null.c

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/*
  FUSE: Filesystem in Userspace
  Copyright (C) 2001-2007  Miklos Szeredi <miklos@szeredi.hu>

  This program can be distributed under the terms of the GNU GPL.
  See the file COPYING.
*/

#define FUSE_USE_VERSION 31

#include <fuse.h>
#include <fuse_lowlevel.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <time.h>
#include <errno.h>

static int null_getattr(const char *path, struct stat *stbuf,
                        struct fuse_file_info *fi)
{
        (void) fi;

        if(strcmp(path, "/") != 0)
                return -ENOENT;

        stbuf->st_mode = S_IFREG | 0644;
        stbuf->st_nlink = 1;
        stbuf->st_uid = getuid();
        stbuf->st_gid = getgid();
        stbuf->st_size = (1ULL << 32); /* 4G */
        stbuf->st_blocks = 0;
        stbuf->st_atime = stbuf->st_mtime = stbuf->st_ctime = time(NULL);

        return 0;
}

static int null_truncate(const char *path, off_t size,
                         struct fuse_file_info *fi)
{
        (void) size;
        (void) fi;

        if(strcmp(path, "/") != 0)
                return -ENOENT;

        return 0;
}

static int null_open(const char *path, struct fuse_file_info *fi)
{
        (void) fi;

        if(strcmp(path, "/") != 0)
                return -ENOENT;

        return 0;
}

static int null_read(const char *path, char *buf, size_t size,
                     off_t offset, struct fuse_file_info *fi)
{
        (void) buf;
        (void) offset;
        (void) fi;

        if(strcmp(path, "/") != 0)
                return -ENOENT;

        if (offset >= (1ULL << 32))
                return 0;

        memset(buf, 0, size);
        return size;
}

static int null_write(const char *path, const char *buf, size_t size,
                      off_t offset, struct fuse_file_info *fi)
{
        (void) buf;
        (void) offset;
        (void) fi;

        if(strcmp(path, "/") != 0)
                return -ENOENT;

        return size;
}

static struct fuse_operations null_oper = {
        .getattr        = null_getattr,
        .truncate       = null_truncate,
        .open           = null_open,
        .read           = null_read,
        .write          = null_write,
};

int main(int argc, char *argv[])
{
        struct fuse_args args = FUSE_ARGS_INIT(argc, argv);
        struct fuse_cmdline_opts opts;
        struct stat stbuf;

        if (fuse_parse_cmdline(&args, &opts) != 0)
                return 1;

        if (!opts.mountpoint) {
                fprintf(stderr, "missing mountpoint parameter\n");
                return 1;
        }

        if (stat(opts.mountpoint, &stbuf) == -1) {
                fprintf(stderr ,"failed to access mountpoint %s: %s\n",
                        opts.mountpoint, strerror(errno));
                return 1;
        }
        if (!S_ISREG(stbuf.st_mode)) {
                fprintf(stderr, "mountpoint is not a regular file\n");
                return 1;
        }

        return fuse_main(argc, argv, &null_oper, NULL);
}