基于OpenHarmony标准系统的C++公共基础类库案例：rwlock 原创

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。

本案例已基于凌蒙派-RK3568开发板验证过，如有需要相关代码，请参考：

https://gitee.com/Lockzhiner-Electronics/lockzhiner-rk3568-openharmony/tree/master/samples/a25_utils_rwlock

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 <rwlock.h>

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::Utils::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::Utils::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 <typename RWLockable>

2.4.2、~UniqueWriteGuard

析构函数。

~UniqueWriteGuard();

2.5、OHOS::Utils::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 <typename RWLockable>

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-build
sudo apt install generate-ninja
# 规范化BUILD.gn
gn 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::Utils::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_rwlock
2017-8-5 20:7:8, thread_read_0: start
2017-8-5 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 sec
2017-8-5 20:7:8, thread_read_1: start
2017-8-5 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 sec
2017-8-5 20:7:8, thread_read_2: start
2017-8-5 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 sec
2017-8-5 20:7:8, thread_write_0: start
2017-8-5 20:7:8, thread_write_0: LockWrite wait...
2017-8-5 20:7:8, thread_write_1: start
2017-8-5 20:7:8, thread_write_1: LockWrite wait...
2017-8-5 20:7:9, thread_read_0: UnLockRead
2017-8-5 20:7:9, thread_read_1: UnLockRead
2017-8-5 20:7:9, thread_read_2: UnLockRead
2017-8-5 20:7:9, thread_write_1: LockWrite success and write count++ and sleep 1 sec
2017-8-5 20:7:10, thread_read_0: LockRead wait...
2017-8-5 20:7:10, thread_write_1: UnLockWrite
2017-8-5 20:7:10, thread_write_0: LockWrite success and write count++ and sleep 1 sec
2017-8-5 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 = : UnLockWrite
2 and sleep 1 sec
2017-8-5 20:7:11, thread_read_1: LockRead success and read count = 2 and sleep 1 sec
2017-8-5 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: UnLockRead
2017-8-5 20:7:12, thread_read_0: UnLockRead
2017-8-5 20:7:12, thread_write_0: LockWrite success and write count++ and sleep 1 sec
2017-8-5 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: UnLockWrite
2017-8-5 20:7:13, thread_write_1: LockWrite success and write count++ and sleep 1 sec
2017-8-5 20:7:14, thread_write_0: LockWrite wait...
2017-8-5 20:7:14, thread_write_1: UnLockWrite
2017-8-5 20:7:14, thread_write_0: LockWrite success and write count++ and sleep 1 sec
2017-8-5 20:7:15, thread_read_0: LockRead success and read count = 2017-8-5 20:7:15, thread_write_0: UnLockWrite
2017-8-5 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 sec
5 and sleep 1 sec
2017-8-5 20:7:16, thread_write_0: LockWrite wait...
2017-8-5 20:7:16, thread_read_1: UnLockRead
2017-8-5 20:7:16, thread_read_0: UnLockRead
2017-8-5 20:7:16, thread_write_1: LockWrite success and write count++ and sleep 1 sec
2017-8-5 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: UnLockWrite
2017-8-5 20:7:17, thread_write_0: LockWrite success and write count++ and sleep 1 sec
2017-8-5 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: UnLockWrite
2017-8-5 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 sec
2017-8-5 20:7:19, thread_read_0: LockRead success and read count = 8 and sleep 1 sec
2017-8-5 20:7:19, thread_read_2: LockRead success and read count = 8 and sleep 1 sec
2017-8-5 20:7:20, thread_write_1: LockWrite wait...
2017-8-5 20:7:20, thread_read_1: UnLockRead
2017-8-5 20:7:20, thread_read_0: UnLockRead
2017-8-5 20:7:20, thread_read_2: UnLockRead
2017-8-5 20:7:20, thread_write_1: LockWrite success and write count++ and sleep 1 sec
2017-8-5 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: UnLockWrite
2017-8-5 20:7:21, thread_write_0: LockWrite success and write count++ and sleep 1 sec
2017-8-5 20:7:22, thread_write_0: UnLockWrite
2017-8-5 20:7:22, thread_read_0: LockRead success and read count = 10 and sleep 1 sec
2017-8-5 20:7:22, thread_read_1: LockRead success and read count = 10 and sleep 1 sec
2017-8-5 20:7:22, thread_read_2: LockRead success and read count = 10 and sleep 1 sec
2017-8-5 20:7:23, thread_read_0: UnLockRead
2017-8-5 20:7:23, thread_read_1: UnLockRead
2017-8-5 20:7:23, thread_read_2: UnLockRead
2017-8-5 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 sec
2017-8-5 20:7:25, thread_read_2: UnLockRead
2017-8-5 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 sec
2017-8-5 20:7:27, thread_read_2: UnLockRead
#