55 lines
1.8 KiB
C
55 lines
1.8 KiB
C
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/*=============================================================================
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This file is part of FLINT.
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FLINT is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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FLINT is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with FLINT; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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=============================================================================*/
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/******************************************************************************
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Copyright (C) 2009 William Hart
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******************************************************************************/
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#include <mpir.h>
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const mp_limb_t revtab0[1] = { 0 };
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const mp_limb_t revtab1[2] = { 0, 1 };
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const mp_limb_t revtab2[4] = { 0, 2, 1, 3 };
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const mp_limb_t revtab3[8] = { 0, 4, 2, 6, 1, 5, 3, 7 };
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const mp_limb_t revtab4[16] = { 0, 8, 4, 12, 2, 10, 6, 14, 1, 9, 5, 13, 3, 11, 7, 15 };
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const mp_limb_t * revtab[5] = { revtab0, revtab1, revtab2, revtab3, revtab4 };
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/*
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computes the reverse binary of a binary number of the given number of bits
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*/
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mp_limb_t mpn_revbin(mp_limb_t in, mp_limb_t bits)
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{
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mp_limb_t out = 0, i;
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if (bits <= 4)
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return revtab[bits][in];
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for (i = 0; i < bits; i++)
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{
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out <<= 1;
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out += (in & 1);
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in >>= 1;
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}
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return out;
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}
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