godot-xterm/addons/godot_xterm/native/src/pseudoterminal.cpp

#include "pseudoterminal.h"
#include <libgen.h>
#include <sys/wait.h>
#include <termios.h>
#include <unistd.h>

// Platform specific includes.
#if defined(PLATFORM_LINUX)
#include <pty.h>
#endif
#if defined(PLATFORM_OSX)
#include <sys/ioctl.h>
#include <util.h>
#endif

using namespace godot;

void Pseudoterminal::_register_methods() {

  register_method("_init", &Pseudoterminal::_init);
  register_method("_ready", &Pseudoterminal::_ready);

  register_method("write", &Pseudoterminal::write);
  register_method("resize", &Pseudoterminal::resize);

  register_signal<Pseudoterminal>((char *)"data_sent", "data",
                                  GODOT_VARIANT_TYPE_POOL_BYTE_ARRAY);
  register_signal<Pseudoterminal>((char *)"exited", "status",
                                  GODOT_VARIANT_TYPE_INT);
}

Pseudoterminal::Pseudoterminal() {}

Pseudoterminal::~Pseudoterminal() { pty_thread.join(); }

void Pseudoterminal::_init() {
  bytes_to_write = 0;
  pty_thread = std::thread(&Pseudoterminal::process_pty, this);
}

void Pseudoterminal::process_pty() {
  int fd;
  char *name;
  int status;

  should_process_pty = true;

  struct termios termios = {};
  termios.c_iflag = IGNPAR | ICRNL;
  termios.c_oflag = 0;
  termios.c_cflag = B38400 | CRTSCTS | CS8 | CLOCAL | CREAD;
  termios.c_lflag = ICANON;
  termios.c_cc[VMIN] = 1;
  termios.c_cc[VTIME] = 0;

  pid_t pty_pid = forkpty(&fd, NULL, NULL, NULL);

  if (pty_pid == -1) {
    ERR_PRINT(
        String("Error forking pty: {0}").format(Array::make(strerror(errno))));
    should_process_pty = false;
    return;
  } else if (pty_pid == 0) {
    /* Child */

    char termenv[11] = {"TERM=xterm"};
    putenv(termenv);

    char colortermenv[20] = {"COLORTERM=truecolor"};
    putenv(colortermenv);

    char *shell = getenv("SHELL");
    char *argv[] = {basename(shell), NULL};
    execvp(shell, argv);
  } else {
    Vector2 zero = Vector2(0, 0);

    /* Parent */
    while (1) {
      {
        std::lock_guard<std::mutex> guard(size_mutex);
        if (size != zero) {
          struct winsize ws;
          memset(&ws, 0, sizeof(ws));
          ws.ws_col = size.x;
          ws.ws_row = size.y;

          ioctl(fd, TIOCSWINSZ, &ws);
        }
      }

      if (waitpid(pty_pid, &status, WNOHANG)) {
        emit_signal("exited", status);
        return;
      }

      int ready = -1;
      fd_set read_fds;
      fd_set write_fds;

      FD_ZERO(&read_fds);
      FD_SET(fd, &read_fds);
      FD_SET(fd, &write_fds);

      struct timeval timeout;
      timeout.tv_sec = 10;
      timeout.tv_usec = 0;

      ready = select(fd + 1, &read_fds, &write_fds, NULL, &timeout);

      if (ready > 0) {
        if (FD_ISSET(fd, &write_fds)) {
          std::lock_guard<std::mutex> guard(write_buffer_mutex);

          if (bytes_to_write > 0) {
            ::write(fd, write_buffer, bytes_to_write);
            bytes_to_write = 0;
          }
        }

        if (FD_ISSET(fd, &read_fds)) {
          std::lock_guard<std::mutex> guard(read_buffer_mutex);

          int ret;
          int bytes_read = 0;

          bytes_read = read(fd, read_buffer, MAX_READ_BUFFER_LENGTH);

          // TODO: handle error (-1)
          if (bytes_read <= 0)
            continue;

          PoolByteArray data = PoolByteArray();
          data.resize(bytes_read);
          memcpy(data.write().ptr(), read_buffer, bytes_read);

          emit_signal("data_sent", PoolByteArray(data));
        }
      }
    }
  }
}

void Pseudoterminal::_ready() {}

void Pseudoterminal::write(PoolByteArray data) {
  std::lock_guard<std::mutex> guard(write_buffer_mutex);
  bytes_to_write = data.size();
  memcpy(write_buffer, data.read().ptr(), bytes_to_write);
}

void Pseudoterminal::resize(Vector2 new_size) {
  std::lock_guard<std::mutex> guard(size_mutex);
  size = new_size;
}