Sine wave generator (buggy)

wave-gen.c

#include <stdio.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <string.h>
#include <arpa/inet.h>
#include <math.h>
#include <malloc.h>

struct wavehdr {
	char chunk_id[4];
	int chunk_size;
	char format[4];

	char subchunk1_id[4];
	int subchunk1_size;
	short audio_fmt;
	short nr_channels;
	int sample_rate;
	int byte_rate;
	short block_align;
	short bits_per_sample;

	char subchunk2_id[4];
	int subchunk2_size;
} __attribute__ ((packed));

int main(int argc, char *argv[])
{
	struct stat fbuf;
	int fsize;
	struct wavehdr whdr;
	int fdout;
	int read_bytes = 0;
	int sample_rate = 44100;
	int len_in_sec = atoi(argv[1]);
	int sine_freq = atoi(argv[2]);
	int nr_samples = len_in_sec * sample_rate;
	double i, period;
	int samples_per_sine_hz = sample_rate / sine_freq;
	short int *buf;
	int index;

	strcpy(whdr.chunk_id, "RIFF");
	strcpy(whdr.format, "WAVE");
	strcpy(whdr.subchunk1_id, "fmt ");
	strcpy(whdr.subchunk2_id, "data");

	whdr.subchunk1_size = 0x10; //Fixed for PCM
	whdr.audio_fmt = 0x1; //PCM
	whdr.nr_channels = 2; //stereo
	whdr.sample_rate = sample_rate; //CD Quality
	whdr.bits_per_sample = 16;
	whdr.byte_rate = (whdr.sample_rate * whdr.nr_channels * whdr.bits_per_sample) / 8;
	whdr.block_align = whdr.nr_channels * whdr.bits_per_sample / 8;
	whdr.subchunk2_size = nr_samples * whdr.nr_channels * whdr.bits_per_sample / 8;
	whdr.chunk_size = 4 + (8 + whdr.subchunk1_size) + (8 + whdr.subchunk2_size);

	fdout = open("/tmp/testwave", O_RDWR | O_CREAT, 0644);
	if (fdout < 0) {
		printf("create failed\n");
		goto exit;
	}

	write(fdout, &whdr, sizeof(whdr));

	period = (float) (360.0 / samples_per_sine_hz);
	i = 0;
	buf = (short int *)malloc(32*1024*sizeof(short int));
	if (!buf) {
		printf("Failed to allocate memory\n");
		close(fdout);
	}
	index = 0;
	while (nr_samples--) {
		double dx = sin((double)i * M_PI/180) ;
		short int x = ((short int) (sin((double)i * M_PI/180) * 0x7fff));
	//	printf("x = %x dx = %lf\n",x, dx);
		if (index < 32*1024)
			buf[index++] = x;
		else {
			write(fdout, buf, index * sizeof(short int));
			write(fdout, buf, index * sizeof(short int));
			index = 0;
		}
		i += period;
		if (i >= 360)
			i -= 360;
	}
	if (index) {
		write(fdout, buf, index * sizeof(short int));
		write(fdout, buf, index * sizeof(short int));
		free(buf);
	}
	close(fdout);
exit:
	return 0;
}