怎样用C++实现文件加锁机制 跨平台文件锁fcntl与_lock_file

#include <iostream>
#include <fstream>
#include <fcntl.h>
#include <unistd.h>
#include <cerrno>

class FileLock {
public:
    FileLock(const std::string& filename) : filename_(filename), fd_(-1) {}

    bool lock() {
        fd_ = open(filename_.c_str(), O_RDWR);
        if (fd_ == -1) {
            std::cerr << "Failed to open file: " << filename_ << std::endl;
            return false;
        }

        struct flock fl;
        fl.l_type = F_WRLCK;  // Write lock (exclusive lock)
        fl.l_whence = SEEK_SET;
        fl.l_start = 0;
        fl.l_len = 0;         // Lock the entire file

        if (fcntl(fd_, F_SETLK, &fl) == -1) { // F_SETLK: non-blocking lock request
            if (errno == EACCES || errno == EAGAIN) {
                std::cerr << "File is already locked by another process." << std::endl;
            } else {
                std::cerr << "Failed to lock file: " << filename_ << ", error: " << strerror(errno) << std::endl;
            }
            close(fd_);
            fd_ = -1;
            return false;
        }

        return true;
    }

    bool unlock() {
        if (fd_ == -1) {
            return true; // Not locked
        }

        struct flock fl;
        fl.l_type = F_UNLCK;
        fl.l_whence = SEEK_SET;
        fl.l_start = 0;
        fl.l_len = 0;

        if (fcntl(fd_, F_SETLK, &fl) == -1) {
            std::cerr << "Failed to unlock file: " << filename_ << ", error: " << strerror(errno) << std::endl;
            return false;
        }

        close(fd_);
        fd_ = -1;
        return true;
    }

    ~FileLock() {
        unlock();
    }

private:
    std::string filename_;
    int fd_;
};

int main() {
    FileLock lock("test.txt");

    if (lock.lock()) {
        std::cout << "File locked successfully." << std::endl;

        // Perform file operations here
        std::ofstream outfile("test.txt", std::ios::app);
        outfile << "This is a test." << std::endl;
        outfile.close();

        std::cout << "Writing to file completed." << std::endl;

        lock.unlock();
        std::cout << "File unlocked." << std::endl;
    } else {
        std::cerr << "Failed to lock file." << std::endl;
    }

    return 0;
}

#include <iostream>
#include <fstream>
#include <io.h>
#include <fcntl.h>
#include <share.h>
#include <windows.h>

class FileLock {
public:
    FileLock(const std::string& filename) : filename_(filename), fd_(-1) {}

    bool lock() {
        // Open file in exclusive mode
        fd_ = _sopen(filename_.c_str(), _O_RDWR, _SH_DENYNO, _S_IREAD | _S_IWRITE);

        if (fd_ == -1) {
            std::cerr << "Failed to open file: " << filename_ << std::endl;
            return false;
        }

        // Lock the file
        if (_locking(fd_, _LK_LOCK, 1024) == -1) {
            std::cerr << "Failed to lock file: " << filename_ << std::endl;
            _close(fd_);
            fd_ = -1;
            return false;
        }

        return true;
    }

    bool unlock() {
        if (fd_ == -1) {
            return true; // Not locked
        }

        if (_locking(fd_, _LK_UNLCK, 1024) == -1) {
            std::cerr << "Failed to unlock file: " << filename_ << std::endl;
            return false;
        }

        _close(fd_);
        fd_ = -1;
        return true;
    }

    ~FileLock() {
        unlock();
    }

private:
    std::string filename_;
    int fd_;
};

int main() {
    FileLock lock("test.txt");

    if (lock.lock()) {
        std::cout << "File locked successfully." << std::endl;

        // Perform file operations here
        std::ofstream outfile("test.txt", std::ios::app);
        outfile << "This is a test." << std::endl;
        outfile.close();

        std::cout << "Writing to file completed." << std::endl;

        lock.unlock();
        std::cout << "File unlocked." << std::endl;
    } else {
        std::cerr << "Failed to lock file." << std::endl;
    }

    return 0;
}