source/libs/gmp/gmp-src/mpf/cmp_si.c

   1 /* mpf_cmp_si -- Compare a float with a signed integer.
   2
   3 Copyright 1993-1995, 1999-2002, 2004, 2012, 2015 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
  35 int
  36 mpf_cmp_si (mpf_srcptr u, long int vval) __GMP_NOTHROW
  37 {
  38   mp_srcptr up;
  39   mp_size_t usize;
  40   mp_exp_t uexp;
  41   mp_limb_t ulimb;
  42   int usign;
  43   unsigned long abs_vval;
  44
  45   usize = SIZ (u);
  46
  47   /* 1. Are the signs different?  */
  48   if ((usize < 0) == (vval < 0)) /* don't use xor, type size may differ */
  49     {
  50       /* U and V are both non-negative or both negative.  */
  51       if (usize == 0)
  52         /* vval >= 0 */
  53         return -(vval != 0);
  54       if (vval == 0)
  55         /* usize >= 0 */
  56         return usize != 0;
  57       /* Fall out.  */
  58     }
  59   else
  60     {
  61       /* Either U or V is negative, but not both.  */
  62       return usize >= 0 ? 1 : -1;
  63     }
  64
  65   /* U and V have the same sign and are both non-zero.  */
  66
  67   /* 2. Are the exponents different (V's exponent == 1)?  */
  68   uexp = EXP (u);
  69   usign = usize >= 0 ? 1 : -1;
  70   usize = ABS (usize);
  71   abs_vval = ABS_CAST (unsigned long, vval);
  72
  73 #if GMP_NAIL_BITS != 0
  74   if (uexp != 1 + (abs_vval > GMP_NUMB_MAX))
  75     return (uexp < 1 + (abs_vval > GMP_NUMB_MAX)) ? -usign : usign;
  76 #else
  77   if (uexp != 1)
  78     return (uexp < 1) ? -usign : usign;
  79 #endif
  80
  81   up = PTR (u);
  82
  83   ASSERT (usize > 0);
  84   ulimb = up[--usize];
  85 #if GMP_NAIL_BITS != 0
  86   if (uexp == 2)
  87     {
  88       if ((ulimb >> GMP_NAIL_BITS) != 0)
  89         return usign;
  90       ulimb = (ulimb << GMP_NUMB_BITS);
  91       if (usize != 0) ulimb |= up[--usize];
  92     }
  93 #endif
  94
  95   /* 3. Compare the most significant mantissa limb with V.  */
  96   if (ulimb != abs_vval)
  97     return (ulimb < abs_vval) ? -usign : usign;
  98
  99   /* Ignore zeroes at the low end of U.  */
 100   for (; *up == 0; ++up)
 101     --usize;
 102
 103   /* 4. Now, if the number of limbs are different, we have a difference
 104      since we have made sure the trailing limbs are not zero.  */
 105   if (usize > 0)
 106     return usign;
 107
 108   /* Wow, we got zero even if we tried hard to avoid it.  */
 109   return 0;
 110 }