gcc/gcc/alloc-pool.c

/* Functions to support a pool of allocatable objects.
   Copyright (C) 1987, 1997, 1998, 1999, 2000, 2001, 2003
   Free Software Foundation, Inc.
   Contributed by Daniel Berlin <dan@cgsoftware.com>

This file is part of GCC.

GCC 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 2, or (at your option) any later
version.

GCC 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 GCC; see the file COPYING.  If not, write to the Free
Software Foundation, 59 Temple Place - Suite 330, Boston, MA
02111-1307, USA.  */

#include "config.h"
#include "system.h"
#include "alloc-pool.h"

/* Redefine abort to report an internal error w/o coredump, and
   reporting the location of the error in the source file.  This logic
   is duplicated in rtl.h and tree.h because every file that needs the
   special abort includes one or both.  toplev.h gets too few files,
   system.h gets too many.  */

extern void fancy_abort (const char *, int, const char *)
    ATTRIBUTE_NORETURN;
#define abort() fancy_abort (__FILE__, __LINE__, __FUNCTION__)

#define align_four(x) (((x+3) >> 2) << 2)
#define align_eight(x) (((x+7) >> 3) << 3)

/* The internal allocation object.  */
typedef struct allocation_object_def
{
#ifdef ENABLE_CHECKING
  /* The ID of alloc pool which the object was allocated from.  */
  ALLOC_POOL_ID_TYPE id;
#endif

  union
    {
      /* The data of the object.  */
      char data[1];

      /* Because we want any type of data to be well aligned after the ID,
	 the following elements are here.  They are never accessed so
	 the allocated object may be even smaller than this structure.  */
      char *align_p;
      HOST_WIDEST_INT align_i;
      long double align_ld;
    } u;
} allocation_object;

/* Convert a pointer to allocation_object from a pointer to user data.  */
#define ALLOCATION_OBJECT_PTR_FROM_USER_PTR(X)				\
   ((allocation_object *) (((char *) (X))				\
			   - offsetof (allocation_object, u.data)))

/* Convert a pointer to user data from a pointer to allocation_object.  */
#define USER_PTR_FROM_ALLOCATION_OBJECT_PTR(X)				\
   ((void *) (((allocation_object *) (X))->u.data))

#ifdef ENABLE_CHECKING
/* Last used ID.  */
static ALLOC_POOL_ID_TYPE last_id;
#endif

/* Create a pool of things of size SIZE, with NUM in each block we
   allocate.  */

alloc_pool
create_alloc_pool (const char *name, size_t size, size_t num)
{
  alloc_pool pool;
  size_t pool_size, header_size;

  if (!name)
    abort ();

  /* Make size large enough to store the list header.  */
  if (size < sizeof (alloc_pool_list))
    size = sizeof (alloc_pool_list);

  /* Now align the size to a multiple of 4.  */
  size = align_four (size);

#ifdef ENABLE_CHECKING
  /* Add the aligned size of ID.  */
  size += offsetof (allocation_object, u.data);
#endif

  /* Um, we can't really allocate 0 elements per block.  */
  if (num == 0)
    abort ();

  /* Find the size of the pool structure, and the name.  */
  pool_size = sizeof (struct alloc_pool_def);

  /* and allocate that much memory.  */
  pool = xmalloc (pool_size);

  /* Now init the various pieces of our pool structure.  */
  pool->name = xstrdup (name);
  pool->elt_size = size;
  pool->elts_per_block = num;

  /* List header size should be a multiple of 8 */
  header_size = align_eight (sizeof (struct alloc_pool_list_def));

  pool->block_size = (size * num) + header_size;
  pool->free_list = NULL;
  pool->elts_allocated = 0;
  pool->elts_free = 0;
  pool->blocks_allocated = 0;
  pool->block_list = NULL;

#ifdef ENABLE_CHECKING
  /* Increase the last used ID and use it for this pool.
     ID == 0 is used for free elements of pool so skip it.  */
  last_id++;
  if (last_id == 0)
    last_id++;

  pool->id = last_id;
#endif

  return (pool);
}

/* Free all memory allocated for the given memory pool.  */
void
free_alloc_pool (alloc_pool pool)
{
  alloc_pool_list block, next_block;

#ifdef ENABLE_CHECKING
  if (!pool)
    abort ();
#endif

  /* Free each block allocated to the pool.  */
  for (block = pool->block_list; block != NULL; block = next_block)
    {
      next_block = block->next;
      free (block);
    }
  /* Lastly, free the pool and the name.  */
  free (pool->name);
  free (pool);
}

/* Allocates one element from the pool specified.  */
void *
pool_alloc (alloc_pool pool)
{
  alloc_pool_list header;
  char *block;

#ifdef ENABLE_CHECKING
  if (!pool)
    abort ();
#endif

  /* If there are no more free elements, make some more!.  */
  if (!pool->free_list)
    {
      size_t i;
      alloc_pool_list block_header;

      /* Make the block.  */
      block = xmalloc (pool->block_size);
      block_header = (alloc_pool_list) block;
      block += align_eight (sizeof (struct alloc_pool_list_def));

      /* Throw it on the block list.  */
      block_header->next = pool->block_list;
      pool->block_list = block_header;

      /* Now put the actual block pieces onto the free list.  */
      for (i = 0; i < pool->elts_per_block; i++, block += pool->elt_size)
      {
#ifdef ENABLE_CHECKING
	/* Mark the element to be free.  */
	((allocation_object *) block)->id = 0;
#endif
        header = (alloc_pool_list) USER_PTR_FROM_ALLOCATION_OBJECT_PTR (block);
        header->next = pool->free_list;
        pool->free_list = header;
      }
      /* Also update the number of elements we have free/allocated, and
         increment the allocated block count.  */
      pool->elts_allocated += pool->elts_per_block;
      pool->elts_free += pool->elts_per_block;
      pool->blocks_allocated += 1;
    }

  /* Pull the first free element from the free list, and return it.  */
  header = pool->free_list;
  pool->free_list = header->next;
  pool->elts_free--;

#ifdef ENABLE_CHECKING
  /* Set the ID for element.  */
  ALLOCATION_OBJECT_PTR_FROM_USER_PTR (header)->id = pool->id;
#endif

  return ((void *) header);
}

/* Puts PTR back on POOL's free list.  */
void
pool_free (alloc_pool pool, void *ptr)
{
  alloc_pool_list header;

#ifdef ENABLE_CHECKING
  if (!ptr)
    abort ();

  /* Check whether the PTR was allocated from POOL.  */
  if (pool->id != ALLOCATION_OBJECT_PTR_FROM_USER_PTR (ptr)->id)
    abort ();

  /* Mark the element to be free.  */
  ALLOCATION_OBJECT_PTR_FROM_USER_PTR (ptr)->id = 0;
#else
  /* Check if we free more than we allocated, which is Bad (TM).  */
  if (pool->elts_free + 1 > pool->elts_allocated)
    abort ();
#endif

  header = (alloc_pool_list) ptr;
  header->next = pool->free_list;
  pool->free_list = header;
  pool->elts_free++;
}