A Uint256 version of the "official" cairo memset, to initiate an array of Uint256

uint256_memset.cairo

from starkware.cairo.common.uint256 import Uint256

func uint256_memset(dst: Uint256*, value: Uint256, n: felt):
  struct LoopFrame:
    member dst : Uint256*
  end

  if n == 0:
    return ()
  end

  %{ vm_enter_scope({'n': ids.n}) %}
  tempvar frame = LoopFrame(dst=dst)

  loop:
  let frame = [cast(ap - LoopFrame.SIZE, LoopFrame*)]
  assert [frame.dst] = value

  let continue_loop = [ap]
  # Reserve space for continue_loop.
  let next_frame = cast(ap + 1, LoopFrame*)
  next_frame.dst = frame.dst + Uint256.SIZE; ap++
  %{
    n -= 1
    ids.continue_loop = 1 if n > 0 else 0
  %}
  static_assert next_frame + LoopFrame.SIZE == ap + 1
  jmp loop if continue_loop != 0; ap++
  # Assert that the loop executed n times.
  assert n = (cast(next_frame.dst, felt) - cast(dst, felt)) / Uint256.SIZE

  %{ vm_exit_scope() %}
  return ()
end