source/libs/gmp/gmp-src/mpz/mul.c

   1 /* mpz_mul -- Multiply two integers.
   2
   3 Copyright 1991, 1993, 1994, 1996, 2000, 2001, 2005, 2009, 2011, 2012 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 either:
  10
  11   * the GNU Lesser General Public License as published by the Free
  12     Software Foundation; either version 3 of the License, or (at your
  13     option) any later version.
  14
  15 or
  16
  17   * the GNU General Public License as published by the Free Software
  18     Foundation; either version 2 of the License, or (at your option) any
  19     later version.
  20
  21 or both in parallel, as here.
  22
  23 The GNU MP Library is distributed in the hope that it will be useful, but
  24 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  25 or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  26 for more details.
  27
  28 You should have received copies of the GNU General Public License and the
  29 GNU Lesser General Public License along with the GNU MP Library.  If not,
  30 see https://www.gnu.org/licenses/.  */
  31
  32 #include <stdio.h> /* for NULL */
  33 #include "gmp.h"
  34 #include "gmp-impl.h"
  35
  36
  37 void
  38 mpz_mul (mpz_ptr w, mpz_srcptr u, mpz_srcptr v)
  39 {
  40   mp_size_t usize;
  41   mp_size_t vsize;
  42   mp_size_t wsize;
  43   mp_size_t sign_product;
  44   mp_ptr up, vp;
  45   mp_ptr wp;
  46   mp_ptr free_me;
  47   size_t free_me_size;
  48   mp_limb_t cy_limb;
  49   TMP_DECL;
  50
  51   usize = SIZ (u);
  52   vsize = SIZ (v);
  53   sign_product = usize ^ vsize;
  54   usize = ABS (usize);
  55   vsize = ABS (vsize);
  56
  57   if (usize < vsize)
  58     {
  59       MPZ_SRCPTR_SWAP (u, v);
  60       MP_SIZE_T_SWAP (usize, vsize);
  61     }
  62
  63   if (vsize == 0)
  64     {
  65       SIZ (w) = 0;
  66       return;
  67     }
  68
  69 #if HAVE_NATIVE_mpn_mul_2
  70   if (vsize <= 2)
  71     {
  72       wp = MPZ_REALLOC (w, usize+vsize);
  73       if (vsize == 1)
  74         cy_limb = mpn_mul_1 (wp, PTR (u), usize, PTR (v)[0]);
  75       else
  76         {
  77           cy_limb = mpn_mul_2 (wp, PTR (u), usize, PTR (v));
  78           usize++;
  79         }
  80       wp[usize] = cy_limb;
  81       usize += (cy_limb != 0);
  82       SIZ (w) = (sign_product >= 0 ? usize : -usize);
  83       return;
  84     }
  85 #else
  86   if (vsize == 1)
  87     {
  88       wp = MPZ_REALLOC (w, usize+1);
  89       cy_limb = mpn_mul_1 (wp, PTR (u), usize, PTR (v)[0]);
  90       wp[usize] = cy_limb;
  91       usize += (cy_limb != 0);
  92       SIZ (w) = (sign_product >= 0 ? usize : -usize);
  93       return;
  94     }
  95 #endif
  96
  97   TMP_MARK;
  98   free_me = NULL;
  99   up = PTR (u);
 100   vp = PTR (v);
 101   wp = PTR (w);
 102
 103   /* Ensure W has space enough to store the result.  */
 104   wsize = usize + vsize;
 105   if (ALLOC (w) < wsize)
 106     {
 107       if (wp == up || wp == vp)
 108         {
 109           free_me = wp;
 110           free_me_size = ALLOC (w);
 111         }
 112       else
 113         (*__gmp_free_func) (wp, (size_t) ALLOC (w) * GMP_LIMB_BYTES);
 114
 115       ALLOC (w) = wsize;
 116       wp = __GMP_ALLOCATE_FUNC_LIMBS (wsize);
 117       PTR (w) = wp;
 118     }
 119   else
 120     {
 121       /* Make U and V not overlap with W.  */
 122       if (wp == up)
 123         {
 124           /* W and U are identical.  Allocate temporary space for U.  */
 125           up = TMP_ALLOC_LIMBS (usize);
 126           /* Is V identical too?  Keep it identical with U.  */
 127           if (wp == vp)
 128             vp = up;
 129           /* Copy to the temporary space.  */
 130           MPN_COPY (up, wp, usize);
 131         }
 132       else if (wp == vp)
 133         {
 134           /* W and V are identical.  Allocate temporary space for V.  */
 135           vp = TMP_ALLOC_LIMBS (vsize);
 136           /* Copy to the temporary space.  */
 137           MPN_COPY (vp, wp, vsize);
 138         }
 139     }
 140
 141   if (up == vp)
 142     {
 143       mpn_sqr (wp, up, usize);
 144       cy_limb = wp[wsize - 1];
 145     }
 146   else
 147     {
 148       cy_limb = mpn_mul (wp, up, usize, vp, vsize);
 149     }
 150
 151   wsize -= cy_limb == 0;
 152
 153   SIZ (w) = sign_product < 0 ? -wsize : wsize;
 154   if (free_me != NULL)
 155     (*__gmp_free_func) (free_me, free_me_size * GMP_LIMB_BYTES);
 156   TMP_FREE;
 157 }