118 lines
3.1 KiB
C
118 lines
3.1 KiB
C
/* mpz_div -- divide two integers and produce a quotient.
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Copyright (C) 1991 Free Software Foundation, Inc.
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This file is part of the GNU MP Library.
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The GNU MP Library is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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The GNU MP Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with the GNU MP Library; see the file COPYING. If not, write to
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the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */
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#include "gmp.h"
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#include "gmp-impl.h"
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#include "longlong.h"
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void
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#ifdef __STDC__
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mpz_div (MP_INT *quot, const MP_INT *num, const MP_INT *den)
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#else
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mpz_div (quot, num, den)
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MP_INT *quot;
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const MP_INT *num;
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const MP_INT *den;
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#endif
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{
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mp_srcptr np, dp;
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mp_ptr qp, rp;
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mp_size nsize = num->size;
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mp_size dsize = den->size;
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mp_size qsize, rsize;
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mp_size sign_quotient = nsize ^ dsize;
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unsigned normalization_steps;
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nsize = ABS (nsize);
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dsize = ABS (dsize);
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/* Ensure space is enough for quotient. */
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qsize = nsize - dsize + 1; /* qsize cannot be bigger than this. */
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if (qsize <= 0)
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{
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quot->size = 0;
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return;
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}
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if (quot->alloc < qsize)
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_mpz_realloc (quot, qsize);
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qp = quot->d;
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np = num->d;
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dp = den->d;
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rp = (mp_ptr) alloca ((nsize + 1) * BYTES_PER_MP_LIMB);
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count_leading_zeros (normalization_steps, dp[dsize - 1]);
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/* Normalize the denominator and the numerator. */
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if (normalization_steps != 0)
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{
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mp_ptr tp;
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mp_limb ndigit;
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/* Shift up the denominator setting the most significant bit of
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the most significant word. Use temporary storage not to clobber
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the original contents of the denominator. */
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tp = (mp_ptr) alloca (dsize * BYTES_PER_MP_LIMB);
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(void) mpn_lshift (tp, dp, dsize, normalization_steps);
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dp = tp;
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/* Shift up the numerator, possibly introducing a new most
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significant word. Move the shifted numerator in the remainder
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meanwhile. */
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ndigit = mpn_lshift (rp, np, nsize, normalization_steps);
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if (ndigit != 0)
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{
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rp[nsize] = ndigit;
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rsize = nsize + 1;
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}
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else
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rsize = nsize;
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}
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else
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{
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/* The denominator is already normalized, as required.
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Copy it to temporary space if it overlaps with the quotient. */
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if (dp == qp)
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{
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dp = (mp_ptr) alloca (dsize * BYTES_PER_MP_LIMB);
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MPN_COPY ((mp_ptr) dp, qp, dsize);
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}
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/* Move the numerator to the remainder. */
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MPN_COPY (rp, np, nsize);
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rsize = nsize;
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}
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qsize = rsize - dsize + mpn_div (qp, rp, rsize, dp, dsize);
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/* Normalize the quotient. We may have at most one leading
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zero-word, so no loop is needed. */
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if (qsize > 0)
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qsize -= (qp[qsize - 1] == 0);
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if (sign_quotient < 0)
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qsize = -qsize;
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quot->size = qsize;
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alloca (0);
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}
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