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4c74403188
Change-Id: Iae65e95cfa0d92091b8b0a424ae36d88efa76aa9 Reviewed-on: https://review.haiku-os.org/c/buildtools/+/3020 Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>
119 lines
3.6 KiB
C
119 lines
3.6 KiB
C
/* mpf_set_q (mpf_t rop, mpq_t op) -- Convert the rational op to the float rop.
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Copyright 1996, 1999, 2001, 2002, 2004, 2005, 2016 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 either:
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* the GNU Lesser General Public License as published by the Free
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Software Foundation; either version 3 of the License, or (at your
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option) any later version.
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or
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* the GNU General Public License as published by the Free Software
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Foundation; either version 2 of the License, or (at your option) any
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later version.
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or both in parallel, as here.
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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 General Public License
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for more details.
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You should have received copies of the GNU General Public License and the
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GNU Lesser General Public License along with the GNU MP Library. If not,
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see https://www.gnu.org/licenses/. */
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#include "gmp-impl.h"
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/* As usual the aim is to produce PREC(r) limbs, with the high non-zero. The
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basic mpn_div_q produces a quotient of nsize-dsize+1 limbs, with either the
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high or second highest limb non-zero. We arrange for nsize-dsize+1 to equal
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prec+1, hence giving either prec or prec+1 result limbs at PTR(r).
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nsize-dsize+1 == prec+1 is achieved by adjusting num(q), either dropping low
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limbs if it's too big, or padding with low zeros if it's too small. The
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full given den(q) is always used.
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We cannot truncate den(q), because even when it's much bigger than prec the
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last limbs can still influence the final quotient. Often they don't, but we
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leave optimization of that to mpn_div_q.
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Enhancements:
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The high quotient limb is non-zero when high{np,dsize} > {dp,dsize}. We
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could make that comparison and use qsize==prec instead of qsize==prec+1,
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to save one limb in the division. */
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void
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mpf_set_q (mpf_t r, mpq_srcptr q)
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{
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mp_srcptr np, dp;
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mp_size_t prec, nsize, dsize, qsize, prospective_qsize, tsize, zeros;
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mp_size_t sign_quotient, high_zero;
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mp_ptr qp, tp;
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mp_exp_t exp;
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TMP_DECL;
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ASSERT (SIZ(&q->_mp_den) > 0); /* canonical q */
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nsize = SIZ (&q->_mp_num);
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dsize = SIZ (&q->_mp_den);
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if (UNLIKELY (nsize == 0))
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{
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SIZ (r) = 0;
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EXP (r) = 0;
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return;
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}
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TMP_MARK;
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prec = PREC (r);
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qp = PTR (r);
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sign_quotient = nsize;
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nsize = ABS (nsize);
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np = PTR (&q->_mp_num);
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dp = PTR (&q->_mp_den);
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prospective_qsize = nsize - dsize + 1; /* q from using given n,d sizes */
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exp = prospective_qsize; /* ie. number of integer limbs */
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qsize = prec + 1; /* desired q */
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zeros = qsize - prospective_qsize; /* n zeros to get desired qsize */
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tsize = nsize + zeros; /* size of intermediate numerator */
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tp = TMP_ALLOC_LIMBS (tsize + 1); /* +1 for mpn_div_q's scratch */
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if (zeros > 0)
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{
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/* pad n with zeros into temporary space */
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MPN_ZERO (tp, zeros);
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MPN_COPY (tp+zeros, np, nsize);
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np = tp; /* mpn_div_q allows this overlap */
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}
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else
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{
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/* shorten n to get desired qsize */
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np -= zeros;
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}
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ASSERT (tsize-dsize+1 == qsize);
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mpn_div_q (qp, np, tsize, dp, dsize, tp);
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/* strip possible zero high limb */
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high_zero = (qp[qsize-1] == 0);
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qsize -= high_zero;
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exp -= high_zero;
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EXP (r) = exp;
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SIZ (r) = sign_quotient >= 0 ? qsize : -qsize;
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TMP_FREE;
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}
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