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

1.1     ! maekawa     1: /* mpz_tdiv_q -- divide two integers and produce a quotient.
        !             2:
        !             3: Copyright (C) 1991, 1993, 1994, 1996 Free Software Foundation, Inc.
        !             4:
        !             5: This file is part of the GNU MP Library.
        !             6:
        !             7: The GNU MP 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 GNU MP 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 GNU MP 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:
        !            26: void
        !            27: #if __STDC__
        !            28: mpz_tdiv_q (mpz_ptr quot, mpz_srcptr num, mpz_srcptr den)
        !            29: #else
        !            30: mpz_tdiv_q (quot, num, den)
        !            31:      mpz_ptr quot;
        !            32:      mpz_srcptr num;
        !            33:      mpz_srcptr den;
        !            34: #endif
        !            35: {
        !            36:   mp_srcptr np, dp;
        !            37:   mp_ptr qp, rp;
        !            38:   mp_size_t nsize = num->_mp_size;
        !            39:   mp_size_t dsize = den->_mp_size;
        !            40:   mp_size_t qsize, rsize;
        !            41:   mp_size_t sign_quotient = nsize ^ dsize;
        !            42:   unsigned normalization_steps;
        !            43:   mp_limb_t q_limb;
        !            44:   TMP_DECL (marker);
        !            45:
        !            46:   nsize = ABS (nsize);
        !            47:   dsize = ABS (dsize);
        !            48:
        !            49:   /* Ensure space is enough for quotient. */
        !            50:
        !            51:   qsize = nsize - dsize + 1;   /* qsize cannot be bigger than this.  */
        !            52:   if (qsize <= 0)
        !            53:     {
        !            54:       quot->_mp_size = 0;
        !            55:       return;
        !            56:     }
        !            57:
        !            58:   if (quot->_mp_alloc < qsize)
        !            59:     _mpz_realloc (quot, qsize);
        !            60:
        !            61:   qp = quot->_mp_d;
        !            62:   np = num->_mp_d;
        !            63:   dp = den->_mp_d;
        !            64:
        !            65:   /* Optimize division by a single-limb divisor.  */
        !            66:   if (dsize == 1)
        !            67:     {
        !            68:       mpn_divmod_1 (qp, np, nsize, dp[0]);
        !            69:       qsize -= qp[qsize - 1] == 0;
        !            70:       quot->_mp_size = sign_quotient >= 0 ? qsize : -qsize;
        !            71:       return;
        !            72:     }
        !            73:
        !            74:   TMP_MARK (marker);
        !            75:
        !            76:   rp = (mp_ptr) TMP_ALLOC ((nsize + 1) * BYTES_PER_MP_LIMB);
        !            77:
        !            78:   count_leading_zeros (normalization_steps, dp[dsize - 1]);
        !            79:
        !            80:   /* Normalize the denominator, i.e. make its most significant bit set by
        !            81:      shifting it NORMALIZATION_STEPS bits to the left.  Also shift the
        !            82:      numerator the same number of steps (to keep the quotient the same!).  */
        !            83:   if (normalization_steps != 0)
        !            84:     {
        !            85:       mp_ptr tp;
        !            86:       mp_limb_t nlimb;
        !            87:
        !            88:       /* Shift up the denominator setting the most significant bit of
        !            89:         the most significant word.  Use temporary storage not to clobber
        !            90:         the original contents of the denominator.  */
        !            91:       tp = (mp_ptr) TMP_ALLOC (dsize * BYTES_PER_MP_LIMB);
        !            92:       mpn_lshift (tp, dp, dsize, normalization_steps);
        !            93:       dp = tp;
        !            94:
        !            95:       /* Shift up the numerator, possibly introducing a new most
        !            96:         significant word.  Move the shifted numerator in the remainder
        !            97:         meanwhile.  */
        !            98:       nlimb = mpn_lshift (rp, np, nsize, normalization_steps);
        !            99:       if (nlimb != 0)
        !           100:        {
        !           101:          rp[nsize] = nlimb;
        !           102:          rsize = nsize + 1;
        !           103:        }
        !           104:       else
        !           105:        rsize = nsize;
        !           106:     }
        !           107:   else
        !           108:     {
        !           109:       /* The denominator is already normalized, as required.  Copy it to
        !           110:         temporary space if it overlaps with the quotient.  */
        !           111:       if (dp == qp)
        !           112:        {
        !           113:          dp = (mp_ptr) TMP_ALLOC (dsize * BYTES_PER_MP_LIMB);
        !           114:          MPN_COPY ((mp_ptr) dp, qp, dsize);
        !           115:        }
        !           116:
        !           117:       /* Move the numerator to the remainder.  */
        !           118:       MPN_COPY (rp, np, nsize);
        !           119:       rsize = nsize;
        !           120:     }
        !           121:
        !           122:   q_limb = mpn_divmod (qp, rp, rsize, dp, dsize);
        !           123:
        !           124:   qsize = rsize - dsize;
        !           125:   if (q_limb)
        !           126:     {
        !           127:       qp[qsize] = q_limb;
        !           128:       qsize += 1;
        !           129:     }
        !           130:
        !           131:   quot->_mp_size = sign_quotient >= 0 ? qsize : -qsize;
        !           132:   TMP_FREE (marker);
        !           133: }