/**
 * Looking Glass
 * Copyright © 2017-2026 The Looking Glass Authors
 * https://looking-glass.io
 *
 * 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
 */

#ifndef _H_LG_COMMON_LOCKING_
#define _H_LG_COMMON_LOCKING_

#include "time.h"

#include <stdatomic.h>

#define LG_LOCK_MODE "Atomic"
typedef atomic_flag LG_Lock;
#define LG_LOCK_INIT(x) atomic_flag_clear(&(x))
#define LG_LOCK(x) \
  while(atomic_flag_test_and_set_explicit(&(x), memory_order_acquire)) { ; }
#define LG_UNLOCK(x) \
  atomic_flag_clear_explicit(&(x), memory_order_release);
#define LG_LOCK_FREE(x)

typedef struct LG_RWLock
{
  atomic_uint readers;
  atomic_uint writers;
  atomic_flag writer;
}
LG_RWLock;

#define LG_RWLOCK_INIT(x) do { \
  atomic_init(&(x).readers, 0); \
  atomic_init(&(x).writers, 0); \
  atomic_flag_clear(&(x).writer); \
} while (0)

#define LG_LOCK_SHARED(x) do { \
  for (;;) \
  { \
    while (atomic_load_explicit( \
        &(x).writers, memory_order_seq_cst)) { ; } \
    atomic_fetch_add_explicit(&(x).readers, 1, memory_order_seq_cst); \
    if (!atomic_load_explicit(&(x).writers, memory_order_seq_cst)) \
      break; \
    atomic_fetch_sub_explicit(&(x).readers, 1, memory_order_seq_cst); \
  } \
} while (0)

#define LG_UNLOCK_SHARED(x) \
  atomic_fetch_sub_explicit(&(x).readers, 1, memory_order_seq_cst)

#define LG_LOCK_EXCLUSIVE(x) do { \
  atomic_fetch_add_explicit(&(x).writers, 1, memory_order_seq_cst); \
  while (atomic_flag_test_and_set_explicit( \
      &(x).writer, memory_order_seq_cst)) { ; } \
  while (atomic_load_explicit( \
      &(x).readers, memory_order_seq_cst)) { ; } \
} while (0)

#define LG_UNLOCK_EXCLUSIVE(x) do { \
  atomic_flag_clear_explicit(&(x).writer, memory_order_seq_cst); \
  atomic_fetch_sub_explicit(&(x).writers, 1, memory_order_seq_cst); \
} while (0)

#define LG_RWLOCK_FREE(x)

#define INTERLOCKED_INC(x) atomic_fetch_add((x), 1)
#define INTERLOCKED_DEC(x) atomic_fetch_sub((x), 1)

#define INTERLOCKED_SECTION(lock, ...) \
  LG_LOCK(lock) \
  __VA_ARGS__ \
  LG_UNLOCK(lock)

#endif
