/*
 * pa_cosine.c
 * Generate a cosine wave
 *
 * Author: Christopher Dobrian
 *
 * This program uses the PortAudio Portable Audio Library.
 * For more information see: http://www.portaudio.com
 *
 */

#include <stdio.h>
#include <math.h>
#include "portaudio.h"

#define NUM_SECONDS   (4)
#define SAMPLE_RATE   (44100)
#define BUFFER_SIZE   (256)
#define TWOPI         (6.283185307179586)
#define FREQUENCY     1000.

typedef struct {
    float amplitude;
    float frequency;
    float phase;
    unsigned long count;
} paAudioData;

/* This routine will be called by the PortAudio engine when audio is needed. */

static int cosineCallback( void *inputBuffer, void *outputBuffer, unsigned long framesPerBuffer, PaTimestamp outTime, void *userData );

static int cosineCallback( void *inputBuffer, void *outputBuffer, unsigned long framesPerBuffer, PaTimestamp outTime, void *userData )
{

    /* Cast data passed through stream to the format of the local structure. */
    paAudioData *data = (paAudioData*)userData;
    // float *in = (float*)inputBuffer; // input buffer only needed for input
    float *out = (float*)outputBuffer;
	
    unsigned int i; // just a counter
    float A = data->amplitude;
    float twopiFoverR = TWOPI*data->frequency/SAMPLE_RATE;
    float phase = data->phase;
    float y; // temp variable for output sample
	
    for( i = 0 ; i < framesPerBuffer ; i++ )
    {
        y = A*cos(twopiFoverR*(data->count++)+phase);
        *out++ = y;		/* left channel */
        *out++ = y;		/* right channel*/
    }

    return 0;
}

/*******************************************************************/

static paAudioData data;

int main(void);

int main(void)
{
	PortAudioStream *stream;
	PaError err;
	
	printf("PortAudio: Cosine Wave, %.2f Hz.\n", FREQUENCY);

/* Initialize data for use by callback. */
	data.amplitude = 0.5;
	data.frequency = FREQUENCY;
        data.phase = 0.;

/* Initialize library before making any other calls. */
	err = Pa_Initialize();
	if( err != paNoError ) goto error;

/* Open an audio I/O stream. */
	err = Pa_OpenDefaultStream(
				&stream,
				0,              /* no input channels */
				2,              /* stereo output */
				paFloat32,      /* 32 bit floating point output */
				SAMPLE_RATE,
				BUFFER_SIZE,            /* frames per buffer */
				0,              /* number of buffers, if zero then use default minimum */
				cosineCallback,
				&data );
	if( err != paNoError ) goto error;

	err = Pa_StartStream( stream );
	if( err != paNoError ) goto error;

/* Sleep for several seconds. */
	Pa_Sleep(NUM_SECONDS*1000);

	err = Pa_StopStream( stream );
	if( err != paNoError ) goto error;

	err = Pa_CloseStream( stream );
	if( err != paNoError ) goto error;

	Pa_Terminate();
	printf("Calculated %ld samples.\n", data.count);
	printf("Finished.\n");
	return err;

error:
	Pa_Terminate();
	fprintf( stderr, "An error occured while using the portaudio stream.\n" ); 
	fprintf( stderr, "Error number: %d\n", err );
	fprintf( stderr, "Error message: %s\n", Pa_GetErrorText( err ) );
	return err;
}