extmidi.cpp

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/*
 * This file is part of OpenTTD.
 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
 * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
 */
 
#include "../stdafx.h"
#include "../debug.h"
#include "../string_func.h"
#include "../core/alloc_func.hpp"
#include "../sound/sound_driver.hpp"
#include "../video/video_driver.hpp"
#include "../gfx_func.h"
#include "extmidi.h"
#include "../base_media_base.h"
#include "../thread.h"
#include "midifile.hpp"
#include <fcntl.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <signal.h>
#include <sys/stat.h>
 
#include "../safeguards.h"
 
#ifndef EXTERNAL_PLAYER
 
#define EXTERNAL_PLAYER "timidity"
#endif
 
static FMusicDriver_ExtMidi iFMusicDriver_ExtMidi;
 
std::optional<std::string_view> MusicDriver_ExtMidi::Start(const StringList &parm)
{
  if (VideoDriver::GetInstance()->GetName() == "allegro" ||
      SoundDriver::GetInstance()->GetName() == "allegro") {
    return "the extmidi driver does not work when Allegro is loaded.";
  }
 
  const char *command = GetDriverParam(parm, "cmd");
#ifndef MIDI_ARG
  if (StrEmpty(command)) command = EXTERNAL_PLAYER;
#else
  if (StrEmpty(command)) command = EXTERNAL_PLAYER " " MIDI_ARG;
#endif
 
  this->command_tokens.clear();
 
  std::string_view view = command;
  for (;;) {
    auto pos = view.find(' ');
    this->command_tokens.emplace_back(view.substr(0, pos));
 
    if (pos == std::string_view::npos) break;
    view.remove_prefix(pos + 1);
  }
 
  this->song.clear();
  this->pid = -1;
  return std::nullopt;
}
 
void MusicDriver_ExtMidi::Stop()
{
  this->song.clear();
  this->DoStop();
}
 
void MusicDriver_ExtMidi::PlaySong(const MusicSongInfo &song)
{
  std::string filename = MidiFile::GetSMFFile(song);
  if (!filename.empty()) {
    this->song = std::move(filename);
    this->DoStop();
  }
}
 
void MusicDriver_ExtMidi::StopSong()
{
  this->song.clear();
  this->DoStop();
}
 
bool MusicDriver_ExtMidi::IsSongPlaying()
{
  if (this->pid != -1 && waitpid(this->pid, nullptr, WNOHANG) == this->pid) {
    this->pid = -1;
  }
  if (this->pid == -1 && !this->song.empty()) this->DoPlay();
  return this->pid != -1;
}
 
void MusicDriver_ExtMidi::SetVolume(uint8_t)
{
  Debug(driver, 1, "extmidi: set volume not implemented");
}
 
void MusicDriver_ExtMidi::DoPlay()
{
  this->pid = fork();
  switch (this->pid) {
    case 0: {
      close(0);
      int d = open("/dev/null", O_RDONLY);
      if (d != -1 && dup2(d, 1) != -1 && dup2(d, 2) != -1) {
        /* execvp is nasty as it *allows* the passed parameters to be written
         * for backward compatibility, however we are a fork so do not care. */
        std::vector<char *> parameters;
        for (auto &token : this->command_tokens) parameters.emplace_back(token.data());
        parameters.emplace_back(this->song.data());
        parameters.emplace_back(nullptr);
 
        execvp(parameters[0], parameters.data());
      }
      _exit(1);
    }
 
    case -1:
      Debug(driver, 0, "extmidi: couldn't fork: {}", strerror(errno));
      [[fallthrough]];
 
    default:
      this->song.clear();
      break;
  }
}
 
static bool KillWait(pid_t &pid, int signal)
{
  /* First try to stop for about a second;
   * 1 seconds = 1000 milliseconds, 50 ms per cycle => 20 cycles. */
  for (int i = 0; i < 20; i++) {
    kill(pid, signal);
    if (waitpid(pid, nullptr, WNOHANG) == pid) {
      /* It has shut down, so we are done */
      pid = -1;
      return true;
    }
    /* Wait 50 milliseconds. */
    CSleep(50);
  }
 
  return false;
}
 
void MusicDriver_ExtMidi::DoStop()
{
  if (this->pid <= 0) return;
 
  if (KillWait(this->pid, SIGINT)) return;
 
  if (KillWait(this->pid, SIGTERM)) return;
 
  Debug(driver, 0, "extmidi: gracefully stopping failed, trying the hard way");
  /* Gracefully stopping failed. Do it the hard way
   * and wait till the process finally died. */
  kill(this->pid, SIGKILL);
  waitpid(this->pid, nullptr, 0);
  this->pid = -1;
}