基于OpenHarmony标准系统的C++公共基础类库案例：rwlock

1、程序简介

该程序是基于OpenHarmony的C++公共基础类库的读写锁：rwlock。

本案例主要完成如下工作：

创建3个读线程，每个读线程循环5次，每次循环获取读锁，将公共资源变量打印，睡眠1秒，然后释放读锁，最后再睡眠1秒。

创建3个写线程，每个写线程循环5次，每次循环获取写锁，将公共资源变量打印，睡眠1秒，然后释放读锁，最后再睡眠1秒。

2、基础知识

C++公共基础类库为标准系统提供了一些常用的C++开发工具类，包括：

文件、路径、字符串相关操作的能力增强接口

读写锁、信号量、定时器、线程增强及线程池等接口

安全数据容器、数据序列化等接口

各子系统的错误码相关定义

2.1、添加C++公共基础类库依赖

修改需调用模块的BUILD.gn，在external_deps或deps中添加如下：

ohos_shared_library("xxxxx") { ... external_deps = [ ... # 动态库依赖(可选) "c_utils:utils", # 静态库依赖(可选) "c_utils:utilsbase", # Rust动态库依赖(可选) "c_utils:utils_rust", ] ...}

一般而言，我们只需要填写"c_utils:utils"即可。

2.2、rwlock头文件

C++公共基础类库的rwlock头文件在：//commonlibrary/c_utils/base/include/rwlock.h

可在源代码中添加如下：

#include

OpenHarmony读写锁分为如下三大类：

（1）RWLock类

OHOS::RWLock

（2）UniqueWriteGuard类

OHOS::UniqueWriteGuard

（3）UniqueReadGuard类

OHOS::UniqueReadGuard

2.3、OHOS::RWLock接口说明

2.3.1、RWLock

构造函数。

RWLock() : RWLock(true);RWLock(bool writeFirst);

参数说明：

参数名称	类型	参数说明
writeFirst	bool	是否优先写模式

2.3.2、~RWLock

析构函数。

~RWLock();

2.3.3、LockRead

获取读锁。

void LockRead();

2.3.4、UnLockRead

释放读锁。

void UnLockRead();

2.3.5、LockWrite

获取写锁。

void LockWrite();

2.3.6、UnLockWrite

获取写锁。

void UnLockWrite();

2.4、OHOS::UniqueWriteGuard接口说明

2.4.1、UniqueWriteGuard

构造函数。

UniqueWriteGuard(RWLockable &rwLockable)

参数说明：

参数名称	类型	参数说明
rwLockable	RWLockable	template

2.4.2、~UniqueWriteGuard

析构函数。

~UniqueWriteGuard();

2.5、OHOS::UniqueReadGuard接口说明

2.5.1、UniqueReadGuard

构造函数。

UniqueReadGuard(RWLockable &rwLockable)

参数说明：

参数名称	类型	参数说明
rwLockable	RWLockable	template

2.5.2、~UniqueReadGuard

析构函数。

~UniqueReadGuard();

3、程序解析

3.1、创建编译引导

在上一级目录BUILD.gn文件添加一行编译引导语句。

import("//build/ohos.gni")
group("samples") { deps = [ "a25_utils_rwlock:utils_rwlock", # 添加该行 ]}

"a25_utils_rwlock:utils_rwlock",该行语句表示引入 参与编译。

3.2、创建编译项目

创建a25_utils_rwlock目录，并添加如下文件：

a25_utils_rwlock├── utils_rwlock_sample.cpp # .cpp源代码├──BUILD.gn#GN文件

3.3、创建BUILD.gn

编辑BUILD.gn文件。

import("//build/ohos.gni")ohos_executable("utils_rwlock") { sources = [ "utils_rwlock_sample.cpp" ] include_dirs = [ "//commonlibrary/c_utils/base/include", "//commonlibrary/c_utils/base:utils", "//third_party/googletest:gtest_main", "//third_party/googletest/googletest/include" ] external_deps = [ "c_utils:utils" ] part_name = "product_rk3568" install_enable = true}

注意：

（1）BUILD.gn中所有的TAB键必须转化为空格，否则会报错。如果自己不知道如何规范化，可以：

# 安装gn工具sudo apt-get install ninja-buildsudo apt install generate-ninja# 规范化BUILD.gngn format BUILD.gn

3.4、创建源代码

3.4.1、创建读写锁和公共资源变量

static OHOS::RWLock m_rwlock(true);static int m_count = 0;

3.4.2、创建线程池并设置

int main(int argc, char **argv){ OHOS::ThreadPool threads("name_semaphore_threads"); int threads_start = 6; ...... threads.SetMaxTaskNum(128); threads.Start(threads_start); ......}

3.4.3、启动3个读线程和3个写线程

调用AddTask()添加子线程。

// 启动读线程for (int i = 0; i < 3; i++) { str_name = "thread_read_" + to_string(i); auto task = std::bind(funcRead, str_name); threads.AddTask(task);}
// 启动写线程for (int i = 0; i < 3; i++) { str_name = "thread_write_" + to_string(i); auto task = std::bind(funcWrite, str_name); threads.AddTask(task);}

3.4.4、编写读线程

读线程完成如下步骤：

调用LockRead()获取读锁；

如果获取到读锁，打印公共资源变量，并睡眠1秒；

调用UnLockRead()释放读锁；

睡眠1秒；

上述操作循环5次；

static void funcRead(const string& name){ cout << get_curtime() << ", " << name << ": start\n";
for (int i = 0; i < 5; i++) { cout << get_curtime() << ", " << name << ": LockRead wait..." << endl; m_rwlock.LockRead(); cout << get_curtime() << ", " << name << ": LockRead success and read count = " << m_count << " and sleep 1 sec" << endl; sleep(1); m_rwlock.UnLockRead(); cout << get_curtime() << ", " << name << ": UnLockRead" << endl; sleep(1); }}

3.4.5、编写写线程

写线程完成如下步骤：

调用LockWrite()获取写锁；

如果获取到读锁，公共资源变量累加1，并睡眠1秒；

调用UnLockWrite()释放写锁；

睡眠1秒；

上述操作循环5次；

static void funcWrite(const string& name){ cout << get_curtime() << ", " << name << ": start\n";
for (int i = 0; i < 5; i++) { cout << get_curtime() << ", " << name << ": LockWrite wait..." << endl; m_rwlock.LockWrite(); cout << get_curtime() << ", " << name << ": LockWrite success and write count++ and sleep 1 sec" << endl; m_count++; sleep(1); m_rwlock.UnLockWrite(); cout << get_curtime() << ", " << name << ": UnLockWrite" << endl; sleep(1); }}

4、编译步骤

进入OpenHarmony编译环境，运行命令：

hb build -f

5、运行结果

# utils_rwlock2017-8-5 208, thread_read_0: start2017-8-5 20:7:8, thread_read_0: LockRead wait...2017-8-5 20:7:8, thread_read_0: LockRead success and read count = 0 and sleep 1 sec2017-8-5 20:7:8, thread_read_1: start2017-8-5 20:7:8, thread_read_1: LockRead wait...2017-8-5 20:7:8, thread_read_1: LockRead success and read count = 0 and sleep 1 sec2017-8-5 20:7:8, thread_read_2: start2017-8-5 20:7:8, thread_read_2: LockRead wait...2017-8-5 20:7:8, thread_read_2: LockRead success and read count = 0 and sleep 1 sec2017-8-5 20:7:8, thread_write_0: start2017-8-5 20:7:8, thread_write_0: LockWrite wait...2017-8-5 20:7:8, thread_write_1: start2017-8-5 20:7:8, thread_write_1: LockWrite wait...2017-8-5 20:7:9, thread_read_0: UnLockRead2017-8-5 20:7:9, thread_read_1: UnLockRead2017-8-5 20:7:9, thread_read_2: UnLockRead2017-8-5 20:7:9, thread_write_1: LockWrite success and write count++ and sleep 1 sec2017-8-5 20:7:10, thread_read_0: LockRead wait...2017-8-5 20:7:10, thread_write_1: UnLockWrite2017-8-5 20:7:10, thread_write_0: LockWrite success and write count++ and sleep 1 sec2017-8-5 20:7:10, thread_read_1: LockRead wait...2017-8-5 20:7:10, thread_read_2: LockRead wait...2017-8-5 20:7:112017-8-5 20:7:11, thread_write_0, thread_read_0: LockRead success and read count = : UnLockWrite2 and sleep 1 sec2017-8-5 20:7:11, thread_read_1: LockRead success and read count = 2 and sleep 1 sec2017-8-5 20:7:11, thread_write_1: LockWrite wait...2017-8-5 20:7:12, thread_write_0: LockWrite wait...2017-8-5 20:7:12, thread_read_1: UnLockRead2017-8-5 20:7:12, thread_read_0: UnLockRead2017-8-5 20:7:12, thread_write_0: LockWrite success and write count++ and sleep 1 sec2017-8-5 20:7:13, thread_read_1: LockRead wait...2017-8-5 20:7:13, thread_read_0: LockRead wait...2017-8-5 20:7:13, thread_write_0: UnLockWrite2017-8-5 20:7:13, thread_write_1: LockWrite success and write count++ and sleep 1 sec2017-8-5 20:7:14, thread_write_0: LockWrite wait...2017-8-5 20:7:14, thread_write_1: UnLockWrite2017-8-5 20:7:14, thread_write_0: LockWrite success and write count++ and sleep 1 sec2017-8-5 20:7:15, thread_read_0: LockRead success and read count = 2017-8-5 20:7:15, thread_write_0: UnLockWrite2017-8-5 20:7:15, thread_write_1: LockWrite wait...2017-8-5 20:7:15, thread_read_1: LockRead success and read count = 5 and sleep 1 sec5 and sleep 1 sec2017-8-5 20:7:16, thread_write_0: LockWrite wait...2017-8-5 20:7:16, thread_read_1: UnLockRead2017-8-5 20:7:16, thread_read_0: UnLockRead2017-8-5 20:7:16, thread_write_1: LockWrite success and write count++ and sleep 1 sec2017-8-5 20:7:17, thread_read_1: LockRead wait...2017-8-5 20:7:17, thread_read_0: LockRead wait...2017-8-5 20:7:17, thread_write_1: UnLockWrite2017-8-5 20:7:17, thread_write_0: LockWrite success and write count++ and sleep 1 sec2017-8-5 20:7:18, thread_write_1: LockWrite wait...2017-8-5 20:7:18, thread_write_1: LockWrite success and write count++ and sleep 1 sec2017-8-5 20:7:18,thread_write_0: UnLockWrite2017-8-5 20:7:192017-8-5 20:7:19, thread_write_0, thread_write_1: UnLockWrite: LockWrite wait...2017-8-5 20:7:19,
thread_read_1: LockRead success and read count = 8 and sleep 1 sec2017-8-5 20:7:19, thread_read_0: LockRead success and read count = 8 and sleep 1 sec2017-8-5 20:7:19, thread_read_2: LockRead success and read count = 8 and sleep 1 sec2017-8-5 20:7:20, thread_write_1: LockWrite wait...2017-8-5 20:7:20, thread_read_1: UnLockRead2017-8-5 20:7:20, thread_read_0: UnLockRead2017-8-5 20:7:20, thread_read_2: UnLockRead2017-8-5 20:7:20, thread_write_1: LockWrite success and write count++ and sleep 1 sec2017-8-5 20:7:21, thread_read_1: LockRead wait...2017-8-5 20:7:21, thread_read_0: LockRead wait...2017-8-5 20:7:21, thread_read_2: LockRead wait...2017-8-5 20:7:21, thread_write_1: UnLockWrite2017-8-5 20:7:21, thread_write_0: LockWrite success and write count++ and sleep 1 sec2017-8-5 20:7:22, thread_write_0: UnLockWrite2017-8-5 20:7:22, thread_read_0: LockRead success and read count = 10 and sleep 1 sec2017-8-5 20:7:22, thread_read_1: LockRead success and read count = 10 and sleep 1 sec2017-8-5 20:7:22, thread_read_2: LockRead success and read count = 10 and sleep 1 sec2017-8-5 20:7:23, thread_read_0: UnLockRead2017-8-5 20:7:23, thread_read_1: UnLockRead2017-8-5 20:7:23, thread_read_2: UnLockRead2017-8-5 20:7:24, thread_read_2: LockRead wait...2017-8-5 20:7:24, thread_read_2: LockRead success and read count = 10 and sleep 1 sec2017-8-5 20:7:25, thread_read_2: UnLockRead2017-8-5 20:7:26, thread_read_2: LockRead wait...2017-8-5 20:7:26, thread_read_2: LockRead success and read count = 10 and sleep 1 sec2017-8-5 20:7:27, thread_read_2: UnLockRead#