Marshalling RDR3 native struct/array out-params: DataView with 8-byte stride, little-endian, zero-based offsets

Context

Several RDR3 natives return data through a caller-supplied byte buffer instead of a return value (notification toast structs, GET_SCENARIO_POINTS_IN_AREA, the game-event queue, weapon-DLC structs). The undocumented part is how to pack/read that buffer.

The recipe (jo_libs convention)

local view = DataView.ArrayBuffer(8 * N)      -- N = field/element count
view:SetInt32(8 * i, value)                   -- write field i
local got = nativeCall(..., view:Buffer())    -- pass the raw buffer
local x = view:GetInt32(8 * j)                 -- read field j

Key rules agents get wrong:

Every field is 8-byte aligned — read/write at offset 8*i even for Int32/BOOL fields.
Offsets are zero-based; endianness defaults to little (note: differs from the JS DataView API).
For array natives, allocate a couple of slack slots (8 * (max+2)) and skip zero entries.
GET_EVENT_DATA's size arg is the RAGE element count (bytes/8), not a byte length.

Verified instances

Notification toasts — notification/client.lua:75-93.
GET_SCENARIO_POINTS_IN_AREA (0x345EC3B7EBDE1CB5): DataView.ArrayBuffer(8*(max+2)), read ids at GetInt32(j*8-8) — entity/client.lua:277-289.
Game-event queue (GET_EVENT_DATA 0x57EC5FA4D4D6AFCA): fields at 8*i — game-events/g_client.lua:33-55.
Weapon-DLC struct with GetFixedString(56,64) — dataview/client.lua:44-58. This buffer recipe is undocumented in the corpus.

Linked natives

GET_EVENT_DATA (0x57EC5FA4D4D6AFCA)
GET_SCENARIO_POINTS_IN_AREA (0x345EC3B7EBDE1CB5)

Tags: dataview, buffer, struct, out-param, marshalling, invokenative, rdr3
Category: natives
Source: jo_libs-fleet
Created: 2026-05-31T09:39:12.365Z