subprocess.hpp

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#pragma once
 
#include <asmgrader/common/class_traits.hpp>
#include <asmgrader/common/error_types.hpp>
#include <asmgrader/common/expected.hpp>
#include <asmgrader/common/linux.hpp>
 
#include <chrono>
#include <cstddef>
#include <optional>
#include <string>
#include <vector>
 
#include <sys/types.h>
#include <time.h>
#include <unistd.h>
 
namespace asmgrader {
 
class Subprocess : NonCopyable
{
public:
    explicit Subprocess(std::string exec, std::vector<std::string> args);
    virtual ~Subprocess();
    Subprocess(Subprocess&&) noexcept;
    Subprocess& operator=(Subprocess&&) noexcept;
 
    template <typename Rep, typename Period>
    Result<std::string> read_stdout(const std::chrono::duration<Rep, Period>& timeout) {
        return read_stdout_poll_impl(std::chrono::duration_cast<std::chrono::milliseconds>(timeout).count());
    }
 
    Result<std::string> read_stdout();
 
    const std::string& get_full_stdout();
 
    Result<void> send_stdin(const std::string& str);
 
    // Forks the current process to start a new subprocess as specified
    virtual Result<void> start();
 
    // Blocks until exit. An alias for ``wait_for_exit(A VERY LONG TIME)``
    int wait_for_exit();
 
    // Blocks until exit or timeout
    virtual Result<int> wait_for_exit(std::chrono::microseconds timeout);
 
    bool is_alive() const;
 
    Result<void> close_pipes();
 
    pid_t get_pid() const { return child_pid_; }
 
    std::optional<int> get_exit_code() const { return exit_code_; }
 
    virtual Result<void> kill();
 
    virtual Result<void> restart();
 
protected:
    // Allow derived classes to customize initialization
    Subprocess() = default;
    virtual Result<void> create(const std::string& exec, const std::vector<std::string>& args);
 
    virtual Result<void> init_child();
    virtual Result<void> init_parent();
 
private:
    pid_t child_pid_{};
    linux::Pipe stdin_pipe_{};
    linux::Pipe stdout_pipe_{};
 
    std::string stdout_buffer_;
    std::size_t stdout_cursor_{};
 
    Result<std::string> read_stdout_poll_impl(int timeout_ms);
 
    Result<void> read_stdout_impl();
 
    std::optional<int> exit_code_;
 
    std::string exec_;
    std::vector<std::string> args_;
};
 
} // namespace asmgrader