查看“Data Types”的源代码

All data sent over the network is [[wikipedia:Endianness#Big-endian|big-endian]], that is the bytes are sent from most significant byte to least significant byte. The majority of everyday computers are little-endian, therefore it may be necessary to change the endianness before sending data over the network.

{| class="wikitable"
 |-
 ! Name
 ! Size (bytes)
 ! Encodes
 ! Notes
 |-
 ! Boolean
 | 1
 | false or true
 | Value can be either true (<code>0x01</code>) or false (<code>0x00</code>)
 |-
 ! Byte
 | 1
 | -128 to 127
 | Signed 8-bit integer, [[wikipedia:Two's complement|two's complement]]
 |-
 ! Unsigned Byte
 | 1
 | 0 to 255
 | Unsigned 8-bit integer
 |-
 ! Short
 | 2
 | -32768 to 32767
 | Signed 16-bit integer, two's complement
 |-
 ! Unsigned Short
 | 2
 | 0 to 65535
 | Unsigned 16-bit integer
 |-
 ! Int
 | 4
 | -2147483648 to 2147483647
 | Signed 32-bit integer, two's complement
 |-
 ! Long
 | 8
 | -9223372036854775808 to 9223372036854775807
 | Signed 64-bit integer, two's complement
 |-
 ! Float
 | 4
 | [[wikipedia:Single-precision floating-point format|Single-precision 32-bit IEEE 754 floating point]]
 | 
 |-
 ! Double
 | 8
 | [[wikipedia:Double-precision floating-point format|Double-precision 64-bit IEEE 754 floating point]]
 | 
 |-
 ! String
 | ≥ 1 <br />≤&nbsp;2147483652
 | A sequence of [[wikipedia:Unicode|Unicode]] code points
 | [[wikipedia:UTF-8|UTF-8]] string prefixed with its size in bytes as a VarInt
 |-
 ! Chat
 | ≥ 1 <br />≤&nbsp;2147483652
 | See [[Chat]]
 | Encoded as a String
 |- 
 ! VarInt
 | ≥ 1 <br />≤ 5
 | -2147483648 to 2147483647
 | [http://developers.google.com/protocol-buffers/docs/encoding#varints Protocol Buffer Varint], encoding a two's complement signed 32-bit integer
 |-
 ! VarLong
 | ≥ 1 <br />≤ 10
 | -9223372036854775808 to 9223372036854775807
 | [http://developers.google.com/protocol-buffers/docs/encoding#varints Protocol Buffer Varint], encoding a two's complement signed 64-bit integer
 |-
 ! Chunk
 | Varies
 | A vertical chunk column
 | See [[SMP Map Format#Data]]
 |-
 ! Metadata
 | Varies
 | See [[Entities#Entity Metadata Format]]
 | 
 |- 
 ! Slot
 | Varies
 | See [[Slot Data]]
 | 
 |-
 ! Object Data
 | 4 or 10
 | See [[Object Data]]
 | 
 |-
 ! NBT Tag
 | Varies
 | See [[NBT]]
 | 
 |-
 ! Position 
 | 8
 | Integer/block position: x (-33554432 to 33554431), y (-2048 to 2047), z (-33554432 to 33554431)
 | x as a 26-bit integer, followed by y as a 12-bit integer, followed by z as a 26-bit integer (all signed, two's complement). See also [[#Position|the section below]].
 |-
 ! Angle
 | 1
 | Rotation angle in steps of 1/256 of a full turn
 | Whether or not this is signed does not matter, since the resulting angles are the same.
 |-
 ! UUID
 | 16
 | A [[wikipedia:Universally_unique_identifier|UUID]]
 | The vanilla Minecraft server internally sends this as two longs.

<pre>this.writeLong(uuid.getMostSignificantBits());
this.writeLong(uuid.getLeastSignificantBits());</pre>
 |-
 ! Optional X
 | 0 or size of X
 | A field of type X, or nothing
 | Whether or not the field is present must be known from the context.
 |-
 ! Array of X
 | count times size of X
 | Zero or more fields of type X
 | The count must be known from the context.
 |-
 ! Byte Array
 | Varies
 | Depends on context
 | This is just a sequence of zero or more bytes, its meaning should be explained somewhere else, e.g. in the packet description. The length must also be known from the context.
 |}

=== 位置 ===

64-bit value split in to three parts

* x: 26 MSBs
* z: 26 LSBs
* y: 12 bits between them

Encoded as followed:

 ((x & 0x3FFFFFF) << 38) | ((y & 0xFFF) << 26) | (z & 0x3FFFFFF)

And decoded as:

 long val; // Encoded value
 x = val >> 38;
 y = (val >> 26) & 0xFFF
 z = val << 38 >> 38

Note: The details of bit shifting are rather language dependent; the above may work in Java but probably won't in other languages without some tweaking.

=== 定点数据 ===

Some fields may be stored as [https://en.wikipedia.org/wiki/Fixed-point_arithmetic fixed-point numbers], where a certain number of bits represents the signed integer part (number to the left of the decimal point) and the rest represents the fractional part (to the right). Floating points (float and double), in contrast, keep the number itself (mantissa) in one chunk, while the location of the decimal point (exponent) is stored beside it. 

Essentially, while fixed-point numbers have lower range than floating points, their fractional precision is greater for higher values. This makes them ideal for representing global coordinates of an entity in Minecraft, as it's more important to store the integer part accurately than position them more precisely within a single block (or meter). 

Coordinates are often represented as a 32-bit integer, where 5 of the least-significant bits are dedicated to the fractional part, and the rest store the integer part.

Java lacks support for fractional integers directly, but you can represent them as integers. To convert from a double to this integer representation, use the following formulas:
  abs_int = (int)double * 32;
And back again:

  double = (double)abs_int / 32;