2.2.2.8.3.2.1 XBLOCK

XBLOCKs are used when the data associated with a node data that exceeds 8,176 bytes in size. The XBLOCK expands the data that is associated with a node by using an array of BIDs that reference data blocks that contain the data stream associated with the node. A BLOCKTRAILER is present at the end of an XBLOCK, and the end of the BLOCKTRAILER MUST be aligned on a 64-byte boundary.

Unicode:

0	1	2	3	4	5	6	7	8	9	1 0	1	2	3	4	5	6	7	8	9	2 0	1	2	3	4	5	6	7	8	9	3 0	1
btype								cLevel								cEnt
lcbTotal
rgbid (variable)
...
rgbPadding (variable, optional)
...
blockTrailer (16 bytes)
...
...

ANSI:

0	1	2	3	4	5	6	7	8	9	1 0	1	2	3	4	5	6	7	8	9	2 0	1	2	3	4	5	6	7	8	9	3 0	1
btype								cLevel								cEnt
lcbTotal
rgbid (variable)
...
rgbPadding (variable, optional)
...
blockTrailer
...
...

btype (1 byte): Block type; MUST be set to 0x01 to indicate an XBLOCK or XXBLOCK.

cLevel (1 byte): MUST be set to 0x01 to indicate an XBLOCK.

cEnt (2 bytes): The count of BID entries in the XBLOCK.

lcbTotal (4 bytes): Total count of bytes of all the external data stored in the data blocks referenced by XBLOCK.

rgbid (variable): Array of BIDs that reference data blocks. The size is equal to the number of entries indicated by cEnt multiplied by the size of a BID (8 bytes for Unicode PST files, 4 bytes for ANSI PST files).

rgbPadding (variable, optional): This field is present if the total size of all of the other fields is not a multiple of 64. The size of this field is the smallest number of bytes required to make the size of the XBLOCK a multiple of 64. Implementations MUST ignore this field.

blockTrailer (ANSI: 12 bytes; Unicode: 16 bytes): A BLOCKTRAILER structure (section 2.2.2.8.1).