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Annotation of OpenXM_contrib/gmp/mpz/tdiv_q.c, Revision 1.1.1.1

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: }