Data Types

所有通过网络发送的数据均为大端序（big-endian，这意味着字节被从高位向低位发送。日常中大多数的计算机为小端序，所以可能需要在发送数据到网络之前将其转换为大端序。

Name	Size (bytes)	Encodes	Notes
Boolean	1	false or true	Value can be either true (0x01) or false (0x00)
Byte	1	-128 to 127	Signed 8-bit integer, 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	Single-precision 32-bit IEEE 754 floating point
Double	8	Double-precision 64-bit IEEE 754 floating point
String	≥ 1 ≤ 2147483652	A sequence of Unicode code points	UTF-8 string prefixed with its size in bytes as a VarInt
Chat	≥ 1 ≤ 2147483652	See Chat	Encoded as a String
VarInt	≥ 1 ≤ 5	-2147483648 to 2147483647	Protocol Buffer Varint, encoding a two's complement signed 32-bit integer
VarLong	≥ 1 ≤ 10	-9223372036854775808 to 9223372036854775807	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 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 UUID	The vanilla Minecraft server internally sends this as two longs. this.writeLong(uuid.getMostSignificantBits()); this.writeLong(uuid.getLeastSignificantBits());
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

分成 3 部分的 64 个比特位

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

像这样编码：

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

像这样解码:

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

Note: 位移的细节是和编程语言相关的；以上代码若没有调整可能在 Java 中正确运行但在其他语言中无法正确运行????。

定点数据

有些域可能会被存储为 定点数(fixed point)，即使用一定数量的比特位来存储小数的整数部分（小数点的左边），其余比特位表示小数部分 (小数点的右边)。浮点数 (float 和 double) 则相反，它将数字本身（底数）放在一个块里， 小数点的位置（指数）在其一旁存储。

实际上，虽然定点数的范围比浮点数小，但他们对于更高数值的精度更高。这使得他们成为在Minecraft中表示一个实体的全局坐标的理想选择，因为比起在一个方块（或一米）中精确的确定他们的位置而言，存储表示他们所在方块的整数部分显得更重要。

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;