C++ DECL_G函数代码示例

/* Nautilus loves to use access(2) to test everything about a file,
 * such as whether it's executable.  Therefore treat this a lot like
 * mount_local_getattr.
 */
static int
mount_local_access (const char *path, int mask)
{
  struct stat statbuf;
  int r;
  struct fuse_context *fuse;
  int ok = 1;
  DECL_G ();
  DEBUG_CALL ("%s, %d", path, mask);

  if (g->ml_read_only && (mask & W_OK))
    return -EROFS;

  r = mount_local_getattr (path, &statbuf);
  if (r < 0 || mask == F_OK) {
    debug (g, "%s: mount_local_getattr returned r = %d", path, r);
    return r;
  }

  fuse = fuse_get_context ();

  /* Root user should be able to access everything, so only bother
   * with these fine-grained tests for non-root.  (RHBZ#1106548).
   */
  if (fuse->uid != 0) {
    if (mask & R_OK)
      ok = ok &&
        (  fuse->uid == statbuf.st_uid ? statbuf.st_mode & S_IRUSR
           : fuse->gid == statbuf.st_gid ? statbuf.st_mode & S_IRGRP
           : statbuf.st_mode & S_IROTH);
    if (mask & W_OK)
      ok = ok &&
        (  fuse->uid == statbuf.st_uid ? statbuf.st_mode & S_IWUSR
           : fuse->gid == statbuf.st_gid ? statbuf.st_mode & S_IWGRP
           : statbuf.st_mode & S_IWOTH);
    if (mask & X_OK)
      ok = ok &&
        (  fuse->uid == statbuf.st_uid ? statbuf.st_mode & S_IXUSR
           : fuse->gid == statbuf.st_gid ? statbuf.st_mode & S_IXGRP
           : statbuf.st_mode & S_IXOTH);
  }

  debug (g, "%s: "
         "testing access mask%s%s%s%s: "
         "caller UID:GID = %ju:%ju, "
         "file UID:GID = %ju:%ju, "
         "file mode = %o, "
         "result = %s",
         path,
         mask & R_OK ? " R_OK" : "",
         mask & W_OK ? " W_OK" : "",
         mask & X_OK ? " X_OK" : "",
         mask == 0 ? " 0" : "",
         (uintmax_t) fuse->uid, (uintmax_t) fuse->gid,
         (uintmax_t) statbuf.st_uid, (uintmax_t) statbuf.st_gid,
         statbuf.st_mode,
         ok ? "OK" : "EACCESS");

  return ok ? 0 : -EACCES;
}

static int
mount_local_read (const char *path, char *buf, size_t size, off_t offset,
                  struct fuse_file_info *fi)
{
  char *r;
  size_t rsize;
  const size_t limit = 2 * 1024 * 1024;
  DECL_G ();
  DEBUG_CALL ("%s, %p, %zu, %ld", path, buf, size, (long) offset);

  /* The guestfs protocol limits size to somewhere over 2MB.  We just
   * reduce the requested size here accordingly and push the problem
   * up to every user.  http://www.jwz.org/doc/worse-is-better.html
   */
  if (size > limit)
    size = limit;

  r = guestfs_pread (g, path, size, offset, &rsize);
  if (r == NULL)
    RETURN_ERRNO;

  /* This should never happen, but at least it stops us overflowing
   * the output buffer if it does happen.
   */
  if (rsize > size)
    rsize = size;

  memcpy (buf, r, rsize);
  free (r);

  return rsize;
}

static int
mount_local_readlink (const char *path, char *buf, size_t size)
{
  const char *r;
  int free_it = 0;
  size_t len;
  DECL_G ();
  DEBUG_CALL ("%s, %p, %zu", path, buf, size);

  r = rlc_lookup (g, path);
  if (!r) {
    r = guestfs_readlink (g, path);
    if (r == NULL)
      RETURN_ERRNO;
    free_it = 1;
  }

  /* Note this is different from the real readlink(2) syscall.  FUSE wants
   * the string to be always nul-terminated, even if truncated.
   */
  len = strlen (r);
  if (len > size - 1)
    len = size - 1;

  memcpy (buf, r, len);
  buf[len] = '\0';

  if (free_it) {
    char *tmp = (char *) r;
    free (tmp);
  }

  return 0;
}

static int
mount_local_statfs (const char *path, struct statvfs *stbuf)
{
  CLEANUP_FREE_STATVFS struct guestfs_statvfs *r;
  DECL_G ();
  DEBUG_CALL ("%s, %p", path, stbuf);

  r = guestfs_statvfs (g, path);
  if (r == NULL)
    RETURN_ERRNO;

  stbuf->f_bsize = r->bsize;
  stbuf->f_frsize = r->frsize;
  stbuf->f_blocks = r->blocks;
  stbuf->f_bfree = r->bfree;
  stbuf->f_bavail = r->bavail;
  stbuf->f_files = r->files;
  stbuf->f_ffree = r->ffree;
  stbuf->f_favail = r->favail;
  stbuf->f_fsid = r->fsid;
  stbuf->f_flag = r->flag;
  stbuf->f_namemax = r->namemax;

  return 0;
}

/* Ditto as above. */
static int
mount_local_listxattr (const char *path, char *list, size_t size)
{
  DECL_G ();
  DEBUG_CALL ("%s, %p, %zu", path, list, size);

  const struct guestfs_xattr_list *xattrs;
  int free_attrs = 0;

  xattrs = xac_lookup (g, path);
  if (xattrs == NULL) {
    xattrs = guestfs_lgetxattrs (g, path);
    if (xattrs == NULL)
      RETURN_ERRNO;
    free_attrs = 1;
  }

  /* Calculate how much space is required to hold the result. */
  size_t space = 0;
  size_t len;
  size_t i;
  for (i = 0; i < xattrs->len; ++i) {
    len = strlen (xattrs->val[i].attrname) + 1;
    space += len;
  }

  /* The listxattr man page is unclear, but if list == NULL then we
   * return the space required (the caller then makes a second syscall
   * after allocating the required amount of space).  If list != NULL
   * then it's not clear what we should do, but it appears we should
   * copy as much as possible and return -ERANGE if there's not enough
   * space in the buffer.
   */
  ssize_t r;
  if (list == NULL) {
    r = space;
    goto out;
  }

  r = 0;
  for (i = 0; i < xattrs->len; ++i) {
    len = strlen (xattrs->val[i].attrname) + 1;
    if (size >= len) {
      memcpy (list, xattrs->val[i].attrname, len);
      size -= len;
      list += len;
      r += len;
    } else {
      r = -ERANGE;
      break;
    }
  }

 out:
  if (free_attrs)
    guestfs_free_xattr_list ((struct guestfs_xattr_list *) xattrs);

  return r;
}

/* The guestfs(3) API for getting xattrs is much easier to use
 * than the real syscall.  Unfortunately we now have to emulate
 * the real syscall using that API :-(
 */
static int
mount_local_getxattr (const char *path, const char *name, char *value,
                      size_t size)
{
  DECL_G ();
  DEBUG_CALL ("%s, %s, %p, %zu", path, name, value, size);

  const struct guestfs_xattr_list *xattrs;
  int free_attrs = 0;

  xattrs = xac_lookup (g, path);
  if (xattrs == NULL) {
    xattrs = guestfs_lgetxattrs (g, path);
    if (xattrs == NULL)
      RETURN_ERRNO;
    free_attrs = 1;
  }

  /* Find the matching attribute (index in 'i'). */
  ssize_t r;
  size_t i;
  for (i = 0; i < xattrs->len; ++i) {
    if (STREQ (xattrs->val[i].attrname, name))
      break;
  }

  if (i == xattrs->len) {       /* not found */
    r = -ENOATTR;
    goto out;
  }

  /* The getxattr man page is unclear, but if value == NULL then we
   * return the space required (the caller then makes a second syscall
   * after allocating the required amount of space).  If value != NULL
   * then it's not clear what we should do, but it appears we should
   * copy as much as possible and return -ERANGE if there's not enough
   * space in the buffer.
   */
  size_t sz = xattrs->val[i].attrval_len;
  if (value == NULL) {
    r = sz;
    goto out;
  }

  if (sz <= size)
    r = sz;
  else {
    r = -ERANGE;
    sz = size;
  }
  memcpy (value, xattrs->val[i].attrval, sz);

out:
  if (free_attrs)
    guestfs_free_xattr_list ((struct guestfs_xattr_list *) xattrs);

  return r;
}

static int
mount_local_release (const char *path, struct fuse_file_info *fi)
{
  DECL_G ();
  DEBUG_CALL ("%s", path);

  /* Just a stub. This method is optional and can safely be left
   * unimplemented.
   */
  return 0;
}

/* All this function needs to do is to check that the requested open
 * flags are valid.  See the notes in <fuse/fuse.h>.
 */
static int
mount_local_open (const char *path, struct fuse_file_info *fi)
{
  const int flags = fi->flags & O_ACCMODE;
  DECL_G ();
  DEBUG_CALL ("%s, 0%o", path, (unsigned) fi->flags);

  if (g->ml_read_only && flags != O_RDONLY)
    return -EROFS;

  return 0;
}

static int
mount_local_flush(const char *path, struct fuse_file_info *fi)
{
  DECL_G ();
  DEBUG_CALL ("%s", path);

  /* Just a stub. This method is called whenever FUSE wants to flush the
   * pending changes (f.ex. to attributes) to a file.  Since we don't have
   * anything to do and don't want FUSE to think something went badly,
   * just return 0.
   */
  return 0;
}

/* Emulate this by calling sync. */
static int
mount_local_fsync (const char *path, int isdatasync,
                   struct fuse_file_info *fi)
{
  int r;
  DECL_G ();
  DEBUG_CALL ("%s, %d", path, isdatasync);

  r = guestfs_sync (g);
  if (r == -1)
    RETURN_ERRNO;

  return 0;
}

static int
mount_local_truncate (const char *path, off_t size)
{
  int r;
  DECL_G ();
  DEBUG_CALL ("%s, %ld", path, (long) size);

  if (g->ml_read_only) return -EROFS;

  dir_cache_invalidate (g, path);

  r = guestfs_truncate_size (g, path, size);
  if (r == -1)
    RETURN_ERRNO;

  return 0;
}

static int
mount_local_chown (const char *path, uid_t uid, gid_t gid)
{
  int r;
  DECL_G ();
  DEBUG_CALL ("%s, %ju, %ju", path, (uintmax_t) uid, (uintmax_t) gid);

  if (g->ml_read_only) return -EROFS;

  dir_cache_invalidate (g, path);

  r = guestfs_lchown (g, uid, gid, path);
  if (r == -1)
    RETURN_ERRNO;

  return 0;
}

static int
mount_local_symlink (const char *from, const char *to)
{
  int r;
  DECL_G ();
  DEBUG_CALL ("%s, %s", from, to);

  if (g->ml_read_only) return -EROFS;

  dir_cache_invalidate (g, to);

  r = guestfs_ln_s (g, from, to);
  if (r == -1)
    RETURN_ERRNO;

  return 0;
}

static int
mount_local_unlink (const char *path)
{
  int r;
  DECL_G ();
  DEBUG_CALL ("%s", path);

  if (g->ml_read_only) return -EROFS;

  dir_cache_invalidate (g, path);

  r = guestfs_rm (g, path);
  if (r == -1)
    RETURN_ERRNO;

  return 0;
}

static int
mount_local_mknod (const char *path, mode_t mode, dev_t rdev)
{
  int r;
  DECL_G ();
  DEBUG_CALL ("%s, 0%o, 0x%jx", path, mode, (uintmax_t) rdev);

  if (g->ml_read_only) return -EROFS;

  dir_cache_invalidate (g, path);

  r = guestfs_mknod (g, mode, major (rdev), minor (rdev), path);
  if (r == -1)
    RETURN_ERRNO;

  return 0;
}