/* wav.c : PUBLIC DOMAIN - Jon Mayo - August 22, 2006
 * - You may remove any comments you wish, modify this code any way you wish,
 *   and distribute any way you wish.*/
/* simple WAV audio file exporter */

#include <stdio.h>
#include <stdlib.h>

/* used for making temp variables in macros */
#define make_name2(x,y) x##y
#define make_name(x,y) make_name2(x,y)
#define var(x) make_name(x,__LINE__)

/* WRite Little-Endian 32-bit value */
#define WR_LE32BIT(dest, offset, value) do { \
		unsigned var(tmp)=value; \
		(dest)[offset]=var(tmp)%256; \
		(dest)[offset+1]=(var(tmp)/256)%256; \
		(dest)[offset+2]=(var(tmp)/65536L)%256; \
		(dest)[offset+3]=(var(tmp)/16777216L)%256; \
	} while(0)

/* WRite Little-Endian 16-bit value */
#define WR_LE16BIT(dest, offset, value) do { \
		unsigned var(tmp)=value; \
		(dest)[offset]=var(tmp)%256; \
		(dest)[offset+1]=(var(tmp)/256)%256; \
	} while(0)


/* saves a single channel 16-bit sound file */
static int wav_save(const char *filename, short *data, unsigned nr_samples, unsigned sample_rate) {
	unsigned chunk_sz;
	FILE *f;
	unsigned i;
	unsigned char header[44] = {
		/* RIFF header */
		'R', 'I', 'F', 'F',	/* 000 - chunk id 'RIFF' */
		0, 0, 0, 0,		/* 004 - chunk size */
		'W', 'A', 'V', 'E',	/* 008 - riff format 'WAVE' */
		/* fmt sub-chunk */
		'f', 'm', 't', ' ',	/* 012 - 'fmt ' sub-chunk */
		16, 0, 0, 0,		/* 016 - sub-chunk size */
		1, 0,			/* 020 - 1 = PCM (Linear) */
		1, 0,			/* 022 - Number of channels */
		0, 0, 0, 0,		/* 024 - Sample rate */	
		0, 0, 0, 0, 		/* 028 - Byte rate */
		0, 0,			/* 032 - Bytes per sample */
		16, 0, 			/* 034 - Bits per sample */
		/* data sub-chunk */
		'd', 'a', 't', 'a',	/* 036 - 'data' sub-chunk */
		0, 0, 0, 0,		/* 040 - number of bytes for the data */
	};

	/* chunk size */
	chunk_sz=sizeof header - 8 + nr_samples * 16/8;
	WR_LE32BIT(header, 4, chunk_sz);
	WR_LE32BIT(header, 24, sample_rate);
	WR_LE32BIT(header, 28, sample_rate*1*16/8); /* byte rate */
	WR_LE16BIT(header, 32, 1 * 16/8); /* block alignment */
	WR_LE32BIT(header, 40, nr_samples * 16/8); /* data length */

	f=fopen(filename, "wb");
	if(!f) {
		perror(filename);
		return 0;
	}

	if(fwrite(header, sizeof header, 1, f)!=1) {
		perror(filename);
		fclose(f);
		return 0;
	}

	for(i=0;i<nr_samples;i++) {
		unsigned char data_encoded[2];
		WR_LE16BIT(data_encoded,0,data[i]);
		if(fwrite(data_encoded, sizeof data_encoded, 1, f)!=1) {
			perror(filename);
			fclose(f);
			return 0;
		}
	}
	
	fclose(f);
#ifndef NDEBUG
	fprintf(stderr, "%s:WAVE audio, PCM, 16 bit, mono %u Hz, %g seconds (%u samples)\n", filename, sample_rate, (double)nr_samples/(double)sample_rate, nr_samples);
#endif
	return 1;
}

#ifdef STAND_ALONE
/* example that makes a simple 1 second tone. requires math libraries to be
 * linked in. 
 */
#include <math.h>
#define NR(x) (sizeof(x)/sizeof*(x))
int main() {
	/* fills it with sine-wave data */
	short data[22050];
	const unsigned sample_rate=44100;
	const double frequency=1000.;
	int i;

	for(i=0;i<NR(data);i++) {
		data[i]=sin((2.*M_PI*(double)i*frequency)/(double)sample_rate)*32768.;
		/* guess what frequency this would be: 
		 * data[i]=sin(i)*32768.; 
		 */
	}
	if(!wav_save("test.wav", data, NR(data), sample_rate)) {
		fprintf(stderr, "FAILED!\n");
		return EXIT_FAILURE;
	}
	return 0;
}
#endif