1 /* mpn_subcnd_n -- Compute R = U - V if CND != 0 or R = U if CND == 0. 2 3 THIS IS AN INTERNAL FUNCTION WITH A MUTABLE INTERFACE. IT IS ONLY 4 SAFE TO REACH THIS FUNCTION THROUGH DOCUMENTED INTERFACES. 5 6 Copyright 1992, 1993, 1994, 1996, 2000, 2002, 2008, 2009 Free Software 7 Foundation, Inc. 8 9 This file is part of the GNU MP Library. 10 11 The GNU MP Library is free software; you can redistribute it and/or modify 12 it under the terms of the GNU Lesser General Public License as published by 13 the Free Software Foundation; either version 3 of the License, or (at your 14 option) any later version. 15 16 The GNU MP Library is distributed in the hope that it will be useful, but 17 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 18 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 19 License for more details. 20 21 You should have received a copy of the GNU Lesser General Public License 22 along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. */ 23 24 #include "gmp.h" 25 #include "gmp-impl.h" 26 27 28 #if GMP_NAIL_BITS == 0 29 30 mp_limb_t 31 mpn_subcnd_n (mp_ptr rp, mp_srcptr up, mp_srcptr vp, mp_size_t n, mp_limb_t cnd) 32 { 33 mp_limb_t ul, vl, sl, rl, cy, cy1, cy2, mask; 34 35 ASSERT (n >= 1); 36 ASSERT (MPN_SAME_OR_SEPARATE_P (rp, up, n)); 37 ASSERT (MPN_SAME_OR_SEPARATE_P (rp, vp, n)); 38 39 mask = -(mp_limb_t) (cnd != 0); 40 cy = 0; 41 do 42 { 43 ul = *up++; 44 vl = *vp++ & mask; 45 sl = ul - vl; 46 cy1 = sl > ul; 47 rl = sl - cy; 48 cy2 = rl > sl; 49 cy = cy1 | cy2; 50 *rp++ = rl; 51 } 52 while (--n != 0); 53 54 return cy; 55 } 56 57 #endif 58 59 #if GMP_NAIL_BITS >= 1 60 61 mp_limb_t 62 mpn_subcnd_n (mp_ptr rp, mp_srcptr up, mp_srcptr vp, mp_size_t n, mp_limb_t cnd) 63 { 64 mp_limb_t ul, vl, rl, cy, mask; 65 66 ASSERT (n >= 1); 67 ASSERT (MPN_SAME_OR_SEPARATE_P (rp, up, n)); 68 ASSERT (MPN_SAME_OR_SEPARATE_P (rp, vp, n)); 69 70 mask = -(mp_limb_t) (cnd != 0); 71 cy = 0; 72 do 73 { 74 ul = *up++; 75 vl = *vp++ & mask; 76 rl = ul - vl - cy; 77 cy = rl >> (GMP_LIMB_BITS - 1); 78 *rp++ = rl & GMP_NUMB_MASK; 79 } 80 while (--n != 0); 81 82 return cy; 83 } 84 85 #endif 86