/* -*-C-*-

$Id: transact.c,v 1.9 2007/01/05 21:19:25 cph Exp $

Copyright (C) 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994,
    1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
    2006, 2007 Massachusetts Institute of Technology

This file is part of MIT/GNU Scheme.

MIT/GNU Scheme 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.

MIT/GNU Scheme 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 MIT/GNU Scheme; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301,
USA.

*/

#include <stdio.h>
#include "config.h"
#include "outf.h"
#include "dstack.h"

static void
DEFUN (error, (procedure_name, message),
       CONST char * procedure_name AND
       CONST char * message)
{
  outf_fatal ("%s: %s\n", procedure_name, message);
  outf_flush_fatal ();
  abort ();
}

enum transaction_state { active, aborting, committing };

struct transaction
{
  PTR checkpoint;
  enum transaction_state state;
};

static struct transaction * current_transaction;

static void
DEFUN (guarantee_current_transaction, (proc), CONST char * proc)
{
  if (current_transaction == 0)
    error (proc, "no transaction");
  switch (current_transaction -> state)
    {
    case committing: error (proc, "commit in progress"); break;
    case aborting: error (proc, "abort in progress"); break;
    case active: break;
    }
}

void
DEFUN_VOID (transaction_initialize)
{
  current_transaction = 0;
}

void
DEFUN_VOID (transaction_begin)
{
  PTR checkpoint = dstack_position;
  struct transaction * transaction =
    (dstack_alloc (sizeof (struct transaction)));
  (transaction -> checkpoint) = checkpoint;
  (transaction -> state) = active;
  dstack_bind ((&current_transaction), transaction);
}

void
DEFUN_VOID (transaction_abort)
{
  guarantee_current_transaction ("transaction_abort");
  (current_transaction -> state) = aborting;
  dstack_set_position (current_transaction -> checkpoint);
}

void
DEFUN_VOID (transaction_commit)
{
  guarantee_current_transaction ("transaction_commit");
  (current_transaction -> state) = committing;
  dstack_set_position (current_transaction -> checkpoint);
}

struct action
{
  enum transaction_action_type type;
  void EXFUN ((*procedure), (PTR environment));
  PTR environment;
};

static void
DEFUN (execute_action, (action), PTR action)
{
  if ((((struct action *) action) -> type) !=
      (((current_transaction -> state) == committing)
       ? tat_abort : tat_commit))
    (* (((struct action *) action) -> procedure))
      (((struct action *) action) -> environment);
}

void
DEFUN (transaction_record_action, (type, procedure, environment),
       enum transaction_action_type type AND
       void EXFUN ((*procedure), (PTR environment)) AND
       PTR environment)
{
  guarantee_current_transaction ("transaction_record_action");
  {
    struct action * action = (dstack_alloc (sizeof (struct action)));
    (action -> type) = type;
    (action -> procedure) = procedure;
    (action -> environment) = environment;
    dstack_protect (execute_action, action);
  }
}
