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1 : : // SPDX-License-Identifier: GPL-2.0-or-later 2 : : /* mpihelp-add_1.c - MPI helper functions 3 : : * Copyright (C) 1994, 1996, 1997, 1998, 4 : : * 2000 Free Software Foundation, Inc. 5 : : * 6 : : * This file is part of GnuPG. 7 : : * 8 : : * Note: This code is heavily based on the GNU MP Library. 9 : : * Actually it's the same code with only minor changes in the 10 : : * way the data is stored; this is to support the abstraction 11 : : * of an optional secure memory allocation which may be used 12 : : * to avoid revealing of sensitive data due to paging etc. 13 : : * The GNU MP Library itself is published under the LGPL; 14 : : * however I decided to publish this code under the plain GPL. 15 : : */ 16 : : 17 : : #include "mpi-internal.h" 18 : : #include "longlong.h" 19 : : 20 : : mpi_limb_t 21 : 16068 : mpihelp_add_n(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr, 22 : : mpi_ptr_t s2_ptr, mpi_size_t size) 23 : : { 24 : 16068 : mpi_limb_t x, y, cy; 25 : 16068 : mpi_size_t j; 26 : : 27 : : /* The loop counter and index J goes from -SIZE to -1. This way 28 : : the loop becomes faster. */ 29 : 16068 : j = -size; 30 : : 31 : : /* Offset the base pointers to compensate for the negative indices. */ 32 : 16068 : s1_ptr -= j; 33 : 16068 : s2_ptr -= j; 34 : 16068 : res_ptr -= j; 35 : : 36 : 16068 : cy = 0; 37 : 214656 : do { 38 : 214656 : y = s2_ptr[j]; 39 : 214656 : x = s1_ptr[j]; 40 : 214656 : y += cy; /* add previous carry to one addend */ 41 : 214656 : cy = y < cy; /* get out carry from that addition */ 42 : 214656 : y += x; /* add other addend */ 43 : 214656 : cy += y < x; /* get out carry from that add, combine */ 44 : 214656 : res_ptr[j] = y; 45 [ + + ]: 214656 : } while (++j); 46 : : 47 : 16068 : return cy; 48 : : }