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+/* __gmp_extract_double -- convert from double to array of mp_limb_t.
+
+Copyright (C) 1996 Free Software Foundation, Inc.
+
+This file is part of the GNU MP Library.
+
+The GNU MP Library is free software; you can redistribute it and/or modify
+it under the terms of the GNU Library General Public License as published by
+the Free Software Foundation; either version 2 of the License, or (at your
+option) any later version.
+
+The GNU MP Library is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public
+License for more details.
+
+You should have received a copy of the GNU Library General Public License
+along with the GNU MP Library; see the file COPYING.LIB. If not, write to
+the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+MA 02111-1307, USA. */
+
+#include "gmp.h"
+#include "gmp-impl.h"
+
+#ifdef XDEBUG
+#undef _GMP_IEEE_FLOATS
+#endif
+
+#ifndef _GMP_IEEE_FLOATS
+#define _GMP_IEEE_FLOATS 0
+#endif
+
+/* Extract a non-negative double in d. */
+
+int
+#if __STDC__
+__gmp_extract_double (mp_ptr rp, double d)
+#else
+__gmp_extract_double (rp, d)
+ mp_ptr rp;
+ double d;
+#endif
+{
+ long exp;
+ unsigned sc;
+ mp_limb_t manh, manl;
+
+ /* BUGS
+
+ 1. Should handle Inf and NaN in IEEE specific code.
+ 2. Handle Inf and NaN also in default code, to avoid hangs.
+ 3. Generalize to handle all BITS_PER_MP_LIMB >= 32.
+ 4. This lits is incomplete and misspelled.
+ */
+
+ if (d == 0.0)
+ {
+ rp[0] = 0;
+ rp[1] = 0;
+#if BITS_PER_MP_LIMB == 32
+ rp[2] = 0;
+#endif
+ return 0;
+ }
+
+#if _GMP_IEEE_FLOATS
+ {
+ union ieee_double_extract x;
+ x.d = d;
+
+ exp = x.s.exp;
+ sc = (unsigned) (exp + 2) % BITS_PER_MP_LIMB;
+#if BITS_PER_MP_LIMB == 64
+ manl = (((mp_limb_t) 1 << 63)
+ | ((mp_limb_t) x.s.manh << 43) | ((mp_limb_t) x.s.manl << 11));
+#else
+ manh = ((mp_limb_t) 1 << 31) | (x.s.manh << 11) | (x.s.manl >> 21);
+ manl = x.s.manl << 11;
+#endif
+ }
+#else
+ {
+ /* Unknown (or known to be non-IEEE) double format. */
+ exp = 0;
+ if (d >= 1.0)
+ {
+ if (d * 0.5 == d)
+ abort ();
+
+ while (d >= 32768.0)
+ {
+ d *= (1.0 / 65536.0);
+ exp += 16;
+ }
+ while (d >= 1.0)
+ {
+ d *= 0.5;
+ exp += 1;
+ }
+ }
+ else if (d < 0.5)
+ {
+ while (d < (1.0 / 65536.0))
+ {
+ d *= 65536.0;
+ exp -= 16;
+ }
+ while (d < 0.5)
+ {
+ d *= 2.0;
+ exp -= 1;
+ }
+ }
+
+ sc = (unsigned) exp % BITS_PER_MP_LIMB;
+
+ d *= MP_BASE_AS_DOUBLE;
+#if BITS_PER_MP_LIMB == 64
+ manl = d;
+#else
+ manh = d;
+ manl = (d - manh) * MP_BASE_AS_DOUBLE;
+#endif
+
+ exp += 1022;
+ }
+#endif
+
+ exp = (unsigned) (exp + 1) / BITS_PER_MP_LIMB - 1024 / BITS_PER_MP_LIMB + 1;
+
+#if BITS_PER_MP_LIMB == 64
+ if (sc != 0)
+ {
+ rp[1] = manl >> (BITS_PER_MP_LIMB - sc);
+ rp[0] = manl << sc;
+ }
+ else
+ {
+ rp[1] = manl;
+ rp[0] = 0;
+ }
+#else
+ if (sc != 0)
+ {
+ rp[2] = manh >> (BITS_PER_MP_LIMB - sc);
+ rp[1] = (manl >> (BITS_PER_MP_LIMB - sc)) | (manh << sc);
+ rp[0] = manl << sc;
+ }
+ else
+ {
+ rp[2] = manh;
+ rp[1] = manl;
+ rp[0] = 0;
+ }
+#endif
+
+ return exp;
+}