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hello_ll.c

/*
  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.

  gcc -Wall `pkg-config fuse --cflags --libs` hello_ll.c -o hello_ll
*/

#define FUSE_USE_VERSION 26

#include <fuse_lowlevel.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#include <assert.h>

static const char *hello_str = "Hello World!\n";
static const char *hello_name = "hello";

static int hello_stat(fuse_ino_t ino, struct stat *stbuf)
{
      stbuf->st_ino = ino;
      switch (ino) {
      case 1:
            stbuf->st_mode = S_IFDIR | 0755;
            stbuf->st_nlink = 2;
            break;

      case 2:
            stbuf->st_mode = S_IFREG | 0444;
            stbuf->st_nlink = 1;
            stbuf->st_size = strlen(hello_str);
            break;

      default:
            return -1;
      }
      return 0;
}

static void hello_ll_getattr(fuse_req_t req, fuse_ino_t ino,
                       struct fuse_file_info *fi)
{
      struct stat stbuf;

      (void) fi;

      memset(&stbuf, 0, sizeof(stbuf));
      if (hello_stat(ino, &stbuf) == -1)
            fuse_reply_err(req, ENOENT);
      else
            fuse_reply_attr(req, &stbuf, 1.0);
}

static void hello_ll_lookup(fuse_req_t req, fuse_ino_t parent, const char *name)
{
      struct fuse_entry_param e;

      if (parent != 1 || strcmp(name, hello_name) != 0)
            fuse_reply_err(req, ENOENT);
      else {
            memset(&e, 0, sizeof(e));
            e.ino = 2;
            e.attr_timeout = 1.0;
            e.entry_timeout = 1.0;
            hello_stat(e.ino, &e.attr);

            fuse_reply_entry(req, &e);
      }
}

00077 struct dirbuf {
      char *p;
      size_t size;
};

static void dirbuf_add(fuse_req_t req, struct dirbuf *b, const char *name,
                   fuse_ino_t ino)
{
      struct stat stbuf;
      size_t oldsize = b->size;
      b->size += fuse_add_direntry(req, NULL, 0, name, NULL, 0);
      b->p = (char *) realloc(b->p, b->size);
      memset(&stbuf, 0, sizeof(stbuf));
      stbuf.st_ino = ino;
      fuse_add_direntry(req, b->p + oldsize, b->size - oldsize, name, &stbuf,
                    b->size);
}

#define min(x, y) ((x) < (y) ? (x) : (y))

static int reply_buf_limited(fuse_req_t req, const char *buf, size_t bufsize,
                       off_t off, size_t maxsize)
{
      if (off < bufsize)
            return fuse_reply_buf(req, buf + off,
                              min(bufsize - off, maxsize));
      else
            return fuse_reply_buf(req, NULL, 0);
}

static void hello_ll_readdir(fuse_req_t req, fuse_ino_t ino, size_t size,
                       off_t off, struct fuse_file_info *fi)
{
      (void) fi;

      if (ino != 1)
            fuse_reply_err(req, ENOTDIR);
      else {
            struct dirbuf b;

            memset(&b, 0, sizeof(b));
            dirbuf_add(req, &b, ".", 1);
            dirbuf_add(req, &b, "..", 1);
            dirbuf_add(req, &b, hello_name, 2);
            reply_buf_limited(req, b.p, b.size, off, size);
            free(b.p);
      }
}

static void hello_ll_open(fuse_req_t req, fuse_ino_t ino,
                    struct fuse_file_info *fi)
{
      if (ino != 2)
            fuse_reply_err(req, EISDIR);
      else if ((fi->flags & 3) != O_RDONLY)
            fuse_reply_err(req, EACCES);
      else
            fuse_reply_open(req, fi);
}

static void hello_ll_read(fuse_req_t req, fuse_ino_t ino, size_t size,
                    off_t off, struct fuse_file_info *fi)
{
      (void) fi;

      assert(ino == 2);
      reply_buf_limited(req, hello_str, strlen(hello_str), off, size);
}

static struct fuse_lowlevel_ops hello_ll_oper = {
      .lookup           = hello_ll_lookup,
      .getattr    = hello_ll_getattr,
      .readdir    = hello_ll_readdir,
      .open       = hello_ll_open,
      .read       = hello_ll_read,
};

int main(int argc, char *argv[])
{
      struct fuse_args args = FUSE_ARGS_INIT(argc, argv);
      struct fuse_chan *ch;
      char *mountpoint;
      int err = -1;

      if (fuse_parse_cmdline(&args, &mountpoint, NULL, NULL) != -1 &&
          (ch = fuse_mount(mountpoint, &args)) != NULL) {
            struct fuse_session *se;

            se = fuse_lowlevel_new(&args, &hello_ll_oper,
                               sizeof(hello_ll_oper), NULL);
            if (se != NULL) {
                  if (fuse_set_signal_handlers(se) != -1) {
                        fuse_session_add_chan(se, ch);
                        err = fuse_session_loop(se);
                        fuse_remove_signal_handlers(se);
                        fuse_session_remove_chan(ch);
                  }
                  fuse_session_destroy(se);
            }
            fuse_unmount(mountpoint, ch);
      }
      fuse_opt_free_args(&args);

      return err ? 1 : 0;
}

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