1 files changed, 68 insertions, 0 deletions
diff --git a/src/gl/windows-rwlock.h b/src/gl/windows-rwlock.h
new file mode 100644
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+++ b/src/gl/windows-rwlock.h
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+/* Read-write locks (native Windows implementation).
+   Copyright (C) 2005-2021 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 */