1 /* mpf_eq -- Compare two floats up to a specified bit #. 2 3 Copyright 1993, 1995, 1996, 2001, 2002, 2008, 2009, 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 either: 10 11 * the GNU Lesser General Public License as published by the Free 12 Software Foundation; either version 3 of the License, or (at your 13 option) any later version. 14 15 or 16 17 * the GNU General Public License as published by the Free Software 18 Foundation; either version 2 of the License, or (at your option) any 19 later version. 20 21 or both in parallel, as here. 22 23 The GNU MP Library is distributed in the hope that it will be useful, but 24 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 25 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 26 for more details. 27 28 You should have received copies of the GNU General Public License and the 29 GNU Lesser General Public License along with the GNU MP Library. If not, 30 see https://www.gnu.org/licenses/. */ 31 32 #include "gmp.h" 33 #include "gmp-impl.h" 34 #include "longlong.h" 35 36 int 37 mpf_eq (mpf_srcptr u, mpf_srcptr v, mp_bitcnt_t n_bits) 38 { 39 mp_srcptr up, vp, p; 40 mp_size_t usize, vsize, minsize, maxsize, n_limbs, i, size; 41 mp_exp_t uexp, vexp; 42 mp_limb_t diff; 43 int cnt; 44 45 uexp = u->_mp_exp; 46 vexp = v->_mp_exp; 47 48 usize = u->_mp_size; 49 vsize = v->_mp_size; 50 51 /* 1. Are the signs different? */ 52 if ((usize ^ vsize) >= 0) 53 { 54 /* U and V are both non-negative or both negative. */ 55 if (usize == 0) 56 return vsize == 0; 57 if (vsize == 0) 58 return 0; 59 60 /* Fall out. */ 61 } 62 else 63 { 64 /* Either U or V is negative, but not both. */ 65 return 0; 66 } 67 68 /* U and V have the same sign and are both non-zero. */ 69 70 /* 2. Are the exponents different? */ 71 if (uexp != vexp) 72 return 0; 73 74 usize = ABS (usize); 75 vsize = ABS (vsize); 76 77 up = u->_mp_d; 78 vp = v->_mp_d; 79 80 up += usize; /* point just above most significant limb */ 81 vp += vsize; /* point just above most significant limb */ 82 83 count_leading_zeros (cnt, up[-1]); 84 if ((vp[-1] >> (GMP_LIMB_BITS - 1 - cnt)) != 1) 85 return 0; /* msb positions different */ 86 87 n_bits += cnt - GMP_NAIL_BITS; 88 n_limbs = (n_bits + GMP_NUMB_BITS - 1) / GMP_NUMB_BITS; 89 90 usize = MIN (usize, n_limbs); 91 vsize = MIN (vsize, n_limbs); 92 93 #if 0 94 /* Ignore zeros at the low end of U and V. */ 95 while (up[0] == 0) 96 up++, usize--; 97 while (vp[0] == 0) 98 vp++, vsize--; 99 #endif 100 101 minsize = MIN (usize, vsize); 102 maxsize = usize + vsize - minsize; 103 104 up -= minsize; /* point at most significant common limb */ 105 vp -= minsize; /* point at most significant common limb */ 106 107 /* Compare the most significant part which has explicit limbs for U and V. */ 108 for (i = minsize - 1; i > 0; i--) 109 { 110 if (up[i] != vp[i]) 111 return 0; 112 } 113 114 n_bits -= (maxsize - 1) * GMP_NUMB_BITS; 115 116 size = maxsize - minsize; 117 if (size != 0) 118 { 119 if (up[0] != vp[0]) 120 return 0; 121 122 /* Now either U or V has its limbs consumed, i.e, continues with an 123 infinite number of implicit zero limbs. Check that the other operand 124 has just zeros in the corresponding, relevant part. */ 125 126 if (usize > vsize) 127 p = up - size; 128 else 129 p = vp - size; 130 131 for (i = size - 1; i > 0; i--) 132 { 133 if (p[i] != 0) 134 return 0; 135 } 136 137 diff = p[0]; 138 } 139 else 140 { 141 /* Both U or V has its limbs consumed. */ 142 143 diff = up[0] ^ vp[0]; 144 } 145 146 if (n_bits < GMP_NUMB_BITS) 147 diff >>= GMP_NUMB_BITS - n_bits; 148 149 return diff == 0; 150 } 151