freebsd/contrib/libgmp/stack-alloc.c

/* Stack allocation routines.  This is intended for machines without support
   for the `alloca' function.

Copyright (C) 1996 Free Software Foundation, Inc.

This file is part of the GNU MP Library.

The GNU MP Library is free software; you can redistribute it and/or modify
it under the terms of the GNU Library General Public License as published by
the Free Software Foundation; either version 2 of the License, or (at your
option) any later version.

The GNU MP Library 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 Library General Public
License for more details.

You should have received a copy of the GNU Library General Public License
along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
MA 02111-1307, USA. */

#include "stack-alloc.h"

typedef struct tmp_stack tmp_stack;

void *malloc ();
static unsigned long max_total_allocation = 0;
static unsigned long current_total_allocation = 0;

static tmp_stack xxx = {&xxx, &xxx, 0};
static tmp_stack *current = &xxx;

/* Allocate a block of exactly <size> bytes.  This should only be called
   through the TMP_ALLOC macro, which takes care of rounding/alignment.  */
void *
__tmp_alloc (size)
     unsigned long size;
{
  void *this;

  if (size > (char *) current->end - (char *) current->alloc_point)
    {
      void *chunk;
      tmp_stack *header;
      unsigned long chunk_size;
      unsigned long now;

      /* Allocate a chunk that makes the total current allocation somewhat
	 larger than the maximum allocation ever.  If size is very large, we
	 allocate that much.  */

      now = current_total_allocation + size;
      if (now > max_total_allocation)
	{
	  /* We need more temporary memory than ever before.  Increase
	     for future needs.  */
	  now = now * 3 / 2;
	  chunk_size = now - current_total_allocation + sizeof (tmp_stack);
	  current_total_allocation = now;
	  max_total_allocation = current_total_allocation;
	}
      else
	{
	  chunk_size = max_total_allocation - current_total_allocation + sizeof (tmp_stack);
	  current_total_allocation = max_total_allocation;
	}

      chunk = malloc (chunk_size);
      header = chunk;
      header->end = (char *) chunk + chunk_size;
      header->alloc_point = (char *) chunk + sizeof (tmp_stack);
      header->prev = current;
      current = header;
    }

  this = current->alloc_point;
  current->alloc_point = (char *) this + size;
  return this;
}

/* Typically called at function entry.  <mark> is assigned so that __tmp_free
   can later be used to reclaim all subsecuently allocated storage.  */
void
__tmp_mark (mark)
     tmp_marker *mark;
{
  mark->which_chunk = current;
  mark->alloc_point = current->alloc_point;
}

/* Free everything allocated since <mark> was assigned by __tmp_mark */
void
__tmp_free (mark)
     tmp_marker *mark;
{
  while (mark->which_chunk != current)
    {
      tmp_stack *tmp;

      tmp = current;
      current = tmp->prev;
      current_total_allocation -= (((char *) (tmp->end) - (char *) tmp)
				   - sizeof (tmp_stack));
      free (tmp);
    }
  current->alloc_point = mark->alloc_point;
}