Stream → Schema

Schema

Compiles an ordered field list into a binary schema. Fixed-size schemas — those with no string fields — pre-compute byte offsets at compile time and are eligible for delta compression.

Stream.Schema.New()

Stream.Schema.New(definition: {{ string | {any} }}) → Schema

Pass an ordered array of { fieldName, typeName } pairs. The order determines wire layout — both server and client must use the same definition.

local Stream = RoExpress("Stream")

-- Fixed-size: all fields have known byte widths → delta eligible
local moveSchema = Stream.Schema.New({
    { "pos",    "Vector3"                                    },  -- 12 B
    { "vel",    "Vector3"                                    },  -- 12 B
    { "cf",     "CFrameLight"                                },  -- 16 B
    { "state",  { "flags", "jumping", "sprinting", "crouching" } },  --  1 B
    { "health", "u16"                                       },  --  2 B
})  -- total: 43 bytes per packet

-- Variable-size: string field → not delta eligible
local chatSchema = Stream.Schema.New({
    { "name",    "string" },
    { "message", "string" },
})

Fixed-size vs variable-size. A schema is fixed-size when every field has a known byte width at compile time. Adding even one string field makes the whole schema variable-size, which disables delta compression for that channel.

Built-in types

Type name	Wire size	Notes
`f32`	4 B	Single-precision float
`f64`	8 B	Double-precision float
`u8`	1 B	Unsigned integer 0–255
`u16`	2 B	Unsigned integer 0–65535
`u32`	4 B	Unsigned integer 0–4294967295
`i8`	1 B	Signed integer −128–127
`i16`	2 B	Signed integer −32768–32767
`i32`	4 B	Signed integer −2147483648–2147483647
`bool`	1 B	Boolean stored as u8
`string`	2 + len B	u16 length-prefix. Makes schema variable-size — no delta.
`Vector3`	12 B	3× f32 (X, Y, Z)
`Vector2`	8 B	2× f32 (X, Y)
`Vector3int16`	6 B	3× i16
`Vector2int16`	4 B	2× i16
`CFrame`	28 B	Position (3× f32) + quaternion (Shepperd method, all 4 degenerate cases)
`CFrameLight`	16 B	Position (3× f32) + Y-yaw only. Cheaper for humanoids.
`Color3`	3 B	RGB as u8 (0–255 each)
`Color3float`	12 B	RGB as f32 (full precision)
`BrickColor`	2 B	u16 palette value
`UDim`	8 B	Scale f32 + Offset i32
`UDim2`	16 B	2× UDim
`Rect`	16 B	Min + Max as Vector2
`NumberRange`	8 B	Min f32 + Max f32
`Ray`	24 B	Origin + Direction as Vector3
`PhysicalProperties`	20 B	Density, Friction, Elasticity, FrictionWeight, ElasticityWeight as f32
`{ "flags", ... }`	1 B	Up to 8 named booleans packed into one byte
`{ "enum", EnumType }`	2 B	EnumItem → u16 value

Custom types

Stream.Types.Register("hp", {
    size  = 2,
    write = function(buf, offset, value)
        buffer.writeu16(buf, offset, value)
    end,
    read  = function(buf, offset)
        return buffer.readu16(buf, offset)
    end,
})

Example — movement schema

-- shared.luau — required on both server and client
local RoExpress = require(game.ReplicatedStorage.RoExpress)
local Stream    = RoExpress("Stream")

local moveSchema = Stream.Schema.New({
    { "pos",    "Vector3"                                         },  -- 12 B
    { "vel",    "Vector3"                                         },  -- 12 B
    { "cf",     "CFrameLight"                                     },  -- 16 B
    { "state",  { "flags", "jumping", "sprinting", "crouching" }  },  --  1 B
    { "health", "u16"                                            },  --  2 B
})  -- 43 bytes per packet | fixed-size | delta eligible

return moveSchema

Schema

Stream.Schema.New()

Built-in types

Custom types

Example — movement schema

See also