1/* mpfr_cmp_si_2exp -- compare a floating-point number with a signed
2machine integer multiplied by a power of 2
3
4Copyright 1999, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Free Software Foundation, Inc.
5Contributed by the AriC and Caramel projects, INRIA.
6
7This file is part of the GNU MPFR Library.
8
9The GNU MPFR Library is free software; you can redistribute it and/or modify
10it under the terms of the GNU Lesser General Public License as published by
11the Free Software Foundation; either version 3 of the License, or (at your
12option) any later version.
13
14The GNU MPFR Library is distributed in the hope that it will be useful, but
15WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
16or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
17License for more details.
18
19You should have received a copy of the GNU Lesser General Public License
20along with the GNU MPFR Library; see the file COPYING.LESSER.  If not, see
21http://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
2251 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */
23
24#define MPFR_NEED_LONGLONG_H
25#include "mpfr-impl.h"
26
27/* returns a positive value if b > i*2^f,
28           a negative value if b < i*2^f,
29           zero if b = i*2^f.
30   b must not be NaN.
31*/
32
33int
34mpfr_cmp_si_2exp (mpfr_srcptr b, long int i, mpfr_exp_t f)
35{
36  int si;
37
38  si = i < 0 ? -1 : 1; /* sign of i */
39  if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (b)))
40    {
41      if (MPFR_IS_INF(b))
42        return MPFR_INT_SIGN(b);
43      else if (MPFR_IS_ZERO(b))
44        return i != 0 ? -si : 0;
45      /* NAN */
46      MPFR_SET_ERANGE ();
47      return 0;
48    }
49  else if (MPFR_SIGN(b) != si || i == 0)
50    return MPFR_INT_SIGN (b);
51  else /* b and i are of same sign si */
52    {
53      mpfr_exp_t e;
54      unsigned long ai;
55      int k;
56      mp_size_t bn;
57      mp_limb_t c, *bp;
58
59      ai = SAFE_ABS(unsigned long, i);
60
61      /* ai must be representable in a mp_limb_t */
62      MPFR_ASSERTN(ai == (mp_limb_t) ai);
63
64      e = MPFR_GET_EXP (b); /* 2^(e-1) <= b < 2^e */
65      if (e <= f)
66        return -si;
67      if (f < MPFR_EMAX_MAX - GMP_NUMB_BITS &&
68          e > f + GMP_NUMB_BITS)
69        return si;
70
71      /* now f < e <= f + GMP_NUMB_BITS */
72      c = (mp_limb_t) ai;
73      count_leading_zeros(k, c);
74      if ((int) (e - f) > GMP_NUMB_BITS - k)
75        return si;
76      if ((int) (e - f) < GMP_NUMB_BITS - k)
77        return -si;
78
79      /* now b and i*2^f have the same exponent */
80      c <<= k;
81      bn = (MPFR_PREC(b) - 1) / GMP_NUMB_BITS;
82      bp = MPFR_MANT(b);
83      if (bp[bn] > c)
84        return si;
85      if (bp[bn] < c)
86        return -si;
87
88      /* most significant limbs agree, check remaining limbs from b */
89      while (bn > 0)
90        if (bp[--bn])
91          return si;
92      return 0;
93    }
94}
95
96#undef mpfr_cmp_si
97int
98mpfr_cmp_si (mpfr_srcptr b, long int i)
99{
100  return mpfr_cmp_si_2exp (b, i, 0);
101}
102