shithub: sox

ref: 8284ec8c87352c941cbf410978ab5d571c961467
dir: /src/nulfile.c/

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/*
 * July 5, 1991
 * Copyright 1991 Lance Norskog And Sundry Contributors
 * This source code is freely redistributable and may be used for
 * any purpose.  This copyright notice must be maintained. 
 * Lance Norskog And Sundry Contributors are not responsible for 
 * the consequences of using this software.
 */

/*
 * Sound Tools nul file format driver.
 * Written by Carsten Borchardt 
 * The author is not responsible for the consequences 
 * of using this software
 *
 */

#include <math.h>
#include "st_i.h"

/* Private data for nul file */
typedef struct nulstuff {
	int	rest;			/* bytes remaining in current block */
    unsigned long readsamples;
    unsigned long writesamples;
} *nul_t;

/*
 * Do anything required before you start reading samples.
 * Read file header. 
 *	Find out sampling rate, 
 *	size and encoding of samples, 
 *	mono/stereo/quad.
 */
int st_nulstartread(ft_t ft) 
{
	nul_t sk = (nul_t) ft->priv;
	/* no samples read yet */
	sk->readsamples=0;

	/* if no input rate is given as parameter, switch to 
	 * default parameter
	 */
	if(ft->info.rate == 0){
	    /* input rate not set, switch to default */
	    ft->info.rate = 44100;
	    ft->info.size = ST_SIZE_WORD;
	    ft->info.encoding = ST_ENCODING_SIGN2;
	    ft->info.channels = 2;
	}
	ft->comment = "nul file";
	
	/* only SIGINT will stop us from reading nul data.. 
	 *
	 */
	sigintreg(ft);	/* Prepare to catch SIGINT */

	return (ST_SUCCESS);
}

/*
 * Read up to len samples, we read always '0'
 * Convert to signed longs.
 * Place in buf[].
 * Return number of samples read.
 */

st_ssize_t st_nulread(ft_t ft, st_sample_t *buf, st_ssize_t len) 
{
	nul_t sk = (nul_t) ft->priv;
	int done = 0;
	st_sample_t l;
	for(; done < len; done++) {
	    if (ft->file.eof)
		break;
	    l = 0; /* nul samples are always 0 */
	    sk->readsamples++;
	    *buf++ = l;
	}
	return done;
}

/*
 * Do anything required when you stop reading samples.  
 * Don't close input file! 
 * .. nothing to be done
 */
int st_nulstopread(ft_t ft) 
{ 
    return (ST_SUCCESS);
}

int st_nulstartwrite(ft_t ft) 
{
	nul_t sk = (nul_t) ft->priv;
	sk->writesamples=0;
	return(ST_SUCCESS);
	
}

st_ssize_t st_nulwrite(ft_t ft, st_sample_t *buf, st_ssize_t len) 
{
	nul_t sk = (nul_t) ft->priv;
	while(len--)
	    sk->writesamples++;
	st_writeb(ft, (*buf++ >> 24) ^ 0x80);
	return (ST_SUCCESS);
	
}

int st_nulstopwrite(ft_t ft) 
{
    /* nothing to do */
    return (ST_SUCCESS);
}