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

   1 /* mpz_get_si(integer) -- Return the least significant digit from INTEGER.
   2
   3 Copyright 1991, 1993-1995, 2000-2002, 2006, 2012 Free Software Foundation, Inc.
   4
   5 This file is part of the GNU MP Library.
   6
   7 The GNU MP Library is free software; you can redistribute it and/or modify
   8 it under the terms of either:
   9
  10   * the GNU Lesser General Public License as published by the Free
  11     Software Foundation; either version 3 of the License, or (at your
  12     option) any later version.
  13
  14 or
  15
  16   * the GNU General Public License as published by the Free Software
  17     Foundation; either version 2 of the License, or (at your option) any
  18     later version.
  19
  20 or both in parallel, as here.
  21
  22 The GNU MP Library is distributed in the hope that it will be useful, but
  23 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  24 or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  25 for more details.
  26
  27 You should have received copies of the GNU General Public License and the
  28 GNU Lesser General Public License along with the GNU MP Library.  If not,
  29 see https://www.gnu.org/licenses/.  */
  30
  31 #include "gmp.h"
  32 #include "gmp-impl.h"
  33
  34 signed long int
  35 mpz_get_si (mpz_srcptr z) __GMP_NOTHROW
  36 {
  37   mp_ptr zp = PTR (z);
  38   mp_size_t size = SIZ (z);
  39   mp_limb_t zl = zp[0];
  40
  41 #if GMP_NAIL_BITS != 0
  42   if (ULONG_MAX > GMP_NUMB_MAX && ABS (size) >= 2)
  43     zl |= zp[1] << GMP_NUMB_BITS;
  44 #endif
  45
  46   if (size > 0)
  47     return zl & LONG_MAX;
  48   else if (size < 0)
  49     /* This expression is necessary to properly handle 0x80000000 */
  50     return -1 - (long) ((zl - 1) & LONG_MAX);
  51   else
  52     return 0;
  53 }