hello_ll.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.

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

#define FUSE_USE_VERSION 26

#include <ganesha_fuse_ll_wrap.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);
    }
}

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;
}