/*

     File: MyOpenALSupport.c

 Abstract: MyOpenALSupport.h

  Version: 1.2

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 */

#include "MyOpenALSupport.h"

void* MyGetOpenALAudioData(CFURLRef inFileURL, ALsizei *outDataSize, ALenum *outDataFormat, ALsizei*    outSampleRate)

{

    OSStatus                        err = noErr;    

    SInt64                          theFileLengthInFrames = 0;

    AudioStreamBasicDescription     theFileFormat;

    UInt32                          thePropertySize = sizeof(theFileFormat);

    ExtAudioFileRef                 extRef = NULL;

    void*                           theData = NULL;

    AudioStreamBasicDescription     theOutputFormat;

    // Open a file with ExtAudioFileOpen()

    err = ExtAudioFileOpenURL(inFileURL, &extRef);

    if(err) { printf("MyGetOpenALAudioData: ExtAudioFileOpenURL FAILED, Error = %ld\n", err); goto Exit; }

    // Get the audio data format

    err = ExtAudioFileGetProperty(extRef, kExtAudioFileProperty_FileDataFormat, &thePropertySize, &theFileFormat);

    if(err) { printf("MyGetOpenALAudioData: ExtAudioFileGetProperty(kExtAudioFileProperty_FileDataFormat) FAILED, Error = %ld\n", err); goto Exit; }

    if (theFileFormat.mChannelsPerFrame > 2)  { printf("MyGetOpenALAudioData - Unsupported Format, channel count is greater than stereo\n"); goto Exit;}

    // Set the client format to 16 bit signed integer (native-endian) data

    // Maintain the channel count and sample rate of the original source format

    theOutputFormat.mSampleRate = theFileFormat.mSampleRate;

    theOutputFormat.mChannelsPerFrame = theFileFormat.mChannelsPerFrame;

    theOutputFormat.mFormatID = kAudioFormatLinearPCM;

    theOutputFormat.mBytesPerPacket = 2 * theOutputFormat.mChannelsPerFrame;

    theOutputFormat.mFramesPerPacket = 1;

    theOutputFormat.mBytesPerFrame = 2 * theOutputFormat.mChannelsPerFrame;

    theOutputFormat.mBitsPerChannel = 16;

    theOutputFormat.mFormatFlags = kAudioFormatFlagsNativeEndian | kAudioFormatFlagIsPacked | kAudioFormatFlagIsSignedInteger;

    // Set the desired client (output) data format

    err = ExtAudioFileSetProperty(extRef, kExtAudioFileProperty_ClientDataFormat, sizeof(theOutputFormat), &theOutputFormat);

    if(err) { printf("MyGetOpenALAudioData: ExtAudioFileSetProperty(kExtAudioFileProperty_ClientDataFormat) FAILED, Error = %ld\n", err); goto Exit; }

    // Get the total frame count

    thePropertySize = sizeof(theFileLengthInFrames);

    err = ExtAudioFileGetProperty(extRef, kExtAudioFileProperty_FileLengthFrames, &thePropertySize, &theFileLengthInFrames);

    if(err) { printf("MyGetOpenALAudioData: ExtAudioFileGetProperty(kExtAudioFileProperty_FileLengthFrames) FAILED, Error = %ld\n", err); goto Exit; }

    // Read all the data into memory

    UInt32 theFramesToRead = (UInt32)theFileLengthInFrames;     

    UInt32 dataSize = theFramesToRead * theOutputFormat.mBytesPerFrame;;

    theData = malloc(dataSize);

    if (theData)

    {

        AudioBufferList     theDataBuffer;

        theDataBuffer.mNumberBuffers = 1;

        theDataBuffer.mBuffers[0].mDataByteSize = dataSize;

        theDataBuffer.mBuffers[0].mNumberChannels = theOutputFormat.mChannelsPerFrame;

        theDataBuffer.mBuffers[0].mData = theData;

        // Read the data into an AudioBufferList

        err = ExtAudioFileRead(extRef, &theFramesToRead, &theDataBuffer);

        if(err == noErr)

        {

            // success

            *outDataSize = (ALsizei)dataSize;

            *outDataFormat = (theOutputFormat.mChannelsPerFrame > 1) ? AL_FORMAT_STEREO16 : AL_FORMAT_MONO16;

            *outSampleRate = (ALsizei)theOutputFormat.mSampleRate;

        }

        else 

        { 

            // failure

            free (theData);

            theData = NULL; // make sure to return NULL

            printf("MyGetOpenALAudioData: ExtAudioFileRead FAILED, Error = %ld\n", err); goto Exit;

        }   

    }

Exit:

    // Dispose the ExtAudioFileRef, it is no longer needed

    if (extRef) ExtAudioFileDispose(extRef);

    return theData;

}