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1d92226b JJ |
1 | /* mpn_add_n -- Add two limb vectors of equal, non-zero length. |
2 | ||
1b78544f | 3 | Copyright (C) 1992, 1993, 1994, 1996 Free Software Foundation, Inc. |
1d92226b JJ |
4 | |
5 | This file is part of the GNU MP Library. | |
6 | ||
7 | The GNU MP Library is free software; you can redistribute it and/or modify | |
8 | it under the terms of the GNU Lesser General Public License as published by | |
9 | the Free Software Foundation; either version 2.1 of the License, or (at your | |
10 | option) any later version. | |
11 | ||
12 | The GNU MP Library is distributed in the hope that it will be useful, but | |
13 | WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY | |
14 | or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public | |
15 | License for more details. | |
16 | ||
17 | You should have received a copy of the GNU Lesser General Public License | |
18 | along with the GNU MP Library; see the file COPYING.LIB. If not, write to | |
19 | the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, | |
20 | MA 02111-1307, USA. */ | |
21 | ||
a855debf | 22 | #include <config.h> |
1d92226b JJ |
23 | #include "gmp-impl.h" |
24 | ||
25 | mp_limb_t | |
26 | #if __STDC__ | |
27 | mpn_add_n (mp_ptr res_ptr, mp_srcptr s1_ptr, mp_srcptr s2_ptr, mp_size_t size) | |
28 | #else | |
29 | mpn_add_n (res_ptr, s1_ptr, s2_ptr, size) | |
30 | register mp_ptr res_ptr; | |
31 | register mp_srcptr s1_ptr; | |
32 | register mp_srcptr s2_ptr; | |
33 | mp_size_t size; | |
34 | #endif | |
35 | { | |
36 | register mp_limb_t x, y, cy; | |
37 | register mp_size_t j; | |
38 | ||
39 | /* The loop counter and index J goes from -SIZE to -1. This way | |
40 | the loop becomes faster. */ | |
41 | j = -size; | |
42 | ||
43 | /* Offset the base pointers to compensate for the negative indices. */ | |
44 | s1_ptr -= j; | |
45 | s2_ptr -= j; | |
46 | res_ptr -= j; | |
47 | ||
48 | cy = 0; | |
49 | do | |
50 | { | |
51 | y = s2_ptr[j]; | |
52 | x = s1_ptr[j]; | |
53 | y += cy; /* add previous carry to one addend */ | |
54 | cy = (y < cy); /* get out carry from that addition */ | |
55 | y = x + y; /* add other addend */ | |
56 | cy = (y < x) + cy; /* get out carry from that add, combine */ | |
57 | res_ptr[j] = y; | |
58 | } | |
59 | while (++j != 0); | |
60 | ||
61 | return cy; | |
62 | } |