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Annotation of OpenXM_contrib/gmp/mpz/cfdiv_q_2exp.c, Revision 1.1

1.1     ! ohara       1: /* mpz_cdiv_q_2exp, mpz_fdiv_q_2exp -- quotient from mpz divided by 2^n.
        !             2:
        !             3: Copyright 1991, 1993, 1994, 1996, 1998, 1999, 2001, 2002 Free Software
        !             4: Foundation, Inc.
        !             5:
        !             6: This file is part of the GNU MP Library.
        !             7:
        !             8: The GNU MP Library is free software; you can redistribute it and/or modify
        !             9: it under the terms of the GNU Lesser General Public License as published by
        !            10: the Free Software Foundation; either version 2.1 of the License, or (at your
        !            11: option) any later version.
        !            12:
        !            13: The GNU MP Library is distributed in the hope that it will be useful, but
        !            14: WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
        !            15: or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
        !            16: License for more details.
        !            17:
        !            18: You should have received a copy of the GNU Lesser General Public License
        !            19: along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
        !            20: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
        !            21: MA 02111-1307, USA. */
        !            22:
        !            23: #include "gmp.h"
        !            24: #include "gmp-impl.h"
        !            25:
        !            26:
        !            27: /* dir==1 for ceil, dir==-1 for floor */
        !            28:
        !            29: static void __gmpz_cfdiv_q_2exp _PROTO ((REGPARM_3_1 (mpz_ptr w, mpz_srcptr u, unsigned long cnt, int dir))) REGPARM_ATTR (1);
        !            30: #define cfdiv_q_2exp(w,u,cnt,dir)  __gmpz_cfdiv_q_2exp (REGPARM_3_1 (w,u,cnt,dir))
        !            31:
        !            32: static void
        !            33: cfdiv_q_2exp (mpz_ptr w, mpz_srcptr u, unsigned long cnt, int dir)
        !            34: {
        !            35:   mp_size_t  wsize, usize, abs_usize, limb_cnt, i;
        !            36:   mp_srcptr  up;
        !            37:   mp_ptr     wp;
        !            38:   mp_limb_t  round, rmask;
        !            39:
        !            40:   usize = SIZ (u);
        !            41:   abs_usize = ABS (usize);
        !            42:   limb_cnt = cnt / GMP_NUMB_BITS;
        !            43:   wsize = abs_usize - limb_cnt;
        !            44:   if (wsize <= 0)
        !            45:     {
        !            46:       /* u < 2**cnt, so result 1, 0 or -1 according to rounding */
        !            47:       PTR(w)[0] = 1;
        !            48:       SIZ(w) = (usize == 0 || (usize ^ dir) < 0 ? 0 : dir);
        !            49:       return;
        !            50:     }
        !            51:
        !            52:   /* +1 limb to allow for mpn_add_1 below */
        !            53:   MPZ_REALLOC (w, wsize+1);
        !            54:
        !            55:   /* Check for rounding if direction matches u sign.
        !            56:      Set round if we're skipping non-zero limbs.  */
        !            57:   up = PTR(u);
        !            58:   round = 0;
        !            59:   rmask = ((usize ^ dir) >= 0 ? MP_LIMB_T_MAX : 0);
        !            60:   if (rmask != 0)
        !            61:     for (i = 0; i < limb_cnt && round == 0; i++)
        !            62:       round = up[i];
        !            63:
        !            64:   wp = PTR(w);
        !            65:   cnt %= GMP_NUMB_BITS;
        !            66:   if (cnt != 0)
        !            67:     {
        !            68:       round |= rmask & mpn_rshift (wp, up + limb_cnt, wsize, cnt);
        !            69:       wsize -= (wp[wsize - 1] == 0);
        !            70:     }
        !            71:   else
        !            72:     MPN_COPY_INCR (wp, up + limb_cnt, wsize);
        !            73:
        !            74:   if (round != 0)
        !            75:     {
        !            76:       if (wsize != 0)
        !            77:        {
        !            78:           mp_limb_t cy;
        !            79:          cy = mpn_add_1 (wp, wp, wsize, CNST_LIMB(1));
        !            80:          wp[wsize] = cy;
        !            81:          wsize += cy;
        !            82:        }
        !            83:       else
        !            84:        {
        !            85:          /* We shifted something to zero.  */
        !            86:          wp[0] = 1;
        !            87:          wsize = 1;
        !            88:        }
        !            89:     }
        !            90:   SIZ(w) = (usize >= 0 ? wsize : -wsize);
        !            91: }
        !            92:
        !            93:
        !            94: void
        !            95: mpz_cdiv_q_2exp (mpz_ptr w, mpz_srcptr u, unsigned long cnt)
        !            96: {
        !            97:   cfdiv_q_2exp (w, u, cnt, 1);
        !            98: }
        !            99:
        !           100: void
        !           101: mpz_fdiv_q_2exp (mpz_ptr w, mpz_srcptr u, unsigned long cnt)
        !           102: {
        !           103:   cfdiv_q_2exp (w, u, cnt, -1);
        !           104: }