fish-shell/src/fds.h

/** Facilities for working with file descriptors. */

#ifndef FISH_FDS_H
#define FISH_FDS_H

#include <algorithm>

/// A helper class for managing and automatically closing a file descriptor.
class autoclose_fd_t {
    int fd_;

   public:
    // Closes the fd if not already closed.
    void close();

    // Returns the fd.
    int fd() const { return fd_; }

    // Returns the fd, transferring ownership to the caller.
    int acquire() {
        int temp = fd_;
        fd_ = -1;
        return temp;
    }

    // Resets to a new fd, taking ownership.
    void reset(int fd) {
        if (fd == fd_) return;
        close();
        fd_ = fd;
    }

    // \return if this has a valid fd.
    bool valid() const { return fd_ >= 0; }

    autoclose_fd_t(const autoclose_fd_t &) = delete;
    void operator=(const autoclose_fd_t &) = delete;
    autoclose_fd_t(autoclose_fd_t &&rhs) : fd_(rhs.fd_) { rhs.fd_ = -1; }

    void operator=(autoclose_fd_t &&rhs) {
        close();
        std::swap(this->fd_, rhs.fd_);
    }

    explicit autoclose_fd_t(int fd = -1) : fd_(fd) {}
    ~autoclose_fd_t() { close(); }
};

/// Close a file descriptor \p fd, retrying on EINTR.
void exec_close(int fd);

#endif