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48 lines
1.3 KiB
48 lines
1.3 KiB
// SPDX-License-Identifier: GPL-2.0-or-later |
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/* mpihelp-add_1.c - MPI helper functions |
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* Copyright (C) 1994, 1996, 1997, 1998, |
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* 2000 Free Software Foundation, Inc. |
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* |
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* This file is part of GnuPG. |
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* |
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* Note: This code is heavily based on the GNU MP Library. |
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* Actually it's the same code with only minor changes in the |
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* way the data is stored; this is to support the abstraction |
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* of an optional secure memory allocation which may be used |
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* to avoid revealing of sensitive data due to paging etc. |
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* The GNU MP Library itself is published under the LGPL; |
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* however I decided to publish this code under the plain GPL. |
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*/ |
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#include "mpi-internal.h" |
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#include "longlong.h" |
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mpi_limb_t |
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mpihelp_add_n(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr, |
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mpi_ptr_t s2_ptr, mpi_size_t size) |
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{ |
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mpi_limb_t x, y, cy; |
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mpi_size_t j; |
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/* The loop counter and index J goes from -SIZE to -1. This way |
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the loop becomes faster. */ |
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j = -size; |
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/* Offset the base pointers to compensate for the negative indices. */ |
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s1_ptr -= j; |
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s2_ptr -= j; |
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res_ptr -= j; |
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cy = 0; |
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do { |
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y = s2_ptr[j]; |
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x = s1_ptr[j]; |
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y += cy; /* add previous carry to one addend */ |
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cy = y < cy; /* get out carry from that addition */ |
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y += x; /* add other addend */ |
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cy += y < x; /* get out carry from that add, combine */ |
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res_ptr[j] = y; |
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} while (++j); |
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return cy; |
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}
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