//-------------------------------------------------------------------
//	pcmplay.cpp
//
//	This program plays back the Waveform Audio File (.wav) whose
//	filename is provided by the user as a command-line argument.
//
//		  compile using:  $ make pcmplay
//		  execute using:  $ pcmplay <filename>	
//	
//	Online reference: "Audio Programming," 4Front Technologies,
//		<http://www.4front-tech.com/pguide/audio.html>
//
//	programmer: ALLAN CRUSE
//	written on: 11 SEP 2005
//-------------------------------------------------------------------

#include <stdio.h>	// for fprintf(), perror() 
#include <fcntl.h>	// for open() 
#include <stdlib.h>	// for exit() 
#include <unistd.h>	// for read(), write(), close() 
#include <string.h>	// for strncmp()
#include <sys/mman.h>	// for mmap()
#include <sys/ioctl.h>	// for ioctl()
#include <sys/soundcard.h>	

char devname[] = "/dev/audio";

int main( int argc, char **argv )
{
	// check for required command-line argument
	if ( argc == 1 )
		{
		fprintf( stderr, "usage: pcmplay <filename> \n" ); 
		exit(1); 
		}

	// setup the filename for waveform audio data
	char	wavname[ 100 ];
	strncpy( wavname, argv[ 1 ], 95 );
	strtok( wavname, ". \n\t" );
	strcat( wavname, ".wav" );

	// memory-map the data file to user-space 
	int	wav = open( wavname, O_RDONLY );
	if ( wav < 0 ) { perror( wavname ); exit(1); }
	int	filesize = lseek( wav, 0, SEEK_END );
	int	prot = PROT_READ;
	int	flag = MAP_PRIVATE;
	char	*mm = (char*)mmap( NULL, filesize, prot, flag, wav, 0 );
	if ( mm == MAP_FAILED ) { perror( "mmap" ); exit(1); }

	// verify the .wav file-format
	fprintf( stdout, "\nplaying \'%s\' (%d bytes)\n", wavname, filesize );	
	if (( strncmp( mm+0, "RIFF", 4 ) )||( strncmp( mm+8, "WAVE", 4 ) ))
		{ fprintf( stderr, "Not a Waveform Audio file\n" ); exit(1); }

	// extract the audio playback parameters
	char	*fmt = mm+12;
	int	chunkSize = *(int*)(fmt+4);
	if ( strncmp( fmt, "fmt ", 4 ) ) 
		{ fprintf( stderr, "format-chunk not found\n" ); exit(1); } 
	
	short	formatTag = *(short*)(fmt+8);
	short	nChannels = *(short*)(fmt+10);
	int	samplesPerSec = *(int*)(fmt+12);
	int	avBytesPerSec = *(int*)(fmt+16);
	short	blockAlignmnt = *(int*)(fmt+20);
	short	bitsPerSample = *(int*)(fmt+22);

	if (( formatTag != 1 )||( chunkSize != 16 )) 
		{ fprintf( stderr, "unsupported format\n" ); exit(1); }

	// locate the DATA chunk and its waveform data
	int	morebytes = filesize - 12;
	char	*dat = fmt + 8 + chunkSize;
	chunkSize = *(int*)(dat + 4 );
	while ( morebytes > 0 )
		{
		if ( strncmp( dat, "data", 4 ) == 0 ) break;
		dat += 8 + chunkSize;
		morebytes -= 8 + chunkSize;
		}
	dat += 8;	// point past the chunk-header to the chunk-data
	if ( morebytes < 8 ) { perror( "data-chunk not found\n" ); exit(1); }

	// open the audio device-file and set its playback parameters 
	int	bits = ( bitsPerSample == 8 ) ? AFMT_U8 : AFMT_S16_BE;
	int	chns = ( nChannels == 1 ) ? 1 : 2;
	int	rate = samplesPerSec;
	int	dev = open( devname, O_WRONLY );
	if ( dev < 0 ) { perror( devname ); exit(1); }
	if (( ioctl( dev, SNDCTL_DSP_SETFMT, &bits ) < 0 )
		||( ioctl( dev, SNDCTL_DSP_CHANNELS, &chns ) < 0 )
		||( ioctl( dev, SNDCTL_DSP_SPEED, &rate ) < 0 ))
		{ perror( "audio format not supported\n" ); exit(1); }
	
	// main loop to playback the waveform audio data	
	int	bytes_to_play = chunkSize;
	while ( bytes_to_play > 0 )
		{
		int	nbytes = write( dev, dat, bytes_to_play );
		bytes_to_play -= nbytes;
		dat += nbytes;
		}
	close( dev );

	// report the playback duration
	double	duration = (double)chunkSize / avBytesPerSec; 
	fprintf( stdout, "finished playing after %0.2f seconds\n\n", duration );
}