1121666Sharti/* mpn_sec_tabselect. 2121666Sharti 3121666ShartiCopyright 2007-2009, 2011, 2013 Free Software Foundation, Inc. 4 5This file is part of the GNU MP Library. 6 7The GNU MP Library is free software; you can redistribute it and/or modify 8it under the terms of either: 9 10 * the GNU Lesser General Public License as published by the Free 11 Software Foundation; either version 3 of the License, or (at your 12 option) any later version. 13 14or 15 16 * the GNU General Public License as published by the Free Software 17 Foundation; either version 2 of the License, or (at your option) any 18 later version. 19 20or both in parallel, as here. 21 22The GNU MP Library is distributed in the hope that it will be useful, but 23WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 24or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 25for more details. 26 27You should have received copies of the GNU General Public License and the 28GNU Lesser General Public License along with the GNU MP Library. If not, 29see https://www.gnu.org/licenses/. */ 30 31#include "gmp-impl.h" 32 33 34/* Select entry `which' from table `tab', which has nents entries, each `n' 35 limbs. Store the selected entry at rp. Reads entire table to avoid 36 side-channel information leaks. O(n*nents). */ 37void 38mpn_sec_tabselect (volatile mp_limb_t *rp, volatile const mp_limb_t *tab, 39 mp_size_t n, mp_size_t nents, mp_size_t which) 40{ 41 mp_size_t k, i; 42 mp_limb_t mask; 43 volatile const mp_limb_t *tp; 44 45 for (k = 0; k < nents; k++) 46 { 47 mask = -(mp_limb_t) (which == k); 48 tp = tab + n * k; 49 for (i = 0; i < n; i++) 50 { 51 rp[i] = (rp[i] & ~mask) | (tp[i] & mask); 52 } 53 } 54} 55