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1 : : // SPDX-License-Identifier: GPL-2.0-or-later 2 : : /* mpihelp-mul_1.c - MPI helper functions 3 : : * 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 the 9 : : * way the data is stored; this is to support the abstraction 10 : : * of an optional secure memory allocation which may be used 11 : : * 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 : : 19 : : mpi_limb_t 20 : 1683 : mpihelp_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 : 1683 : mpi_limb_t cy_limb; 24 : 1683 : mpi_size_t j; 25 : 1683 : mpi_limb_t prod_high, prod_low; 26 : : 27 : : /* The loop counter and index J goes from -S1_SIZE to -1. This way 28 : : * the loop becomes faster. */ 29 : 1683 : j = -s1_size; 30 : : 31 : : /* Offset the base pointers to compensate for the negative indices. */ 32 : 1683 : s1_ptr -= j; 33 : 1683 : res_ptr -= j; 34 : : 35 : 1683 : cy_limb = 0; 36 : 13464 : do { 37 [ + + ]: 13464 : umul_ppmm(prod_high, prod_low, s1_ptr[j], s2_limb); 38 : 13464 : prod_low += cy_limb; 39 [ + + ]: 13464 : cy_limb = (prod_low < cy_limb ? 1 : 0) + prod_high; 40 : 13464 : res_ptr[j] = prod_low; 41 [ + + ]: 13464 : } while (++j); 42 : : 43 : 1683 : return cy_limb; 44 : : }