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1// SPDX-License-Identifier: GPL-2.0-or-later2/* mpihelp-mul_1.c - MPI helper functions3 * Copyright (C) 1994, 1996, 1997, 1998, 2001 Free Software Foundation, Inc.4 *5 * This file is part of GnuPG.6 *7 * Note: This code is heavily based on the GNU MP Library.8 * Actually it's the same code with only minor changes in the9 * way the data is stored; this is to support the abstraction10 * of an optional secure memory allocation which may be used11 * to avoid revealing of sensitive data due to paging etc.12 * The GNU MP Library itself is published under the LGPL;13 * however I decided to publish this code under the plain GPL.14 */15 16#include "mpi-internal.h"17#include "longlong.h"18 19mpi_limb_t20mpihelp_mul_1(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr, mpi_size_t s1_size,21 mpi_limb_t s2_limb)22{23 mpi_limb_t cy_limb;24 mpi_size_t j;25 mpi_limb_t prod_high, prod_low;26 27 /* The loop counter and index J goes from -S1_SIZE to -1. This way28 * the loop becomes faster. */29 j = -s1_size;30 31 /* Offset the base pointers to compensate for the negative indices. */32 s1_ptr -= j;33 res_ptr -= j;34 35 cy_limb = 0;36 do {37 umul_ppmm(prod_high, prod_low, s1_ptr[j], s2_limb);38 prod_low += cy_limb;39 cy_limb = (prod_low < cy_limb ? 1 : 0) + prod_high;40 res_ptr[j] = prod_low;41 } while (++j);42 43 return cy_limb;44}45