Use lazy_static initialisation or compile time optimisation to prevent re-initialisation of script hash

[phklive]

Use lazy_static initialisation or compile time optimisation to prevent re-initialisation of script hash every time a swap script is used:

miden-base/miden-lib/src/notes/mod.rs

Lines 119 to 142 in d901d51

	/// Utility function generating RECIPIENT for the P2ID note script created by the SWAP script
	fn build_p2id_recipient(target: AccountId, serial_num: Word) -> Result<Digest, NoteError> {
	// TODO: add lazy_static initialization or compile-time optimization instead of re-generating
	// the script hash every time we call the SWAP script
	let assembler = assembler();
	let p2id_bytes = include_bytes!(concat!(env!("OUT_DIR"), "/assets/P2ID.masb"));
	let note_script_ast =
	ProgramAst::from_bytes(p2id_bytes).map_err(NoteError::NoteDeserializationError)?;
	let (note_script, _) = NoteScript::new(note_script_ast, &assembler)?;
	let script_hash = note_script.hash();
	let serial_num_hash = Hasher::merge(&[serial_num.into(), Digest::default()]);
	let merge_script = Hasher::merge(&[serial_num_hash, script_hash]);
	Ok(Hasher::merge(&[
	merge_script,
	Hasher::hash_elements(&[target.into(), ZERO, ZERO, ZERO]),
	]))
	}

To improve this function

[bobbinth]

This should be solved by migrating to the MAST-based script format.

[bobbinth]

Closed by #939.