1/* Read-write locks (native Windows implementation).
2   Copyright (C) 2005-2022 Free Software Foundation, Inc.
3
4   This file is free software: you can redistribute it and/or modify
5   it under the terms of the GNU Lesser General Public License as
6   published by the Free Software Foundation; either version 2.1 of the
7   License, or (at your option) any later version.
8
9   This file is distributed in the hope that it will be useful,
10   but WITHOUT ANY WARRANTY; without even the implied warranty of
11   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12   GNU Lesser General Public License for more details.
13
14   You should have received a copy of the GNU Lesser General Public License
15   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
16
17/* Written by Bruno Haible <bruno@clisp.org>, 2005.
18   Based on GCC's gthr-win32.h.  */
19
20#ifndef _WINDOWS_RWLOCK_H
21#define _WINDOWS_RWLOCK_H
22
23#define WIN32_LEAN_AND_MEAN  /* avoid including junk */
24#include <windows.h>
25
26#include "windows-initguard.h"
27
28/* It is impossible to implement read-write locks using plain locks, without
29   introducing an extra thread dedicated to managing read-write locks.
30   Therefore here we need to use the low-level Event type.  */
31
32typedef struct
33        {
34          HANDLE *array; /* array of waiting threads, each represented by an event */
35          unsigned int count; /* number of waiting threads */
36          unsigned int alloc; /* length of allocated array */
37          unsigned int offset; /* index of first waiting thread in array */
38        }
39        glwthread_carray_waitqueue_t;
40typedef struct
41        {
42          glwthread_initguard_t guard; /* protects the initialization */
43          CRITICAL_SECTION lock; /* protects the remaining fields */
44          glwthread_carray_waitqueue_t waiting_readers; /* waiting readers */
45          glwthread_carray_waitqueue_t waiting_writers; /* waiting writers */
46          int runcount; /* number of readers running, or -1 when a writer runs */
47        }
48        glwthread_rwlock_t;
49
50#define GLWTHREAD_RWLOCK_INIT { GLWTHREAD_INITGUARD_INIT }
51
52#ifdef __cplusplus
53extern "C" {
54#endif
55
56extern void glwthread_rwlock_init (glwthread_rwlock_t *lock);
57extern int glwthread_rwlock_rdlock (glwthread_rwlock_t *lock);
58extern int glwthread_rwlock_wrlock (glwthread_rwlock_t *lock);
59extern int glwthread_rwlock_tryrdlock (glwthread_rwlock_t *lock);
60extern int glwthread_rwlock_trywrlock (glwthread_rwlock_t *lock);
61extern int glwthread_rwlock_unlock (glwthread_rwlock_t *lock);
62extern int glwthread_rwlock_destroy (glwthread_rwlock_t *lock);
63
64#ifdef __cplusplus
65}
66#endif
67
68#endif /* _WINDOWS_RWLOCK_H */
69