contrib/gmp/mpz/mul.c

   1 /* mpz_mul -- Multiply two integers.
   2
   3 Copyright 1991, 1993, 1994, 1996, 2000, 2001, 2005, 2009, 2011 Free
   4 Software Foundation, 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;
  37   mp_size_t vsize;
  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   usize = SIZ (u);
  48   vsize = SIZ (v);
  49   sign_product = usize ^ vsize;
  50   usize = ABS (usize);
  51   vsize = ABS (vsize);
  52
  53   if (usize < vsize)
  54     {
  55       MPZ_SRCPTR_SWAP (u, v);
  56       MP_SIZE_T_SWAP (usize, vsize);
  57     }
  58
  59   if (vsize == 0)
  60     {
  61       SIZ(w) = 0;
  62       return;
  63     }
  64
  65 #if HAVE_NATIVE_mpn_mul_2
  66   if (vsize <= 2)
  67     {
  68       MPZ_REALLOC (w, usize+vsize);
  69       wp = PTR(w);
  70       if (vsize == 1)
  71         cy_limb = mpn_mul_1 (wp, PTR(u), usize, PTR(v)[0]);
  72       else
  73         {
  74           cy_limb = mpn_mul_2 (wp, PTR(u), usize, PTR(v));
  75           usize++;
  76         }
  77       wp[usize] = cy_limb;
  78       usize += (cy_limb != 0);
  79       SIZ(w) = (sign_product >= 0 ? usize : -usize);
  80       return;
  81     }
  82 #else
  83   if (vsize == 1)
  84     {
  85       MPZ_REALLOC (w, usize+1);
  86       wp = PTR(w);
  87       cy_limb = mpn_mul_1 (wp, PTR(u), usize, PTR(v)[0]);
  88       wp[usize] = cy_limb;
  89       usize += (cy_limb != 0);
  90       SIZ(w) = (sign_product >= 0 ? usize : -usize);
  91       return;
  92     }
  93 #endif
  94
  95   TMP_MARK;
  96   free_me = NULL;
  97   up = PTR(u);
  98   vp = PTR(v);
  99   wp = PTR(w);
 100
 101   /* Ensure W has space enough to store the result.  */
 102   wsize = usize + vsize;
 103   if (ALLOC(w) < wsize)
 104     {
 105       if (wp == up || wp == vp)
 106         {
 107           free_me = wp;
 108           free_me_size = ALLOC(w);
 109         }
 110       else
 111         (*__gmp_free_func) (wp, ALLOC(w) * BYTES_PER_MP_LIMB);
 112
 113       ALLOC(w) = wsize;
 114       wp = (mp_ptr) (*__gmp_allocate_func) (wsize * BYTES_PER_MP_LIMB);
 115       PTR(w) = wp;
 116     }
 117   else
 118     {
 119       /* Make U and V not overlap with W.  */
 120       if (wp == up)
 121         {
 122           /* W and U are identical.  Allocate temporary space for U.  */
 123           up = TMP_ALLOC_LIMBS (usize);
 124           /* Is V identical too?  Keep it identical with U.  */
 125           if (wp == vp)
 126             vp = up;
 127           /* Copy to the temporary space.  */
 128           MPN_COPY (up, wp, usize);
 129         }
 130       else if (wp == vp)
 131         {
 132           /* W and V are identical.  Allocate temporary space for V.  */
 133           vp = TMP_ALLOC_LIMBS (vsize);
 134           /* Copy to the temporary space.  */
 135           MPN_COPY (vp, wp, vsize);
 136         }
 137     }
 138
 139   if (up == vp)
 140     {
 141       mpn_sqr (wp, up, usize);
 142       cy_limb = wp[wsize - 1];
 143     }
 144   else
 145     {
 146       cy_limb = mpn_mul (wp, up, usize, vp, vsize);
 147     }
 148
 149   wsize -= cy_limb == 0;
 150
 151   SIZ(w) = sign_product < 0 ? -wsize : wsize;
 152   if (free_me != NULL)
 153     (*__gmp_free_func) (free_me, free_me_size * BYTES_PER_MP_LIMB);
 154   TMP_FREE;
 155 }