/* crypto/bn/bn_lib.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.]

 */

 /*

 © Portions copyright (c) 2006 Nokia Corporation.  All rights reserved.

 */

#ifndef BN_DEBUG

# undef NDEBUG /* avoid conflicting definitions */

# define NDEBUG

#endif

#include <assert.h>

#include <limits.h>

#include <stdio.h>

#include "cryptlib.h"

#include "bn_lcl.h"

#if (defined(SYMBIAN) && (defined(__WINSCW__) || defined(__WINS__)))

#include "libcrypto_wsd_macros.h"

#include "libcrypto_wsd.h"

#endif

const char BN_version[]="Big Number" OPENSSL_VERSION_PTEXT;

/* This stuff appears to be completely unused, so is deprecated */

#ifndef OPENSSL_NO_DEPRECATED

/* For a 32 bit machine

 * 2 -   4 ==  128

 * 3 -   8 ==  256

 * 4 -  16 ==  512

 * 5 -  32 == 1024

 * 6 -  64 == 2048

 * 7 - 128 == 4096

 * 8 - 256 == 8192

 */

static int bn_limit_bits=0;

static int bn_limit_num=8;        /* (1<<bn_limit_bits) */

static int bn_limit_bits_low=0;

static int bn_limit_num_low=8;    /* (1<<bn_limit_bits_low) */

static int bn_limit_bits_high=0;

static int bn_limit_num_high=8;   /* (1<<bn_limit_bits_high) */

static int bn_limit_bits_mont=0;

static int bn_limit_num_mont=8;   /* (1<<bn_limit_bits_mont) */

EXPORT_C void BN_set_params(int mult, int high, int low, int mont)

	{

	if (mult >= 0)

		{

		if (mult > (int)(sizeof(int)*8)-1)

			mult=sizeof(int)*8-1;

		bn_limit_bits=mult;

		bn_limit_num=1<<mult;

		}

	if (high >= 0)

		{

		if (high > (int)(sizeof(int)*8)-1)

			high=sizeof(int)*8-1;

		bn_limit_bits_high=high;

		bn_limit_num_high=1<<high;

		}

	if (low >= 0)

		{

		if (low > (int)(sizeof(int)*8)-1)

			low=sizeof(int)*8-1;

		bn_limit_bits_low=low;

		bn_limit_num_low=1<<low;

		}

	if (mont >= 0)

		{

		if (mont > (int)(sizeof(int)*8)-1)

			mont=sizeof(int)*8-1;

		bn_limit_bits_mont=mont;

		bn_limit_num_mont=1<<mont;

		}

	}

EXPORT_C int BN_get_params(int which)

	{

	if      (which == 0) return(bn_limit_bits);

	else if (which == 1) return(bn_limit_bits_high);

	else if (which == 2) return(bn_limit_bits_low);

	else if (which == 3) return(bn_limit_bits_mont);

	else return(0);

	}

#endif

#ifdef EMULATOR

GET_STATIC_VAR_FROM_TLS(data_one,bn_lib,BN_ULONG)

#define data_one (*GET_WSD_VAR_NAME(data_one,bn_lib, s)())

GET_STATIC_VAR_FROM_TLS(const_one,bn_lib,BIGNUM)

#define const_one (*GET_WSD_VAR_NAME(const_one,bn_lib, s)())

#endif

EXPORT_C const BIGNUM *BN_value_one(void)

	{

#ifndef EMULATOR 	

	static BN_ULONG data_one=1L;

	static BIGNUM const_one={&data_one,1,1,0,BN_FLG_STATIC_DATA};

#endif	

	return(&const_one);

	}

#ifdef EMULATOR	

GET_STATIC_ARRAY_FROM_TLS(data,bn_lib,char)

#define data (GET_WSD_VAR_NAME(data,bn_lib, s)())

GET_STATIC_VAR_FROM_TLS(init,bn_lib,int)

#define init (*GET_WSD_VAR_NAME(init,bn_lib, s)())

#endif	

EXPORT_C char *BN_options(void)

	{

#ifndef EMULATOR	

	static int init=0;

	static char data[16];

#endif	

	if (!init)

		{

		init++;

#ifdef BN_LLONG

		BIO_snprintf(data,sizeof data,"bn(%d,%d)",

			     (int)sizeof(BN_ULLONG)*8,(int)sizeof(BN_ULONG)*8);

#else

		BIO_snprintf(data,sizeof data,"bn(%d,%d)",

			     (int)sizeof(BN_ULONG)*8,(int)sizeof(BN_ULONG)*8);

#endif

		}

	return((char*)data);

	}

EXPORT_C int BN_num_bits_word(BN_ULONG l)

	{

	static const char bits[256]={

		0,1,2,2,3,3,3,3,4,4,4,4,4,4,4,4,

		5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,

		6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,

		6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,

		7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,

		7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,

		7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,

		7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,

		8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,

		8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,

		8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,

		8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,

		8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,

		8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,

		8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,

		8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,

		};

#if defined(SIXTY_FOUR_BIT_LONG)

	if (l & 0xffffffff00000000L)

		{

		if (l & 0xffff000000000000L)

			{

			if (l & 0xff00000000000000L)

				{

				return(bits[(int)(l>>56)]+56);

				}

			else	return(bits[(int)(l>>48)]+48);

			}

		else

			{

			if (l & 0x0000ff0000000000L)

				{

				return(bits[(int)(l>>40)]+40);

				}

			else	return(bits[(int)(l>>32)]+32);

			}

		}

	else

#else

#ifdef SIXTY_FOUR_BIT

	if (l & 0xffffffff00000000LL)

		{

		if (l & 0xffff000000000000LL)

			{

			if (l & 0xff00000000000000LL)

				{

				return(bits[(int)(l>>56)]+56);

				}

			else	return(bits[(int)(l>>48)]+48);

			}

		else

			{

			if (l & 0x0000ff0000000000LL)

				{

				return(bits[(int)(l>>40)]+40);

				}

			else	return(bits[(int)(l>>32)]+32);

			}

		}

	else

#endif

#endif

		{

#if defined(THIRTY_TWO_BIT) || defined(SIXTY_FOUR_BIT) || defined(SIXTY_FOUR_BIT_LONG)

		if (l & 0xffff0000L)

			{

			if (l & 0xff000000L)

				return(bits[(int)(l>>24L)]+24);

			else	return(bits[(int)(l>>16L)]+16);

			}

		else

#endif

			{

#if defined(SIXTEEN_BIT) || defined(THIRTY_TWO_BIT) || defined(SIXTY_FOUR_BIT) || defined(SIXTY_FOUR_BIT_LONG)

			if (l & 0xff00L)

				return(bits[(int)(l>>8)]+8);

			else	

#endif

				return(bits[(int)(l   )]  );

			}

		}

	}

EXPORT_C int BN_num_bits(const BIGNUM *a)

	{

	int i = a->top - 1;

	bn_check_top(a);

	if (BN_is_zero(a)) return 0;

	return ((i*BN_BITS2) + BN_num_bits_word(a->d[i]));

	}

EXPORT_C void BN_clear_free(BIGNUM *a)

	{

	int i;

	if (a == NULL) return;

	bn_check_top(a);

	if (a->d != NULL)

		{

		OPENSSL_cleanse(a->d,a->dmax*sizeof(a->d[0]));

		if (!(BN_get_flags(a,BN_FLG_STATIC_DATA)))

			OPENSSL_free(a->d);

		}

	i=BN_get_flags(a,BN_FLG_MALLOCED);

	OPENSSL_cleanse(a,sizeof(BIGNUM));

	if (i)

		OPENSSL_free(a);

	}

EXPORT_C void BN_free(BIGNUM *a)

	{

	if (a == NULL) return;

	bn_check_top(a);

	if ((a->d != NULL) && !(BN_get_flags(a,BN_FLG_STATIC_DATA)))

		OPENSSL_free(a->d);

	if (a->flags & BN_FLG_MALLOCED)

		OPENSSL_free(a);

	else

		{

#ifndef OPENSSL_NO_DEPRECATED

		a->flags|=BN_FLG_FREE;

#endif

		a->d = NULL;

		}

	}

EXPORT_C void BN_init(BIGNUM *a)

	{

	memset(a,0,sizeof(BIGNUM));

	bn_check_top(a);

	}

EXPORT_C BIGNUM *BN_new(void)

	{

	BIGNUM *ret;

	if ((ret=(BIGNUM *)OPENSSL_malloc(sizeof(BIGNUM))) == NULL)

		{

		BNerr(BN_F_BN_NEW,ERR_R_MALLOC_FAILURE);

		return(NULL);

		}

	ret->flags=BN_FLG_MALLOCED;

	ret->top=0;

	ret->neg=0;

	ret->dmax=0;

	ret->d=NULL;

	bn_check_top(ret);

	return(ret);

	}

/* This is used both by bn_expand2() and bn_dup_expand() */

/* The caller MUST check that words > b->dmax before calling this */

static BN_ULONG *bn_expand_internal(const BIGNUM *b, int words)

	{

	BN_ULONG *A,*a = NULL;

	const BN_ULONG *B;

	int i;

	bn_check_top(b);

	if (words > (INT_MAX/(4*BN_BITS2)))

		{

		BNerr(BN_F_BN_EXPAND_INTERNAL,BN_R_BIGNUM_TOO_LONG);

		return NULL;

		}

	if (BN_get_flags(b,BN_FLG_STATIC_DATA))

		{

		BNerr(BN_F_BN_EXPAND_INTERNAL,BN_R_EXPAND_ON_STATIC_BIGNUM_DATA);

		return(NULL);

		}

	a=A=(BN_ULONG *)OPENSSL_malloc(sizeof(BN_ULONG)*words);

	if (A == NULL)

		{

		BNerr(BN_F_BN_EXPAND_INTERNAL,ERR_R_MALLOC_FAILURE);

		return(NULL);

		}

#if 1

	B=b->d;

	/* Check if the previous number needs to be copied */

	if (B != NULL)

		{

		for (i=b->top>>2; i>0; i--,A+=4,B+=4)

			{

			/*

			 * The fact that the loop is unrolled

			 * 4-wise is a tribute to Intel. It's

			 * the one that doesn't have enough

			 * registers to accomodate more data.

			 * I'd unroll it 8-wise otherwise:-)

			 *

			 *		<appro@fy.chalmers.se>

			 */

			BN_ULONG a0,a1,a2,a3;

			a0=B[0]; a1=B[1]; a2=B[2]; a3=B[3];

			A[0]=a0; A[1]=a1; A[2]=a2; A[3]=a3;

			}

		switch (b->top&3)

			{

		case 3:	A[2]=B[2];

		case 2:	A[1]=B[1];

		case 1:	A[0]=B[0];

		case 0: /* workaround for ultrix cc: without 'case 0', the optimizer does

		         * the switch table by doing a=top&3; a--; goto jump_table[a];

		         * which fails for top== 0 */

			;

			}

		}

#else

	memset(A,0,sizeof(BN_ULONG)*words);

	memcpy(A,b->d,sizeof(b->d[0])*b->top);

#endif

	return(a);

	}

/* This is an internal function that can be used instead of bn_expand2()

 * when there is a need to copy BIGNUMs instead of only expanding the

 * data part, while still expanding them.

 * Especially useful when needing to expand BIGNUMs that are declared

 * 'const' and should therefore not be changed.

 * The reason to use this instead of a BN_dup() followed by a bn_expand2()

 * is memory allocation overhead.  A BN_dup() followed by a bn_expand2()

 * will allocate new memory for the BIGNUM data twice, and free it once,

 * while bn_dup_expand() makes sure allocation is made only once.

 */

#ifndef OPENSSL_NO_DEPRECATED

EXPORT_C BIGNUM *bn_dup_expand(const BIGNUM *b, int words)

	{

	BIGNUM *r = NULL;

	bn_check_top(b);

	/* This function does not work if

	 *      words <= b->dmax && top < words

	 * because BN_dup() does not preserve 'dmax'!

	 * (But bn_dup_expand() is not used anywhere yet.)

	 */

	if (words > b->dmax)

		{

		BN_ULONG *a = bn_expand_internal(b, words);

		if (a)

			{

			r = BN_new();

			if (r)

				{

				r->top = b->top;

				r->dmax = words;

				r->neg = b->neg;

				r->d = a;

				}

			else

				{

				/* r == NULL, BN_new failure */

				OPENSSL_free(a);

				}

			}

		/* If a == NULL, there was an error in allocation in

		   bn_expand_internal(), and NULL should be returned */

		}

	else

		{

		r = BN_dup(b);

		}

	bn_check_top(r);

	return r;

	}

#endif

/* This is an internal function that should not be used in applications.

 * It ensures that 'b' has enough room for a 'words' word number

 * and initialises any unused part of b->d with leading zeros.

 * It is mostly used by the various BIGNUM routines. If there is an error,

 * NULL is returned. If not, 'b' is returned. */

EXPORT_C BIGNUM *bn_expand2(BIGNUM *b, int words)

	{

	bn_check_top(b);

	if (words > b->dmax)

		{

		BN_ULONG *a = bn_expand_internal(b, words);

		if(!a) return NULL;

		if(b->d) OPENSSL_free(b->d);

		b->d=a;

		b->dmax=words;

		}

/* None of this should be necessary because of what b->top means! */

#if 0

	/* NB: bn_wexpand() calls this only if the BIGNUM really has to grow */

	if (b->top < b->dmax)

		{

		int i;

		BN_ULONG *A = &(b->d[b->top]);

		for (i=(b->dmax - b->top)>>3; i>0; i--,A+=8)

			{

			A[0]=0; A[1]=0; A[2]=0; A[3]=0;

			A[4]=0; A[5]=0; A[6]=0; A[7]=0;

			}

		for (i=(b->dmax - b->top)&7; i>0; i--,A++)

			A[0]=0;

		assert(A == &(b->d[b->dmax]));

		}

#endif

	bn_check_top(b);

	return b;

	}

EXPORT_C BIGNUM *BN_dup(const BIGNUM *a)

	{

	BIGNUM *t;

	if (a == NULL) return NULL;

	bn_check_top(a);

	t = BN_new();

	if (t == NULL) return NULL;

	if(!BN_copy(t, a))

		{

		BN_free(t);

		return NULL;

		}

	bn_check_top(t);

	return t;

	}

EXPORT_C BIGNUM *BN_copy(BIGNUM *a, const BIGNUM *b)

	{

	int i;

	BN_ULONG *A;

	const BN_ULONG *B;

	bn_check_top(b);

	if (a == b) return(a);

	if (bn_wexpand(a,b->top) == NULL) return(NULL);

#if 1

	A=a->d;

	B=b->d;

	for (i=b->top>>2; i>0; i--,A+=4,B+=4)

		{

		BN_ULONG a0,a1,a2,a3;

		a0=B[0]; a1=B[1]; a2=B[2]; a3=B[3];

		A[0]=a0; A[1]=a1; A[2]=a2; A[3]=a3;

		}

	switch (b->top&3)

		{

		case 3: A[2]=B[2];

		case 2: A[1]=B[1];

		case 1: A[0]=B[0];

		case 0: ; /* ultrix cc workaround, see comments in bn_expand_internal */

		}

#else

	memcpy(a->d,b->d,sizeof(b->d[0])*b->top);

#endif

	a->top=b->top;

	a->neg=b->neg;

	bn_check_top(a);

	return(a);

	}

EXPORT_C void BN_swap(BIGNUM *a, BIGNUM *b)

	{

	int flags_old_a, flags_old_b;

	BN_ULONG *tmp_d;

	int tmp_top, tmp_dmax, tmp_neg;

	bn_check_top(a);

	bn_check_top(b);

	flags_old_a = a->flags;

	flags_old_b = b->flags;

	tmp_d = a->d;

	tmp_top = a->top;

	tmp_dmax = a->dmax;

	tmp_neg = a->neg;

	a->d = b->d;

	a->top = b->top;

	a->dmax = b->dmax;

	a->neg = b->neg;

	b->d = tmp_d;

	b->top = tmp_top;

	b->dmax = tmp_dmax;

	b->neg = tmp_neg;

	a->flags = (flags_old_a & BN_FLG_MALLOCED) | (flags_old_b & BN_FLG_STATIC_DATA);

	b->flags = (flags_old_b & BN_FLG_MALLOCED) | (flags_old_a & BN_FLG_STATIC_DATA);

	bn_check_top(a);

	bn_check_top(b);

	}

EXPORT_C void BN_clear(BIGNUM *a)

	{

	bn_check_top(a);

	if (a->d != NULL)

		memset(a->d,0,a->dmax*sizeof(a->d[0]));

	a->top=0;

	a->neg=0;

	}

EXPORT_C BN_ULONG BN_get_word(const BIGNUM *a)

	{

	if (a->top > 1)

		return BN_MASK2;

	else if (a->top == 1)

		return a->d[0];

	/* a->top == 0 */

	return 0;

	}

EXPORT_C int BN_set_word(BIGNUM *a, BN_ULONG w)

	{

	bn_check_top(a);

	if (bn_expand(a,(int)sizeof(BN_ULONG)*8) == NULL) return(0);

	a->neg = 0;

	a->d[0] = w;

	a->top = (w ? 1 : 0);

	bn_check_top(a);

	return(1);

	}

EXPORT_C BIGNUM *BN_bin2bn(const unsigned char *s, int len, BIGNUM *ret)

	{

	unsigned int i,m;

	unsigned int n;

	BN_ULONG l;

	BIGNUM  *bn = NULL;

	if (ret == NULL)

		ret = bn = BN_new();

	if (ret == NULL) return(NULL);

	bn_check_top(ret);

	l=0;

	n=len;

	if (n == 0)

		{

		ret->top=0;

		return(ret);

		}

	i=((n-1)/BN_BYTES)+1;

	m=((n-1)%(BN_BYTES));

	if (bn_wexpand(ret, (int)i) == NULL)

		{

		if (bn) BN_free(bn);

		return NULL;

		}

	ret->top=i;

	ret->neg=0;

	while (n--)

		{

		l=(l<<8L)| *(s++);

		if (m-- == 0)

			{

			ret->d[--i]=l;

			l=0;

			m=BN_BYTES-1;

			}

		}

	/* need to call this due to clear byte at top if avoiding

	 * having the top bit set (-ve number) */

	bn_correct_top(ret);

	return(ret);

	}

/* ignore negative */

EXPORT_C int BN_bn2bin(const BIGNUM *a, unsigned char *to)

	{

	int n,i;

	BN_ULONG l;

	bn_check_top(a);

	n=i=BN_num_bytes(a);

	while (i--)

		{

		l=a->d[i/BN_BYTES];

		*(to++)=(unsigned char)(l>>(8*(i%BN_BYTES)))&0xff;

		}

	return(n);

	}

EXPORT_C int BN_ucmp(const BIGNUM *a, const BIGNUM *b)

	{

	int i;

	BN_ULONG t1,t2,*ap,*bp;

	bn_check_top(a);

	bn_check_top(b);

	i=a->top-b->top;

	if (i != 0) return(i);

	ap=a->d;

	bp=b->d;

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

		{

		t1= ap[i];

		t2= bp[i];

		if (t1 != t2)

			return((t1 > t2) ? 1 : -1);

		}

	return(0);

	}

EXPORT_C int BN_cmp(const BIGNUM *a, const BIGNUM *b)

	{

	int i;

	int gt,lt;

	BN_ULONG t1,t2;

	if ((a == NULL) || (b == NULL))

		{

		if (a != NULL)

			return(-1);

		else if (b != NULL)

			return(1);

		else

			return(0);

		}

	bn_check_top(a);

	bn_check_top(b);

	if (a->neg != b->neg)

		{

		if (a->neg)

			return(-1);

		else	return(1);

		}

	if (a->neg == 0)

		{ gt=1; lt= -1; }

	else	{ gt= -1; lt=1; }

	if (a->top > b->top) return(gt);

	if (a->top < b->top) return(lt);

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

		{

		t1=a->d[i];

		t2=b->d[i];

		if (t1 > t2) return(gt);

		if (t1 < t2) return(lt);

		}

	return(0);

	}

EXPORT_C int BN_set_bit(BIGNUM *a, int n)

	{

	int i,j,k;

	if (n < 0)

		return 0;

	i=n/BN_BITS2;

	j=n%BN_BITS2;

	if (a->top <= i)

		{

		if (bn_wexpand(a,i+1) == NULL) return(0);

		for(k=a->top; k<i+1; k++)

			a->d[k]=0;

		a->top=i+1;

		}

	a->d[i]|=(((BN_ULONG)1)<<j);

	bn_check_top(a);

	return(1);

	}

EXPORT_C int BN_clear_bit(BIGNUM *a, int n)

	{

	int i,j;

	bn_check_top(a);

	if (n < 0) return 0;

	i=n/BN_BITS2;

	j=n%BN_BITS2;

	if (a->top <= i) return(0);

	a->d[i]&=(~(((BN_ULONG)1)<<j));

	bn_correct_top(a);

	return(1);

	}

EXPORT_C int BN_is_bit_set(const BIGNUM *a, int n)

	{

	int i,j;

	bn_check_top(a);

	if (n < 0) return 0;

	i=n/BN_BITS2;

	j=n%BN_BITS2;

	if (a->top <= i) return 0;

	return(((a->d[i])>>j)&((BN_ULONG)1));

	}

EXPORT_C int BN_mask_bits(BIGNUM *a, int n)

	{

	int b,w;

	bn_check_top(a);

	if (n < 0) return 0;

	w=n/BN_BITS2;

	b=n%BN_BITS2;

	if (w >= a->top) return 0;

	if (b == 0)

		a->top=w;

	else

		{

		a->top=w+1;

		a->d[w]&= ~(BN_MASK2<<b);

		}

	bn_correct_top(a);

	return(1);

	}

EXPORT_C void BN_set_negative(BIGNUM *a, int b)

	{

	if (b && !BN_is_zero(a))

		a->neg = 1;

	else

		a->neg = 0;

	}

EXPORT_C int bn_cmp_words(const BN_ULONG *a, const BN_ULONG *b, int n)

	{

	int i;

	BN_ULONG aa,bb;

	aa=a[n-1];

	bb=b[n-1];

	if (aa != bb) return((aa > bb)?1:-1);

	for (i=n-2; i>=0; i--)

		{

		aa=a[i];

		bb=b[i];

		if (aa != bb) return((aa > bb)?1:-1);

		}

	return(0);

	}

/* Here follows a specialised variants of bn_cmp_words().  It has the

   property of performing the operation 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...  */

EXPORT_C int bn_cmp_part_words(const BN_ULONG *a, const BN_ULONG *b,

	int cl, int dl)

	{

	int n,i;

	n = cl-1;

	if (dl < 0)

		{

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

			{

			if (b[n-i] != 0)

				return -1; /* a < b */

			}

		}

	if (dl > 0)

		{

		for (i=dl; i>0; i--)

			{

			if (a[n+i] != 0)

				return 1; /* a > b */

			}

		}

	return bn_cmp_words(a,b,cl);

	}