The Slot data structure is how Minecraft represents an item and its associated data in the Minecraft Protocol.
The structure consists of at least a short, which gives the
-1 signifies that the slot is empty, and no further data follows.
If the block ID is not
-1, three more fields follow. These fields are a byte (item count), a short (item damage) and at least another byte.
If the byte is
0, there is no NBT data, and no further data follows. Otherwise the byte is the start of an NBT blob of the following format:
COMPOUND '' LIST 'StoredEnchantments' COMPOUND SHORT 'id' SHORT 'lvl' END COMPOUND ... END ... END INT 'Unbreakable' ... END
See NBT for more information about the NBT format, and for the contained information and its format.
ff ff | empty slot 01 16 01 00 00 00 | a diamond pickaxe 01 16 01 00 00 01 04 CA FE BA BE | a diamond pickaxe with (made-up) NBT data