Struct

import { Struct, FFIType, ffi } from 'arkffi';

const Point = Struct({
  x: FFIType.int32,
  y: FFIType.int32,
});

const buf = Point.create({ x: 10, y: 20 });
const ptr = ffi.ptr(buf);

const read = Point.fromPtr(somePtr);
console.log(read.x, read.y);

function Struct(fields: Record<string, string | StructSchema>): StructSchema;

readonly size: number;

create(obj: Record<string, number | bigint | ArrayBuffer>): ArrayBuffer;

fromPtr(ptr: number, byteOffset?: number): Record<string, number>;

get(buf: ArrayBuffer, field: string): number;
set(buf: ArrayBuffer, field: string, value: number): void;

// C: struct Inner { double x, y; };
// C: struct Outer { struct Inner pos; const char* name; };
const Inner = Struct({
  x: FFIType.double,
  y: FFIType.double,
});
const Outer = Struct({
  pos: Inner,
  name: FFIType.ptr,
});

let buf = Outer.create({
  pos: Inner.create({ x: 1.0, y: 2.0 }),
  name: 0x1234,
});

let r = Outer.fromPtr(ptr);
let innerR = Inner.fromPtr(r.pos);
console.log(innerR.x, innerR.y); // 1.0, 2.0

// C: complex_t complex_add(complex_t a, complex_t b);
const Complex = Struct({ real: FFIType.double, imag: FFIType.double });
const lib = dlopen(LIB_NAME, {
  complex_add: { args: [Complex, Complex], returns: Complex },
});

let a = Complex.create({ real: 1, imag: 2 });
let b = Complex.create({ real: 3, imag: 4 });
let ptr: number = lib.symbols.complex_add(a, b);
let result = Complex.fromPtr(ptr); // { real: 4, imag: 6 }

const Mixed = Struct({
  a: FFIType.int8_t,     // offset 0, size 1
  b: FFIType.int32,       // offset 4 (3 byte padding), size 4
  c: FFIType.int8_t,      // offset 8, size 1
});                        // total 12 bytes (3 byte final padding)

const buf = Mixed.create({ a: 1, b: 2, c: 3 });

// C: void setPoint(struct Point* p, int x, int y)

const Point = Struct({ x: 'i', y: 'i' });
const lib = dlopen('lib.so', {
  setPoint: { args: [FFIType.ptr, FFIType.int32, FFIType.int32], returns: 'i' },
});

const buf = Point.create({ x: 0, y: 0 });
lib.symbols.setPoint(ffi.ptr(buf), 42, 99);

const result = Point.fromPtr(ffi.ptr(buf));
console.log(result.x, result.y);