i=0;
sl@0: 	for (;;)
sl@0: 		{
sl@0: 		if (a->d[i] >= w)
sl@0: 			{
sl@0: 			a->d[i]-=w;
sl@0: 			break;
sl@0: 			}
sl@0: 		else
sl@0: 			{
sl@0: 			a->d[i]=(a->d[i]-w)&BN_MASK2;
sl@0: 			i++;
sl@0: 			w=1;
sl@0: 			}
sl@0: 		}
sl@0: 	if ((a->d[i] == 0) && (i == (a->top-1)))
sl@0: 		a->top--;
sl@0: 	bn_check_top(a);
sl@0: 	return(1);
sl@0: 	}
sl@0: 
sl@0: EXPORT_C int BN_mul_word(BIGNUM *a, BN_ULONG w)
sl@0: 	{
sl@0: 	BN_ULONG ll;
sl@0: 
sl@0: 	bn_check_top(a);
sl@0: 	w&=BN_MASK2;
sl@0: 	if (a->top)
sl@0: 		{
sl@0: 		if (w == 0)
sl@0: 			BN_zero(a);
sl@0: 		else
sl@0: 			{
sl@0: 			ll=bn_mul_words(a->d,a->d,a->top,w);
sl@0: 			if (ll)
sl@0: 				{
sl@0: 				if (bn_wexpand(a,a->top+1) == NULL) return(0);
sl@0: 				a->d[a->top++]=ll;
sl@0: 				}
sl@0: 			}
sl@0: 		}
sl@0: 	bn_check_top(a);
sl@0: 	return(1);
sl@0: 	}
sl@0: