1 /* mpz_addmul, mpz_submul -- add or subtract multiple. 2 3 Copyright 2001, 2004, 2005, 2012 Free Software Foundation, Inc. 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 either: 9 10 * the GNU Lesser General Public License as published by the Free 11 Software Foundation; either version 3 of the License, or (at your 12 option) any later version. 13 14 or 15 16 * the GNU General Public License as published by the Free Software 17 Foundation; either version 2 of the License, or (at your option) any 18 later version. 19 20 or both in parallel, as here. 21 22 The GNU MP Library is distributed in the hope that it will be useful, but 23 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 24 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 25 for more details. 26 27 You should have received copies of the GNU General Public License and the 28 GNU Lesser General Public License along with the GNU MP Library. If not, 29 see https://www.gnu.org/licenses/. */ 30 31 #include "gmp-impl.h" 32 33 34 /* expecting x and y both with non-zero high limbs */ 35 #define mpn_cmp_twosizes_lt(xp,xsize, yp,ysize) \ 36 ((xsize) < (ysize) \ 37 || ((xsize) == (ysize) && mpn_cmp (xp, yp, xsize) < 0)) 38 39 40 /* sub>=0 means an addmul w += x*y, sub<0 means a submul w -= x*y. 41 42 The signs of w, x and y are fully accounted for by each flipping "sub". 43 44 The sign of w is retained for the result, unless the absolute value 45 submul underflows, in which case it flips. */ 46 47 static void __gmpz_aorsmul (REGPARM_3_1 (mpz_ptr w, mpz_srcptr x, mpz_srcptr y, mp_size_t sub)) REGPARM_ATTR (1); 48 #define mpz_aorsmul(w,x,y,sub) __gmpz_aorsmul (REGPARM_3_1 (w, x, y, sub)) 49 50 REGPARM_ATTR (1) static void 51 mpz_aorsmul (mpz_ptr w, mpz_srcptr x, mpz_srcptr y, mp_size_t sub) 52 { 53 mp_size_t xsize, ysize, tsize, wsize, wsize_signed; 54 mp_ptr wp, tp; 55 mp_limb_t c, high; 56 TMP_DECL; 57 58 /* w unaffected if x==0 or y==0 */ 59 xsize = SIZ(x); 60 ysize = SIZ(y); 61 if (xsize == 0 || ysize == 0) 62 return; 63 64 /* make x the bigger of the two */ 65 if (ABS(ysize) > ABS(xsize)) 66 { 67 MPZ_SRCPTR_SWAP (x, y); 68 MP_SIZE_T_SWAP (xsize, ysize); 69 } 70 71 sub ^= ysize; 72 ysize = ABS(ysize); 73 74 /* use mpn_addmul_1/mpn_submul_1 if possible */ 75 if (ysize == 1) 76 { 77 mpz_aorsmul_1 (w, x, PTR(y)[0], sub); 78 return; 79 } 80 81 sub ^= xsize; 82 xsize = ABS(xsize); 83 84 wsize_signed = SIZ(w); 85 sub ^= wsize_signed; 86 wsize = ABS(wsize_signed); 87 88 tsize = xsize + ysize; 89 wp = MPZ_REALLOC (w, MAX (wsize, tsize) + 1); 90 91 if (wsize_signed == 0) 92 { 93 /* Nothing to add to, just set w=x*y. No w==x or w==y overlap here, 94 since we know x,y!=0 but w==0. */ 95 high = mpn_mul (wp, PTR(x),xsize, PTR(y),ysize); 96 tsize -= (high == 0); 97 SIZ(w) = (sub >= 0 ? tsize : -tsize); 98 return; 99 } 100 101 TMP_MARK; 102 tp = TMP_ALLOC_LIMBS (tsize); 103 104 high = mpn_mul (tp, PTR(x),xsize, PTR(y),ysize); 105 tsize -= (high == 0); 106 ASSERT (tp[tsize-1] != 0); 107 if (sub >= 0) 108 { 109 mp_srcptr up = wp; 110 mp_size_t usize = wsize; 111 112 if (usize < tsize) 113 { 114 up = tp; 115 usize = tsize; 116 tp = wp; 117 tsize = wsize; 118 119 wsize = usize; 120 } 121 122 c = mpn_add (wp, up,usize, tp,tsize); 123 wp[wsize] = c; 124 wsize += (c != 0); 125 } 126 else 127 { 128 mp_srcptr up = wp; 129 mp_size_t usize = wsize; 130 131 if (mpn_cmp_twosizes_lt (up,usize, tp,tsize)) 132 { 133 up = tp; 134 usize = tsize; 135 tp = wp; 136 tsize = wsize; 137 138 wsize = usize; 139 wsize_signed = -wsize_signed; 140 } 141 142 ASSERT_NOCARRY (mpn_sub (wp, up,usize, tp,tsize)); 143 wsize = usize; 144 MPN_NORMALIZE (wp, wsize); 145 } 146 147 SIZ(w) = (wsize_signed >= 0 ? wsize : -wsize); 148 149 TMP_FREE; 150 } 151 152 153 void 154 mpz_addmul (mpz_ptr w, mpz_srcptr u, mpz_srcptr v) 155 { 156 mpz_aorsmul (w, u, v, (mp_size_t) 0); 157 } 158 159 void 160 mpz_submul (mpz_ptr w, mpz_srcptr u, mpz_srcptr v) 161 { 162 mpz_aorsmul (w, u, v, (mp_size_t) -1); 163 } 164