/*
 *  Wavetable2.c
 *  Wavetable2
 *
 *  Fill a table with values describing a waveform
 *  Then synthesize a tone by reading cyclically through that table
 *  Calculate the actual sample value by means of
 *  linear interpolation between two adjacent sample indices
 *  (more accurate than simple truncation of sample index)
 *
 *  Created by Christopher Dobrian on Tue Jan 20 2004.
 *
 */

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

#define	SAMPLE_RATE		(44100.)
#define	TABLE_LENGTH	1024
#define	BUFFER_SIZE		256
#define TWOPI			(6.283185307179586)
#define NUM_SECONDS		(4.)
#define FREQUENCY		(440.)
#define MAX_AMP			(0.5)

typedef struct {
    float	frequency;
    float	amplitude;
    float	phase;
    float	*wavetable;
    float	n;
} wave; // data to pass to callback function

const float oneoversr = 1./SAMPLE_RATE;


// fill a table with one cycle of a sine waveform
void filltable( float *table, unsigned long length);
// This routine will be called by the PortAudio engine when audio is needed.
static int sineCallback( void *inputBuffer, void *outputBuffer, unsigned long framesPerBuffer, PaTimestamp outTime, void *userData );
int main(void);

void filltable( float *table, unsigned long length) {
    unsigned long i;
    const float twopioverlength = 8.*atan(1.)/length; // or TWOPI/length
    
	for ( i = 0; i < length; i++)
		*(table++) = sin(i*twopioverlength);
	*table = 0.; // final (returning) point for interpolation purposes
	
	return;
}

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

    /* Cast data passed through stream to the format of the local structure. */
    wave *data = (wave*)userData;
    // float *in = (float*)inputBuffer; // input buffer only needed for input
    float *out = (float*)outputBuffer;
	
    unsigned int i; // a counter
	float f; // hold fractional part of sample index
    float y; // temp variable for output sample
	
    for( i = 0 ; i < framesPerBuffer ; i++ )
    {
        f = data->n - (int)data->n; // get fractional part of index
		// use it to interpolate between the two closest sample indices
		y = data->amplitude*((1.-f)*(data->wavetable[(int)data->n])+f*(data->wavetable[(int)data->n+1]));
        data->n += data->frequency*TABLE_LENGTH*oneoversr; // increment the wave's counter
        while ( data->n > TABLE_LENGTH) data->n -= TABLE_LENGTH; // keep it in range
		*out++ = y;		/* left channel */
        *out++ = y;		/* right channel*/
    }

    return 0;
}

int main(void) {
	PortAudioStream *stream;
	PaError err;
	wave	wave2; // my data structure
	float	table2[TABLE_LENGTH+1]; // wavetable with final interpolation point
        
    filltable( table2, TABLE_LENGTH);
	
	printf("PortAudio: Sine Wave, %.2f Hz.\n", FREQUENCY);

// Initialize data for use by callback.
	wave2.frequency = FREQUENCY;
    wave2.amplitude = MAX_AMP;
    wave2.phase = 0.;
    wave2.wavetable = table2;
    wave2.n = 0. + wave2.phase*TABLE_LENGTH;

// 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 */
				sineCallback,
				&wave2 );
	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("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;
}