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Diffstat (limited to 'mpz/tdiv_q.c')
-rw-r--r-- | mpz/tdiv_q.c | 133 |
1 files changed, 133 insertions, 0 deletions
diff --git a/mpz/tdiv_q.c b/mpz/tdiv_q.c new file mode 100644 index 000000000..b4d36368b --- /dev/null +++ b/mpz/tdiv_q.c @@ -0,0 +1,133 @@ +/* mpz_tdiv_q -- divide two integers and produce a quotient. + +Copyright (C) 1991, 1993, 1994, 1996 Free Software Foundation, Inc. + +This file is part of the GNU MP Library. + +The GNU MP Library is free software; you can redistribute it and/or modify +it under the terms of the GNU Library General Public License as published by +the Free Software Foundation; either version 2 of the License, or (at your +option) any later version. + +The GNU MP Library is distributed in the hope that it will be useful, but +WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY +or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public +License for more details. + +You should have received a copy of the GNU Library General Public License +along with the GNU MP Library; see the file COPYING.LIB. If not, write to +the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, +MA 02111-1307, USA. */ + +#include "gmp.h" +#include "gmp-impl.h" +#include "longlong.h" + +void +#if __STDC__ +mpz_tdiv_q (mpz_ptr quot, mpz_srcptr num, mpz_srcptr den) +#else +mpz_tdiv_q (quot, num, den) + mpz_ptr quot; + mpz_srcptr num; + mpz_srcptr den; +#endif +{ + mp_srcptr np, dp; + mp_ptr qp, rp; + mp_size_t nsize = num->_mp_size; + mp_size_t dsize = den->_mp_size; + mp_size_t qsize, rsize; + mp_size_t sign_quotient = nsize ^ dsize; + unsigned normalization_steps; + mp_limb_t q_limb; + TMP_DECL (marker); + + nsize = ABS (nsize); + dsize = ABS (dsize); + + /* Ensure space is enough for quotient. */ + + qsize = nsize - dsize + 1; /* qsize cannot be bigger than this. */ + if (qsize <= 0) + { + quot->_mp_size = 0; + return; + } + + if (quot->_mp_alloc < qsize) + _mpz_realloc (quot, qsize); + + qp = quot->_mp_d; + np = num->_mp_d; + dp = den->_mp_d; + + /* Optimize division by a single-limb divisor. */ + if (dsize == 1) + { + mpn_divmod_1 (qp, np, nsize, dp[0]); + qsize -= qp[qsize - 1] == 0; + quot->_mp_size = sign_quotient >= 0 ? qsize : -qsize; + return; + } + + TMP_MARK (marker); + + rp = (mp_ptr) TMP_ALLOC ((nsize + 1) * BYTES_PER_MP_LIMB); + + count_leading_zeros (normalization_steps, dp[dsize - 1]); + + /* Normalize the denominator, i.e. make its most significant bit set by + shifting it NORMALIZATION_STEPS bits to the left. Also shift the + numerator the same number of steps (to keep the quotient the same!). */ + if (normalization_steps != 0) + { + mp_ptr tp; + mp_limb_t nlimb; + + /* Shift up the denominator setting the most significant bit of + the most significant word. Use temporary storage not to clobber + the original contents of the denominator. */ + tp = (mp_ptr) TMP_ALLOC (dsize * BYTES_PER_MP_LIMB); + mpn_lshift (tp, dp, dsize, normalization_steps); + dp = tp; + + /* Shift up the numerator, possibly introducing a new most + significant word. Move the shifted numerator in the remainder + meanwhile. */ + nlimb = mpn_lshift (rp, np, nsize, normalization_steps); + if (nlimb != 0) + { + rp[nsize] = nlimb; + rsize = nsize + 1; + } + else + rsize = nsize; + } + else + { + /* The denominator is already normalized, as required. Copy it to + temporary space if it overlaps with the quotient. */ + if (dp == qp) + { + dp = (mp_ptr) TMP_ALLOC (dsize * BYTES_PER_MP_LIMB); + MPN_COPY ((mp_ptr) dp, qp, dsize); + } + + /* Move the numerator to the remainder. */ + MPN_COPY (rp, np, nsize); + rsize = nsize; + } + + q_limb = mpn_divmod (qp, rp, rsize, dp, dsize); + + qsize = rsize - dsize; + if (q_limb) + { + qp[qsize] = q_limb; + qsize += 1; + } + + quot->_mp_size = sign_quotient >= 0 ? qsize : -qsize; + TMP_FREE (marker); +} |