1.2 File Information Block

The file information block (FIB) contains much of the information that is exchanged between the user process and the ACP. The FIB must be writable.

The FIB is passed by a descriptor (see Figure 1-2). A short FIB can be used in ACP calls that do not need arguments near the end of the FIB. The ACP treats the omitted portion of the FIB as if it were 0. Figure 1-3 shows the format of a typical short FIB that would be used to open an existing file.

Figure 1-3 Typical Short FIB

Table 1-1 gives a brief description of the FIB fields. More detailed descriptions are provided in “ACP Subfunctions” and “Major Functions”.

Table 1-1 Contents of the FIB

Field	Meaning
FIB$L_ACCTL	Contains flag bits that control the access to the file. “Input Parameters”, “Input Parameters”, “Input Parameters”, and “Input Parameters”, and “Delete File” describe the FIB$L_ACCTL field flag bits.
FIB$L_ACL_STATUS	Status of the requested ACL attribute operation, if any. The ACL attributes are included in Table 1-7. If no ACL attributes are given, SS$_NORMAL is returned here.
FIB$L_ACLCTX	Maintains position context when processing ACL attributes from the attribute (P5) list.
FIB$B_ALALIGN	Contains the interpretation mode of the allocation (FIB$W_ALLOC) field.
FIB$W_ALLOC	Contains the desired physical location of the blocks being allocated. Interpretation of the field is controlled by the FIB$B_ALALIGN field. The following subfields are defined:
	Subfield	Meaning
	FIB$W_LOC_FID	Three-word related file ID for RFI placement.
	FIB$W_LOC_NUM	Related file number.
	FIB$W_LOC_SEQ	Related file sequence number.
	FIB$B_LOC_RVN	Related file relative volume number (RVN) or placement RVN.
	FIB$B_LOC_NMX	Related file number extension.
	FIB$L_LOC_ADDR	Placement logical block number (LBN), cylinder, or virtual block number (VBN).
	FIB$B_ALOPTS	Contains option bits that control the placement of allocated blocks. “Input Parameters” describes the FIB$B_ALOPTS field flag bits.
FIB$L_ALT_ACCESS	A 32-bit mask that represents an access mask to check against file protection; for example, opens a file for read access and checks whether it can be deleted. The mask has the same configuration as the standard protection mask.
FIB$W_CNTRLFUNC	In an IO$_ACPCONTROL function, this field contains the code that specifies which ACP control function is to be performed (see “ACP Control”). This field overlays FIB$W_EXCTL.
FIB$L_CNTRLVAL	Contains a control function value used in an IO$_ACPCONTROL function (see “ACP Control”). The interpretation of the value depends on the control function specified in FIB$W_CNTRLFUNC. This field overlays FIB$L_EXSZ.
FIB$W_DID	Contains the file identifier of the directory file. For Files-11 On-Disk Structure Level 1 and Level 2, the following subfields are defined:
	Subfield	Meaning
	FIB$W_DID_NUM	File number.
	FIB$W_DID_SEQ	File sequence number.
	FIB$W_DID_RVN	Relative volume number (only for magnetic tape devices).
	FIB$B_DID_RVN	Relative volume number (only for disk devices).
	FIB$B_DID_NMX	File number extension (only for disk devices).
FIB$W_EXCTL	Contains flag bits that specify extend control for disk devices. “Input Parameters” and “Input Parameters” describe the FIB$W_EXCTL field flag bits.
FIB$L_EXSZ	Specifies the number of blocks to be allocated in an extend operation on a disk file.
FIB$L_EXVBN	Specifies the starting disk file virtual block number at which a file is to be truncated.
FIB$W_FID	Specifies the file identification. You supply the file identifier when it is known; the ACP returns the file identifier when it becomes known; for example, as a result of a create or directory lookup. A 0 file identifier can be specified when an operation is performed on a file that is already open on a particular channel. The ACP returns the file identifier of the open file. For Files-11 On-Disk Structure Level 1 and Level 2, the following subfields are defined:
	Subfields	Meaning
	FIB$W_FID_NUM	File number.
	FIB$W_FID_SEQ	File sequence number.
	FIB$W_FID_RVN	Relative volume number (only for magnetic tape devices).
	FIB$B_FID_RVN	Relative volume number (only for disk devices).
	FIB$B_FID_NMX	File number extension (only for disk devices).
	FIB$W_FID_DIRNUM	Directory number of the file identifier. This is the path table record number of the directory that describes the file.
	FIB$L_FID_RECNUM	Record number of the first directory record for the file within the current directory.
FIB$B_NAME_FORMAT_IN	Contains the format of the input file specification. “Input Parameters” describes the FIB$B_NAME_FORMAT_IN field flag bits.
FIB$B_NAME_FORMAT_OUT	Contains the format of the output file specification. “Input Parameters” describes the FIB$B_NAME_FORMAT_OUT field flag bits.
FIB$W_NMCTL	Contains flag bits that control the processing of a name string in a directory operation. “Input Parameters” and “Input Parameters” describe the FIB$W_NMCTL field flag bits.
FIB$L_STATUS	Access status. Applies to all major functions. The following bits are supported:
	Subfields	Meaning
	FIB$V_ALT_REQ	Set to indicate whether the alternate access bit is required for the current operation. If not set, the alternate access bit is optional.
	FIB$V_ALT_GRANTED	If FIB$V_ALT_REQ = 0, the FIB bit returned from the file system is set if the alternate access check succeeded. Programmers can control the security information being propagated as well as the source of this information by setting the following bits (which apply only to the IO$_CREATE and IO$_MODIFY functions).
	FIB$V_DIRACL	Propagate the ACL from the parent directory to the file, assuming the file is a directory file.
	FIB$V_EXCLPREVIOUS	Set to indicate that propagation may not occur from a previous version of the file.
	FIB$V_ALIAS_ENTRY	Set on any file system operation where the directory backlink in the file header is different (and nonzero) from the directory id specified in the FIB.
	FIB$V_NOCOPYACL	Set to indicate that the ACL should not be propagated from the parent directory (or a previous version of the file) to the file.
	FIB$V_NOCOPYOWNER	Set to indicate that the owner UIC should not be propagated from the parent directory (or a previous version of the file) to the file.
	FIB$V_NOCOPYPROT	Set to indicate that the UIC-based protection should not be propagated from the parent directory (or a previous version of the file) to the file.
	FIB$V_PROPAGATE	Propagate attributes from the parent directory (or previous version of the file). If you set the FIB$V_NOCOPYACL, FIB$V_NOCOPYOWNER, or FIB$V_NOCOPYPROT bits, you must also set FIB$V_PROPAGATE or a SS$_BADPARAM error results.
FIB$W_VERLIMIT	Contains the version limit of the directory entry.
FIB$L_WCC	Maintains position context when processing wildcard directory operations.
FIB$B_WSIZE	Controls the size of the file window used to map a disk file. If a window size of 255 is specified, the file is completely mapped by using segmented windows.