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aa9bc17601
BMakefiles and other bits will follow. Requested by: Andrey Chernov Made world by: Chuck Robey
161 lines
3.3 KiB
C
161 lines
3.3 KiB
C
/* __gmp_extract_double -- convert from double to array of mp_limb_t.
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Copyright (C) 1996 Free Software Foundation, Inc.
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This file is part of the GNU MP Library.
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The GNU MP Library is free software; you can redistribute it and/or modify
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it under the terms of the GNU Library General Public License as published by
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the Free Software Foundation; either version 2 of the License, or (at your
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option) any later version.
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The GNU MP Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public
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License for more details.
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You should have received a copy of the GNU Library General Public License
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along with the GNU MP Library; see the file COPYING.LIB. If not, write to
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the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
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MA 02111-1307, USA. */
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#include "gmp.h"
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#include "gmp-impl.h"
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#ifdef XDEBUG
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#undef _GMP_IEEE_FLOATS
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#endif
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#ifndef _GMP_IEEE_FLOATS
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#define _GMP_IEEE_FLOATS 0
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#endif
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#define MP_BASE_AS_DOUBLE (2.0 * ((mp_limb_t) 1 << (BITS_PER_MP_LIMB - 1)))
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/* Extract a non-negative double in d. */
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int
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#if __STDC__
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__gmp_extract_double (mp_ptr rp, double d)
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#else
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__gmp_extract_double (rp, d)
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mp_ptr rp;
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double d;
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#endif
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{
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long exp;
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unsigned sc;
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mp_limb_t manh, manl;
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/* BUGS
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1. Should handle Inf and NaN in IEEE specific code.
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2. Handle Inf and NaN also in default code, to avoid hangs.
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3. Generalize to handle all BITS_PER_MP_LIMB >= 32.
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4. This lits is incomplete and misspelled.
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*/
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if (d == 0.0)
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{
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rp[0] = 0;
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rp[1] = 0;
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#if BITS_PER_MP_LIMB == 32
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rp[2] = 0;
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#endif
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return 0;
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}
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#if _GMP_IEEE_FLOATS
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{
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union ieee_double_extract x;
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x.d = d;
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exp = x.s.exp;
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sc = (unsigned) (exp + 2) % BITS_PER_MP_LIMB;
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#if BITS_PER_MP_LIMB == 64
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manl = (((mp_limb_t) 1 << 63)
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| ((mp_limb_t) x.s.manh << 43) | ((mp_limb_t) x.s.manl << 11));
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#else
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manh = ((mp_limb_t) 1 << 31) | (x.s.manh << 11) | (x.s.manl >> 21);
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manl = x.s.manl << 11;
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#endif
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}
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#else
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{
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/* Unknown (or known to be non-IEEE) double format. */
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exp = 0;
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if (d >= 1.0)
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{
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if (d * 0.5 == d)
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abort ();
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while (d >= 32768.0)
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{
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d *= (1.0 / 65536.0);
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exp += 16;
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}
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while (d >= 1.0)
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{
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d *= 0.5;
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exp += 1;
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}
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}
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else if (d < 0.5)
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{
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while (d < (1.0 / 65536.0))
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{
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d *= 65536.0;
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exp -= 16;
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}
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while (d < 0.5)
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{
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d *= 2.0;
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exp -= 1;
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}
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}
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sc = (unsigned) exp % BITS_PER_MP_LIMB;
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d *= MP_BASE_AS_DOUBLE;
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#if BITS_PER_MP_LIMB == 64
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manl = d;
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#else
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manh = d;
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manl = (d - manh) * MP_BASE_AS_DOUBLE;
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#endif
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exp += 1022;
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}
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#endif
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exp = (unsigned) (exp + 1) / BITS_PER_MP_LIMB - 1024 / BITS_PER_MP_LIMB + 1;
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#if BITS_PER_MP_LIMB == 64
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if (sc != 0)
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{
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rp[1] = manl >> (BITS_PER_MP_LIMB - sc);
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rp[0] = manl << sc;
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}
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else
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{
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rp[1] = manl;
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rp[0] = 0;
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}
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#else
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if (sc != 0)
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{
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rp[2] = manh >> (BITS_PER_MP_LIMB - sc);
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rp[1] = (manl >> (BITS_PER_MP_LIMB - sc)) | (manh << sc);
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rp[0] = manl << sc;
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}
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else
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{
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rp[2] = manh;
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rp[1] = manl;
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rp[0] = 0;
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}
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#endif
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return exp;
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}
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