| // SPDX-License-Identifier: GPL-2.0-or-later |
| /* mpihelp-add_2.c - MPI helper functions |
| * Copyright (C) 1994, 1996, 1997, 1998, 2001 Free Software Foundation, Inc. |
| * This file is part of GnuPG. |
| * Note: This code is heavily based on the GNU MP Library. |
| * Actually it's the same code with only minor changes in the |
| * way the data is stored; this is to support the abstraction |
| * of an optional secure memory allocation which may be used |
| * to avoid revealing of sensitive data due to paging etc. |
| * The GNU MP Library itself is published under the LGPL; |
| * however I decided to publish this code under the plain GPL. |
| #include "mpi-internal.h" |
| mpihelp_sub_n(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr, |
| mpi_ptr_t s2_ptr, mpi_size_t size) |
| /* The loop counter and index J goes from -SIZE to -1. This way |
| the loop becomes faster. */ |
| /* Offset the base pointers to compensate for the negative indices. */ |
| y += cy; /* add previous carry to subtrahend */ |
| cy = y < cy; /* get out carry from that addition */ |
| y = x - y; /* main subtract */ |
| cy += y > x; /* get out carry from the subtract, combine */ |