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。

坐标通常被表示为一个 32 位的整型，低 5 位被用来存储小数部分，剩余的用来存储整数部分。

Java 缺乏对带小数部分的整型的直接支持，但你可以将他们表示为整型(integer)。如果要从一个 double 转换到这个整型表示，使用以下公式：

 abs_int = (int)double * 32;

逆向过程：

 double = (double)abs_int / 32;