1 /* mpi-scan.c - MPI functions
2 * Copyright (C) 1998, 1999, 2000, 2001 Free Software Foundation, Inc.
4 * This file is part of GnuPG.
6 * GnuPG is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
11 * GnuPG is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
21 #include "mpi-internal.h"
25 * Scan through an mpi and return byte for byte. a -1 is returned to indicate
26 * the end of the mpi. Scanning is done from the lsb to the msb, returned
27 * values are in the range of 0 .. 255.
29 * FIXME: This code is VERY ugly!
32 mpi_getbyte( const MPI a, unsigned idx )
40 for(n=0,i=0; i < a->nlimbs; i++ ) {
42 for( j=0; j < BYTES_PER_MPI_LIMB; j++, n++ )
44 return (limb >> j*8) & 0xff;
51 * Put a value at position IDX into A. idx counts from lsb to msb
54 mpi_putbyte( MPI a, unsigned idx, int xc )
63 for(n=0,i=0; i < a->alloced; i++ ) {
65 for( j=0; j < BYTES_PER_MPI_LIMB; j++, n++ )
67 #if BYTES_PER_MPI_LIMB == 4
69 limb = (limb & 0xffffff00) | c;
71 limb = (limb & 0xffff00ff) | (c<<8);
73 limb = (limb & 0xff00ffff) | (c<<16);
75 limb = (limb & 0x00ffffff) | (c<<24);
76 #elif BYTES_PER_MPI_LIMB == 8
78 limb = (limb & 0xffffffffffffff00) | c;
80 limb = (limb & 0xffffffffffff00ff) | (c<<8);
82 limb = (limb & 0xffffffffff00ffff) | (c<<16);
84 limb = (limb & 0xffffffff00ffffff) | (c<<24);
86 limb = (limb & 0xffffff00ffffffff) | (c<<32);
88 limb = (limb & 0xffff00ffffffffff) | (c<<40);
90 limb = (limb & 0xff00ffffffffffff) | (c<<48);
92 limb = (limb & 0x00ffffffffffffff) | (c<<56);
94 #error please enhance this function, its ugly - i know.
102 log_bug("index out of range\n");
107 * Count the number of zerobits at the low end of A
110 mpi_trailing_zeros( const MPI a )
112 unsigned n, count = 0;
114 for(n=0; n < a->nlimbs; n++ ) {
117 mpi_limb_t alimb = a->d[n];
119 count_trailing_zeros( nn, alimb );
123 count += BITS_PER_MPI_LIMB;