Annotation of OpenXM_contrib/gmp/mpz/get_d.c, Revision 1.1.1.2
1.1 maekawa 1: /* double mpz_get_d (mpz_t src) -- Return the double approximation to SRC.
2:
1.1.1.2 ! maekawa 3: Copyright (C) 1996, 1997, 2000 Free Software Foundation, Inc.
1.1 maekawa 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
1.1.1.2 ! maekawa 8: it under the terms of the GNU Lesser General Public License as published by
! 9: the Free Software Foundation; either version 2.1 of the License, or (at your
1.1 maekawa 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
1.1.1.2 ! maekawa 14: or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
1.1 maekawa 15: License for more details.
16:
1.1.1.2 ! maekawa 17: You should have received a copy of the GNU Lesser General Public License
1.1 maekawa 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"
1.1.1.2 ! maekawa 24: #include "longlong.h"
! 25:
! 26:
! 27: static int
! 28: #if __STDC__
! 29: mpn_zero_p (mp_ptr p, mp_size_t n)
! 30: #else
! 31: mpn_zero_p (p, n)
! 32: mp_ptr p;
! 33: mp_size_t n;
! 34: #endif
! 35: {
! 36: mp_size_t i;
! 37:
! 38: for (i = 0; i < n; i++)
! 39: {
! 40: if (p[i] != 0)
! 41: return 0;
! 42: }
! 43:
! 44: return 1;
! 45: }
! 46:
1.1 maekawa 47:
48: double
49: #if __STDC__
50: mpz_get_d (mpz_srcptr src)
51: #else
52: mpz_get_d (src)
53: mpz_srcptr src;
54: #endif
55: {
56: double res;
1.1.1.2 ! maekawa 57: mp_size_t size;
1.1 maekawa 58: int negative;
59: mp_ptr qp;
1.1.1.2 ! maekawa 60: mp_limb_t hz, lz;
! 61: int cnt;
1.1 maekawa 62:
63: size = SIZ(src);
64: if (size == 0)
65: return 0.0;
66:
67: negative = size < 0;
68: size = ABS (size);
69: qp = PTR(src);
70:
1.1.1.2 ! maekawa 71: if (size == 1)
! 72: {
! 73: res = qp[size - 1];
! 74: }
! 75: else if (size == 2)
! 76: {
! 77: res = MP_BASE_AS_DOUBLE * qp[size - 1] + qp[size - 2];
! 78: }
! 79: else
! 80: {
! 81: count_leading_zeros (cnt, qp[size - 1]);
! 82:
! 83: #if BITS_PER_MP_LIMB == 32
! 84: if (cnt == 0)
! 85: {
! 86: hz = qp[size - 1];
! 87: lz = qp[size - 2];
! 88: }
! 89: else
! 90: {
! 91: hz = (qp[size - 1] << cnt) | (qp[size - 2] >> BITS_PER_MP_LIMB - cnt);
! 92: lz = (qp[size - 2] << cnt) | (qp[size - 3] >> BITS_PER_MP_LIMB - cnt);
! 93: }
! 94: #if _GMP_IEEE_FLOATS
! 95: /* Take bits from less significant limbs, but only if they may affect
! 96: the result. */
! 97: if ((lz & 0x7ff) == 0x400)
! 98: {
! 99: if (cnt != 0)
! 100: lz += ((qp[size - 3] << cnt) != 0 || ! mpn_zero_p (qp, size - 3));
! 101: else
! 102: lz += (! mpn_zero_p (qp, size - 2));
! 103: }
! 104: #endif
! 105: res = MP_BASE_AS_DOUBLE * hz + lz;
! 106: res = __gmp_scale2 (res, (size - 2) * BITS_PER_MP_LIMB - cnt);
! 107: #endif
! 108: #if BITS_PER_MP_LIMB == 64
! 109: if (cnt == 0)
! 110: hz = qp[size - 1];
! 111: else
! 112: hz = (qp[size - 1] << cnt) | (qp[size - 2] >> BITS_PER_MP_LIMB - cnt);
! 113: #if _GMP_IEEE_FLOATS
! 114: if ((hz & 0x7ff) == 0x400)
! 115: {
! 116: if (cnt != 0)
! 117: hz += ((qp[size - 2] << cnt) != 0 || ! mpn_zero_p (qp, size - 2));
! 118: else
! 119: hz += (! mpn_zero_p (qp, size - 1));
! 120: }
! 121: #endif
! 122: res = hz;
! 123: res = __gmp_scale2 (res, (size - 1) * BITS_PER_MP_LIMB - cnt);
! 124: #endif
! 125: }
1.1 maekawa 126:
127: return negative ? -res : res;
128: }
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