// 音频格式
typedef Uint16 SDL_AudioFormat;

// audio flags
#define SDL_AUDIO_MASK_BITSIZE       (0xFF)
#define SDL_AUDIO_MASK_DATATYPE      (1<<8)
#define SDL_AUDIO_MASK_ENDIAN        (1<<12)
#define SDL_AUDIO_MASK_SIGNED        (1<<15)
#define SDL_AUDIO_BITSIZE(x)         (x & SDL_AUDIO_MASK_BITSIZE)
#define SDL_AUDIO_ISFLOAT(x)         (x & SDL_AUDIO_MASK_DATATYPE)
#define SDL_AUDIO_ISBIGENDIAN(x)     (x & SDL_AUDIO_MASK_ENDIAN)
#define SDL_AUDIO_ISSIGNED(x)        (x & SDL_AUDIO_MASK_SIGNED)
#define SDL_AUDIO_ISINT(x)           (!SDL_AUDIO_ISFLOAT(x))
#define SDL_AUDIO_ISLITTLEENDIAN(x)  (!SDL_AUDIO_ISBIGENDIAN(x))
#define SDL_AUDIO_ISUNSIGNED(x)      (!SDL_AUDIO_ISSIGNED(x))

/**
 *  \name Audio format flags
 *
 *  Defaults to LSB byte order.
 */
/* @{ */
#define AUDIO_U8        0x0008  /**< Unsigned 8-bit samples */
#define AUDIO_S8        0x8008  /**< Signed 8-bit samples */
#define AUDIO_U16LSB    0x0010  /**< Unsigned 16-bit samples */
#define AUDIO_S16LSB    0x8010  /**< Signed 16-bit samples */
#define AUDIO_U16MSB    0x1010  /**< As above, but big-endian byte order */
#define AUDIO_S16MSB    0x9010  /**< As above, but big-endian byte order */
#define AUDIO_U16       AUDIO_U16LSB
#define AUDIO_S16       AUDIO_S16LSB
/* @} */

/**
 *  \name int32 support
 */
/* @{ */
#define AUDIO_S32LSB    0x8020  /**< 32-bit integer samples */
#define AUDIO_S32MSB    0x9020  /**< As above, but big-endian byte order */
#define AUDIO_S32       AUDIO_S32LSB
/* @} */

/**
 *  \name float32 support
 */
/* @{ */
#define AUDIO_F32LSB    0x8120  /**< 32-bit floating point samples */
#define AUDIO_F32MSB    0x9120  /**< As above, but big-endian byte order */
#define AUDIO_F32       AUDIO_F32LSB
/* @} */

/**
 *  \name Native audio byte ordering
 */
/* @{ */
#if SDL_BYTEORDER == SDL_LIL_ENDIAN
#define AUDIO_U16SYS    AUDIO_U16LSB
#define AUDIO_S16SYS    AUDIO_S16LSB
#define AUDIO_S32SYS    AUDIO_S32LSB
#define AUDIO_F32SYS    AUDIO_F32LSB
#else
#define AUDIO_U16SYS    AUDIO_U16MSB
#define AUDIO_S16SYS    AUDIO_S16MSB
#define AUDIO_S32SYS    AUDIO_S32MSB
#define AUDIO_F32SYS    AUDIO_F32MSB
#endif
/* @} */

/**
 *  \name Allow change flags
 *
 *  Which audio format changes are allowed when opening a device.
 */
/* @{ */
#define SDL_AUDIO_ALLOW_FREQUENCY_CHANGE    0x00000001
#define SDL_AUDIO_ALLOW_FORMAT_CHANGE       0x00000002
#define SDL_AUDIO_ALLOW_CHANNELS_CHANGE     0x00000004
#define SDL_AUDIO_ALLOW_SAMPLES_CHANGE      0x00000008
#define SDL_AUDIO_ALLOW_ANY_CHANGE          (SDL_AUDIO_ALLOW_FREQUENCY_CHANGE|SDL_AUDIO_ALLOW_FORMAT_CHANGE|SDL_AUDIO_ALLOW_CHANNELS_CHANGE|SDL_AUDIO_ALLOW_SAMPLES_CHANGE)
/* @} */

/**
 *  This function is called when the audio device needs more data.
 *
 *  \param userdata An application-specific parameter saved in
 *                  the SDL_AudioSpec structure
 *  \param stream A pointer to the audio data buffer.
 *  \param len    The length of that buffer in bytes.
 *
 *  Once the callback returns, the buffer will no longer be valid.
 *  Stereo samples are stored in a LRLRLR ordering.
 *
 *  You can choose to avoid callbacks and use SDL_QueueAudio() instead, if
 *  you like. Just open your audio device with a NULL callback.
 */
typedef void (SDLCALL * SDL_AudioCallback) (void *userdata, Uint8 * stream,
                                            int len);

/**
 *  The calculated values in this structure are calculated by SDL_OpenAudio().
 *
 *  For multi-channel audio, the default SDL channel mapping is:
 *  2:  FL FR                       (stereo)
 *  3:  FL FR LFE                   (2.1 surround)
 *  4:  FL FR BL BR                 (quad)
 *  5:  FL FR FC BL BR              (quad + center)
 *  6:  FL FR FC LFE SL SR          (5.1 surround - last two can also be BL BR)
 *  7:  FL FR FC LFE BC SL SR       (6.1 surround)
 *  8:  FL FR FC LFE BL BR SL SR    (7.1 surround)
 */
typedef struct SDL_AudioSpec
{
    int freq;                   /**< DSP frequency -- samples per second */
    SDL_AudioFormat format;     /**< Audio data format */
    Uint8 channels;             /**< Number of channels: 1 mono, 2 stereo */
    Uint8 silence;              /**< Audio buffer silence value (calculated) */
    Uint16 samples;             /**< Audio buffer size in sample FRAMES (total samples divided by channel count) */
    Uint16 padding;             /**< Necessary for some compile environments */
    Uint32 size;                /**< Audio buffer size in bytes (calculated) */
    SDL_AudioCallback callback; /**< Callback that feeds the audio device (NULL to use SDL_QueueAudio()). */
    void *userdata;             /**< Userdata passed to callback (ignored for NULL callbacks). */
} SDL_AudioSpec;

struct SDL_AudioCVT;
typedef void (SDLCALL * SDL_AudioFilter) (struct SDL_AudioCVT * cvt,
                                          SDL_AudioFormat format);
/**
 *  \brief Upper limit of filters in SDL_AudioCVT
 *
 *  The maximum number of SDL_AudioFilter functions in SDL_AudioCVT is
 *  currently limited to 9. The SDL_AudioCVT.filters array has 10 pointers,
 *  one of which is the terminating NULL pointer.
 */
#define SDL_AUDIOCVT_MAX_FILTERS 9

typedef struct SDL_AudioCVT
{
    int needed;                 /**< Set to 1 if conversion possible */
    SDL_AudioFormat src_format; /**< Source audio format */
    SDL_AudioFormat dst_format; /**< Target audio format */
    double rate_incr;           /**< Rate conversion increment */
    Uint8 *buf;                 /**< Buffer to hold entire audio data */
    int len;                    /**< Length of original audio buffer */
    int len_cvt;                /**< Length of converted audio buffer */
    int len_mult;               /**< buffer must be len*len_mult big */
    double len_ratio;           /**< Given len, final size is len*len_ratio */
    SDL_AudioFilter filters[SDL_AUDIOCVT_MAX_FILTERS + 1]; /**< NULL-terminated list of filter functions */
    int filter_index;           /**< Current audio conversion function */
} SDL_AUDIOCVT_PACKED SDL_AudioCVT;

typedef enum
{
    SDL_AUDIO_STOPPED = 0,
    SDL_AUDIO_PLAYING,
    SDL_AUDIO_PAUSED
} SDL_AudioStatus;

/**
 *  Loads a WAV from a file.
 *  Compatibility convenience function.
 */
#define SDL_LoadWAV(file, spec, audio_buf, audio_len) \
    SDL_LoadWAV_RW(SDL_RWFromFile(file, "rb"),1, spec,audio_buf,audio_len)

struct SDL_AudioCVT;
typedef void (SDLCALL * SDL_AudioFilter) (struct SDL_AudioCVT * cvt,
                                          SDL_AudioFormat format);

/**
 *  \brief Upper limit of filters in SDL_AudioCVT
 *
 *  The maximum number of SDL_AudioFilter functions in SDL_AudioCVT is
 *  currently limited to 9. The SDL_AudioCVT.filters array has 10 pointers,
 *  one of which is the terminating NULL pointer.
 */
#define SDL_AUDIOCVT_MAX_FILTERS 9

#define SDL_AUDIOCVT_PACKED __attribute__((packed))
#else
#define SDL_AUDIOCVT_PACKED
#endif
/* */
typedef struct SDL_AudioCVT
{
    int needed;                 /**< Set to 1 if conversion possible */
    SDL_AudioFormat src_format; /**< Source audio format */
    SDL_AudioFormat dst_format; /**< Target audio format */
    double rate_incr;           /**< Rate conversion increment */
    Uint8 *buf;                 /**< Buffer to hold entire audio data */
    int len;                    /**< Length of original audio buffer */
    int len_cvt;                /**< Length of converted audio buffer */
    int len_mult;               /**< buffer must be len*len_mult big */
    double len_ratio;           /**< Given len, final size is len*len_ratio */
    SDL_AudioFilter filters[SDL_AUDIOCVT_MAX_FILTERS + 1]; /**< NULL-terminated list of filter functions */
    int filter_index;           /**< Current audio conversion function */
} SDL_AUDIOCVT_PACKED SDL_AudioCVT;