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 the GNU Lesser General Public License as published by 15 the Free Software Foundation; either version 3 of the License, or (at your 16 option) any later version. 17 18 The GNU MP Library is distributed in the hope that it will be useful, but 19 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 20 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 21 License for more details. 22 23 You should have received a copy of the GNU Lesser General Public License 24 along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. */ 25 26 27 #include "gmp.h" 28 #include "gmp-impl.h" 29 30 /* Gets {pp,n} and (sign?-1:1)*{np,n}. Computes at once: 31 {pp,n} <- ({pp,n}+{np,n})/2^{ps+1} 32 {pn,n} <- ({pp,n}-{np,n})/2^{ns+1} 33 Finally recompose them obtaining: 34 {pp,n+off} <- {pp,n}+{np,n}*2^{off*GMP_NUMB_BITS} 35 */ 36 void 37 mpn_toom_couple_handling (mp_ptr pp, mp_size_t n, mp_ptr np, 38 int nsign, mp_size_t off, int ps, int ns) 39 { 40 if (nsign) { 41 #ifdef HAVE_NATIVE_mpn_rsh1sub_n 42 mpn_rsh1sub_n (np, pp, np, n); 43 #else 44 mpn_sub_n (np, pp, np, n); 45 mpn_rshift (np, np, n, 1); 46 #endif 47 } else { 48 #ifdef HAVE_NATIVE_mpn_rsh1add_n 49 mpn_rsh1add_n (np, pp, np, n); 50 #else 51 mpn_add_n (np, pp, np, n); 52 mpn_rshift (np, np, n, 1); 53 #endif 54 } 55 56 #ifdef HAVE_NATIVE_mpn_rsh1sub_n 57 if (ps == 1) 58 mpn_rsh1sub_n (pp, pp, np, n); 59 else 60 #endif 61 { 62 mpn_sub_n (pp, pp, np, n); 63 if (ps > 0) 64 mpn_rshift (pp, pp, n, ps); 65 } 66 if (ns > 0) 67 mpn_rshift (np, np, n, ns); 68 pp[n] = mpn_add_n (pp+off, pp+off, np, n-off); 69 ASSERT_NOCARRY (mpn_add_1(pp+n, np+n-off, off, pp[n]) ); 70 } 71