/* 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, write to the Free Software

 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA

 */

#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 )

{

  mpi_size_t xsize;

  unsigned int i;

  unsigned int nlimbs = (n/BITS_PER_MPI_LIMB);

  unsigned int nbits = (n%BITS_PER_MPI_LIMB);

  if (mpi_is_immutable (x))

    {

      mpi_immutable_failed ();

      return;

    }

  if ( x == a )

    {

      /* In-place operation.  */

      if ( nlimbs >= x->nlimbs )

        {

          x->nlimbs = 0;

          return;

        }

      if (nlimbs)

        {

          for (i=0; i < x->nlimbs - nlimbs; i++ )

            x->d[i] = x->d[i+nlimbs];

          x->d[i] = 0;

          x->nlimbs -= nlimbs;

        }

      if ( x->nlimbs && nbits )

        _gcry_mpih_rshift ( x->d, x->d, x->nlimbs, nbits );

    }

  else if ( nlimbs )

    {

      /* Copy and shift by more or equal bits than in a limb. */

      xsize = a->nlimbs;

      x->sign = a->sign;

      RESIZE_IF_NEEDED (x, xsize);

      x->nlimbs = xsize;

      for (i=0; i < a->nlimbs; i++ )

        x->d[i] = a->d[i];

      x->nlimbs = i;

      if ( nlimbs >= x->nlimbs )

        {

          x->nlimbs = 0;

          return;

        }

      if (nlimbs)

        {

          for (i=0; i < x->nlimbs - nlimbs; i++ )

            x->d[i] = x->d[i+nlimbs];

          x->d[i] = 0;

          x->nlimbs -= nlimbs;

        }

      if ( x->nlimbs && nbits )

        _gcry_mpih_rshift ( x->d, x->d, x->nlimbs, nbits );

    }

  else

    {

      /* Copy and shift by less than bits in a limb.  */

      xsize = a->nlimbs;

      x->sign = a->sign;

      RESIZE_IF_NEEDED (x, xsize);

      x->nlimbs = xsize;

      if ( xsize )

        {

          if (nbits )

            _gcry_mpih_rshift (x->d, a->d, x->nlimbs, nbits );

          else

            {

              /* The rshift helper function is not specified for

                 NBITS==0, thus we do a plain copy here. */

              for (i=0; i < x->nlimbs; i++ )

                x->d[i] = a->d[i];

            }

        }

    }

  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);

  if (mpi_is_immutable (x))

    {

      mpi_immutable_failed ();

      return;

    }

  if (x == a && !n)

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

  if ( x != a )

    {

      /* Copy A to X.  */

      unsigned int alimbs = a->nlimbs;

      int asign  = a->sign;

      mpi_ptr_t xp, ap;

      RESIZE_IF_NEEDED (x, alimbs+nlimbs+1);

      xp = x->d;

      ap = a->d;

      MPN_COPY (xp, ap, alimbs);

      x->nlimbs = alimbs;

      x->flags = a->flags;

      x->sign = asign;

    }

  if (nlimbs && !nbits)

    {

      /* Shift a full number of limbs.  */

      _gcry_mpi_lshift_limbs (x, nlimbs);

    }

  else if (n)

    {

      /* We use a very dump approach: Shift left by the number of

         limbs plus one and than fix it up by an rshift.  */

      _gcry_mpi_lshift_limbs (x, nlimbs+1);

      mpi_rshift (x, x, BITS_PER_MPI_LIMB - nbits);

    }

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

}