//-------------------------------------------------------------------
//	makewave.cpp
//
//	This program generates the Pulse Code Modulation data for a
//	musical tone of one second's duration having a given pitch,
//	and stores it as a .wav format file (named 'wavetone.wav').
//
//		     compile using:  $ make makewave
//
//	NOTE: The Waveform Audio File Format is a fully-documented, 
//	proprietary format, developed jointly by IBM and Microsoft,
//	originally for the Windows 3.1 operating system in 1991 and
//	widely adopted for exchange of broadcast audio information. 
//	Although their specification has been subsequently expanded
//	and updated, the original document is online as "Multimedia 
//	Programming Interface and Data Specifications 1.0," (1991).
//
//	programmer: ALLAN CRUSE
//	written on: 11 SEP 2005
//-------------------------------------------------------------------

#include <stdio.h>	// for printf(), perror() 
#include <fcntl.h>	// for open() 
#include <stdlib.h>	// for exit() 
#include <unistd.h>	// for write(), close() 

#define SAMPLE_RATE	8000
#define NUM_SAMPLES	SAMPLE_RATE

unsigned char	pulsecode[ NUM_SAMPLES ];
char 	filename[] = "wavetone.wav";

int main( int argc, char **argv )
{
	// specify our default parameters for tone generation
	int	sampleRate = SAMPLE_RATE, numSamples = NUM_SAMPLES;
	int	frequency = 440, amplitude = 64, silence = 128;	

	// accept an alternate frequency as a command-line argument
	if ( argc > 1 ) 
		{
		int	input = atoi( argv[1] );
		if ((input > 0)||(input < sampleRate/2)) frequency = input;
		else	{ printf( "frequency out-of-range\n" ), exit(1); }
		} 

	// apply our 'Timer-Counter' model for Square Wave generation 
	int	latchValue = sampleRate / frequency;
	int	countValue = 0;
	for (int sample = 0; sample < NUM_SAMPLES; sample++)
		{
		if ( countValue == 0 ) countValue = latchValue;
		int	flipflop = ( countValue < latchValue/2 ) ? -1 : 1; 
		pulsecode[ sample ] = silence + flipflop * amplitude;
		--countValue;
		} 

	//----------------------------------------------
	// now store the pulse-code data as a .wav file
	//----------------------------------------------

	// setup the .wav file parameters
	int	fmt_ChunkSize = 16;
	int	dataChunkSize = numSamples;
	int	riffChunkSize = 4 + (8+fmt_ChunkSize) + (8+dataChunkSize);
	int	formatTag = 1; 
	int	nChannels = 1;
	int	bitsPerSample = 8;
	int	samplesPerSec = sampleRate;
	int	avBytesPerSec = samplesPerSec * nChannels;
	int	frameAlignmnt = nChannels * (bitsPerSample/8);

	// open the .wav file for writing
	int	fd = open( filename, O_WRONLY | O_CREAT | O_TRUNC, 0666 );
	if ( fd < 0 ) { perror( filename ); exit(1); }

	// write the RIFF chunk
	write( fd, "RIFF", 4 );
	write( fd, &riffChunkSize, 4 );
	write( fd, "WAVE", 4 );

	// write the FORMAT chunk
	write( fd, "fmt ", 4 );
	write( fd, &fmt_ChunkSize, 4 );
	write( fd, &formatTag, 2 );
	write( fd, &nChannels, 2 );
	write( fd, &samplesPerSec, 4 );
	write( fd, &avBytesPerSec, 4 );
	write( fd, &frameAlignmnt, 2 );
	write( fd, &bitsPerSample, 2 );
	
	// write the DATA chunk
	write( fd, "data", 4 );
	write( fd, &dataChunkSize, 4 );
	write( fd, pulsecode, numSamples );

	// close the .wav file 
	close( fd );

	// show the filename and filesize to our user
	printf( "\npulse-code data saved as \'%s\' ", filename );
	printf( "(%d bytes) \n\n", 8+riffChunkSize );
}