A stream header gives the names, and the position and length of a particular table or heap. Note that the length of a Stream header structure is not fixed, but depends on the length of its name field (a variable length null-terminated string).
| Offset | Size | Field | Description |
|---|---|---|---|
| 0 | 4 | Offset | Memory offset to start of this stream from start of the metadata root (§II.24.2.1) |
| 4 | 4 | Size | Size of this stream in bytes, shall be a multiple of 4. |
| 8 | Name | Name of the stream as null-terminated variable length array of ASCII characters, padded to the next 4-byte boundary with \0 characters. The name is limited to 32 characters. |
Both logical tables and heaps are stored in streams. There are five possible kinds of streams. A stream header with name "#Strings" that points to the physical representation of the string heap where identifier strings are stored; a stream header with name "#US" that points to the physical representation of the user string heap; a stream header with name "#Blob" that points to the physical representation of the blob heap, a stream header with name "#GUID" that points to the physical representation of the GUID heap; and a stream header with name "#~" that points to the physical representation of a set of tables.
Each kind of stream shall occur at most once, that is, a meta-data file shall not contain two "#US" streams, or five "#Blob" streams. Streams need not be there if they are empty.
The next subclauses describe the structure of each kind of stream in more detail.