/usr/include/gf2x/gf2x_mul8.h is in libgf2x-dev 1.1-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 | /* This file is part of the gf2x library.
Copyright 2007, 2008, 2009
Richard Brent, Pierrick Gaudry, Emmanuel Thome', Paul Zimmermann
This program 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.
This program 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 this program; see the file COPYING. If not, write to the Free
Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
02111-1307, USA.
*/
#ifndef GF2X_MUL8_H_
#define GF2X_MUL8_H_
#include "gf2x.h"
/* All gf2x source files for lowlevel functions must include gf2x-small.h
* This is mandatory for the tuning mechanism. */
#include "gf2x/gf2x-small.h"
/* 3 calls to mul4, i.e., 27 multiplications */
GF2X_STORAGE_CLASS_mul8
void gf2x_mul8 (unsigned long *c, const unsigned long *a, const unsigned long *b)
{
/* specialized Karatsuba, RPB 20070518 */
/* slightly faster on bogong than version with loops */
/* this version uses minimal temporary storage (12 = 3*n/2 words) */
unsigned long aa[4], bb[4], cc[4];
gf2x_mul4 (c+8, a+4, b+4);
gf2x_mul4 (c, a, b);
cc[0] = c[4] ^ c[8];
cc[1] = c[5] ^ c[9];
cc[2] = c[6] ^ c[10];
cc[3] = c[7] ^ c[11];
aa[0] = a[0] ^ a[4];
aa[1] = a[1] ^ a[5];
aa[2] = a[2] ^ a[6];
aa[3] = a[3] ^ a[7];
bb[0] = b[0] ^ b[4];
bb[1] = b[1] ^ b[5];
bb[2] = b[2] ^ b[6];
bb[3] = b[3] ^ b[7];
gf2x_mul4 (c+4, aa, bb);
c[4] ^= c[0] ^ cc[0];
c[5] ^= c[1] ^ cc[1];
c[6] ^= c[2] ^ cc[2];
c[7] ^= c[3] ^ cc[3];
c[8] ^= c[12] ^ cc[0];
c[9] ^= c[13] ^ cc[1];
c[10] ^= c[14] ^ cc[2];
c[11] ^= c[15] ^ cc[3];
}
#endif /* GF2X_MUL8_H_ */
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