def-/offset.nim

Last active September 10, 2020 16:47

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	template offset(Typ, member): int {.immediate.} =
	var dummy: Typ
	cast[int](dummy.member.addr) -% cast[int](dummy.addr)

	type Foo = object
	x: int
	y: int

	echo offset(Foo, y)

HugoP707 commented Sep 10, 2020

a more correct and updated way of doing it would be this:

template offset(Typ, field: untyped): ByteAddress =
  var dummy: Typ
  cast[ByteAddress](dummy.field.addr) -% cast[ByteAddress](dummy.addr)

type Foo = object
  x: int
  y: int

echo offset(Foo, y)

(i changed the argument name because i liked it more, the other one are fine too)

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