加载WAV音频文件的接口

int DSound_Load_WAV(char *filename, int control_flags)
{
// this function loads a .wav file, sets up the directsound 
// buffer and loads the data into memory, the function returns 
// the id number of the sound


HMMIO 			hwav;    // handle to wave file
MMCKINFO		parent,  // parent chunk
                child;   // child chunk
WAVEFORMATEX    wfmtx;   // wave format structure

int	sound_id = -1,       // id of sound to be loaded
	index;               // looping variable

UCHAR *snd_buffer,       // temporary sound buffer to hold voc data
      *audio_ptr_1=NULL, // data ptr to first write buffer 
	  *audio_ptr_2=NULL; // data ptr to second write buffer

DWORD audio_length_1=0,  // length of first write buffer
	  audio_length_2=0;  // length of second write buffer
			
// step one: are there any open id's ?
for (index=0; index < MAX_SOUNDS; index++)
	{	
    // make sure this sound is unused
	if (sound_fx[index].state==SOUND_NULL)
	   {
	   sound_id = index;
	   break;
	   } // end if

	} // end for index

// did we get a free id?
if (sound_id==-1)
	return(-1);

// set up chunk info structure
parent.ckid 	    = (FOURCC)0;
parent.cksize 	    = 0;
parent.fccType	    = (FOURCC)0;
parent.dwDataOffset = 0;
parent.dwFlags		= 0;

// copy data
child = parent;

// open the WAV file
if ((hwav = mmioOpen(filename, NULL, MMIO_READ | MMIO_ALLOCBUF))==NULL)
    return(-1);

// descend into the RIFF 
parent.fccType = mmioFOURCC('W', 'A', 'V', 'E');

if (mmioDescend(hwav, &parent, NULL, MMIO_FINDRIFF))
    {
    // close the file
    mmioClose(hwav, 0);

    // return error, no wave section
    return(-1); 	
    } // end if

// descend to the WAVEfmt 
child.ckid = mmioFOURCC('f', 'm', 't', ' ');

if (mmioDescend(hwav, &child, &parent, 0))
    {
    // close the file
    mmioClose(hwav, 0);

    // return error, no format section
    return(-1); 	
    } // end if

// now read the wave format information from file
if (mmioRead(hwav, (char *)&wfmtx, sizeof(wfmtx)) != sizeof(wfmtx))
    {
    // close file
    mmioClose(hwav, 0);

    // return error, no wave format data
    return(-1);
    } // end if

// make sure that the data format is PCM
if (wfmtx.wFormatTag != WAVE_FORMAT_PCM)
    {
    // close the file
    mmioClose(hwav, 0);

    // return error, not the right data format
    return(-1); 
    } // end if

// now ascend up one level, so we can access data chunk
if (mmioAscend(hwav, &child, 0))
   {
   // close file
   mmioClose(hwav, 0);

   // return error, couldn't ascend
   return(-1); 	
   } // end if

// descend to the data chunk 
child.ckid = mmioFOURCC('d', 'a', 't', 'a');

if (mmioDescend(hwav, &child, &parent, MMIO_FINDCHUNK))
    {
    // close file
    mmioClose(hwav, 0);

    // return error, no data
    return(-1); 	
    } // end if

// finally!!!! now all we have to do is read the data in and
// set up the directsound buffer

// allocate the memory to load sound data
snd_buffer = (UCHAR *)malloc(child.cksize);

// read the wave data 
mmioRead(hwav, (char *)snd_buffer, child.cksize);

// close the file
mmioClose(hwav, 0);

// set rate and size in data structure
sound_fx[sound_id].rate  = wfmtx.nSamplesPerSec;
sound_fx[sound_id].size  = child.cksize;
sound_fx[sound_id].state = SOUND_LOADED;

// set up the format data structure
memset(&pcmwf, 0, sizeof(WAVEFORMATEX));

pcmwf.wFormatTag	  = WAVE_FORMAT_PCM;  // pulse code modulation
pcmwf.nChannels		  = 1;                // mono 
pcmwf.nSamplesPerSec  = 11025;            // always this rate
pcmwf.nBlockAlign	  = 1;                
pcmwf.nAvgBytesPerSec = pcmwf.nSamplesPerSec * pcmwf.nBlockAlign;
pcmwf.wBitsPerSample  = 8;
pcmwf.cbSize		  = 0;

// prepare to create sounds buffer
dsbd.dwSize			= sizeof(DSBUFFERDESC);
dsbd.dwFlags		= control_flags | DSBCAPS_STATIC | DSBCAPS_LOCSOFTWARE;
dsbd.dwBufferBytes	= child.cksize;
dsbd.lpwfxFormat	= &pcmwf;

// create the sound buffer
if (FAILED(lpds->CreateSoundBuffer(&dsbd,&sound_fx[sound_id].dsbuffer,NULL)))
   {
   // release memory
   free(snd_buffer);

   // return error
   return(-1);
   } // end if

// copy data into sound buffer
if (FAILED(sound_fx[sound_id].dsbuffer->Lock(0,					 
								      child.cksize,			
								      (void **) &audio_ptr_1, 
								      &audio_length_1,
								      (void **)&audio_ptr_2, 
								      &audio_length_2,
								      DSBLOCK_FROMWRITECURSOR)))
								 return(0);

// copy first section of circular buffer
memcpy(audio_ptr_1, snd_buffer, audio_length_1);

// copy last section of circular buffer
memcpy(audio_ptr_2, (snd_buffer+audio_length_1),audio_length_2);

// unlock the buffer
if (FAILED(sound_fx[sound_id].dsbuffer->Unlock(audio_ptr_1, 
									    audio_length_1, 
									    audio_ptr_2, 
									    audio_length_2)))
 							     return(0);

// release the temp buffer
free(snd_buffer);

// return id
return(sound_id);

} // end DSound_Load_WAV