157 lines
4.1 KiB
C
157 lines
4.1 KiB
C
/* mpz_addmul, mpz_submul -- add or subtract multiple.
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Copyright 2001, 2004, 2005 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 Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or (at your
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option) any later version.
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The GNU MP Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with the GNU MP Library; see the file COPYING.LIB. If not, write to
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the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
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MA 02110-1301, USA. */
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#include "gmp.h"
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#include "gmp-impl.h"
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/* expecting x and y both with non-zero high limbs */
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#define mpn_cmp_twosizes_lt(xp,xsize, yp,ysize) \
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((xsize) < (ysize) \
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|| ((xsize) == (ysize) && mpn_cmp (xp, yp, xsize) < 0))
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/* sub>=0 means an addmul w += x*y, sub<0 means a submul w -= x*y.
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The signs of w, x and y are fully accounted for by each flipping "sub".
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The sign of w is retained for the result, unless the absolute value
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submul underflows, in which case it flips. */
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static void __gmpz_aorsmul _PROTO ((REGPARM_3_1 (mpz_ptr w, mpz_srcptr x, mpz_srcptr y, mp_size_t sub))) REGPARM_ATTR (1);
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#define mpz_aorsmul(w,x,y,sub) __gmpz_aorsmul (REGPARM_3_1 (w, x, y, sub))
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REGPARM_ATTR (1) static void
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mpz_aorsmul (mpz_ptr w, mpz_srcptr x, mpz_srcptr y, mp_size_t sub)
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{
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mp_size_t xsize, ysize, tsize, wsize, wsize_signed;
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mp_ptr wp, tp;
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mp_limb_t c, high;
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TMP_DECL;
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/* w unaffected if x==0 or y==0 */
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xsize = SIZ(x);
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ysize = SIZ(y);
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if (xsize == 0 || ysize == 0)
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return;
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/* make x the bigger of the two */
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if (ABS(ysize) > ABS(xsize))
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{
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MPZ_SRCPTR_SWAP (x, y);
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MP_SIZE_T_SWAP (xsize, ysize);
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}
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sub ^= ysize;
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ysize = ABS(ysize);
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/* use mpn_addmul_1/mpn_submul_1 if possible */
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if (ysize == 1)
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{
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mpz_aorsmul_1 (w, x, PTR(y)[0], sub);
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return;
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}
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sub ^= xsize;
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xsize = ABS(xsize);
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wsize_signed = SIZ(w);
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sub ^= wsize_signed;
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wsize = ABS(wsize_signed);
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tsize = xsize + ysize;
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MPZ_REALLOC (w, MAX (wsize, tsize) + 1);
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wp = PTR(w);
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if (wsize_signed == 0)
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{
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/* Nothing to add to, just set w=x*y. No w==x or w==y overlap here,
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since we know x,y!=0 but w==0. */
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high = mpn_mul (wp, PTR(x),xsize, PTR(y),ysize);
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tsize -= (high == 0);
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SIZ(w) = (sub >= 0 ? tsize : -tsize);
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return;
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}
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TMP_MARK;
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tp = TMP_ALLOC_LIMBS (tsize);
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high = mpn_mul (tp, PTR(x),xsize, PTR(y),ysize);
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tsize -= (high == 0);
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ASSERT (tp[tsize-1] != 0);
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if (sub >= 0)
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{
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mp_srcptr up = wp;
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mp_size_t usize = wsize;
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if (usize < tsize)
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{
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up = tp;
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usize = tsize;
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tp = wp;
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tsize = wsize;
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wsize = usize;
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}
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c = mpn_add (wp, up,usize, tp,tsize);
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wp[wsize] = c;
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wsize += (c != 0);
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}
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else
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{
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mp_srcptr up = wp;
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mp_size_t usize = wsize;
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if (mpn_cmp_twosizes_lt (up,usize, tp,tsize))
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{
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up = tp;
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usize = tsize;
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tp = wp;
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tsize = wsize;
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wsize = usize;
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wsize_signed = -wsize_signed;
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}
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ASSERT_NOCARRY (mpn_sub (wp, up,usize, tp,tsize));
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wsize = usize;
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MPN_NORMALIZE (wp, wsize);
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}
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SIZ(w) = (wsize_signed >= 0 ? wsize : -wsize);
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TMP_FREE;
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}
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void
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mpz_addmul (mpz_ptr w, mpz_srcptr u, mpz_srcptr v)
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{
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mpz_aorsmul (w, u, v, (mp_size_t) 0);
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}
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void
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mpz_submul (mpz_ptr w, mpz_srcptr u, mpz_srcptr v)
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{
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mpz_aorsmul (w, u, v, (mp_size_t) -1);
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}
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