90 lines
2.3 KiB
C
90 lines
2.3 KiB
C
/* mpf_mul_2exp -- Multiply a float by 2^n.
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Copyright (C) 1993, 1994, 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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void
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#if __STDC__
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mpf_mul_2exp (mpf_ptr r, mpf_srcptr u, unsigned long int exp)
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#else
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mpf_mul_2exp (r, u, exp)
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mpf_ptr r;
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mpf_srcptr u;
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unsigned long int exp;
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#endif
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{
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mp_srcptr up;
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mp_ptr rp = r->_mp_d;
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mp_size_t usize;
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mp_size_t abs_usize;
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mp_size_t prec = r->_mp_prec;
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mp_exp_t uexp = u->_mp_exp;
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usize = u->_mp_size;
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if (usize == 0)
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{
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r->_mp_size = 0;
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r->_mp_exp = 0;
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return;
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}
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abs_usize = ABS (usize);
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up = u->_mp_d;
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if (abs_usize > prec)
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{
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up += abs_usize - prec;
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abs_usize = prec;
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}
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if (exp % BITS_PER_MP_LIMB == 0)
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{
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if (rp != up)
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MPN_COPY (rp, up, abs_usize);
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r->_mp_size = usize >= 0 ? abs_usize : -abs_usize;
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r->_mp_exp = uexp + exp / BITS_PER_MP_LIMB;
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}
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else
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{
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mp_limb_t cy_limb;
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if (r != u)
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{
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cy_limb = mpn_lshift (rp, up, abs_usize, exp % BITS_PER_MP_LIMB);
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rp[abs_usize] = cy_limb;
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cy_limb = cy_limb != 0;
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}
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else
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{
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/* Use mpn_rshift since mpn_lshift operates downwards, and we
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therefore would clobber part of U before using that part. */
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cy_limb = mpn_rshift (rp + 1, up, abs_usize, -exp % BITS_PER_MP_LIMB);
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rp[0] = cy_limb;
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cy_limb = rp[abs_usize] != 0;
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}
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abs_usize += cy_limb;
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r->_mp_size = usize >= 0 ? abs_usize : -abs_usize;
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r->_mp_exp = uexp + exp / BITS_PER_MP_LIMB + cy_limb;
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}
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}
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