Slot Data

The slot data structure is how minecraft represents an item and its associated data in the minecraft protocol

Packets

• 0x0F player block placement
• 0x66 window click
• 0x67 set slot
• 0x68 window items (as an array)
• 0x6B creative inventory action

Format

The structure consists of at least a short, which gives the item/block ID [1]. A value of -1 signifies that the slot is empty, and no further data follows.

For non-empty slots, at least two further fields follow. These fields are a byte (item count) and a short (damage/block metadata)

For certain block IDs, given below, further data follows. First, a short gives the length of a proceeding byte array. A value of -1 signifies no further data.

The byte array (if present) contains gzipped (that is RFC 1952 rather than RFC 1950) NBT data. The format of this data is as follows:

 COMPOUND: ''
   LIST: 'ench'
     COMPOUND
       SHORT: 'id'
       SHORT: 'lvl'
     END
     COMPOUND
       ...etc
     END
 END

Each of the inner, untagged COMPOUNDs represents an enchantment, with its ID[2] and level given as child SHORT elements.

Enchantable items

Every item that has a "damage bar" in-game is considered enchantable by the protocol, though the notchian server/client do not support enchantment of some items. These include: hoes, flint and steel, fishing rods and shears.

 0x103, #Flint and steel
 0x105, #Bow
 0x15A, #Fishing rod
 0x167, #Shears
 
 #TOOLS
 #sword, shovel, pickaxe, axe, hoe
 0x10C, 0x10D, 0x10E, 0x10F, 0x122, #WOOD
 0x110, 0x111, 0x112, 0x113, 0x123, #STONE
 0x10B, 0x100, 0x101, 0x102, 0x124, #IRON
 0x114, 0x115, 0x116, 0x117, 0x125, #DIAMOND
 0x11B, 0x11C, 0x11D, 0x11E, 0x126, #GOLD
 
 #ARMOUR
 #helmet, chestplate, leggings, boots
 0x12A, 0x12B, 0x12C, 0x12D, #LEATHER
 0x12E, 0x12F, 0x130, 0x131, #CHAIN
 0x132, 0x133, 0x134, 0x135, #IRON
 0x136, 0x137, 0x138, 0x139, #DIAMOND
 0x13A, 0x13B, 0x13C, 0x13D  #GOLD

Or, more simply:

       private static bool CanEnchant(short value)
       {
           return  (256 <= value && value <= 259) ||
                   (267 <= value && value <= 279) ||
                   (283 <= value && value <= 286) ||
                   (290 <= value && value <= 294) ||
                   (298 <= value && value <= 317) ||
                   value == 261 || value == 359 ||
                   value == 346;
       }