contrib/gmp/mpz/mul.c

   1 /* mpz_mul -- Multiply two integers.
   2
   3 Copyright 1991, 1993, 1994, 1996, 2000, 2001, 2005 Free Software Foundation,
   4 Inc.
   5
   6 This file is part of the GNU MP Library.
   7
   8 The GNU MP Library is free software; you can redistribute it and/or modify
   9 it under the terms of the GNU Lesser General Public License as published by
  10 the Free Software Foundation; either version 3 of the License, or (at your
  11 option) any later version.
  12
  13 The GNU MP Library is distributed in the hope that it will be useful, but
  14 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  15 or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
  16 License for more details.
  17
  18 You should have received a copy of the GNU Lesser General Public License
  19 along with the GNU MP Library.  If not, see http://www.gnu.org/licenses/.  */
  20
  21 #include <stdio.h> /* for NULL */
  22 #include "gmp.h"
  23 #include "gmp-impl.h"
  24 #ifdef BERKELEY_MP
  25 #include "mp.h"
  26 #endif
  27
  28
  29 void
  30 #ifndef BERKELEY_MP
  31 mpz_mul (mpz_ptr w, mpz_srcptr u, mpz_srcptr v)
  32 #else /* BERKELEY_MP */
  33 mult (mpz_srcptr u, mpz_srcptr v, mpz_ptr w)
  34 #endif /* BERKELEY_MP */
  35 {
  36   mp_size_t usize = u->_mp_size;
  37   mp_size_t vsize = v->_mp_size;
  38   mp_size_t wsize;
  39   mp_size_t sign_product;
  40   mp_ptr up, vp;
  41   mp_ptr wp;
  42   mp_ptr free_me;
  43   size_t free_me_size;
  44   mp_limb_t cy_limb;
  45   TMP_DECL;
  46
  47   sign_product = usize ^ vsize;
  48   usize = ABS (usize);
  49   vsize = ABS (vsize);
  50
  51   if (usize < vsize)
  52     {
  53       MPZ_SRCPTR_SWAP (u, v);
  54       MP_SIZE_T_SWAP (usize, vsize);
  55     }
  56
  57   if (vsize == 0)
  58     {
  59       SIZ(w) = 0;
  60       return;
  61     }
  62
  63 #if HAVE_NATIVE_mpn_mul_2
  64   if (vsize <= 2)
  65     {
  66       MPZ_REALLOC (w, usize+vsize);
  67       wp = PTR(w);
  68       if (vsize == 1)
  69         cy_limb = mpn_mul_1 (wp, PTR(u), usize, PTR(v)[0]);
  70       else
  71         {
  72           cy_limb = mpn_mul_2 (wp, PTR(u), usize, PTR(v));
  73           usize++;
  74         }
  75       wp[usize] = cy_limb;
  76       usize += (cy_limb != 0);
  77       SIZ(w) = (sign_product >= 0 ? usize : -usize);
  78       return;
  79     }
  80 #else
  81   if (vsize == 1)
  82     {
  83       MPZ_REALLOC (w, usize+1);
  84       wp = PTR(w);
  85       cy_limb = mpn_mul_1 (wp, PTR(u), usize, PTR(v)[0]);
  86       wp[usize] = cy_limb;
  87       usize += (cy_limb != 0);
  88       SIZ(w) = (sign_product >= 0 ? usize : -usize);
  89       return;
  90     }
  91 #endif
  92
  93   TMP_MARK;
  94   free_me = NULL;
  95   up = u->_mp_d;
  96   vp = v->_mp_d;
  97   wp = w->_mp_d;
  98
  99   /* Ensure W has space enough to store the result.  */
 100   wsize = usize + vsize;
 101   if (w->_mp_alloc < wsize)
 102     {
 103       if (wp == up || wp == vp)
 104         {
 105           free_me = wp;
 106           free_me_size = w->_mp_alloc;
 107         }
 108       else
 109         (*__gmp_free_func) (wp, w->_mp_alloc * BYTES_PER_MP_LIMB);
 110
 111       w->_mp_alloc = wsize;
 112       wp = (mp_ptr) (*__gmp_allocate_func) (wsize * BYTES_PER_MP_LIMB);
 113       w->_mp_d = wp;
 114     }
 115   else
 116     {
 117       /* Make U and V not overlap with W.  */
 118       if (wp == up)
 119         {
 120           /* W and U are identical.  Allocate temporary space for U.  */
 121           up = (mp_ptr) TMP_ALLOC (usize * BYTES_PER_MP_LIMB);
 122           /* Is V identical too?  Keep it identical with U.  */
 123           if (wp == vp)
 124             vp = up;
 125           /* Copy to the temporary space.  */
 126           MPN_COPY (up, wp, usize);
 127         }
 128       else if (wp == vp)
 129         {
 130           /* W and V are identical.  Allocate temporary space for V.  */
 131           vp = (mp_ptr) TMP_ALLOC (vsize * BYTES_PER_MP_LIMB);
 132           /* Copy to the temporary space.  */
 133           MPN_COPY (vp, wp, vsize);
 134         }
 135     }
 136
 137   cy_limb = mpn_mul (wp, up, usize, vp, vsize);
 138   wsize = usize + vsize;
 139   wsize -= cy_limb == 0;
 140
 141   w->_mp_size = sign_product < 0 ? -wsize : wsize;
 142   if (free_me != NULL)
 143     (*__gmp_free_func) (free_me, free_me_size * BYTES_PER_MP_LIMB);
 144   TMP_FREE;
 145 }