]>
Commit | Line | Data |
---|---|---|
6b628d36 | 1 | /* mpn_sub_n -- Subtract two limb vectors of equal, non-zero length. |
28f540f4 | 2 | |
d614a753 | 3 | Copyright (C) 1992-2020 Free Software Foundation, Inc. |
28f540f4 RM |
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 | |
6d84f89a AJ |
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 | |
28f540f4 RM |
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 | |
6d84f89a | 14 | or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public |
28f540f4 RM |
15 | License for more details. |
16 | ||
6d84f89a | 17 | You should have received a copy of the GNU Lesser General Public License |
59ba27a6 | 18 | along with the GNU MP Library; see the file COPYING.LIB. If not, see |
5a82c748 | 19 | <https://www.gnu.org/licenses/>. */ |
28f540f4 | 20 | |
9d13fb24 | 21 | #include <gmp.h> |
28f540f4 RM |
22 | #include "gmp-impl.h" |
23 | ||
b928942e | 24 | mp_limb_t |
6b628d36 | 25 | mpn_sub_n (mp_ptr res_ptr, mp_srcptr s1_ptr, mp_srcptr s2_ptr, mp_size_t size) |
28f540f4 | 26 | { |
b928942e | 27 | register mp_limb_t x, y, cy; |
28f540f4 RM |
28 | register mp_size_t j; |
29 | ||
30 | /* The loop counter and index J goes from -SIZE to -1. This way | |
31 | the loop becomes faster. */ | |
32 | j = -size; | |
33 | ||
34 | /* Offset the base pointers to compensate for the negative indices. */ | |
35 | s1_ptr -= j; | |
36 | s2_ptr -= j; | |
37 | res_ptr -= j; | |
38 | ||
39 | cy = 0; | |
40 | do | |
41 | { | |
42 | y = s2_ptr[j]; | |
43 | x = s1_ptr[j]; | |
44 | y += cy; /* add previous carry to subtrahend */ | |
45 | cy = (y < cy); /* get out carry from that addition */ | |
46 | y = x - y; /* main subtract */ | |
47 | cy = (y > x) + cy; /* get out carry from the subtract, combine */ | |
48 | res_ptr[j] = y; | |
49 | } | |
50 | while (++j != 0); | |
51 | ||
52 | return cy; | |
53 | } |