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glibc/stdlib/add_n.c
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/* mpn_add_n -- Add two limb vectors of equal, non-zero length. | |
Copyright (C) 1992-2016 Free Software Foundation, Inc. | |
This file is part of the GNU MP Library. | |
The GNU MP Library is free software; you can redistribute it and/or modify | |
it under the terms of the GNU Lesser General Public License as published by | |
the Free Software Foundation; either version 2.1 of the License, or (at your | |
option) any later version. | |
The GNU MP Library is distributed in the hope that it will be useful, but | |
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY | |
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public | |
License for more details. | |
You should have received a copy of the GNU Lesser General Public License | |
along with the GNU MP Library; see the file COPYING.LIB. If not, see | |
<http://www.gnu.org/licenses/>. */ | |
#include <gmp.h> | |
#include "gmp-impl.h" | |
mp_limb_t | |
mpn_add_n (mp_ptr res_ptr, mp_srcptr s1_ptr, mp_srcptr s2_ptr, mp_size_t size) | |
{ | |
register mp_limb_t x, y, cy; | |
register mp_size_t j; | |
/* The loop counter and index J goes from -SIZE to -1. This way | |
the loop becomes faster. */ | |
j = -size; | |
/* Offset the base pointers to compensate for the negative indices. */ | |
s1_ptr -= j; | |
s2_ptr -= j; | |
res_ptr -= j; | |
cy = 0; | |
do | |
{ | |
y = s2_ptr[j]; | |
x = s1_ptr[j]; | |
y += cy; /* add previous carry to one addend */ | |
cy = (y < cy); /* get out carry from that addition */ | |
y = x + y; /* add other addend */ | |
cy = (y < x) + cy; /* get out carry from that add, combine */ | |
res_ptr[j] = y; | |
} | |
while (++j != 0); | |
return cy; | |
} |