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/* mpfr_set_z -- set a floating-point number from a multiple-precision integer
Copyright (C) 1999, 2001 Free Software Foundation, Inc.
This file is part of the MPFR Library.
The MPFR Library is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or (at your
option) any later version.
The MPFR 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 Lesser General Public
License for more details.
You should have received a copy of the GNU Lesser General Public License
along with the MPFR 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 "mpfr.h"
#include "mpfr-impl.h"
#include "gmp-impl.h"
#include "longlong.h"
/* set f to the integer z */
int
mpfr_set_z (mpfr_ptr f, mpz_srcptr z, mp_rnd_t rnd)
{
mp_size_t fn, zn, dif, sh;
int k, sign_z;
mp_limb_t *fp = MPFR_MANT(f), *zp, cc, c2;
MPFR_CLEAR_FLAGS (f); /* z cannot be NaN nor Inf */
sign_z = mpz_cmp_ui (z, 0);
if (sign_z==0) {
MPFR_SET_ZERO(f);
return 0;
}
fn = 1 + (MPFR_PREC(f)-1)/BITS_PER_MP_LIMB;
zn = ABS(SIZ(z));
dif = zn-fn;
zp = PTR(z);
count_leading_zeros(k, zp[zn-1]);
MPFR_EXP(f) = zn*BITS_PER_MP_LIMB-k;
if (MPFR_SIGN(f)*sign_z<0) MPFR_CHANGE_SIGN(f);
if (dif>=0) { /* number has to be truncated */
if (k) {
mpn_lshift(fp, zp + dif, fn, k);
if (dif) *fp += zp[dif-1] >> (BITS_PER_MP_LIMB-k);
}
else MPN_COPY(fp, zp + dif, fn);
sh = fn*BITS_PER_MP_LIMB-MPFR_PREC(f);
cc = *fp & ((MP_LIMB_T_ONE << sh) - 1);
*fp = *fp & ~cc;
if (rnd==GMP_RNDN) {
if (sh) c2 = MP_LIMB_T_ONE << (sh - 1);
else { /* sh=0 */
c2 = MP_LIMB_T_HIGHBIT;
dif--;
cc = (dif>=0) ? ((zp[dif])<<k) : 0;
if (dif>0 && k) cc += zp[dif-1] >> (BITS_PER_MP_LIMB-k);
}
/* now compares cc to c2 */
if (cc>c2) { mpfr_add_one_ulp(f); return cc; }
else if (cc<c2) goto towards_zero;
else {
cc=0;
while (dif>0 && (cc=zp[dif-1])==0) dif--;
if (cc) { mpfr_add_one_ulp(f); return cc; }
else /* exactly in middle: inexact in both cases */
if (*fp & (MP_LIMB_T_ONE << sh)) { mpfr_add_one_ulp(f); return 1; }
else return 1;
}
}
else if ((sign_z>0 && rnd==GMP_RNDU) || (sign_z<0 && rnd==GMP_RNDD)) {
/* round towards infinity */
/* result is exact iff all remaining bits are zero */
if (dif>0 && cc==0) cc=zp[--dif]<<k;
while (cc==0 && dif>0) cc=zp[--dif];
if (cc) { mpfr_add_one_ulp(f); return 1; }
else return 0;
}
else { /* round towards zero */
/* result is exact iff all remaining bits are zero */
towards_zero:
if (cc==0 && dif>0) cc=zp[--dif]<<k;
while (cc==0 && dif>0) cc=zp[--dif];
return cc;
}
}
else {
if (k) mpn_lshift(fp-dif, zp, zn, k);
else MPN_COPY(fp-dif, zp, zn);
/* fill with zeroes */
MPN_ZERO(fp, -dif);
return 0; /* result is exact */
}
}
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