1 /* mpz_add, mpz_sub -- add or subtract integers. 2 3 Copyright 1991, 1993, 1994, 1996, 2000, 2001, 2011, 2012 Free Software 4 Foundation, Inc. 5 6 This file is part of the GNU MP Library. 7 8 The GNU MP Library is free software; you can redistribute it and/or modify 9 it under the terms of the GNU Lesser General Public License as published by 10 the Free Software Foundation; either version 3 of the License, or (at your 11 option) any later version. 12 13 The GNU MP Library is distributed in the hope that it will be useful, but 14 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 15 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 16 License for more details. 17 18 You should have received a copy of the GNU Lesser General Public License 19 along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. */ 20 21 #include "gmp.h" 22 #include "gmp-impl.h" 23 24 25 #ifdef OPERATION_add 26 #define FUNCTION mpz_add 27 #define VARIATION 28 #endif 29 #ifdef OPERATION_sub 30 #define FUNCTION mpz_sub 31 #define VARIATION - 32 #endif 33 34 #ifndef FUNCTION 35 Error, need OPERATION_add or OPERATION_sub 36 #endif 37 38 39 void 40 FUNCTION (mpz_ptr w, mpz_srcptr u, mpz_srcptr v) 41 { 42 mp_srcptr up, vp; 43 mp_ptr wp; 44 mp_size_t usize, vsize, wsize; 45 mp_size_t abs_usize; 46 mp_size_t abs_vsize; 47 48 usize = SIZ(u); 49 vsize = VARIATION SIZ(v); 50 abs_usize = ABS (usize); 51 abs_vsize = ABS (vsize); 52 53 if (abs_usize < abs_vsize) 54 { 55 /* Swap U and V. */ 56 MPZ_SRCPTR_SWAP (u, v); 57 MP_SIZE_T_SWAP (usize, vsize); 58 MP_SIZE_T_SWAP (abs_usize, abs_vsize); 59 } 60 61 /* True: ABS_USIZE >= ABS_VSIZE. */ 62 63 /* If not space for w (and possible carry), increase space. */ 64 wsize = abs_usize + 1; 65 wp = MPZ_REALLOC (w, wsize); 66 67 /* These must be after realloc (u or v may be the same as w). */ 68 up = PTR(u); 69 vp = PTR(v); 70 71 if ((usize ^ vsize) < 0) 72 { 73 /* U and V have different sign. Need to compare them to determine 74 which operand to subtract from which. */ 75 76 /* This test is right since ABS_USIZE >= ABS_VSIZE. */ 77 if (abs_usize != abs_vsize) 78 { 79 mpn_sub (wp, up, abs_usize, vp, abs_vsize); 80 wsize = abs_usize; 81 MPN_NORMALIZE (wp, wsize); 82 if (usize < 0) 83 wsize = -wsize; 84 } 85 else if (mpn_cmp (up, vp, abs_usize) < 0) 86 { 87 mpn_sub_n (wp, vp, up, abs_usize); 88 wsize = abs_usize; 89 MPN_NORMALIZE (wp, wsize); 90 if (usize >= 0) 91 wsize = -wsize; 92 } 93 else 94 { 95 mpn_sub_n (wp, up, vp, abs_usize); 96 wsize = abs_usize; 97 MPN_NORMALIZE (wp, wsize); 98 if (usize < 0) 99 wsize = -wsize; 100 } 101 } 102 else 103 { 104 /* U and V have same sign. Add them. */ 105 mp_limb_t cy_limb = mpn_add (wp, up, abs_usize, vp, abs_vsize); 106 wp[abs_usize] = cy_limb; 107 wsize = abs_usize + cy_limb; 108 if (usize < 0) 109 wsize = -wsize; 110 } 111 112 SIZ(w) = wsize; 113 } 114