2.1.1.2.4 Padding and Alignment

Property values stored in the DataBlock portion of a control MUST be stored on alignment boundaries equal to the size of the property value, relative to the beginning of the control in the stream. All 4-byte property values MUST be stored beginning at an offset into the stream, from the beginning of the version number, that is divisible by 4. All 2-byte property values MUST be stored at an offset into the stream, from the beginning of the version number, that is divisible by 2. Extra bytes MUST be added to the stream before any property value that would otherwise be stored starting at an unaligned offset. The value of each of these bytes is undefined, and the bytes MUST be ignored. Padding MUST NOT be added before a property value that is not stored.

After all property values that are less than or equal to 4 bytes in size have been persisted to the stream, extra bytes MUST be added so that the total size, in bytes, of all persisted property values and padding is divisible by 4. The value of these extra bytes at the end of the DataBlock MUST be set to zero, and the bytes MUST be ignored.

Figure 23: Padding in the DataBlock

Property values that are strings are padded to a length that is divisible by 4, as specified in section 2.4.14. Strings that are stored as part of a property of another type are not padded.