#include <cstddef>
#include <cstring>
#include <iostream>
#include <utility>

/// @brief 模拟的 DMA 缓冲区管理
/// 在真实嵌入式项目中，allocate_dma_buffer 和 free_dma_buffer
/// 会对接到实际的内存管理单元或内存池
class DMABuffer {
    void* buffer_;     // 指向 DMA 缓冲区
    std::size_t size_; // 缓冲区大小

  public:
    explicit DMABuffer(std::size_t size) : buffer_(::operator new(size)), size_(size) {
        std::memset(buffer_, 0, size_);
        std::cout << "  [DMA] 分配 " << size << " 字节\n";
    }

    ~DMABuffer() {
        if (buffer_) {
            ::operator delete(buffer_);
            std::cout << "  [DMA] 释放 " << size_ << " 字节\n";
        }
    }

    // 禁止拷贝：DMA 缓冲区不能有两份
    DMABuffer(const DMABuffer&) = delete;
    DMABuffer& operator=(const DMABuffer&) = delete;

    // 允许移动：所有权可以转移
    DMABuffer(DMABuffer&& other) noexcept : buffer_(other.buffer_), size_(other.size_) {
        other.buffer_ = nullptr;
        other.size_ = 0;
        std::cout << "  [DMA] 所有权转移（移动构造）\n";
    }

    DMABuffer& operator=(DMABuffer&& other) noexcept {
        if (this != &other) {
            if (buffer_) {
                ::operator delete(buffer_);
            }
            buffer_ = other.buffer_;
            size_ = other.size_;
            other.buffer_ = nullptr;
            other.size_ = 0;
            std::cout << "  [DMA] 所有权转移（移动赋值）\n";
        }
        return *this;
    }

    void* data() { return buffer_; }
    const void* data() const { return buffer_; }
    std::size_t size() const { return size_; }
};

/// @brief 模拟从 DMA 接收数据
DMABuffer receive_dma(std::size_t expected_size) {
    DMABuffer buf(expected_size);
    // 在真实系统中，这里会触发 DMA 传输并等待完成
    // buf.data() 指向的内存由 DMA 控制器直接写入
    char msg[] = "DMA data received";
    std::memcpy(buf.data(), msg, sizeof(msg));
    return buf; // NRVO 或移动语义确保零拷贝返回
}

int main() {
    std::cout << "=== 嵌入式 DMA 缓冲区管理 ===\n\n";

    // 从 DMA 接收数据——缓冲区所有权从函数转移到 main
    auto rx_buf = receive_dma(1024);
    std::cout << "  接收到: " << static_cast<const char*>(rx_buf.data()) << "\n\n";

    // 把缓冲区转移到处理队列（模拟）
    std::cout << "=== 转移到处理队列 ===\n";
    DMABuffer process_buf = std::move(rx_buf);
    std::cout << "  rx_buf 大小: " << rx_buf.size() << "\n";
    std::cout << "  process_buf 大小: " << process_buf.size() << "\n\n";

    std::cout << "=== 程序结束，资源自动释放 ===\n";
    return 0;
}