null.c

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/*
 * Copyright (C) 2000-2004 by ETH Zurich
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/* @file null.c - a nut/os null device driver
 * @brief A /dev/null device driver
 * This can be useful if your application might write unwanted output to stdout.
 * With this deveice you can redirect stdout to the nullDev which discards any output
 * Any IOCTL will result in OK, and any read will give back zero read bytes
 *
 * 2005.06.21 Matthias Ringwald <matthias.ringwald@inf.ethz.ch>
 *
 */

#include <compiler.h>
#include <stdlib.h>

#include <sys/file.h>
#include <sys/device.h>


static NUTFILE *NullOpen(NUTDEVICE * dev, CONST char *name, int mode, int acc)
{
    NUTFILE *nf;

    nf = malloc(sizeof(NUTFILE));

    // enter data
    nf->nf_next = 0;
    nf->nf_dev = dev;

    return nf;
}


static int NullWrite(NUTFILE * nf, CONST void *buffer, int len)
{
    return len;
}
#ifdef __HARVARD_ARCH__
static int NullWriteP(NUTFILE * nf, PGM_P buffer, int len)
{
    return len;
}
#endif



 
static int NullRead(NUTFILE * nf, void *buffer, int len)
{
    // test for read len. len == 0 => flush fd
    if (len == 0){
        return 0;
    }

        // otherwise also just return 0 bytes without blocking
    return 0;
}

static int NullClose(NUTFILE * nf)
{
        if (nf)
                free (nf);
    return 0;
}

int NullIOCTL(NUTDEVICE * dev, int req, void *conf)
{
    return 0;
}

/* ======================= Devices ======================== */
NUTDEVICE devNull = {
    0,                          
    {'n', 'u', 'l', 'l', 0, 0, 0, 0, 0},
    0,                          
    0,                          
    0,                          
    0,                          
    0,                          
    0,                          
    NullIOCTL,                  
    NullRead,
    NullWrite,
#ifdef __HARVARD_ARCH__
    NullWriteP,
#endif
    NullOpen,
    NullClose,
    0
};