/* make_wav.c
 * Creates a WAV file from an array of ints.
 * Output is monophonic, signed 16-bit samples
 * Fri Jun 18 16:36:23 PDT 2010 Kevin Karplus
 */

#include <stdio.h>
#include <assert.h>

#include "make_wav.h"

void write_little_endian(unsigned int word, int num_bytes, FILE *wav_file)
{
    unsigned buf;
    while(num_bytes>0)
    {   buf = word & 0xff;
    	fwrite(&buf, 1,1, wav_file);
        num_bytes--;
	word >>= 8;
    }
}

/* information about the WAV file format from
	http://ccrma.stanford.edu/courses/422/projects/WaveFormat/
 */

void write_wav(char * filename, unsigned long num_samples, short int * data, int s_rate)
{
    FILE* wav_file;
    unsigned int sample_rate;
    unsigned int num_channels;
    unsigned int bytes_per_sample;
    unsigned int byte_rate;
    unsigned long i;	/* counter for samples */
    
    num_channels = 1;	/* monoaural */
    bytes_per_sample = 2;
    
    if (s_rate<=0) sample_rate = 44100;
    else sample_rate = (unsigned int) s_rate;
    
    byte_rate = sample_rate*num_channels*bytes_per_sample;
    
    wav_file = fopen(filename, "w");
    assert(wav_file);	/* make sure it opened */
    
    /* write RIFF header */
    fwrite("RIFF", 1, 4, wav_file);
    write_little_endian(36 + bytes_per_sample* num_samples*num_channels, 4, wav_file);
    fwrite("WAVE", 1, 4, wav_file);

    /* write fmt  subchunk */
    fwrite("fmt ", 1, 4, wav_file);
    write_little_endian(16, 4, wav_file);	/* SubChunk1Size is 16 */
    write_little_endian(1, 2, wav_file);	/* PCM is format 1 */
    write_little_endian(num_channels, 2, wav_file);
    write_little_endian(sample_rate, 4, wav_file);
    write_little_endian(byte_rate, 4, wav_file);
    write_little_endian(num_channels*bytes_per_sample, 2, wav_file);  /* block align */
    write_little_endian(8*bytes_per_sample, 2, wav_file);  /* bits/sample */
  
    /* write data subchunk */
    fwrite("data", 1, 4, wav_file);
    write_little_endian(bytes_per_sample* num_samples*num_channels, 4, wav_file);
    for (i=0; i< num_samples; i++)
    { 	write_little_endian((unsigned int)(data[i]),bytes_per_sample, wav_file);
    }
    
    fclose(wav_file);
}