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Annotation of OpenXM_contrib/gmp/mpfr/set_z.c, Revision 1.1

1.1     ! maekawa     1: /* mpfr_set_z -- set a floating-point number from a multiple-precision integer
        !             2:
        !             3: Copyright (C) 1999 PolKA project, Inria Lorraine and Loria
        !             4:
        !             5: This file is part of the MPFR Library.
        !             6:
        !             7: The MPFR Library is free software; you can redistribute it and/or modify
        !             8: it under the terms of the GNU Library General Public License as published by
        !             9: the Free Software Foundation; either version 2 of the License, or (at your
        !            10: option) any later version.
        !            11:
        !            12: The MPFR Library is distributed in the hope that it will be useful, but
        !            13: WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
        !            14: or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
        !            15: License for more details.
        !            16:
        !            17: You should have received a copy of the GNU Library General Public License
        !            18: along with the MPFR Library; see the file COPYING.LIB.  If not, write to
        !            19: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
        !            20: MA 02111-1307, USA. */
        !            21:
        !            22: #include "gmp.h"
        !            23: #include "gmp-impl.h"
        !            24: #include "longlong.h"
        !            25: #include "mpfr.h"
        !            26:
        !            27: /* set f to the integer z */
        !            28: int
        !            29: #if __STDC__
        !            30: mpfr_set_z (mpfr_ptr f, mpz_srcptr z, unsigned char rnd)
        !            31: #else
        !            32: mpfr_set_z (f, z, rnd)
        !            33:      mpfr_ptr f;
        !            34:      mpz_srcptr z;
        !            35:      unsigned char rnd;
        !            36: #endif
        !            37: {
        !            38:   int fn, zn, k, dif, sign_z, sh; mp_limb_t *fp = MANT(f), *zp, cc, c2;
        !            39:
        !            40:   sign_z = mpz_cmp_ui(z,0);
        !            41:   if (sign_z==0) return (SIZE(f)=0);
        !            42:   fn = 1 + (PREC(f)-1)/BITS_PER_MP_LIMB;
        !            43:   zn = ABS(SIZ(z));
        !            44:   dif = zn-fn;
        !            45:   zp = PTR(z);
        !            46:   count_leading_zeros(k, zp[zn-1]);
        !            47:   EXP(f) = zn*BITS_PER_MP_LIMB-k;
        !            48:   if (SIGN(f)*sign_z<0) CHANGE_SIGN(f);
        !            49:   if (dif>=0) { /* number has to be truncated */
        !            50:     if (k) {
        !            51:       mpn_lshift(fp, zp + dif, fn, k);
        !            52:       if (dif) *fp += zp[dif-1] >> (BITS_PER_MP_LIMB-k);
        !            53:     }
        !            54:     else MPN_COPY(fp, zp + dif, fn);
        !            55:     sh = fn*BITS_PER_MP_LIMB-PREC(f);
        !            56:     cc = *fp & (((mp_limb_t)1 << sh) - 1);
        !            57:     *fp = *fp & ~cc;
        !            58:     if (rnd==GMP_RNDN) {
        !            59:       if (sh) c2 = (mp_limb_t)1 << (sh-1);
        !            60:       else { /* sh=0 */
        !            61:        c2 = ((mp_limb_t)1) << (BITS_PER_MP_LIMB-1);
        !            62:        dif--;
        !            63:        cc = (dif>=0) ? ((zp[dif])<<k) : 0;
        !            64:        if (dif>0 && k) cc += zp[dif-1] >> (BITS_PER_MP_LIMB-k);
        !            65:       }
        !            66:       /* now compares cc to c2 */
        !            67:       if (cc>c2) { mpfr_add_one_ulp(f); return cc; }
        !            68:       else if (cc<c2) goto towards_zero;
        !            69:       else {
        !            70:        cc=0;
        !            71:        while (dif>0 && (cc=zp[dif-1])==0) dif--;
        !            72:        if (cc) { mpfr_add_one_ulp(f); return cc; }
        !            73:        else /* exactly in middle: inexact in both cases */
        !            74:          if (*fp & ((mp_limb_t)1<<sh)) { mpfr_add_one_ulp(f); return 1; }
        !            75:          else return 1;
        !            76:       }
        !            77:     }
        !            78:     else if ((sign_z>0 && rnd==GMP_RNDU) || (sign_z<0 && rnd==GMP_RNDD)) {
        !            79:       /* round towards infinity */
        !            80:       /* result is exact iff all remaining bits are zero */
        !            81:       if (dif>0 && cc==0) cc=zp[--dif]<<k;
        !            82:       while (cc==0 && dif>0) cc=zp[--dif];
        !            83:       if (cc) { mpfr_add_one_ulp(f); return 1; }
        !            84:       else return 0;
        !            85:     }
        !            86:     else { /* round towards zero */
        !            87:       /* result is exact iff all remaining bits are zero */
        !            88:     towards_zero:
        !            89:       if (cc==0 && dif>0) cc=zp[--dif]<<k;
        !            90:       while (cc==0 && dif>0) cc=zp[--dif];
        !            91:       return cc;
        !            92:     }
        !            93:   }
        !            94:   else {
        !            95:     if (k) mpn_lshift(fp-dif, zp, zn, k);
        !            96:     else MPN_COPY(fp-dif, zp, zn);
        !            97:     /* fill with zeroes */
        !            98:     MPN_ZERO(fp, -dif);
        !            99:     return 0; /* result is exact */
        !           100:   }
        !           101: }
        !           102:
        !           103:
        !           104: