Cpp2_6.html

<article>
    <h1>C++ II: Page 6 - Modern C++: Move Semantics</h1>

    <section>
        <h2>Optimizing Performance</h2>
        <p>Move semantics allow C++ to "transfer" the ownership of resources from one object to another instead of performing expensive copies. This is achieved using rvalue references (<code>&&</code>).</p>
        
        <h3>The Code implementation</h3>
        <pre><code class="language-cpp">/*
 * File: move_semantics.cpp
 * Demonstration of Move Constructor and Move Assignment (Rule of Five)
 */
#include &lt;iostream&gt;
#include &lt;vector&gt;
#include &lt;algorithm&gt;

using namespace std;

class Buffer {
    size_t size;
    int* data;
public:
    Buffer(size_t s) : size(s), data(new int[s]) {}
    ~Buffer() { delete[] data; }

    // 1. Move constructor
    Buffer(Buffer&& other) noexcept : size(other.size), data(other.data) {
        other.size = 0;
        other.data = nullptr;
        cout << "Buffer moved." << endl;
    }

    // 2. Move assignment operator
    Buffer& operator=(Buffer&& other) noexcept {
        if (this != &other) {
            delete[] data;
            size = other.size;
            data = other.data;
            other.size = 0;
            other.data = nullptr;
            cout << "Buffer move-assigned." << endl;
        }
        return *this;
    }
};

int main() {
    Buffer b1(1000);
    // Use std::move to transfer ownership
    Buffer b2 = move(b1); 
    
    Buffer b3(500);
    b3 = move(b2);
    
    return 0;
}

/*
 * Move Semantics Nuances:
 * 1. '&&' indicates an rvalue reference (temporary object).
 * 2. Move constructor takes '&&', steals resources, sets old data to null.
 * 3. std::move() casts an object to an rvalue, enabling a move.
 * 4. Exception safety (noexcept) is required for move constructors.
 * 5. Move semantics drastically improve performance for container classes.
 * 6. Rule of Five: If you implement a destructor, you should consider 
 *    implementing copy constructor, copy assignment, move constructor, 
 *    and move assignment to maintain resource integrity.
 */
        </code></pre>
        <div class="interactive-sim">
            <h3>Move Simulator</h3>
            <button class="sim-button" onclick="
                const out = document.getElementById('sim-output-cpp2_6');
                out.innerHTML = 'Buffer b2 = move(b1);<br>';
                setTimeout(() => out.innerHTML += '>> Resources stolen from b1, b2 owns data!', 800);
            ">Run Simulation</button>
            <div id="sim-output-cpp2_6" class="sim-output"></div>
        </div>
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