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/* Vector API for GDB.

   Copyright (C) 2004, 2005, 2006, 2007, 2008 Free Software Foundation, Inc.

   Contributed by Nathan Sidwell <nathan@codesourcery.com>

   This file is part of GDB.

   This program is free software; you can redistribute it and/or modify

   it under the terms of the GNU General Public License as published by

   the Free Software Foundation; either version 3 of the License, or

   (at your option) any later version.

   This program is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License

   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

#include "defs.h"

#include "vec.h"

struct vec_prefix

{

  unsigned num;

  unsigned alloc;

  void *vec[1];

};

/* Calculate the new ALLOC value, making sure that abs(RESERVE) slots

   are free.  If RESERVE < 0 grow exactly, otherwise grow

   exponentially.  */

static inline unsigned

calculate_allocation (const struct vec_prefix *pfx, int reserve)

{

  unsigned alloc = 0;

  unsigned num = 0;

  if (pfx)

    {

      alloc = pfx->alloc;

      num = pfx->num;

    }

  else if (!reserve)

    /* If there's no prefix, and we've not requested anything, then we

       will create a NULL vector.  */

    return 0;

  /* We must have run out of room.  */

  gdb_assert (alloc - num < (unsigned)(reserve < 0 ? -reserve : reserve));

  if (reserve < 0)

    /* Exact size.  */

    alloc = num + -reserve;

  else

    {

      /* Exponential growth. */

      if (!alloc)

        alloc = 4;

      else if (alloc < 16)

        /* Double when small.  */

        alloc = alloc * 2;

      else

        /* Grow slower when large.  */

        alloc = (alloc * 3 / 2);

      /* If this is still too small, set it to the right size. */

      if (alloc < num + reserve)

        alloc = num + reserve;

    }

  return alloc;

}

/* Ensure there are at least abs(RESERVE) free slots in VEC.  If

   RESERVE < 0 grow exactly, else grow exponentially.  As a special

   case, if VEC is NULL, and RESERVE is 0, no vector will be created. */

void *

vec_p_reserve (void *vec, int reserve)

{

  return vec_o_reserve (vec, reserve,

                        offsetof (struct vec_prefix, vec), sizeof (void *));

}

/* As vec_p_reserve, but for object vectors.  The vector's trailing

   array is at VEC_OFFSET offset and consists of ELT_SIZE sized

   elements.  */

void *

vec_o_reserve (void *vec, int reserve, size_t vec_offset, size_t elt_size)

{

  struct vec_prefix *pfx = vec;

  unsigned alloc = calculate_allocation (pfx, reserve);

  if (!alloc)

    return NULL;

  vec = xrealloc (vec, vec_offset + alloc * elt_size);

  ((struct vec_prefix *)vec)->alloc = alloc;

  if (!pfx)

    ((struct vec_prefix *)vec)->num = 0;

  return vec;

}

#if 0

/* Example uses.  */

DEF_VEC_I (int);

typedef struct X

{

  int i;

} obj_t;

typedef obj_t *ptr_t;

DEF_VEC_P (ptr_t);

DEF_VEC_O (obj_t);

#endif