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