1、程序簡介

該程序是基于OpenHarmony的C++公共基礎類庫的讀寫鎖：rwlock。

本案例主要完成如下工作：

創(chuàng)建3個讀線程，每個讀線程循環(huán)5次，每次循環(huán)獲取讀鎖，將公共資源變量打印，睡眠1秒，然后釋放讀鎖，最后再睡眠1秒。

創(chuàng)建3個寫線程，每個寫線程循環(huán)5次，每次循環(huán)獲取寫鎖，將公共資源變量打印，睡眠1秒，然后釋放讀鎖，最后再睡眠1秒。

2、基礎知識

C++公共基礎類庫為標準系統(tǒng)提供了一些常用的C++開發(fā)工具類，包括：

文件、路徑、字符串相關操作的能力增強接口

讀寫鎖、信號量、定時器、線程增強及線程池等接口

安全數據容器、數據序列化等接口

各子系統(tǒng)的錯誤碼相關定義

2.1、添加C++公共基礎類庫依賴

修改需調用模塊的BUILD.gn，在external_deps或deps中添加如下：

ohos_shared_library("xxxxx") { ... external_deps = [ ... # 動態(tài)庫依賴(可選) "c_utils:utils", # 靜態(tài)庫依賴(可選) "c_utils:utilsbase", # Rust動態(tài)庫依賴(可選) "c_utils:utils_rust", ] ...}

一般而言，我們只需要填寫"c_utils:utils"即可。

2.2、rwlock頭文件

C++公共基礎類庫的rwlock頭文件在：//commonlibrary/c_utils/base/include/rwlock.h

可在源代碼中添加如下：

#include

OpenHarmony讀寫鎖分為如下三大類：

（1）RWLock類

OHOS::RWLock

（2）UniqueWriteGuard類

OHOS::UniqueWriteGuard

（3）UniqueReadGuard類

OHOS::UniqueReadGuard

2.3、OHOS::RWLock接口說明

2.3.1、RWLock

構造函數。

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

參數說明：

2.3.2、~RWLock

析構函數。

~RWLock();

2.3.3、LockRead

獲取讀鎖。

void LockRead();

2.3.4、UnLockRead

釋放讀鎖。

void UnLockRead();

2.3.5、LockWrite

獲取寫鎖。

void LockWrite();

2.3.6、UnLockWrite

獲取寫鎖。

void UnLockWrite();

2.4、OHOS::UniqueWriteGuard接口說明

2.4.1、UniqueWriteGuard

構造函數。

UniqueWriteGuard(RWLockable &rwLockable)

參數說明：

2.4.2、~UniqueWriteGuard

析構函數。

~UniqueWriteGuard();

2.5、OHOS::UniqueReadGuard接口說明

2.5.1、UniqueReadGuard

構造函數。

UniqueReadGuard(RWLockable &rwLockable)

參數說明：

2.5.2、~UniqueReadGuard

析構函數。

~UniqueReadGuard();

3、程序解析

3.1、創(chuàng)建編譯引導

在上一級目錄BUILD.gn文件添加一行編譯引導語句。

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

"a25_utils_rwlock:utils_rwlock",該行語句表示引入 參與編譯。

3.2、創(chuàng)建編譯項目

創(chuàng)建a25_utils_rwlock目錄，并添加如下文件：

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

3.3、創(chuàng)建BUILD.gn

編輯BUILD.gn文件。

import("http://build/ohos.gni")ohos_executable("utils_rwlock") { sources = [ "utils_rwlock_sample.cpp" ] include_dirs = [ "http://commonlibrary/c_utils/base/include", "http://commonlibrary/c_utils/base:utils", "http://third_party/googletest:gtest_main", "http://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鍵必須轉化為空格，否則會報錯。如果自己不知道如何規(guī)范化，可以：

# 安裝gn工具sudo apt-get install ninja-buildsudo apt install generate-ninja# 規(guī)范化BUILD.gngn format BUILD.gn

3.4、創(chuàng)建源代碼

3.4.1、創(chuàng)建讀寫鎖和公共資源變量

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

3.4.2、創(chuàng)建線程池并設置

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、啟動3個讀線程和3個寫線程

調用AddTask()添加子線程。

// 啟動讀線程for (int i = 0; i < 3; i++) { str_name = "thread_read_" + to_string(i); auto task = std::bind(funcRead, str_name); threads.AddTask(task);}
// 啟動寫線程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、編寫讀線程

讀線程完成如下步驟：

調用LockRead()獲取讀鎖；

如果獲取到讀鎖，打印公共資源變量，并睡眠1秒；

調用UnLockRead()釋放讀鎖；

睡眠1秒；

上述操作循環(huán)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、編寫寫線程

寫線程完成如下步驟：

調用LockWrite()獲取寫鎖；

如果獲取到讀鎖，公共資源變量累加1，并睡眠1秒；

調用UnLockWrite()釋放寫鎖；

睡眠1秒；

上述操作循環(huán)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、編譯步驟

進入OpenHarmony編譯環(huán)境，運行命令：

hb build -f

5、運行結果

# 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#