请给我一段运用c++ opt实现虚拟存储管理的代码示例

下面是一个使用C++和Opt实现虚拟存储管理的代码示例：

#include <iostream>
#include <vector>
#include <algorithm>
#include <numeric>
#include <iterator>
#include <boost/program_options.hpp>
#include <boost/algorithm/string.hpp>
#include <boost/filesystem.hpp>
#include <boost/format.hpp>
#include <boost/iostreams/device/mapped_file.hpp>
#include <boost/lexical_cast.hpp>
#include <boost/range/adaptor/transformed.hpp>
#include <boost/range/numeric.hpp>
#include <boost/range/algorithm.hpp>

namespace po = boost::program_options;
namespace fs = boost::filesystem;

struct page_table_entry {
    bool present;
    bool dirty;
    bool referenced;
    std::size_t frame_number;
};

class page_table {
public:
    page_table(std::size_t num_pages, std::size_t page_size) :
        num_pages_(num_pages),
        page_size_(page_size),
        page_table_(num_pages_)
    {
        for (auto& entry : page_table_) {
            entry.present = false;
            entry.dirty = false;
            entry.referenced = false;
            entry.frame_number = 0;
        }
    }

    page_table_entry& operator[](std::size_t page_number) {
        return page_table_.at(page_number);
    }

    const page_table_entry& operator[](std::size_t page_number) const {
        return page_table_.at(page_number);
    }

    std::size_t num_pages() const {
        return num_pages_;
    }

    std::size_t page_size() const {
        return page_size_;
    }

private:
    std::size_t num_pages_;
    std::size_t page_size_;
    std::vector<page_table_entry> page_table_;
};

class memory_manager {
public:
    memory_manager(std::size_t num_frames, std::size_t frame_size) :
        num_frames_(num_frames),
        frame_size_(frame_size),
        page_table_(num_frames / frame_size, frame_size)
    {
        free_frames_.reserve(num_frames_);
        for (std::size_t i = 0; i < num_frames_; i += frame_size_) {
            free_frames_.push_back(i);
        }
    }

    std::size_t allocate_frame() {
        if (free_frames_.empty()) {
            // Perform page replacement
            // ...
        }

        std::size_t frame_number = free_frames_.back();
        free_frames_.pop_back();

        return frame_number;
    }

    void free_frame(std::size_t frame_number) {
        free_frames_.push_back(frame_number);
    }

    page_table& get_page_table() {
        return page_table_;
    }

private:
    std::size_t num_frames_;
    std::size_t frame_size_;
    std::vector<std::size_t> free_frames_;
    page_table page_table_;
};

class virtual_memory_manager {
public:
    virtual_memory_manager(std::size_t num_pages, std::size_t page_size, std::size_t num_frames, std::size_t frame_size) :
        num_pages_(num_pages),
        page_size_(page_size),
        num_frames_(num_frames),
        frame_size_(frame_size),
        memory_manager_(num_frames, frame_size)
    {
    }

    void read(std::size_t page_number, char* buffer) {
        auto& entry = memory_manager_.get_page_table()[page_number];
        if (!entry.present) {
            // Perform page fault
            entry.frame_number = memory_manager_.allocate_frame();
            entry.present = true;
            // Load page from disk into memory
            // ...
        }
        entry.referenced = true;
        std::memcpy(buffer, memory_manager_.get_frame_start_address(entry.frame_number), page_size_);
    }

    void write(std::size_t page_number, const char* buffer) {
        auto& entry = memory_manager_.get_page_table()[page_number];
        if (!entry.present) {
            // Perform page fault
            entry.frame_number = memory_manager_.allocate_frame();
            entry.present = true;
            // Load page from disk into memory
            // ...
        }
        entry.dirty = true;
        entry.referenced = true;
        std::memcpy(memory_manager_.get_frame_start_address(entry.frame_number), buffer, page_size_);
    }

private:
    std::size_t num_pages_;
    std::size_t page_size_;
    std::size_t num_frames_;
    std::size_t frame_size_;
    memory_manager memory_manager_;
};

int main(int argc, char* argv[]) {
    std::size_t num_pages = 1024;
    std::size_t page_size = 4096;
    std::size_t num_frames = 256;
    std::size_t frame_size = 4096;
    std::string input_file;

    po::options_description desc("Options");
    desc.add_options()
        ("help,h", "Print help message")
        ("num-pages,n", po::value<std::size_t>(&num_pages), "Number of pages (default: 1024)")
        ("page-size,s", po::value<std::size_t>(&page_size), "Page size (default: 4096)")
        ("num-frames,m", po::value<std::size_t>(&num_frames), "Number of frames (default: 256)")
        ("frame-size,f", po::value<std::size_t>(&frame_size), "Frame size (default: 4096)")
        ("input-file,i", po::value<std::string>(&input_file), "Input file (required)");

    po::variables_map vm;
    po::store(po::parse_command_line(argc, argv, desc), vm);
    po::notify(vm);

    if (vm.count("help")) {
        std::cout << desc << std::endl;
        return 0;
    }

    if (!vm.count("input-file")) {
        std::cerr << "Error: input file required." << std::endl;
        std::cerr << desc << std::endl;
        return 1;
    }

    if (!fs::exists(input_file)) {
        std::cerr << "Error: input file not found." << std::endl;
        return 1;
    }

    virtual_memory_manager vmm(num_pages, page_size, num_frames, frame_size);

    boost::iostreams::mapped_file_source file(input_file);
    std::size_t file_size = file.size();
    for (std::size_t i = 0; i < file_size; i += page_size) {
        char* buffer = new char[page_size];
        std::memcpy(buffer, file.data() + i, page_size);
        vmm.write(i / page_size, buffer);
        delete[] buffer;
    }

    return 0;
}

这个示例代码实现了一个简单的虚拟存储管理器，包括页表、内存管理器和虚拟内存管理器。它使用Opt库来解析命令行参数，使用Boost.Filesystem库来检查输入文件是否存在，并使用Boost.Iostreams库来将文件映射到内存中。