1  /* mpz_add_ui, mpz_sub_ui -- Add or subtract an mpz_t and an unsigned
       2     one-word integer.
       3  
       4  Copyright 1991, 1993, 1994, 1996, 1999-2002, 2004, 2012, 2013, 2015,
       5  2020 Free Software Foundation, Inc.
       6  
       7  This file is part of the GNU MP Library.
       8  
       9  The GNU MP Library is free software; you can redistribute it and/or modify
      10  it under the terms of either:
      11  
      12    * the GNU Lesser General Public License as published by the Free
      13      Software Foundation; either version 3 of the License, or (at your
      14      option) any later version.
      15  
      16  or
      17  
      18    * the GNU General Public License as published by the Free Software
      19      Foundation; either version 2 of the License, or (at your option) any
      20      later version.
      21  
      22  or both in parallel, as here.
      23  
      24  The GNU MP Library is distributed in the hope that it will be useful, but
      25  WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
      26  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
      27  for more details.
      28  
      29  You should have received copies of the GNU General Public License and the
      30  GNU Lesser General Public License along with the GNU MP Library.  If not,
      31  see https://www.gnu.org/licenses/.  */
      32  
      33  #include "gmp-impl.h"
      34  
      35  
      36  #ifdef OPERATION_add_ui
      37  #define FUNCTION          mpz_add_ui
      38  #define FUNCTION2         mpz_add
      39  #define VARIATION_CMP     >=
      40  #define VARIATION_NEG
      41  #define VARIATION_UNNEG   -
      42  #endif
      43  
      44  #ifdef OPERATION_sub_ui
      45  #define FUNCTION          mpz_sub_ui
      46  #define FUNCTION2         mpz_sub
      47  #define VARIATION_CMP     <
      48  #define VARIATION_NEG     -
      49  #define VARIATION_UNNEG
      50  #endif
      51  
      52  #ifndef FUNCTION
      53  Error, need OPERATION_add_ui or OPERATION_sub_ui
      54  #endif
      55  
      56  
      57  void
      58  FUNCTION (mpz_ptr w, mpz_srcptr u, unsigned long int vval)
      59  {
      60    mp_srcptr up;
      61    mp_ptr wp;
      62    mp_size_t usize, wsize;
      63    mp_size_t abs_usize;
      64  
      65  #if BITS_PER_ULONG > GMP_NUMB_BITS  /* avoid warnings about shift amount */
      66    if (vval > GMP_NUMB_MAX)
      67      {
      68        mpz_t v;
      69        mp_limb_t vl[2];
      70        PTR(v) = vl;
      71        vl[0] = vval & GMP_NUMB_MASK;
      72        vl[1] = vval >> GMP_NUMB_BITS;
      73        SIZ(v) = 2;
      74        FUNCTION2 (w, u, v);
      75        return;
      76      }
      77  #endif
      78  
      79    usize = SIZ (u);
      80    if (usize == 0)
      81      {
      82        MPZ_NEWALLOC (w, 1)[0] = vval;
      83        SIZ (w) = VARIATION_NEG (vval != 0);
      84        return;
      85      }
      86  
      87    abs_usize = ABS (usize);
      88  
      89    if (usize VARIATION_CMP 0)
      90      {
      91        mp_limb_t cy;
      92  
      93        /* If not space for W (and possible carry), increase space.  */
      94        wp = MPZ_REALLOC (w, abs_usize + 1);
      95        /* These must be after realloc (U may be the same as W).  */
      96        up = PTR (u);
      97  
      98        cy = mpn_add_1 (wp, up, abs_usize, (mp_limb_t) vval);
      99        wp[abs_usize] = cy;
     100        wsize = VARIATION_NEG (abs_usize + cy);
     101      }
     102    else
     103      {
     104        /* If not space for W, increase space.  */
     105        wp = MPZ_REALLOC (w, abs_usize);
     106        /* These must be after realloc (U may be the same as W).  */
     107        up = PTR (u);
     108  
     109        /* The signs are different.  Need exact comparison to determine
     110  	 which operand to subtract from which.  */
     111        if (abs_usize == 1 && up[0] < vval)
     112  	{
     113  	  wp[0] = vval - up[0];
     114  	  wsize = VARIATION_NEG 1;
     115  	}
     116        else
     117  	{
     118  	  mpn_sub_1 (wp, up, abs_usize, (mp_limb_t) vval);
     119  	  /* Size can decrease with at most one limb.  */
     120  	  wsize = VARIATION_UNNEG (abs_usize - (wp[abs_usize - 1] == 0));
     121  	}
     122      }
     123  
     124    SIZ (w) = wsize;
     125  }