[文章]基于OpenHarmony标准系统的C++公共基础类库案例：SafeMap

1、程序简介

该程序是基于OpenHarmony的C++公共基础类库的安全关联容器：SafeMap。

OpenHarmony提供了一个线程安全的map实现。SafeMap在STL map基础上封装互斥锁，以确保对map的操作安全。

本案例主要完成如下工作：

• 创建1个子线程，负责每秒调用EnsureInsert()插入元素；
• 创建1个子线程，负责每秒调用Insert()插入元素；
• 创建1个子线程，负责每秒调用Erase()删除元素；
• 创建1个子线程，负责每秒调用FindOldAndSetNew()替换元素的值；**
• 主线程等待上述线程结束，Iterate()和Find()查看所有元素；**
• 主线程等待上述线程结束，清空SafeMap，并调用IsEmpty()查看是否确实是空。

该案例已在凌蒙派-RK3568开发板验证过，如需要源代码，请参考：

https://gitee.com/Lockzhiner-Electronics/lockzhiner-rk3568-openharmony/tree/master/samples/a26_utils_safemap

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、SafeMap头文件

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

可在源代码中添加如下：

#include <safe_map.h>

2.3、OHOS::SafeMap接口说明

2.3.1、SafeMap

构造函数。

SafeMap();
SafeMap(const SafeMap& rhs);

参数说明：

参数名称	类型	参数说明
rhs	SafeMap	复制SafeMap的类对象

2.3.2、~SafeMap

析构函数。

~SafeMap();

2.3.3、Clear

删除map中存储的所有键值对。

void Clear();

2.3.4、EnsureInsert

在map中插入元素。

void EnsureInsert(const K& key, const V& value);

参数说明：

参数名称	类型	参数说明
key	K	需要插入元素的关键字
value	V	需要插入元素的值

2.3.5、Erase

删除map中键为key的键值对。

void Erase(const K& key);

参数说明：

参数名称	类型	参数说明
key	K	需要删除元素的关键字

2.3.6、Find

在map中查找元素。

bool Find(const K& key, V& value);

参数说明：

参数名称	类型	参数说明
key	K	需要查找元素的关键字
value	V	需要查找元素的值

返回值说明：

类型	返回值说明
bool	true表示成功，false表示失败

2.3.7、FindOldAndSetNew

在map中查找元素并将key对应的**oldValue替换为newValue。

bool FindOldAndSetNew(const K& key, V& oldValue, const V& newValue);

参数说明：

参数名称	类型	参数说明
key	K	需要替换元素的关键字
oldValue	V	需要替换元素的原始值
newValue	V	需要替换元素的新值

返回值说明：

类型	返回值说明
bool	true表示成功，false表示失败

2.3.8、Insert

在map中插入新元素。

bool Insert(const K& key, const V& value);

参数说明：

参数名称	类型	参数说明
key	K	需要插入元素的关键字
value	V	需要插入元素的原始值

返回值说明：

类型	返回值说明
bool	true表示成功，false表示失败

2.3.9、IsEmpty

判断map是否为空。

bool IsEmpty();

返回值说明：

类型	返回值说明
bool	true表示空，false表示非空

2.3.10、Iterate

遍历map中的元素。

bool Iterate(const SafeMapCallBack& callback);

参数说明：

参数名称	类型	参数说明
callback	SafeMapCallBack	遍历执行函数

2.3.11、operator=

SafeMap赋值。

SafeMap& operator=(const SafeMap& rhs);

参数说明：

参数名称	类型	参数说明
rhs	SafeMap&	被赋值的SafeMap类对象

返回值说明：

类型	返回值说明
SafeMap	赋值的SafeMap类对象

2.3.12、operator[]

SafeMap索引。

V& operator[](const K& key);

参数说明：

参数名称	类型	参数说明
key	K&	元素的关键字

返回值说明：

类型	返回值说明
V&	返回元素的值

2.3.13、Size

获取map的size大小。

int Size();

返回值说明：

类型	返回值说明
int	map的size大小

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 = [
    "a26_utils_safemap:utils_safemap",		# 添加该行
  ]
}

"a26_utils_safemap:utils_safemap",该行语句表示引入 参与编译。

3.2、创建编译项目

创建a26_utils_safemap目录，并添加如下文件：

a26_utils_safemap
├── utils_safemap_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_safemap") {
  sources = [ "utils_safemap_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SafeMap

#include <safe_map.h>       // SafeMap的头文件

// 定义SafeMap变量
static OHOS::SafeMap<int, string> m_safemap;

3.4.2、创建线程池并设置

int main(int argc, char **argv)
{
    OHOS::ThreadPool threads("name_rwlock_threads");
    string str_name;
	......
    threads.SetMaxTaskNum(128);
    threads.Start(4);
    ......
}

3.4.3、启动4个子线程，并等待结束

调用AddTask()添加子线程，并调用Stop()等待所有子进程结束。

// 开启子线程，使用EnsureInsert插入元素
str_name = "Thread_EnsureInsert";
auto task_ensure_insert = std::bind(map_ensure_insert, str_name);
threads.AddTask(task_ensure_insert);

// 开启子线程，使用Insert插入元素
str_name = "Thread_Insert";
auto task_insert = std::bind(map_insert, str_name);
threads.AddTask(task_insert);

// 开启子线程，使用erase删除元素
str_name = "Thread_Erase";
auto task_erase = std::bind(map_erase, str_name);
threads.AddTask(task_erase);

// 开启子线程，使用FindOldAndSetNew替换元素的值
str_name = "Thread_FindOldAndSetNew";
auto task_findold_and_setnew = std::bind(map_findold_and_setnew, str_name);
threads.AddTask(task_findold_and_setnew);

// 设置结束，并等待结束
threads.Stop();
cout << "Threads Stop" << endl;

3.4.4、编写SafeMap.EnsureInsert()插入元素

void map_ensure_insert(const string& name)
{
    int key = 0;
    string value = "";
    
    for (int i = 0; i < (sizeof(m_map1_insert) / sizeof(struct MapInfo)); i++) {
        key = m_map1_insert[i].key;
        value = m_map1_insert[i].str;
        m_safemap.EnsureInsert(key, value);
        cout << name << ": insert successful and key = " << key << " and value = " << value << endl;
        sleep(1);
    }
}

3.4.5、编写SafeMap.Insert()插入元素

void map_insert(const string& name)
{
    int key = 0;
    string value = "";
    
    for (int i = 0; i < (sizeof(m_map2_insert) / sizeof(struct MapInfo)); i++) {
        key = m_map2_insert[i].key;
        value = m_map2_insert[i].str;
        if (m_safemap.Insert(key, value) == false) {
            cout << name << ": insert failed and key = " << to_string(key) << " and value = " << value << endl;
        } else {
            cout << name << ": insert successful and key = " << to_string(key) << " and value = " << value << endl;
        }
        sleep(1);
    }
}

3.4.6、编写SafeMap.Erase()删除元素

void map_erase(const string& name)
{
    int key = 0;
    string value = "";
    
    for (int i = 0; i < (sizeof(m_map2_insert) / sizeof(struct MapInfo)); i++) {
        key = m_map2_insert[i].key;
        m_safemap.Erase(key);
        cout << name << ": Erase successful and key = " << to_string(key) << endl;
        sleep(1);
    }
}

3.4.7、编写SafeMap.FindOldAndSetNew()替换元素的值

void map_findold_and_setnew(const string& name)
{
    int key = 0;
    string old_value = "";
    string new_value = "";
    
    for (int i = 0; i < (sizeof(m_map1_insert) / sizeof(struct MapInfo)); i++) {
        key = m_map1_reset[i].key;
        old_value = "";
        new_value = m_map1_reset[i].str;
        
        if (m_safemap.FindOldAndSetNew(key, old_value, new_value) == false) {
            cout << name << ": FindOldAndSetNew failed and key = " << to_string(key) << " and old_value = " << old_value << endl;
        } else {
            cout << name << ": FindOldAndSetNew successful and key = " << to_string(key)
                 << " and old_value = " << old_value << " and new_value = " << new_value << endl;
        }
        
        sleep(1);
    }
}

3.4.8、编写枚举所有元素

主要分为如下两种方法：

（1）调用SafeMap.Iterate()

void map_iterate_print(const int key, string& value)
{
    cout << "key = " << to_string(key) << ", value = " << value << endl;
}

int main(int argc, char *argv[])
{
    ......
    cout << "SafeMap Iterate: " << endl;
    m_safemap.Iterate(map_iterate_print);
    ......
}

（2）调用SafeMap.Find()

void map_find_print()
{
    int key = 0;
    string value = "";
    
    for (int i = 0; i < (sizeof(m_map1_insert) / sizeof(struct MapInfo)); i++) {
        key = m_map1_insert[i].key;
        value = "";
        
        if (m_safemap.Find(key, value)) {
            cout << "key = " << to_string(key) << ", value = " << value << endl;
        }
    }
    
    for (int i = 0; i < (sizeof(m_map2_insert) / sizeof(struct MapInfo)); i++) {
        key = m_map2_insert[i].key;
        value = "";
        
        if (m_safemap.Find(key, value)) {
            cout << "key = " << to_string(key) << ", value = " << value << endl;
        }
    }
}

3.4.9、清空SafeMap

int main(int argc, char *argv[])
{
    ......
    cout << "SafeMap Clear" << endl;
    m_safemap.Clear();
    cout << "SafeMap IsEmpty: " << m_safemap.IsEmpty() << endl;
    ......
}

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_safemap
Thread_EnsureInsert: insert successful and key = 1 and value = aaa
Thread_Erase: Erase successful and key = Thread_FindOldAndSetNew: FindOldAndSetNew successful and key = 1 and old_value = aaa and new_value = abc
101
Thread_Insert: insert successful and key = 101 and value = 111
Thread_EnsureInsert: insert successful and key = Thread_FindOldAndSetNew: FindOldAndSetNew successful and key = 2 and old_value = bbb and new_value = bcd
Thread_Insert: insert successful and key = 102 and value = 2222 and value = bbb

Thread_Erase: Erase successful and key = 102
Thread_EnsureInsert: insert successful and key = 3 and value = ccc
Thread_FindOldAndSetNew: FindOldAndSetNew successful and key = 3 and old_value = ccc and new_value = cde
Thread_Insert: insert successful and key = 103 and value = 333
Thread_Erase: Erase successful and key = 103
Thread_EnsureInsert: insert successful and key = 4 and value = ddd
Thread_Insert: insert successful and key = 104Thread_FindOldAndSetNew and value = : FindOldAndSetNew successful and key = 4444 and old_value = ddd and new_value = def

Thread_Erase: Erase successful and key = 104
Thread_EnsureInsert: insert successful and key = 5 and value = eee
Thread_Insert: insert successful and key = 105 and value = 555
Thread_FindOldAndSetNew: FindOldAndSetNew successful and key = 5 and old_value = eee and new_value = efg
Thread_Erase: Erase successful and key = 105
Thread_EnsureInsert: insert successful and key = 6 and value = fff
Thread_FindOldAndSetNew: FindOldAndSetNew successful and key = 6 and old_value = fff and new_value = fghThread_Insert: insert successful and key = 
106 and value = 666
Thread_Erase: Erase successful and key = 106
Thread_EnsureInsert: insert successful and key = 7 and value = ggg
Thread_FindOldAndSetNew: FindOldAndSetNew successful and key = 7 and old_value = ggg and new_value = ghi
Thread_Erase: Erase successful and key = 107
Thread_Insert: insert successful and key = 107 and value = 777
Thread_EnsureInsert: insert successful and key = 8 and value = hhh
Thread_FindOldAndSetNew: FindOldAndSetNew successful and key = 8 and old_value = hhh and new_value = hij
Thread_Erase: Erase successful and key = 108
Thread_Insert: insert successful and key = 108 and value = 888
Thread_EnsureInsert: insert successful and key = 9 and value = iii
Thread_FindOldAndSetNew: FindOldAndSetNew successful and key = 9 and old_value = iii and new_value = ijk
Thread_Erase: Erase successful and key = 109
Thread_Insert: insert successful and key = 109 and value = 999
Thread_EnsureInsert: insert successful and key = 10 and value = jjj
Thread_FindOldAndSetNew: FindOldAndSetNew successful and key = 10 and old_value = jjj and new_value = jkl
Thread_Erase: Erase successful and key = 110
Thread_Insert: insert successful and key = 110 and value = 000
Threads Stop
SafeMap Iterate:
key = 1, value = abc
key = 2, value = bcd
key = 3, value = cde
key = 4, value = def
key = 5, value = efg
key = 6, value = fgh
key = 7, value = ghi
key = 8, value = hij
key = 9, value = ijk
key = 10, value = jkl
key = 108, value = 888
key = 109, value = 999
key = 110, value = 000
SafeMap Find:
key = 1, value = abc
key = 2, value = bcd
key = 3, value = cde
key = 4, value = def
key = 5, value = efg
key = 6, value = fgh
key = 7, value = ghi
key = 8, value = hij
key = 9, value = ijk
key = 10, value = jkl
key = 108, value = 888
key = 109, value = 999
key = 110, value = 000
SafeMap Clear
SafeMap IsEmpty: 1
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