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.h" 32 #include "gmp-impl.h" 33 34 35 /* expecting x and y both with non-zero high limbs */ 36 #define mpn_cmp_twosizes_lt(xp,xsize, yp,ysize) \ 37 ((xsize) < (ysize) \ 38 || ((xsize) == (ysize) && mpn_cmp (xp, yp, xsize) < 0)) 39 40 41 /* sub>=0 means an addmul w += x*y, sub<0 means a submul w -= x*y. 42 43 The signs of w, x and y are fully accounted for by each flipping "sub". 44 45 The sign of w is retained for the result, unless the absolute value 46 submul underflows, in which case it flips. */ 47 48 static void __gmpz_aorsmul (REGPARM_3_1 (mpz_ptr w, mpz_srcptr x, mpz_srcptr y, mp_size_t sub)) REGPARM_ATTR (1); 49 #define mpz_aorsmul(w,x,y,sub) __gmpz_aorsmul (REGPARM_3_1 (w, x, y, sub)) 50 51 REGPARM_ATTR (1) static void 52 mpz_aorsmul (mpz_ptr w, mpz_srcptr x, mpz_srcptr y, mp_size_t sub) 53 { 54 mp_size_t xsize, ysize, tsize, wsize, wsize_signed; 55 mp_ptr wp, tp; 56 mp_limb_t c, high; 57 TMP_DECL; 58 59 /* w unaffected if x==0 or y==0 */ 60 xsize = SIZ(x); 61 ysize = SIZ(y); 62 if (xsize == 0 || ysize == 0) 63 return; 64 65 /* make x the bigger of the two */ 66 if (ABS(ysize) > ABS(xsize)) 67 { 68 MPZ_SRCPTR_SWAP (x, y); 69 MP_SIZE_T_SWAP (xsize, ysize); 70 } 71 72 sub ^= ysize; 73 ysize = ABS(ysize); 74 75 /* use mpn_addmul_1/mpn_submul_1 if possible */ 76 if (ysize == 1) 77 { 78 mpz_aorsmul_1 (w, x, PTR(y)[0], sub); 79 return; 80 } 81 82 sub ^= xsize; 83 xsize = ABS(xsize); 84 85 wsize_signed = SIZ(w); 86 sub ^= wsize_signed; 87 wsize = ABS(wsize_signed); 88 89 tsize = xsize + ysize; 90 wp = MPZ_REALLOC (w, MAX (wsize, tsize) + 1); 91 92 if (wsize_signed == 0) 93 { 94 /* Nothing to add to, just set w=x*y. No w==x or w==y overlap here, 95 since we know x,y!=0 but w==0. */ 96 high = mpn_mul (wp, PTR(x),xsize, PTR(y),ysize); 97 tsize -= (high == 0); 98 SIZ(w) = (sub >= 0 ? tsize : -tsize); 99 return; 100 } 101 102 TMP_MARK; 103 tp = TMP_ALLOC_LIMBS (tsize); 104 105 high = mpn_mul (tp, PTR(x),xsize, PTR(y),ysize); 106 tsize -= (high == 0); 107 ASSERT (tp[tsize-1] != 0); 108 if (sub >= 0) 109 { 110 mp_srcptr up = wp; 111 mp_size_t usize = wsize; 112 113 if (usize < tsize) 114 { 115 up = tp; 116 usize = tsize; 117 tp = wp; 118 tsize = wsize; 119 120 wsize = usize; 121 } 122 123 c = mpn_add (wp, up,usize, tp,tsize); 124 wp[wsize] = c; 125 wsize += (c != 0); 126 } 127 else 128 { 129 mp_srcptr up = wp; 130 mp_size_t usize = wsize; 131 132 if (mpn_cmp_twosizes_lt (up,usize, tp,tsize)) 133 { 134 up = tp; 135 usize = tsize; 136 tp = wp; 137 tsize = wsize; 138 139 wsize = usize; 140 wsize_signed = -wsize_signed; 141 } 142 143 ASSERT_NOCARRY (mpn_sub (wp, up,usize, tp,tsize)); 144 wsize = usize; 145 MPN_NORMALIZE (wp, wsize); 146 } 147 148 SIZ(w) = (wsize_signed >= 0 ? wsize : -wsize); 149 150 TMP_FREE; 151 } 152 153 154 void 155 mpz_addmul (mpz_ptr w, mpz_srcptr u, mpz_srcptr v) 156 { 157 mpz_aorsmul (w, u, v, (mp_size_t) 0); 158 } 159 160 void 161 mpz_submul (mpz_ptr w, mpz_srcptr u, mpz_srcptr v) 162 { 163 mpz_aorsmul (w, u, v, (mp_size_t) -1); 164 } 165