^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1) // SPDX-License-Identifier: GPL-2.0-or-later
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 2) /* mpihelp-mul_2.c - MPI helper functions
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 3) * Copyright (C) 1994, 1996, 1997, 1998, 2001 Free Software Foundation, Inc.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 4) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 5) * This file is part of GnuPG.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 6) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 7) * Note: This code is heavily based on the GNU MP Library.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 8) * Actually it's the same code with only minor changes in the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 9) * way the data is stored; this is to support the abstraction
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 10) * of an optional secure memory allocation which may be used
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 11) * to avoid revealing of sensitive data due to paging etc.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 12) * The GNU MP Library itself is published under the LGPL;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 13) * however I decided to publish this code under the plain GPL.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 14) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 15)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 16) #include "mpi-internal.h"
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 17) #include "longlong.h"
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 18)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 19) mpi_limb_t
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 20) mpihelp_addmul_1(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 21) mpi_size_t s1_size, mpi_limb_t s2_limb)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 22) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 23) mpi_limb_t cy_limb;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 24) mpi_size_t j;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 25) mpi_limb_t prod_high, prod_low;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 26) mpi_limb_t x;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 27)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 28) /* The loop counter and index J goes from -SIZE to -1. This way
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 29) * the loop becomes faster. */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 30) j = -s1_size;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 31) res_ptr -= j;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 32) s1_ptr -= j;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 33)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 34) cy_limb = 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 35) do {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 36) umul_ppmm(prod_high, prod_low, s1_ptr[j], s2_limb);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 37)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 38) prod_low += cy_limb;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 39) cy_limb = (prod_low < cy_limb ? 1 : 0) + prod_high;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 40)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 41) x = res_ptr[j];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 42) prod_low = x + prod_low;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 43) cy_limb += prod_low < x ? 1 : 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 44) res_ptr[j] = prod_low;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 45) } while (++j);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 46) return cy_limb;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 47) }