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/* Read-write locks (native Windows implementation).
Copyright (C) 2005-2020 Free Software Foundation, Inc.
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, 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 <https://www.gnu.org/licenses/>. */
/* Written by Bruno Haible <bruno@clisp.org>, 2005.
Based on GCC's gthr-win32.h. */
#ifndef _WINDOWS_RWLOCK_H
#define _WINDOWS_RWLOCK_H
#define WIN32_LEAN_AND_MEAN /* avoid including junk */
#include <windows.h>
#include "windows-initguard.h"
/* It is impossible to implement read-write locks using plain locks, without
introducing an extra thread dedicated to managing read-write locks.
Therefore here we need to use the low-level Event type. */
typedef struct
{
HANDLE *array; /* array of waiting threads, each represented by an event */
unsigned int count; /* number of waiting threads */
unsigned int alloc; /* length of allocated array */
unsigned int offset; /* index of first waiting thread in array */
}
glwthread_carray_waitqueue_t;
typedef struct
{
glwthread_initguard_t guard; /* protects the initialization */
CRITICAL_SECTION lock; /* protects the remaining fields */
glwthread_carray_waitqueue_t waiting_readers; /* waiting readers */
glwthread_carray_waitqueue_t waiting_writers; /* waiting writers */
int runcount; /* number of readers running, or -1 when a writer runs */
}
glwthread_rwlock_t;
#define GLWTHREAD_RWLOCK_INIT { GLWTHREAD_INITGUARD_INIT }
#ifdef __cplusplus
extern "C" {
#endif
extern void glwthread_rwlock_init (glwthread_rwlock_t *lock);
extern int glwthread_rwlock_rdlock (glwthread_rwlock_t *lock);
extern int glwthread_rwlock_wrlock (glwthread_rwlock_t *lock);
extern int glwthread_rwlock_tryrdlock (glwthread_rwlock_t *lock);
extern int glwthread_rwlock_trywrlock (glwthread_rwlock_t *lock);
extern int glwthread_rwlock_unlock (glwthread_rwlock_t *lock);
extern int glwthread_rwlock_destroy (glwthread_rwlock_t *lock);
#ifdef __cplusplus
}
#endif
#endif /* _WINDOWS_RWLOCK_H */
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