57 lines
1.8 KiB
C
57 lines
1.8 KiB
C
|
/*=============================================================================
|
||
|
|
|
||
|
|
This file is part of FLINT.
|
||
|
|
|
||
|
|
FLINT is free software; you can redistribute it and/or modify
|
||
|
|
it under the terms of the GNU General Public License as published by
|
||
|
|
the Free Software Foundation; either version 2 of the License, or
|
||
|
|
(at your option) any later version.
|
||
|
|
|
||
|
|
FLINT 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 General Public License for more details.
|
||
|
|
|
||
|
|
You should have received a copy of the GNU General Public License
|
||
|
|
along with FLINT; if not, write to the Free Software
|
||
|
|
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
|
||
|
|
|
||
|
|
=============================================================================*/
|
||
|
|
/******************************************************************************
|
||
|
|
|
||
|
|
Copyright (C) 2009 William Hart
|
||
|
|
|
||
|
|
******************************************************************************/
|
||
|
|
|
||
|
|
#include <gmp.h>
|
||
|
|
#include "flint.h"
|
||
|
|
#include "ulong_extras.h"
|
||
|
|
|
||
|
|
const ulong flint_revtab0[1] = { 0 };
|
||
|
|
const ulong flint_revtab1[2] = { 0, 1 };
|
||
|
|
const ulong flint_revtab2[4] = { 0, 2, 1, 3 };
|
||
|
|
const ulong flint_revtab3[8] = { 0, 4, 2, 6, 1, 5, 3, 7 };
|
||
|
|
const ulong flint_revtab4[16] = { 0, 8, 4, 12, 2, 10, 6, 14, 1, 9, 5, 13, 3, 11, 7, 15 };
|
||
|
|
|
||
|
|
const ulong * flint_revtab[5] = { flint_revtab0, flint_revtab1, flint_revtab2, flint_revtab3, flint_revtab4 };
|
||
|
|
|
||
|
|
/*
|
||
|
|
computes the reverse binary of a binary number of the given number of bits
|
||
|
|
*/
|
||
|
|
ulong n_revbin(ulong in, ulong bits)
|
||
|
|
{
|
||
|
|
ulong out = 0, i;
|
||
|
|
|
||
|
|
if (bits <= 4)
|
||
|
|
return flint_revtab[bits][in];
|
||
|
|
|
||
|
|
for (i = 0; i < bits; i++)
|
||
|
|
{
|
||
|
|
out <<= 1;
|
||
|
|
out += (in & 1);
|
||
|
|
in >>= 1;
|
||
|
|
}
|
||
|
|
|
||
|
|
return out;
|
||
|
|
}
|