/src/gmp/mpn/toom_couple_handling.c
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1 | | /* Helper function for high degree Toom-Cook algorithms. |
2 | | |
3 | | Contributed to the GNU project by Marco Bodrato. |
4 | | |
5 | | THE FUNCTION IN THIS FILE IS INTERNAL WITH A MUTABLE INTERFACE. IT IS ONLY |
6 | | SAFE TO REACH IT THROUGH DOCUMENTED INTERFACES. IN FACT, IT IS ALMOST |
7 | | GUARANTEED THAT IT WILL CHANGE OR DISAPPEAR IN A FUTURE GNU MP RELEASE. |
8 | | |
9 | | Copyright 2009, 2010 Free Software Foundation, Inc. |
10 | | |
11 | | This file is part of the GNU MP Library. |
12 | | |
13 | | The GNU MP Library is free software; you can redistribute it and/or modify |
14 | | it under the terms of either: |
15 | | |
16 | | * the GNU Lesser General Public License as published by the Free |
17 | | Software Foundation; either version 3 of the License, or (at your |
18 | | option) any later version. |
19 | | |
20 | | or |
21 | | |
22 | | * the GNU General Public License as published by the Free Software |
23 | | Foundation; either version 2 of the License, or (at your option) any |
24 | | later version. |
25 | | |
26 | | or both in parallel, as here. |
27 | | |
28 | | The GNU MP Library is distributed in the hope that it will be useful, but |
29 | | WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY |
30 | | or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
31 | | for more details. |
32 | | |
33 | | You should have received copies of the GNU General Public License and the |
34 | | GNU Lesser General Public License along with the GNU MP Library. If not, |
35 | | see https://www.gnu.org/licenses/. */ |
36 | | |
37 | | |
38 | | #include "gmp-impl.h" |
39 | | |
40 | | /* Gets {pp,n} and (sign?-1:1)*{np,n}. Computes at once: |
41 | | {pp,n} <- ({pp,n}+{np,n})/2^{ps+1} |
42 | | {pn,n} <- ({pp,n}-{np,n})/2^{ns+1} |
43 | | Finally recompose them obtaining: |
44 | | {pp,n+off} <- {pp,n}+{np,n}*2^{off*GMP_NUMB_BITS} |
45 | | */ |
46 | | void |
47 | | mpn_toom_couple_handling (mp_ptr pp, mp_size_t n, mp_ptr np, |
48 | | int nsign, mp_size_t off, int ps, int ns) |
49 | 0 | { |
50 | 0 | if (nsign) { |
51 | 0 | #ifdef HAVE_NATIVE_mpn_rsh1sub_n |
52 | 0 | mpn_rsh1sub_n (np, pp, np, n); |
53 | | #else |
54 | | mpn_sub_n (np, pp, np, n); |
55 | | mpn_rshift (np, np, n, 1); |
56 | | #endif |
57 | 0 | } else { |
58 | 0 | #ifdef HAVE_NATIVE_mpn_rsh1add_n |
59 | 0 | mpn_rsh1add_n (np, pp, np, n); |
60 | | #else |
61 | | mpn_add_n (np, pp, np, n); |
62 | | mpn_rshift (np, np, n, 1); |
63 | | #endif |
64 | 0 | } |
65 | |
|
66 | 0 | #ifdef HAVE_NATIVE_mpn_rsh1sub_n |
67 | 0 | if (ps == 1) |
68 | 0 | mpn_rsh1sub_n (pp, pp, np, n); |
69 | 0 | else |
70 | 0 | #endif |
71 | 0 | { |
72 | 0 | mpn_sub_n (pp, pp, np, n); |
73 | 0 | if (ps > 0) |
74 | 0 | mpn_rshift (pp, pp, n, ps); |
75 | 0 | } |
76 | 0 | if (ns > 0) |
77 | 0 | mpn_rshift (np, np, n, ns); |
78 | 0 | pp[n] = mpn_add_n (pp+off, pp+off, np, n-off); |
79 | 0 | ASSERT_NOCARRY (mpn_add_1(pp+n, np+n-off, off, pp[n]) ); |
80 | 0 | } |