Struxt is a lightweight library that abstracts binary packing/unpacking into reusable dynamic structures.
Rewritten from the ground up, struxt v3 allows developers to define data structures on-the-fly with Javascript code. This iteration features an api inspired by smart-buffer which allows data to be packed and unpacked via pointer methods.
A basic dynamic structure
import { Struct, Literal } from 'struxt';
import { writeFile } from 'fs/promises';
const Image = new Struct(ptr => {
const width = ptr.u32('width');
const height = ptr.u32('height');
ptr.u8('data', width * height * 4);
});Using strict types with structs
interface Image {
width: number;
height: number;
data: Uint8Array;
}
const Image = new Struct<Image>(ptr => {
// ...
});Deferred data
const PlayerData = new Struct(ptr => {
// Allocate 2 bytes of data to a new pointer.
const length = ptr.defer(2);
// Handle some data.
ptr.f32('position', 3);
ptr.f32('rotation', 3);
ptr.u8('health');
ptr.str('name');
// Add the chunk length to the allocated byte as a uint8.
length.u16(Literal( ptr.getpos() - 2 ));
});Using the built-in pointers system
// Adapted from the Alien Swarm studiomodel format.
export const mstudiohitboxset_t = new Struct(function(buf) {
buf.order('LE');
// Pointers are automatically allocated when packing data.
buf.pointer('i32')(buf => buf.str('name'));
const count_hitboxes = buf.i32('count_hitboxes');
buf.pointer('i32')(buf => buf.struct(mstudiobbox_t, 'hitboxes', count_hitboxes));
});Packing data to a buffer
const my_image: Image = {
width: 8, height: 8,
data: new Uint8Array(64).fill(255)
}
const my_buffer = new ArrayBuffer(Image.length(my_image));
Image.pack(my_image, my_buffer);
writeFile(new Buffer(my_buffer));Unpacking data from a buffer
const my_image = {}
const my_buffer = new Uint8Array([
0, 2, 0, 2,
0, 0, 0, 0,
0, 0, 0, 0,
0, 0, 0, 0
0, 0, 0, 0,
]).buffer;
Image.unpack(my_buffer, my_image);
console.log(my_image);