(CD-ROM)

dir_cdfs(4)

dir (cdfs) -- format of CD-ROM file system (cdfs) directory data structure

Synopsis

   #include <sys/fs/iso9660.h>
   #include <sys/fs/cdfs_inode.h>

Description

In a cdfs file system, the contents of a file or directory are stored in contiguous physical sectors called an extent. The contents of a directory are stored in a single extent. The contents of a file may be stored in multiple non-adjacent extents. More than one file can share the same extent. The first sector of each extent may contain an Extended Attribute Record (XAR) that describes additional attributes of the file or directory (such as the User ID, Group ID, permissions).

Each directory in a cdfs filesystem contains two or more Directory Records. These directory records identify the file and subdirectories owned by the directory. For each file or subdirectory in the directory, there will exist one Directory Record for each extent belonging to that file/subdirectory. Each Directory Record is of variable length and contains information such as:

the name of the file or subdirectory
the location and size of its extent
a System Use Area

Note: For a multi-extent file, there will be one directory record for each extent in the file.

Each Directory Record has a System Use Area (SUA) that stores information about other operating system standards, such as additional file-related information not defined by the ISO-9660 specification. The SUA can be used to store information required to support POSIX standards. For example, the SUA can contain the device file major/minor numbers, which are defined by the POSIX standard. The System Use Sharing Protocol (SUSP) defines how the information in the SUA is defined.

The Directory Record data structure is defined in the iso9660.h header file. For each cdfs file and directory currently being referenced, an in-core data structure, struct cdfs_drec, is used to store the relevant portions of all of the Directory Records belonging to that file or directory. Each cdfs_drec also stores other information relating to the extent and/or Directory Record. The cdfs_drec structure is defined in the cdfs_inode.h header file.

The cdfs_drec structure is as follows:

   struct cdfs_drec {
   	struct cdfs_drec	*drec_NextDR;	/* Pointer to next Dir Rec */
   	struct cdfs_drec	*drec_PrevDR;	/* Pointer to previous Dir Rec */
   	uint_t	drec_Loc;	/* Loc of media DREC (L-Sec #) */
   	uint_t	drec_Offset;	/* # bytes from L-sec start */
   	uint_t	drec_Len;	/* Len of media Dir Rec (Bytes) */
   	uint_t	drec_XarLen;	/* Len of media XAR (Log Blk) */
   	daddr_t	drec_ExtLoc;	/* Location of Extent (L-Blk #) */
   	uint_t	drec_DataLen;	/* Len of File Sec data */
   	timestruc_t	drec_Date;	/* Recording date and time */
   	uint_t	drec_Flags;	/* Flags - See below */
   	uint_t	drec_UnitSz;	/* File Unit Size */
   	uint_t	drec_Interleave;	/* Interleave Gap Size */
   	uint_t	drec_VolSeqNum;	/* Volume Sequence Number */
   	uint_t	drec_FileIDLen;	/* Len of File ID String */
   	uint_t	drec_FileIDOff;	/* Dir Rec offset of File ID */	
   	uint_t	drec_SysUseOff;	/* Dir Rec offset of Sys Use Area */
   	uint_t	drec_SysUseSz;	/* Size of Sys Use Area */
   };

References

cdfs-specific fs_cdfs(4), cdfs-specific inode_cdfs(4)

System Use Sharing Protocol and Rock Ridge Interchange Protocol from Rock Ridge Technical Working Group, ISO 9660 Specification ISO 9660:1988(E), Working Paper for Information Processing: Volume and File Structure of CD-ROM Information Interchange" in Optical Information Systems magazine, January/February 1987