/* mpi-bit.c  -  MPI bit level functions

 * Copyright (C) 1998, 1999, 2001, 2002, 2006 Free Software Foundation, Inc.

 * Copyright (C) 2013  g10 Code GmbH

 *

 * This file is part of Libgcrypt.

 *

 * Libgcrypt is free software; you can redistribute it and/or modify

 * it under the terms of the GNU Lesser General Public License as

 * published by the Free Software Foundation; either version 2.1 of

 * the License, or (at your option) any later version.

 *

 * Libgcrypt is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with this program; if not, see <https://www.gnu.org/licenses/>.

 * SPDX-License-Identifier: LGPL-2.1-or-later

 */

#include <config.h>

#include <stdio.h>

#include <stdlib.h>

#include "mpi-internal.h"

#include "longlong.h"

#ifdef MPI_INTERNAL_NEED_CLZ_TAB

#ifdef __STDC__

const

#endif

unsigned char

_gcry_clz_tab[] =

{

  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,

};

#endif

#define A_LIMB_1 ((mpi_limb_t)1)

/****************

 * Sometimes we have MSL (most significant limbs) which are 0;

 * this is for some reasons not good, so this function removes them.

 */

void

_gcry_mpi_normalize( gcry_mpi_t a )

{

    if( mpi_is_opaque(a) )

  return;

    for( ; a->nlimbs && !a->d[a->nlimbs-1]; a->nlimbs-- )

  ;

}

/****************

 * Return the number of bits in A.

 */

unsigned int

_gcry_mpi_get_nbits (gcry_mpi_t a)

{

    unsigned n;

    if( mpi_is_opaque(a) ) {

  return a->sign; /* which holds the number of bits */

    }

    _gcry_mpi_normalize( a );

    if( a->nlimbs ) {

  mpi_limb_t alimb = a->d[a->nlimbs-1];

  if( alimb )

      count_leading_zeros( n, alimb );

  else

      n = BITS_PER_MPI_LIMB;

  n = BITS_PER_MPI_LIMB - n + (a->nlimbs-1) * BITS_PER_MPI_LIMB;

    }

    else

  n = 0;

    return n;

}

/****************

 * Test whether bit N is set.

 */

int

_gcry_mpi_test_bit( gcry_mpi_t a, unsigned int n )

{

    unsigned int limbno, bitno;

    mpi_limb_t limb;

    limbno = n / BITS_PER_MPI_LIMB;

    bitno  = n % BITS_PER_MPI_LIMB;

    if( limbno >= a->nlimbs )

  return 0; /* too far left: this is a 0 */

    limb = a->d[limbno];

    return (limb & (A_LIMB_1 << bitno))? 1: 0;

}

/****************

 * Set bit N of A.

 */

void

_gcry_mpi_set_bit( gcry_mpi_t a, unsigned int n )

{

  unsigned int i, limbno, bitno;

  if (mpi_is_immutable (a))

    {

      mpi_immutable_failed ();

      return;

    }

  limbno = n / BITS_PER_MPI_LIMB;

  bitno  = n % BITS_PER_MPI_LIMB;

  if ( limbno >= a->nlimbs )

    {

      for (i=a->nlimbs; i < a->alloced; i++)

        a->d[i] = 0;

      mpi_resize (a, limbno+1 );

      a->nlimbs = limbno+1;

    }

  a->d[limbno] |= (A_LIMB_1<<bitno);

}

/****************

 * Set bit N of A. and clear all bits above

 */

void

_gcry_mpi_set_highbit( gcry_mpi_t a, unsigned int n )

{

  unsigned int i, limbno, bitno;

  if (mpi_is_immutable (a))

    {

      mpi_immutable_failed ();

      return;

    }

  limbno = n / BITS_PER_MPI_LIMB;

  bitno  = n % BITS_PER_MPI_LIMB;

  if ( limbno >= a->nlimbs )

    {

      for (i=a->nlimbs; i < a->alloced; i++)

        a->d[i] = 0;

      mpi_resize (a, limbno+1 );

      a->nlimbs = limbno+1;

    }

  a->d[limbno] |= (A_LIMB_1<<bitno);

  for ( bitno++; bitno < BITS_PER_MPI_LIMB; bitno++ )

    a->d[limbno] &= ~(A_LIMB_1 << bitno);

  a->nlimbs = limbno+1;

}

/****************

 * clear bit N of A and all bits above

 */

void

_gcry_mpi_clear_highbit( gcry_mpi_t a, unsigned int n )

{

  unsigned int limbno, bitno;

  if (mpi_is_immutable (a))

    {

      mpi_immutable_failed ();

      return;

    }

  limbno = n / BITS_PER_MPI_LIMB;

  bitno  = n % BITS_PER_MPI_LIMB;

  if( limbno >= a->nlimbs )

    return; /* not allocated, therefore no need to clear bits :-) */

  for( ; bitno < BITS_PER_MPI_LIMB; bitno++ )

    a->d[limbno] &= ~(A_LIMB_1 << bitno);

  a->nlimbs = limbno+1;

}

/****************

 * Clear bit N of A.

 */

void

_gcry_mpi_clear_bit( gcry_mpi_t a, unsigned int n )

{

  unsigned int limbno, bitno;

  if (mpi_is_immutable (a))

    {

      mpi_immutable_failed ();

      return;

    }

  limbno = n / BITS_PER_MPI_LIMB;

  bitno  = n % BITS_PER_MPI_LIMB;

  if (limbno >= a->nlimbs)

    return; /* Don't need to clear this bit, it's far too left.  */

  a->d[limbno] &= ~(A_LIMB_1 << bitno);

}

/****************

 * Shift A by COUNT limbs to the right

 * This is used only within the MPI library

 */

void

_gcry_mpi_rshift_limbs( gcry_mpi_t a, unsigned int count )

{

  mpi_ptr_t ap = a->d;

  mpi_size_t n = a->nlimbs;

  unsigned int i;

  if (mpi_is_immutable (a))

    {

      mpi_immutable_failed ();

      return;

    }

  if (count >= n)

    {

      a->nlimbs = 0;

      return;

    }

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

    ap[i] = ap[i+count];

  ap[i] = 0;

  a->nlimbs -= count;

}

/*

 * Shift A by N bits to the right.

 */

void

_gcry_mpi_rshift ( gcry_mpi_t x, gcry_mpi_t a, unsigned int n )

{

  unsigned int nlimbs = (n/BITS_PER_MPI_LIMB);

  unsigned int nbits = (n%BITS_PER_MPI_LIMB);

  unsigned int i;

  mpi_size_t alimbs;

  mpi_ptr_t xp, ap;

  if (mpi_is_immutable (x))

    {

      mpi_immutable_failed ();

      return;

    }

  alimbs = a->nlimbs;

  if (x != a)

    {

      RESIZE_IF_NEEDED (x, alimbs);

      x->nlimbs = alimbs;

      x->flags = a->flags;

      x->sign = a->sign;

    }

  /* In-place operation.  */

  if (nlimbs >= alimbs)

    {

      x->nlimbs = 0;

      return;

    }

  xp = x->d;

  ap = a->d;

  if (alimbs && nbits)

    {

      _gcry_mpih_rshift (xp, ap + nlimbs, alimbs - nlimbs, nbits);

      if (nlimbs)

  xp[alimbs - nlimbs] = 0;

      x->nlimbs -= nlimbs;

    }

  else if (nlimbs || (x != a))

    {

      for (i = 0; i < alimbs - nlimbs; i++ )

  xp[i] = ap[i + nlimbs];

      if (nlimbs)

  xp[i] = 0;

      x->nlimbs -= nlimbs;

    }

  MPN_NORMALIZE (x->d, x->nlimbs);

}

/****************

 * Shift A by COUNT limbs to the left

 * This is used only within the MPI library

 */

void

_gcry_mpi_lshift_limbs (gcry_mpi_t a, unsigned int count)

{

  mpi_ptr_t ap;

  int n = a->nlimbs;

  int i;

  if (!count || !n)

    return;

  RESIZE_IF_NEEDED (a, n+count);

  ap = a->d;

  for (i = n-1; i >= 0; i--)

    ap[i+count] = ap[i];

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

    ap[i] = 0;

  a->nlimbs += count;

}

/*

 * Shift A by N bits to the left.

 */

void

_gcry_mpi_lshift ( gcry_mpi_t x, gcry_mpi_t a, unsigned int n )

{

  unsigned int nlimbs = (n/BITS_PER_MPI_LIMB);

  unsigned int nbits = (n%BITS_PER_MPI_LIMB);

  mpi_size_t alimbs;

  mpi_ptr_t xp, ap;

  int i;

  if (mpi_is_immutable (x))

    {

      mpi_immutable_failed ();

      return;

    }

  if (x == a && !n)

    return;  /* In-place shift with an amount of zero.  */

  /* Note: might be in-place operation, so a==x or a!=x. */

  alimbs = a->nlimbs;

  RESIZE_IF_NEEDED (x, alimbs + nlimbs + 1);

  xp = x->d;

  ap = a->d;

  if (nbits && alimbs)

    {

      x->nlimbs = alimbs + nlimbs + 1;

      xp[alimbs + nlimbs] = _gcry_mpih_lshift (xp + nlimbs, ap, alimbs, nbits);

    }

  else

    {

      x->nlimbs = alimbs + nlimbs;

      for (i = alimbs - 1; i >= 0; i--)

  xp[i + nlimbs] = ap[i];

    }

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

    xp[i] = 0;

  x->flags = a->flags;

  x->sign = a->sign;

  MPN_NORMALIZE (x->d, x->nlimbs);

}