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git-svn-id: file:///srv/svn/repos/haiku/buildtools/trunk@29042 a95241bf-73f2-0310-859d-f6bbb57e9c96
118 lines
3.5 KiB
C
118 lines
3.5 KiB
C
/* mpfr_get_f -- convert a MPFR number to a GNU MPF number
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Copyright 2005, 2006, 2007 Free Software Foundation, Inc.
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Contributed by the Arenaire and Cacao projects, INRIA.
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This file is part of the MPFR Library.
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The MPFR Library is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or (at your
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option) any later version.
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The MPFR 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 Lesser General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with the MPFR Library; see the file COPYING.LIB. If not, write to
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the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
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MA 02110-1301, USA. */
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#include "mpfr-impl.h"
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/* return value is 0 iff no error occurred in the conversion
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(1 for NaN, +Inf, -Inf that have no equivalent in mpf)
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*/
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int
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mpfr_get_f (mpf_ptr x, mpfr_srcptr y, mp_rnd_t rnd_mode)
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{
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mp_size_t sx, sy;
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mp_prec_t precx, precy;
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mp_limb_t *xp;
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int sh;
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if (MPFR_UNLIKELY(MPFR_IS_SINGULAR(y)))
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{
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if (MPFR_IS_ZERO(y))
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{
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mpf_set_ui (x, 0);
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return 0;
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}
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else /* NaN or Inf */
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return 1;
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}
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sx = PREC(x); /* number of limbs of the mantissa of x */
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precy = MPFR_PREC(y);
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precx = (mp_prec_t) sx * BITS_PER_MP_LIMB;
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sy = MPFR_LIMB_SIZE (y);
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xp = PTR (x);
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/* since mpf numbers are represented in base 2^BITS_PER_MP_LIMB,
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we loose -EXP(y) % BITS_PER_MP_LIMB bits in the most significant limb */
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sh = MPFR_GET_EXP(y) % BITS_PER_MP_LIMB;
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sh = sh <= 0 ? - sh : BITS_PER_MP_LIMB - sh;
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MPFR_ASSERTD (sh >= 0);
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if (precy + sh <= precx) /* we can copy directly */
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{
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mp_size_t ds;
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MPFR_ASSERTN (sx >= sy);
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ds = sx - sy;
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if (sh != 0)
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{
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mp_limb_t out;
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out = mpn_rshift (xp + ds, MPFR_MANT(y), sy, sh);
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MPFR_ASSERTN (ds > 0 || out == 0);
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if (ds > 0)
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xp[--ds] = out;
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}
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else
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MPN_COPY (xp + ds, MPFR_MANT (y), sy);
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if (ds > 0)
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MPN_ZERO (xp, ds);
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EXP(x) = (MPFR_GET_EXP(y) + sh) / BITS_PER_MP_LIMB;
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}
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else /* we have to round to precx - sh bits */
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{
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mpfr_t z;
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mp_size_t sz, ds;
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/* Recall that precx = (mp_prec_t) sx * BITS_PER_MP_LIMB */
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mpfr_init2 (z, precx - sh);
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sz = MPFR_LIMB_SIZE (z);
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mpfr_set (z, y, rnd_mode);
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/* warning, sh may change due to rounding, but then z is a power of two,
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thus we can safely ignore its last bit which is 0 */
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sh = MPFR_GET_EXP(z) % BITS_PER_MP_LIMB;
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sh = sh <= 0 ? - sh : BITS_PER_MP_LIMB - sh;
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MPFR_ASSERTD (sx >= sz);
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ds = sx - sz;
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MPFR_ASSERTD (sh >= 0 && ds <= 1);
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if (sh != 0)
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{
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mp_limb_t out;
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out = mpn_rshift (xp + ds, MPFR_MANT(z), sz, sh);
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/* If sh hasn't changed, it is the number of the non-significant
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bits in the lowest limb of z. Therefore out == 0. */
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MPFR_ASSERTD (out == 0);
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}
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else
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MPN_COPY (xp + ds, MPFR_MANT(z), sz);
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if (ds != 0)
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xp[0] = 0;
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EXP(x) = (MPFR_GET_EXP(z) + sh) / BITS_PER_MP_LIMB;
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mpfr_clear (z);
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}
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/* set size and sign */
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SIZ(x) = (MPFR_FROM_SIGN_TO_INT(MPFR_SIGN(y)) < 0) ? -sx : sx;
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return 0;
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}
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