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Annotation of OpenXM_contrib/gmp/mpf/eq.c, Revision 1.1.1.1

1.1       maekawa     1: /* mpf_eq -- Compare two floats up to a specified bit #.
                      2:
                      3: Copyright (C) 1993, 1995, 1996 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 the GNU Library General Public License as published by
                      9: the Free Software Foundation; either version 2 of the License, or (at your
                     10: option) any later version.
                     11:
                     12: The GNU MP Library is distributed in the hope that it will be useful, but
                     13: WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
                     14: or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
                     15: License for more details.
                     16:
                     17: You should have received a copy of the GNU Library General Public License
                     18: along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
                     19: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
                     20: MA 02111-1307, USA. */
                     21:
                     22: #include "gmp.h"
                     23: #include "gmp-impl.h"
                     24:
                     25: int
                     26: #if __STDC__
                     27: mpf_eq (mpf_srcptr u, mpf_srcptr v, unsigned long int n_bits)
                     28: #else
                     29: mpf_eq (u, v, n_bits)
                     30:      mpf_srcptr u;
                     31:      mpf_srcptr v;
                     32:      unsigned long int n_bits;
                     33: #endif
                     34: {
                     35:   mp_srcptr up, vp;
                     36:   mp_size_t usize, vsize, size, i;
                     37:   mp_exp_t uexp, vexp;
                     38:   int usign;
                     39:
                     40:   uexp = u->_mp_exp;
                     41:   vexp = v->_mp_exp;
                     42:
                     43:   usize = u->_mp_size;
                     44:   vsize = v->_mp_size;
                     45:
                     46:   /* 1. Are the signs different?  */
                     47:   if ((usize ^ vsize) >= 0)
                     48:     {
                     49:       /* U and V are both non-negative or both negative.  */
                     50:       if (usize == 0)
                     51:        return vsize == 0;
                     52:       if (vsize == 0)
                     53:        return 0;
                     54:
                     55:       /* Fall out.  */
                     56:     }
                     57:   else
                     58:     {
                     59:       /* Either U or V is negative, but not both.  */
                     60:       return 0;
                     61:     }
                     62:
                     63:   /* U and V have the same sign and are both non-zero.  */
                     64:
                     65:   usign = usize >= 0 ? 1 : -1;
                     66:
                     67:   /* 2. Are the exponents different?  */
                     68:   if (uexp > vexp)
                     69:     return 0;                  /* ??? handle (uexp = vexp + 1)   */
                     70:   if (vexp > uexp)
                     71:     return 0;                  /* ??? handle (vexp = uexp + 1)   */
                     72:
                     73:   usize = ABS (usize);
                     74:   vsize = ABS (vsize);
                     75:
                     76:   up = u->_mp_d;
                     77:   vp = v->_mp_d;
                     78:
                     79:   /* Ignore zeroes at the low end of U and V.  */
                     80:   while (up[0] == 0)
                     81:     {
                     82:       up++;
                     83:       usize--;
                     84:     }
                     85:   while (vp[0] == 0)
                     86:     {
                     87:       vp++;
                     88:       vsize--;
                     89:     }
                     90:
                     91:   if (usize > vsize)
                     92:     {
                     93:       if (vsize * BITS_PER_MP_LIMB < n_bits)
                     94:        return 0;               /* surely too different */
                     95:       size = vsize;
                     96:     }
                     97:   else if (vsize > usize)
                     98:     {
                     99:       if (usize * BITS_PER_MP_LIMB < n_bits)
                    100:        return 0;               /* surely too different */
                    101:       size = usize;
                    102:     }
                    103:   else
                    104:     {
                    105:       size = usize;
                    106:     }
                    107:
                    108:   if (size > (n_bits + BITS_PER_MP_LIMB - 1) / BITS_PER_MP_LIMB)
                    109:     size = (n_bits + BITS_PER_MP_LIMB - 1) / BITS_PER_MP_LIMB;
                    110:
                    111:   up += usize - size;
                    112:   vp += vsize - size;
                    113:
                    114:   for (i = size - 1; i >= 0; i--)
                    115:     {
                    116:       if (up[i] != vp[i])
                    117:        return 0;
                    118:     }
                    119:
                    120:   return 1;
                    121: }