/* mpi-scan.c  -  MPI functions

 *  Copyright (C) 1998, 2001, 2002, 2003 Free Software Foundation, Inc.

 *

 * 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"

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

 * Scan through an mpi and return byte for byte. a -1 is returned to indicate

 * the end of the mpi. Scanning is done from the lsb to the msb, returned

 * values are in the range of 0 .. 255.

 *

 * FIXME: This code is VERY ugly!

 */

/* int */

/* _gcry_mpi_getbyte( gcry_mpi_t a, unsigned idx ) */

/* { */

/*     int i, j; */

/*     unsigned n; */

/*     mpi_ptr_t ap; */

/*     mpi_limb_t limb; */

/*     ap = a->d; */

/*     for(n=0,i=0; i < a->nlimbs; i++ ) { */

/*  limb = ap[i]; */

/*  for( j=0; j < BYTES_PER_MPI_LIMB; j++, n++ ) */

/*      if( n == idx ) */

/*    return (limb >> j*8) & 0xff; */

/*     } */

/*     return -1; */

/* } */

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

 * Put a value at position IDX into A. idx counts from lsb to msb

 */

/* void */

/* _gcry_mpi_putbyte( gcry_mpi_t a, unsigned idx, int xc ) */

/* { */

/*     int i, j; */

/*     unsigned n; */

/*     mpi_ptr_t ap; */

/*     mpi_limb_t limb, c; */

/*     c = xc & 0xff; */

/*     ap = a->d; */

/*     for(n=0,i=0; i < a->alloced; i++ ) { */

/*  limb = ap[i]; */

/*  for( j=0; j < BYTES_PER_MPI_LIMB; j++, n++ ) */

/*      if( n == idx ) { */

/*        #if BYTES_PER_MPI_LIMB == 4 */

/*    if( j == 0 ) */

/*        limb = (limb & 0xffffff00) | c; */

/*    else if( j == 1 ) */

/*        limb = (limb & 0xffff00ff) | (c<<8); */

/*    else if( j == 2 ) */

/*        limb = (limb & 0xff00ffff) | (c<<16); */

/*    else */

/*        limb = (limb & 0x00ffffff) | (c<<24); */

/*        #elif BYTES_PER_MPI_LIMB == 8 */

/*    if( j == 0 ) */

/*        limb = (limb & 0xffffffffffffff00) | c; */

/*    else if( j == 1 ) */

/*        limb = (limb & 0xffffffffffff00ff) | (c<<8); */

/*    else if( j == 2 ) */

/*        limb = (limb & 0xffffffffff00ffff) | (c<<16); */

/*    else if( j == 3 ) */

/*        limb = (limb & 0xffffffff00ffffff) | (c<<24); */

/*    else if( j == 4 ) */

/*        limb = (limb & 0xffffff00ffffffff) | (c<<32); */

/*    else if( j == 5 ) */

/*        limb = (limb & 0xffff00ffffffffff) | (c<<40); */

/*    else if( j == 6 ) */

/*        limb = (limb & 0xff00ffffffffffff) | (c<<48); */

/*    else */

/*        limb = (limb & 0x00ffffffffffffff) | (c<<56); */

/*        #else */

/*     #error please enhance this function, its ugly - i know. */

/*        #endif */

/*    if( a->nlimbs <= i ) */

/*        a->nlimbs = i+1; */

/*    ap[i] = limb; */

/*    return; */

/*      } */

/*     } */

/*     abort(); /\* index out of range *\/ */

/* } */

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

 * Count the number of zerobits at the low end of A

 */

unsigned

_gcry_mpi_trailing_zeros( gcry_mpi_t a )

{

    unsigned n, count = 0;

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

  if( a->d[n] ) {

      unsigned nn;

      mpi_limb_t alimb = a->d[n];

      count_trailing_zeros( nn, alimb );

      count += nn;

      break;

  }

  count += BITS_PER_MPI_LIMB;

    }

    return count;

}