mirror of https://github.com/macssh/macssh.git
105 lines
3.2 KiB
C
Executable File
105 lines
3.2 KiB
C
Executable File
/* mpfr_set_z -- set a floating-point number from a multiple-precision integer
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Copyright (C) 1999 PolKA project, Inria Lorraine and Loria
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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 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 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 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 MPFR 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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#include "longlong.h"
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#include "mpfr.h"
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/* set f to the integer z */
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int
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#if __STDC__
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mpfr_set_z (mpfr_ptr f, mpz_srcptr z, unsigned char rnd)
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#else
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mpfr_set_z (f, z, rnd)
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mpfr_ptr f;
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mpz_srcptr z;
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unsigned char rnd;
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#endif
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{
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int fn, zn, k, dif, sign_z, sh; mp_limb_t *fp = MANT(f), *zp, cc, c2;
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sign_z = mpz_cmp_ui(z,0);
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if (sign_z==0) return (SIZE(f)=0);
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fn = 1 + (PREC(f)-1)/BITS_PER_MP_LIMB;
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zn = ABS(SIZ(z));
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dif = zn-fn;
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zp = PTR(z);
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count_leading_zeros(k, zp[zn-1]);
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EXP(f) = zn*BITS_PER_MP_LIMB-k;
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if (SIGN(f)*sign_z<0) CHANGE_SIGN(f);
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if (dif>=0) { /* number has to be truncated */
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if (k) {
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mpn_lshift(fp, zp + dif, fn, k);
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if (dif) *fp += zp[dif-1] >> (BITS_PER_MP_LIMB-k);
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}
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else MPN_COPY(fp, zp + dif, fn);
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sh = fn*BITS_PER_MP_LIMB-PREC(f);
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cc = *fp & (((mp_limb_t)1 << sh) - 1);
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*fp = *fp & ~cc;
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if (rnd==GMP_RNDN) {
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if (sh) c2 = (mp_limb_t)1 << (sh-1);
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else { /* sh=0 */
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c2 = ((mp_limb_t)1) << (BITS_PER_MP_LIMB-1);
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dif--;
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cc = (dif>=0) ? ((zp[dif])<<k) : 0;
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if (dif>0 && k) cc += zp[dif-1] >> (BITS_PER_MP_LIMB-k);
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}
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/* now compares cc to c2 */
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if (cc>c2) { mpfr_add_one_ulp(f); return cc; }
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else if (cc<c2) goto towards_zero;
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else {
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cc=0;
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while (dif>0 && (cc=zp[dif-1])==0) dif--;
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if (cc) { mpfr_add_one_ulp(f); return cc; }
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else /* exactly in middle: inexact in both cases */
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if (*fp & ((mp_limb_t)1<<sh)) { mpfr_add_one_ulp(f); return 1; }
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else return 1;
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}
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}
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else if ((sign_z>0 && rnd==GMP_RNDU) || (sign_z<0 && rnd==GMP_RNDD)) {
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/* round towards infinity */
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/* result is exact iff all remaining bits are zero */
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if (dif>0 && cc==0) cc=zp[--dif]<<k;
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while (cc==0 && dif>0) cc=zp[--dif];
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if (cc) { mpfr_add_one_ulp(f); return 1; }
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else return 0;
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}
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else { /* round towards zero */
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/* result is exact iff all remaining bits are zero */
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towards_zero:
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if (cc==0 && dif>0) cc=zp[--dif]<<k;
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while (cc==0 && dif>0) cc=zp[--dif];
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return cc;
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}
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}
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else {
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if (k) mpn_lshift(fp-dif, zp, zn, k);
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else MPN_COPY(fp-dif, zp, zn);
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/* fill with zeroes */
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MPN_ZERO(fp, -dif);
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return 0; /* result is exact */
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}
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}
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