resource.c

/* resource.c
 *
 * External resources associated with a connection, for instance
 * processes and ports. Used to kill or release the resource in
 * question when the connection dies.
 *
 * $Id$ */

/* lsh, an implementation of the ssh protocol
 *
 * Copyright (C) 1998 Niels Mller
 *
 * 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 2 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, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include "resource.h"

#include "gc.h"
#include "werror.h"
#include "xalloc.h"

#include <assert.h>

/* Prototypes */

void dont_free_live_resource(int alive);

#define GABA_DEFINE
#include "resource.h.x"
#undef GABA_DEFINE

/* Forward declarations */

struct resource_node;

void do_mark_resources(struct resource_node **q,
		       void (*mark)(struct lsh_object *o));

void do_free_resources(struct resource_node **q);

#include "resource.c.x"


/* Sanity check */

/* NOTE: This happens normally during gc_final. Under all other
 * circumstances, it's a serious error. */
/* FIXME: Is this still true? */
void
dont_free_live_resource(int alive)
{
  if (alive)
    {
#if 0 && DEBUG_ALLOC
      if (gc_final_p)
	verbose("dont_free_live_resource: "
		"final collection of a live resource!\n");
      else
#endif
	fatal("dont_free_live_resource: "
	      "garbage collecting a live resource!\n");
    }
}

/* For resources that are only marked as dead, and taken care of
 * later. */
static void
do_resource_kill(struct resource *self)
{ self->alive = 0; }

void
init_resource(struct resource *self,
	      void (*k)(struct resource *))
{
  self->alive = 1;
  self->kill = k ? k : do_resource_kill;
}

/* The behaviour of a resource list is somewhat similar to
 * a weak list. Nodes that are dead are unlinked automatically,
 * so that they can be garbage collected. */

struct resource_node
{
  struct resource_node *next;
  struct resource *resource;
};

/* Works as a weak list of resources. */
/* GABA:
   (class
     (name concrete_resource_list)
     (super resource_list)
     (vars
       (q indirect-special "struct resource_node *"
                           do_mark_resources do_free_resources)))
*/

/* Loop over the resources, mark the living and unlink the dead. */
void
do_mark_resources(struct resource_node **q,
		  void (*mark)(struct lsh_object *o))
{
  struct resource_node *n;
  
  while ( (n = *q) )
    {
      if (n->resource->alive)
	{
	  mark(&n->resource->super);
	  q = &n->next;
	}
      else
	{
	  *q = n->next;
	  lsh_space_free(n);
	}
    }
}

/* Free the list. */
void
do_free_resources(struct resource_node **q)
{
  struct resource_node *n;

  for (n = *q; n; )
    {
      struct resource_node *old = n;
      n = n->next;
      lsh_space_free(old);
    }
}


static void
do_remember_resource(struct resource_list *s,
		     struct resource *resource)
{
  CAST(concrete_resource_list, self, s);
  struct resource_node *n;

  if (!self->super.super.alive)
    {
      werror("do_remember_resource: resource list is already dead.\n");
      KILL_RESOURCE(resource);
      return;
    }
  
  NEW_SPACE(n);

  n->resource = resource;
  n->next = self->q;
  self->q = n;
}

static void
do_kill_all(struct resource *s)
{
  CAST(concrete_resource_list, self, s);
  struct resource_node *n;

  for (n = self->q; n; )
    {
      CAST_SUBTYPE(resource, r, n->resource);
      struct resource_node *old = n;

      KILL_RESOURCE(r);
      n = n->next;

      lsh_space_free(old);
    }
  self->q = NULL;
  self->super.super.alive = 0;
}
  
struct resource_list *
make_resource_list(void)
{
  NEW(concrete_resource_list, self);
  init_resource(&self->super.super, do_kill_all);

  trace("make_resource_list: created %xi\n", self);
  self->super.remember = do_remember_resource;
  
  self->q = NULL;

  return &self->super;
}