1/* mpihelp-mul_2.c - MPI helper functions 2 * Copyright (C) 1994, 1996, 1997, 1998, 2001 Free Software Foundation, Inc. 3 * 4 * This file is part of GnuPG. 5 * 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. 10 * 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. 15 * 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 19 * 20 * Note: This code is heavily based on the GNU MP Library. 21 * Actually it's the same code with only minor changes in the 22 * way the data is stored; this is to support the abstraction 23 * of an optional secure memory allocation which may be used 24 * to avoid revealing of sensitive data due to paging etc. 25 * The GNU MP Library itself is published under the LGPL; 26 * however I decided to publish this code under the plain GPL. 27 */ 28 29#include "mpi-internal.h" 30#include "longlong.h" 31 32mpi_limb_t 33mpihelp_addmul_1(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr, 34 mpi_size_t s1_size, mpi_limb_t s2_limb) 35{ 36 mpi_limb_t cy_limb; 37 mpi_size_t j; 38 mpi_limb_t prod_high, prod_low; 39 mpi_limb_t x; 40 41 /* The loop counter and index J goes from -SIZE to -1. This way 42 * the loop becomes faster. */ 43 j = -s1_size; 44 res_ptr -= j; 45 s1_ptr -= j; 46 47 cy_limb = 0; 48 do { 49 umul_ppmm(prod_high, prod_low, s1_ptr[j], s2_limb); 50 51 prod_low += cy_limb; 52 cy_limb = (prod_low < cy_limb ? 1 : 0) + prod_high; 53 54 x = res_ptr[j]; 55 prod_low = x + prod_low; 56 cy_limb += prod_low < x ? 1 : 0; 57 res_ptr[j] = prod_low; 58 } while (++j); 59 return cy_limb; 60} 61