static int check_sig();
int open_file(int rd, int wr);
int close_file();
int read_samples(double *buffer, int64_t len);
int write_samples(double **buffer, int64_t len);
static int check_sig();
int open_file(int rd, int wr);
int close_file();
int read_samples(double *buffer, int64_t len);
int write_samples(double **buffer, int64_t len);