duplicateText.wast

(module
	(memory 1)
	(func (export "duplicateText") (param $ptr i32)
		(local $len i32)
		(local $max i32)
		(loop $continueLen
			(if
				(i32.load8_u
					(i32.add (get_local $ptr) (get_local $len))
				)
				(then
					(set_local $len
						(i32.add (get_local $len) (i32.const 1))
					)
					(br $continueLen)
				)
			)
		)

		(i32.sub
			(get_local $ptr)
			(i32.add (get_local $len))
			(i32.add (get_local $len))
			(i32.add (i32.const 1))
			(i32.shr_u (i32.const 16))

			(current_memory)
		)

		(tee_local $max)
		(if
			(then
				(grow_memory (get_local $max))
				(drop)
			)
		)

		(set_local $max (i32.add (get_local $ptr) (get_local $len)))
		(loop $continueCopy
			(if
				(i32.lt_u (get_local $ptr) (get_local $max))
				(then
					(i32.store8
						(i32.add (get_local $ptr) (get_local $len))
						(i32.load8_u (get_local $ptr))
					)
					(set_local $ptr
						(i32.add (get_local $ptr) (i32.const 1))
					)
					(br $continueCopy)
				)
			)
		)

		(i32.store8
			(i32.add (get_local $max) (get_local $len))
			(i32.const 0)
		)
	)
)