1 /* mpf_eq -- Compare two floats up to a specified bit #. 2 3 Copyright 1993, 1995, 1996, 2001, 2002, 2008, 2009 Free Software Foundation, 4 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 #include "longlong.h" 24 25 int 26 mpf_eq (mpf_srcptr u, mpf_srcptr v, unsigned long int n_bits) 27 { 28 mp_srcptr up, vp, p; 29 mp_size_t usize, vsize, minsize, maxsize, n_limbs, i; 30 mp_exp_t uexp, vexp; 31 mp_limb_t diff; 32 int cnt; 33 34 uexp = u->_mp_exp; 35 vexp = v->_mp_exp; 36 37 usize = u->_mp_size; 38 vsize = v->_mp_size; 39 40 /* 1. Are the signs different? */ 41 if ((usize ^ vsize) >= 0) 42 { 43 /* U and V are both non-negative or both negative. */ 44 if (usize == 0) 45 return vsize == 0; 46 if (vsize == 0) 47 return 0; 48 49 /* Fall out. */ 50 } 51 else 52 { 53 /* Either U or V is negative, but not both. */ 54 return 0; 55 } 56 57 /* U and V have the same sign and are both non-zero. */ 58 59 /* 2. Are the exponents different? */ 60 if (uexp != vexp) 61 return 0; 62 63 usize = ABS (usize); 64 vsize = ABS (vsize); 65 66 up = u->_mp_d; 67 vp = v->_mp_d; 68 69 up += usize; /* point just above most significant limb */ 70 vp += vsize; /* point just above most significant limb */ 71 72 count_leading_zeros (cnt, up[-1]); 73 if ((vp[-1] >> (GMP_LIMB_BITS - 1 - cnt)) != 1) 74 return 0; /* msb positions different */ 75 76 n_bits += cnt - GMP_NAIL_BITS; 77 n_limbs = (n_bits + GMP_NUMB_BITS - 1) / GMP_NUMB_BITS; 78 79 usize = MIN (usize, n_limbs); 80 vsize = MIN (vsize, n_limbs); 81 82 #if 0 83 /* Ignore zeros at the low end of U and V. */ 84 while (up[0] == 0) 85 up++, usize--; 86 while (vp[0] == 0) 87 vp++, vsize--; 88 #endif 89 90 minsize = MIN (usize, vsize); 91 maxsize = usize + vsize - minsize; 92 93 up -= minsize; /* point at most significant common limb */ 94 vp -= minsize; /* point at most significant common limb */ 95 96 /* Compare the most significant part which has explicit limbs for U and V. */ 97 for (i = minsize - 1; i > 0; i--) 98 { 99 if (up[i] != vp[i]) 100 return 0; 101 } 102 103 if (minsize != maxsize) 104 { 105 if (up[0] != vp[0]) 106 return 0; 107 } 108 109 /* Now either U or V has its limbs consumed. Check the the other operand 110 has just zeros in the corresponding, relevant part. */ 111 112 if (usize > vsize) 113 p = up + minsize - maxsize; 114 else 115 p = vp + minsize - maxsize; 116 117 for (i = maxsize - minsize - 1; i > 0; i--) 118 { 119 if (p[i] != 0) 120 return 0; 121 } 122 123 n_bits -= (maxsize - 1) * GMP_NUMB_BITS; 124 125 if (minsize != maxsize) 126 diff = p[0]; 127 else 128 diff = up[0] ^ vp[0]; 129 130 if (n_bits < GMP_NUMB_BITS) 131 diff >>= GMP_NUMB_BITS - n_bits; 132 133 return diff == 0; 134 } 135