Structure
The CFBF file consists of a 512-Byte header record followed by a number of sectors whose size is defined in the header. The literature defines Sectors to be either 512 or 4096 bytes in length, although the format is potentially capable of supporting sectors ranging in size from 128-Bytes upwards in powers of 2 (128, 256, 512, 1024, etc.). The lower limit of 128 is the minimum required to fit a single directory entry in a Directory Sector.
There are several types of sector that may be present in a CFBF:
- File Allocation Table (FAT) Sector - contains chains of sector indices much as a FAT does in the FAT/FAT32 filesystems
- MiniFAT Sectors - similar to the FAT but storing chains of mini-sectors within the Mini-Stream
- Double-Indirect FAT (DIFAT) Sector - contains chains of FAT sector indices
- Directory Sector - contains directory entries
- Stream Sector - contains arbitrary file data
- Range Lock Sector - contains the byte-range locking area of a large file
More detail is given below for the header and each sector type.
Read more about this topic: Compound File Binary Format
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