The Be Book - Classes And Methods

Defined Types

attr_info

Defined In: kernel/fs_attr.h

typedef struct attr_info
   uint32 type;
   off_t size;
} attr_info;

The attr_info structure contains the following members

Field	Description
`type`	Is a constant (`B_STRING_TYPE`, `B_INT32_TYPE`, etc) that describes the type of data that the attribute holds.
`size`	Is the size of the attribute's data, in bytes.

stat

Declared in: posix/sys/stat.h

The stat structure looks like this:

struct stat {
   dev_t         st_dev;
   ino_t         st_ino;
   mode_t        st_mode;
   nlink_t       st_nlink;
   uid_t         st_uid;
   gid_t         st_gid;
   off_t         st_size;
   dev_t         st_rdev;
   size_t        st_blksize;
   time_t        st_atime;
   time_t        st_mtime;
   time_t        st_ctime;
} stat;

And the fields are…

Field	Description
`st_dev`	Identifies the node's device.
`st_ino`	Is the node's "inode" number.

By combining st_dev and st_ino you can roll your own node_ref:

node_ref nref;
stat st;

if (file.GetStat(&st) == B_OK) {
   nref.dev = st.st_dev;
   nref.node = st.st_ino;
}

Meanwhile…

Field	Description
`st_mode`	Describes the node's flavor: plain file, directory or symbolic link. To test the field, pass it to the `S_ISREG()`, `S_ISDIR()`, and `S_ISLNK()` boolean macros: if (`S_ISREG`(`st.st_mode`)) /* it's a "regular" file / else if (`S_ISDIR`(`st.st_mode`)) / it's a directory / else if (`S_ISLNK`(`st.st_mode`)) / it's a symbolic link */
`st_nlink`	Is the number of "hard links" that point to this node.
`st_uid` and `st_gid`	Are the user (owner) and group ids that were described in the `GetOwner()` function.
`st_rdev`	Is, well, no one really knows. It's provided for System V compatibility (hold your applause), but it's unused.
`st_blksize`	Is the "preferred block size" that's used during copying. The cp command line program allocates buffers of this size when it's copying the file's data.
`st_atime`, `st_mtime`, and `st_ctime`	Are the access, modification, and creation times in seconds since January 1, 1970. Access time (`st_atime`) is currently unused.

fs_info

The fs_info structure is defined as:

typedef struct fs_info {
    dev_t     dev;
    ino_t     root;
    uint32    flags;
    off_t     block_size;
    off_t     io_size;
    off_t     total_blocks;
    off_t     free_blocks;
    off_t     total_nodes;
    off_t     free_nodes;
    char      device_name[128];
    char      volume_name[B_FILE_NAME_LENGTH];
    char      fsh_name[B_OS_NAME_LENGTH];
};

The structure's fields are:

dev. The device number of the device.
root. The inode of the root of the device.
flags. Flags describing the device's capabilities.
block_size. The fundamental block size of the device.
io_size. Optimal I/O size of the device.
total_blocks. The total number of blocks on the device.
free_blocks. The number of free (unused) blocks on the device.
total_nodes. The total number of nodes on the device.
free_nodes. The number of free (unused) nodes on the device.
device_name. Name of the device holding the file system.
volume_name. Name of the volume contained by the device.
fsh_name. Name of the file system handler for the device.

The flags can be any combination of the following values, which specify the attributes of the file system on the device:

B_FS_IS_READONLY. The file system on the device is read-only.
B_FS_IS_REMOVABLE. The device contains removable media.
B_FS_IS_PERSISTENT. Data written to the device remains even while the device is off.
B_FS_IS_SHARED. The file system is being shared on a network.
B_FS_HAS_MIME. The file system supports the MIME typing system used by the BeOS.
B_FS_HAS_ATTR. The file system supports node attributes.
B_FS_HAS_QUERY. The file system supports the BeOS query mechanism.

The information in the fs_info structure is guaranteed to be internally consistent, but the structure as a whole should be considered to be out-of-date as soon as you receive it. It provides a picture of a device as it exists just before the info-retrieving function returns. In particular, the number of free blocks and of free nodes can easily change immediately after you receive this information.