[pull] master from parallel101:master

slides/move/CMakeLists.txt

@@ -0,0 +1,10 @@
+cmake_minimum_required(VERSION 3.12)
+
+set(CMAKE_CXX_STANDARD 20)
+
+project(main)
+
+set(SOURCES main.cpp resource.cpp)
+
+add_executable(main ${SOURCES})
+target_compile_options(main PRIVATE -Wall -Wextra)

slides/move/conclude.cpp

@@ -0,0 +1,34 @@
+#include <memory>
+#include <vector>
+
+// 掌管资源的类？四大函数全部删光！然后安心定义析构函数
+struct Resource {
+    Resource() {
+        // 分配资源
+    }
+
+    Resource(Resource &&) = delete;
+    Resource(Resource const &) = delete;            // 可省略不写
+    Resource &operator=(Resource &&) = delete;      // 可省略不写
+    Resource &operator=(Resource const &) = delete; // 可省略不写
+
+    ~Resource() {
+        // 释放资源
+    }
+};
+
+// 如果这个类需要作为参数传递，需要移动怎么办？
+std::unique_ptr<Resource> p = std::make_unique<Resource>();
+
+// 每次都要 std::move 不方便，我想要随心所欲的浅拷贝，就像 Java 对象一样，怎么办？
+std::shared_ptr<Resource> q = std::make_shared<Resource>();
+
+// 不管理资源的类？那就都不用定义了！编译器会自动生成
+struct Student {
+    std::string name;
+    int age;
+    std::vector<int> scores;
+    std::shared_ptr<Resource> bigHouse;
+
+    // 编译器自动生成 Student 的拷贝构造函数为成员全部依次拷贝，不用你自己定义了
+};

slides/move/lifetest.hpp

@@ -0,0 +1,31 @@
+#pragma once
+
+#include <cstdio>
+
+struct C {
+    C() {
+        puts("C()");
+    }
+
+    C(C &&) noexcept {
+        puts("C(C &&)");
+    }
+
+    C(C const &) {
+        puts("C(C const &)");
+    }
+
+    C &operator=(C &&) noexcept {
+        puts("operator=(C &&)");
+        return *this;
+    }
+
+    C &operator=(C const &) {
+        puts("operator=(C const &)");
+        return *this;
+    }
+
+    ~C() {
+        puts("~C()");
+    }
+};

slides/move/main.cpp

@@ -0,0 +1,53 @@
+#include <cstdio>
+#include <iostream>
+#include <string>
+
+using namespace std;
+
+struct IndentGuard {
+    IndentGuard(std::string &indent_) : indent(indent_) {
+        oldIndent = indent;
+        indent += "  ";
+    }
+
+    IndentGuard(IndentGuard &&) = delete;
+
+    ~IndentGuard() {
+        puts("析构函数");
+        indent = oldIndent;
+    }
+
+    std::string oldIndent;
+    std::string &indent;
+};
+
+struct Codegen {
+    std::string code;
+    std::string indent;
+
+    void emit(std::string text) {
+        code += indent + text + "\n";
+    }
+
+    void emit_variable(std::string name) {
+        code += indent + "int " + name + ";\n";
+    }
+
+    void codegen() {
+        emit("int main() {");
+        {
+            IndentGuard guard(indent);
+            emit_variable("i");
+            emit_variable("j");
+        }
+        emit("}");
+        emit_variable("g");
+    }
+};
+
+int main() {
+    Codegen cg;
+    cg.codegen();
+    std::cout << cg.code;
+    return 0;
+}

slides/move/main_finally.cpp

@@ -0,0 +1,69 @@
+#include <cstdio>
+#include <cstdlib>
+#include <ctime>
+#include <functional>
+
+using namespace std;
+
+template <class Callback>
+struct Finally {
+    Callback func;
+    bool valid;
+
+    Finally() : func(), valid(false) {}
+
+    Finally(Callback func) : func(func), valid(true) {
+    }
+
+    Finally(Finally &&that) noexcept : func(std::move(that.func)), valid(that.valid) {
+        that.valid = false; // 如果要支持移动语义，必须有个 bool 变量表示空状态！
+    }
+
+    Finally &operator=(Finally &&that) noexcept {
+        if (this != &that) {
+            if (valid) {
+                func();
+            }
+            func = std::move(that.func);
+            valid = that.valid;
+            that.valid = false;
+        }
+        return *this;
+    }
+
+    void cancel() {
+        valid = false;
+    }
+
+    void trigger() {
+        if (valid) {
+            func();
+        }
+        valid = false;
+    }
+
+    ~Finally() {
+        if (valid) {
+            func();
+        }
+    }
+};
+
+template <class Callback> // C++17 CTAD
+Finally(Callback) -> Finally<Callback>;
+
+int main() {
+    Finally cb = [] {
+        puts("调用了 Finally 回调");
+    };
+    srand(time(NULL));
+    bool success = rand() % 2 == 0;
+    if (success) {
+        puts("操作失败，提前返回");
+        // 此处提前返回导致析构，会自动 trigger
+        return -1;
+    }
+    puts("操作成功");
+    cb.cancel(); // cancel 后，析构不再自动 trigger 了
+    return 0;
+}

slides/move/main_resource.cpp

@@ -0,0 +1,75 @@
+#include <cstdio>
+#include <cstdlib>
+#include <memory>
+
+using namespace std;
+
+//struct Resource {
+//    void *p;
+//
+//    Resource() {
+//        puts("分配资源");
+//        p = malloc(1);
+//    }
+//
+//    Resource(Resource &&) = delete;
+//
+//    ~Resource() {
+//        puts("释放资源");
+//        free(p);
+//    }
+//};
+
+struct Resource {
+private:
+    struct Self {
+        void *p;
+
+        Self() {
+            puts("分配资源");
+            p = malloc(1);
+        }
+
+        Self(Self const &that) {
+            puts("复制资源");
+            p = malloc(1);
+        }
+
+        ~Self() {
+            puts("释放资源");
+            free(p);
+        }
+    };
+
+    shared_ptr<Self> self;
+
+    Resource(shared_ptr<Self> self_) {
+        self = self_;
+    }
+
+public:
+    Resource() {
+        self = make_shared<Self>();
+    }
+
+    Resource(Resource const &) = default;
+
+    Resource clone() const {
+        return make_shared<Self>(*self);
+    }
+
+    void speak() const {
+        printf("旺旺，我的资源句柄是 %p\n", self->p);
+    }
+};
+
+void func(Resource x) {
+    x.speak();
+    auto y = x.clone();
+    y.speak();
+}
+
+int main() {
+    auto x = Resource();
+    func(x);
+}

slides/move/main_respimpl.cpp

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+#include "resource.hpp"
+
+using namespace std;
+
+int main() {
+    Resource res;
+    res.speak();
+    return 0;
+}

slides/move/resource.cpp

@@ -0,0 +1,31 @@
+#include "resource.hpp"
+#include <cstdio>
+
+struct Resource::Self {
+    FILE *p;
+
+    Self() {
+        puts("打开文件");
+        p = fopen("CMakeCache.txt", "r");
+    }
+
+    Self(Self &&) = delete;
+
+    void speak() {
+        printf("使用文件 %p\n", p);
+    }
+
+    ~Self() {
+        puts("关闭文件");
+        fclose(p);
+    }
+};
+
+Resource::Resource() : self(std::make_unique<Self>()) {
+}
+
+void Resource::speak() {
+    return self->speak();
+}
+
+Resource::~Resource() = default;

slides/move/resource.hpp

@@ -0,0 +1,16 @@
+#pragma once
+
+#include <memory>
+
+// P-IMPL 模式
+struct Resource {
+private:
+    struct Self;
+
+    std::unique_ptr<Self> self;
+
+public:
+    Resource();
+    void speak();
+    ~Resource();
+};