复合二进制文档

复合二进制文档（CFBF），简称复合文档，英文全名 Composite Document File V2 Document，是微软开发、用于实现COM结构化存储的文件格式，用于把多个对象内容存放在同一个硬盘文件。
Microsoft已经开放了这个文件格式。广泛用于Microsoft Word与Microsoft Access。也是Advanced Authoring Format的基础。

**文件结构**
CFBF文件头部是512字节，随后跟着是保存数据的扇区。扇区的长度在文件头部指定，通常是512字节或4096字节。 
CFBF的扇区类型:- FAT扇区- MiniFAT扇区：用于Mini-Stream- Double-Indirect FAT （DIFAT）扇区 - 包含FAT扇区索引的链表数据- Directory扇区- Stream扇区 - 包含数据内容- Range Lock扇区 - 包含大文件的上锁的字节范围 

**CFBF文件头**
CFBF头是该文件的最前的512字节。对应于C语言数据结构为：
typedef unsigned long ULONG;    // 4 Bytes
typedef unsigned short USHORT;  // 2 Bytes
typedef short OFFSET;           // 2 Bytes
typedef ULONG SECT;             // 4 Bytes
typedef ULONG FSINDEX;          // 4 Bytes
typedef USHORT FSOFFSET;        // 2 Bytes
typedef USHORT WCHAR;           // 2 Bytes
typedef ULONG DFSIGNATURE;      // 4 Bytes
typedef unsigned char BYTE;     // 1 Byte
typedef unsigned short WORD;    // 2 Bytes
typedef unsigned long DWORD;    // 4 Bytes
typedef ULONG SID;              // 4 Bytes
typedef GUID CLSID;             // 16 Bytes
struct StructuredStorageHeader { // offset from start (bytes), length (bytes)
BYTE _abSig8;             // 00H,08 {0xd0, 0xcf, 0x11, 0xe0, 0xa1, 0xb1,
// 0x1a, 0xe1} for current version
CLSID _clsid;               // 08H,16 reserved must be zero (WriteClassStg/
// GetClassFile uses root directory class id)
USHORT _uMinorVersion;      // 18H,02 minor version of the format: 33 is
// written by reference implementation
USHORT _uDllVersion;        // 1AH,02 major version of the dll/format: 3 for
// 512-byte sectors, 4 for 4 KB sectors
USHORT _uByteOrder;         // 1CH,02 0xFFFE: indicates Intel byte-ordering
USHORT _uSectorShift;       // 1EH,02 size of sectors in power-of-two;
// typically 9 indicating 512-byte sectors
USHORT _uMiniSectorShift;   // 20H,02 size of mini-sectors in power-of-two;
// typically 6 indicating 64-byte mini-sectors
USHORT _usReserved;         // 22H,02 reserved, must be zero
ULONG _ulReserved1;         // 24H,04 reserved, must be zero
FSINDEX _csectDir;          // 28H,04 must be zero for 512-byte sectors,
// number of SECTs in directory chain for 4 KB
// sectors
FSINDEX _csectFat;          // 2CH,04 number of SECTs in the FAT chain
SECT _sectDirStart;         // 30H,04 first SECT in the directory chain
DFSIGNATURE _signature;     // 34H,04 signature used for transactions; must
// be zero. The reference implementation
// does not support transactions
ULONG _ulMiniSectorCutoff;  // 38H,04 maximum size for a mini stream;
// typically 4096 bytes
SECT _sectMiniFatStart;     // 3CH,04 first SECT in the MiniFAT chain
FSINDEX _csectMiniFat;      // 40H,04 number of SECTs in the MiniFAT chain
SECT _sectDifStart;         // 44H,04 first SECT in the DIFAT chain
FSINDEX _csectDif;          // 48H,04 number of SECTs in the DIFAT chain
SECT _sectFat109;         // 4CH,436 the SECTs of first 109 FAT sectors
};

**FAT扇区**
每个FAT条目长度4字节，包含下个FAT链表条目的扇区号，或下述特定值：- FREESECT (0xFFFFFFFF) - 未用扇区- ENDOFCHAIN (0xFFFFFFFE) - FAT链表最后一个扇区- FATSECT (0xFFFFFFFD) - 用于FAT数据存储- DIFSECT (0xFFFFFFFC) - 用于DIFAT数据存储

**词汇表**
 FAT - 文件分配表，也称 SAT - 扇区分配表- DIFAT - Double-Indirect File Allocation Table- FAT Chain - 一群FAT条目指出分配给一个流的那些扇区- Stream - 一个数据对象的内容- Sector - 扇区，占据512或4096个字节

**参见**
 COM结构化存储