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Diffstat (limited to 'extract-dbl.c')
| -rw-r--r-- | extract-dbl.c | 158 |
1 files changed, 158 insertions, 0 deletions
diff --git a/extract-dbl.c b/extract-dbl.c new file mode 100644 index 000000000..d86871a94 --- /dev/null +++ b/extract-dbl.c @@ -0,0 +1,158 @@ +/* __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; +} |