/* General queue data structure for GDB, the GNU debugger.

   Copyright (C) 2012-2019 Free Software Foundation, Inc.

   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/>.  */

#ifndef QUEUE_H
#define QUEUE_H

/* These macros implement functions and structs for a general queue.
   Macro 'DEFINE_QUEUE_P(TYPEDEF)' is to define the new queue type for
   TYPEDEF', and macro 'DECLARE_QUEUE_P' is to declare external queue
   APIs.  The character P indicates TYPEDEF is a pointer (P).  The
   counterpart on object (O) and integer (I) are not implemented.

   An example of their use would be,

   typedef struct foo
   {} *foo_p;

   DEFINE_QUEUE_P (foo_p);
   // A pointer to a queue of foo pointers.  FOO_XFREE is a destructor
   // function for foo instances in queue.
   QUEUE(foo_p) *foo_queue = QUEUE_alloc (foo_p, foo_xfree);

   foo_p foo_var_p;
   // Enqueue and Dequeue
   QUEUE_enque (foo_p, foo_queue, foo_var_p);
   foo_var_p = QUEUE_deque (foo_p, foo_queue);

   static int visit_foo (QUEUE (foo_p) *q, QUEUE_ITER (foo_p) *iter,
			foo_p f, void *data)
   {
     return 1;
   }
   // Iterate over queue.
   QUEUE_iterate (foo_p, foo_queue, visit_foo, &param);

   QUEUE_free (foo_p, foo_queue);  // Free queue.  */

/* Typical enqueue operation.  Put V into queue Q.  */
#define QUEUE_enque(TYPE, Q, V) queue_ ## TYPE ## _enque ((Q), (V))

/* Typical dequeue operation.  Return head element of queue Q and
   remove it.  Q must not be empty.  */
#define QUEUE_deque(TYPE, Q) queue_ ## TYPE ## _deque (Q)

/* Return the head element, but don't remove it from the queue.
   Q must not be empty.  */
#define QUEUE_peek(TYPE, Q) queue_ ## TYPE ## _peek (Q)

/* Return true if queue Q is empty.  */
#define QUEUE_is_empty(TYPE, Q) queue_ ## TYPE ## _is_empty (Q)

/* Allocate memory for queue.  FREE_FUNC is a function to release the
   data put in each queue element.  */
#define QUEUE_alloc(TYPE, FREE_FUNC) queue_ ## TYPE ## _alloc (FREE_FUNC)

/* Length of queue Q.  */
#define QUEUE_length(TYPE, Q) queue_ ## TYPE ## _length (Q)

/* Free queue Q.  Q's free_func is called once for each element.  */
#define QUEUE_free(TYPE, Q) queue_ ## TYPE ## _free (Q)

/* Iterate over elements in the queue Q and call function OPERATE on
   each element.  It is allowed to remove element by OPERATE.  OPERATE
   returns false to terminate the iteration and true to continue the
   iteration.  Return false if iteration is terminated by function
   OPERATE, otherwise return true.  */
#define QUEUE_iterate(TYPE, Q, OPERATE, PARAM)	\
  queue_ ## TYPE ## _iterate ((Q), (OPERATE), (PARAM))

/* Remove the element per the state of iterator ITER from queue Q.
   Leave the caller to release the data in the queue element.  */
#define QUEUE_remove_elem(TYPE, Q, ITER) \
  queue_ ## TYPE ## _remove_elem ((Q), (ITER))

/* Define a new queue implementation.  */

#define QUEUE(TYPE) struct queue_ ## TYPE
#define QUEUE_ELEM(TYPE) struct queue_elem_ ## TYPE
#define QUEUE_ITER(TYPE) struct queue_iter_ ## TYPE
#define QUEUE_ITER_FUNC(TYPE) queue_ ## TYPE ## _operate_func

#define DEFINE_QUEUE_P(TYPE)			\
QUEUE_ELEM (TYPE)				\
{						\
  QUEUE_ELEM (TYPE) *next;			\
						\
  TYPE data;					\
};						\
						\
/* Queue iterator.  */				\
QUEUE_ITER (TYPE)				\
{						\
  /* The current element during traverse.  */	\
  QUEUE_ELEM (TYPE) *p;			\
  /* The previous element of P.  */		\
  QUEUE_ELEM (TYPE) *prev;			\
};						\
						\
QUEUE(TYPE)					\
{						\
  /*  The head and tail of the queue.  */	\
  QUEUE_ELEM (TYPE) *head;			\
  QUEUE_ELEM (TYPE) *tail;			\
  /* Function to release the data put in each	\
     queue element.  */			\
  void (*free_func) (TYPE);			\
};						\
						\
void									\
queue_ ## TYPE ## _enque (QUEUE (TYPE) *q, TYPE v)			\
{									\
  QUEUE_ELEM (TYPE) *p = XNEW (QUEUE_ELEM (TYPE));			\
									\
  gdb_assert (q != NULL);						\
  p->data = v;								\
  p->next = NULL;							\
  if (q->tail == NULL)							\
    {									\
      q->tail = p;							\
      q->head = p;							\
    }									\
  else									\
    {									\
      q->tail->next = p;						\
      q->tail = p;							\
    }									\
}									\
									\
TYPE									\
queue_ ## TYPE ## _deque (QUEUE (TYPE) *q)				\
{									\
  QUEUE_ELEM (TYPE) *p;						\
  TYPE v;								\
									\
  gdb_assert (q != NULL);						\
  p = q->head;								\
  gdb_assert (p != NULL);						\
									\
  if (q->head == q->tail)						\
    {									\
      q->head = NULL;							\
      q->tail = NULL;							\
    }									\
  else									\
    q->head = q->head->next;						\
									\
  v = p->data;								\
									\
  xfree (p);								\
  return v;								\
}									\
									\
TYPE									\
queue_ ## TYPE ## _peek (QUEUE (TYPE) *q)				\
{									\
  gdb_assert (q != NULL);						\
  gdb_assert (q->head != NULL);					\
  return q->head->data;						\
}									\
									\
int									\
queue_ ## TYPE ## _is_empty (QUEUE (TYPE) *q)				\
{									\
  gdb_assert (q != NULL);						\
  return q->head == NULL;						\
}									\
									\
void									\
queue_ ## TYPE ## _remove_elem (QUEUE (TYPE) *q,			\
				QUEUE_ITER (TYPE) *iter)		\
{									\
  gdb_assert (q != NULL);						\
  gdb_assert (iter != NULL && iter->p != NULL);			\
									\
  if (iter->p == q->head || iter->p == q->tail)			\
    {									\
      if (iter->p == q->head)						\
	q->head = iter->p->next;					\
      if (iter->p == q->tail)						\
	q->tail = iter->prev;						\
    }									\
  else									\
    iter->prev->next = iter->p->next;					\
									\
  xfree (iter->p);							\
  /* Indicate that ITER->p has been deleted from QUEUE q.  */		\
  iter->p = NULL;							\
}									\
									\
int									\
queue_ ## TYPE ## _iterate (QUEUE (TYPE) *q,				\
			    QUEUE_ITER_FUNC (TYPE) operate,		\
			    void *data)				\
{									\
  QUEUE_ELEM (TYPE) *next = NULL;					\
  QUEUE_ITER (TYPE) iter = { NULL, NULL };				\
									\
  gdb_assert (q != NULL);						\
									\
  for (iter.p = q->head; iter.p != NULL; iter.p = next)		\
    {									\
      next = iter.p->next;						\
      if (!operate (q, &iter, iter.p->data, data))			\
	return 0;							\
      /* ITER.P was not deleted by function OPERATE.  */		\
      if (iter.p != NULL)						\
	iter.prev = iter.p;						\
    }									\
  return 1;								\
}									\
									\
QUEUE (TYPE) *								\
queue_ ## TYPE ## _alloc (void (*free_func) (TYPE))			\
{									\
  QUEUE (TYPE) *q = XNEW (QUEUE (TYPE));				\
									\
  q->head = NULL;							\
  q->tail = NULL;							\
  q->free_func = free_func;						\
  return q;								\
}									\
									\
int									\
queue_ ## TYPE ## _length (QUEUE (TYPE) *q)				\
{									\
  QUEUE_ELEM (TYPE) *p;						\
  int len = 0;								\
									\
  gdb_assert (q != NULL);						\
									\
  for (p = q->head; p != NULL; p = p->next)				\
    len++;								\
									\
  return len;								\
}									\
									\
void									\
queue_ ## TYPE ## _free (QUEUE (TYPE) *q)				\
{									\
  QUEUE_ELEM (TYPE) *p, *next;						\
									\
  gdb_assert (q != NULL);						\
									\
  for (p = q->head; p != NULL; p = next)				\
    {									\
      next = p->next;							\
      if (q->free_func)						\
	q->free_func (p->data);					\
      xfree (p);							\
    }									\
  xfree (q);								\
}									\

/* External declarations for queue functions.  */
#define DECLARE_QUEUE_P(TYPE)					\
QUEUE (TYPE);							\
QUEUE_ELEM (TYPE);						\
QUEUE_ITER (TYPE);						\
extern void							\
  queue_ ## TYPE ## _enque (QUEUE (TYPE) *q, TYPE v);		\
extern TYPE							\
  queue_ ## TYPE ## _deque (QUEUE (TYPE) *q);			\
extern int queue_ ## TYPE ## _is_empty (QUEUE (TYPE) *q);	\
extern QUEUE (TYPE) *						\
  queue_ ## TYPE ## _alloc (void (*free_func) (TYPE));		\
extern int queue_ ## TYPE ## _length (QUEUE (TYPE) *q);	\
extern TYPE							\
  queue_ ## TYPE ## _peek (QUEUE (TYPE) *q);			\
extern void queue_ ## TYPE ## _free (QUEUE (TYPE) *q);		\
typedef int QUEUE_ITER_FUNC(TYPE) (QUEUE (TYPE) *,		\
				   QUEUE_ITER (TYPE) *,	\
				   TYPE,			\
				   void *);			\
extern int							\
  queue_ ## TYPE ## _iterate (QUEUE (TYPE) *q,			\
			      QUEUE_ITER_FUNC (TYPE) operate,	\
			      void *);				\
extern void							\
  queue_ ## TYPE ## _remove_elem (QUEUE (TYPE) *q,		\
				  QUEUE_ITER (TYPE) *iter);	\

#endif /* QUEUE_H */