用C++写一段桥接模式

为了更好地理解桥接模式，我们可以考虑一个简单的例子：一个音乐播放器程序。该程序需要支持不同的音频格式（例如MP3，WAV，FLAC等），并且还需要能够在不同的操作系统上运行（例如Windows，MacOS，Linux等）。这个问题可以使用桥接模式来解决。

首先，我们需要定义音频播放器接口，包括播放，暂停和停止功能：

// 音频播放器接口
typedef struct _MediaPlayer MediaPlayer;
struct _MediaPlayer {
    void (*play)(MediaPlayer*);
    void (*pause)(MediaPlayer*);
    void (*stop)(MediaPlayer*);
};

然后，我们定义不同音频格式的播放器实现：

// MP3 播放器实现
typedef struct _MP3PlayerImpl MP3PlayerImpl;
struct _MP3PlayerImpl {
    MediaPlayer super;
    // 为 MP3 文件格式添加特殊的功能
};

// WAV 播放器实现
typedef struct _WAVPlayerImpl WAVPlayerImpl;
struct _WAVPlayerImpl {
    MediaPlayer super;
    // 为 WAV 文件格式添加特殊的功能
};

// FLAC 播放器实现
typedef struct _FLACPlayerImpl FLACPlayerImpl;
struct _FLACPlayerImpl {
    MediaPlayer super;
    // 为 FLAC 文件格式添加特殊的功能
};

最后，我们定义操作系统的平台实现：

// Windows 操作系统平台实现
typedef struct _WindowsPlatformImpl WindowsPlatformImpl;
struct _WindowsPlatformImpl {
    MediaPlayer* (*createMediaPlayer)(WindowsPlatformImpl*);
    // 为 Windows 操作系统添加特殊的功能
};

// MacOS 操作系统平台实现
typedef struct _MacOSPlatformImpl MacOSPlatformImpl;
struct _MacOSPlatformImpl {
    MediaPlayer* (*createMediaPlayer)(MacOSPlatformImpl*);
    // 为 MacOS 操作系统添加特殊的功能
};

// Linux 操作系统平台实现
typedef struct _LinuxPlatformImpl LinuxPlatformImpl;
struct _LinuxPlatformImpl {
    MediaPlayer* (*createMediaPlayer)(LinuxPlatformImpl*);
    // 为 Linux 操作系统添加特殊的功能
};

最后，我们可以使用桥接模式来组合不同的实现：

// 桥接模式
typedef struct _MediaPlayerBridge MediaPlayerBridge;
struct _MediaPlayerBridge {
    MediaPlayer* (*createMediaPlayer)(MediaPlayerBridge*);
    void (*setPlatformImpl)(MediaPlayerBridge*, void*);
    void (*setAudioImpl)(MediaPlayerBridge*, void*);
    void* platformImpl;
    void* audioImpl;
};

MediaPlayer* MediaPlayerBridge_createMediaPlayer(MediaPlayerBridge* bridge)
{
    MediaPlayer* player = bridge->createMediaPlayer(bridge);
    return player;
}

void MediaPlayerBridge_setPlatformImpl(MediaPlayerBridge* bridge, void* impl)
{
    bridge->platformImpl = impl;
}

void MediaPlayerBridge_setAudioImpl(MediaPlayerBridge* bridge, void* impl)
{
    bridge->audioImpl = impl;
}

// Windows 平台的播放器
MediaPlayer* WindowsPlatformImpl_createMediaPlayer(WindowsPlatformImpl* impl)
{
    MP3PlayerImpl* player = (MP3PlayerImpl*)malloc(sizeof(MP3PlayerImpl));
    player->super.play = MP3Player_play;
    player->super.pause = MP3Player_pause;
    player->super.stop = MP3Player_stop;
    // 添加 Windows 平台特殊的实现
    return (MediaPlayer*)player;
}

// MacOS 平台的播放器
MediaPlayer* MacOSPlatformImpl_createMediaPlayer(MacOSPlatformImpl* impl)
{
    WAVPlayerImpl* player = (WAVPlayerImpl*)malloc(sizeof(WAVPlayerImpl));
    player->super.play = WAVPlayer_play;
    player->super.pause = WAVPlayer_pause;
    player->super.stop = WAVPlayer_stop;
    // 添加 MacOS 平台特殊的实现
    return (MediaPlayer*)player;
}

// Linux 平台的播放器
MediaPlayer* LinuxPlatformImpl_createMediaPlayer(LinuxPlatformImpl* impl)
{
    FLACPlayerImpl* player = (FLACPlayerImpl*)malloc(sizeof(FLACPlayerImpl));
    player->super.play = FLACPlayer_play;
    player->super.pause = FLACPlayer_pause;
    player->super.stop = FLACPlayer_stop;
    // 添加 Linux 平台特殊的实现
    return (MediaPlayer*)player;
}

int main()
{
    MediaPlayerBridge bridge;
    bridge.createMediaPlayer = NULL;
    bridge.setPlatformImpl = MediaPlayerBridge_setPlatformImpl;
    bridge.setAudioImpl = MediaPlayerBridge_setAudioImpl;
    bridge.platformImpl = NULL;
    bridge.audioImpl = NULL;

    // Windows 平台的 MP3 播放器
    WindowsPlatformImpl windowsImpl;
    windowsImpl.createMediaPlayer = WindowsPlatformImpl_createMediaPlayer;
    bridge.setPlatformImpl(&bridge, &windowsImpl);
    MP3PlayerImpl mp3Impl;
    bridge.setAudioImpl(&bridge, &mp3Impl);
    MediaPlayer* player = MediaPlayerBridge_createMediaPlayer(&bridge);
    player->play(player);

    // MacOS 平台的 WAV 播放器
    MacOSPlatformImpl macosImpl;
    macosImpl.createMediaPlayer = MacOSPlatformImpl_createMediaPlayer;
    bridge.setPlatformImpl(&bridge, &macosImpl);
    WAVPlayerImpl wavImpl;
    bridge.setAudioImpl(&bridge, &wavImpl);
    player = MediaPlayerBridge_createMediaPlayer(&bridge);
    player->play(player);

    // Linux 平台的 FLAC 播放器
    LinuxPlatformImpl linuxImpl;
    linuxImpl.createMediaPlayer = LinuxPlatformImpl_createMediaPlayer;
    bridge.setPlatformImpl(&bridge, &linuxImpl);
    FLACPlayerImpl flacImpl;
    bridge.setAudioImpl(&bridge, &flacImpl);
    player = MediaPlayerBridge_createMediaPlayer(&bridge);
    player->play(player);

    return 0;
}