cfgrammar/idxnewtype.rs
1// This macro generates a struct which exposes a u32 API (but which may, internally, use a smaller
2// storage size).
3
4use std::mem::size_of;
5
6#[cfg(feature = "bincode")]
7use bincode::{Decode, Encode};
8use num_traits::{PrimInt, Unsigned};
9#[cfg(feature = "serde")]
10use serde::{Deserialize, Serialize};
11
12macro_rules! IdxNewtype {
13 ($(#[$attr:meta])* $n: ident) => {
14 $(#[$attr])*
15 #[derive(Clone, Copy, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
16 #[cfg_attr(feature="serde", derive(Serialize, Deserialize))]
17 #[cfg_attr(feature="bincode", derive(Encode, Decode))]
18 pub struct $n<T>(pub T);
19
20 impl<T: PrimInt + Unsigned> From<$n<T>> for usize {
21 fn from($n(st): $n<T>) -> Self {
22 debug_assert!(size_of::<usize>() >= size_of::<T>());
23 num_traits::cast(st).unwrap()
24 }
25 }
26
27 impl<T: PrimInt + Unsigned> From<$n<T>> for u32 {
28 fn from($n(st): $n<T>) -> Self {
29 debug_assert!(size_of::<u32>() >= size_of::<T>());
30 num_traits::cast(st).unwrap()
31 }
32 }
33
34 impl<T: PrimInt + Unsigned> $n<T> {
35 pub fn as_storaget(&self) -> T {
36 let $n(st) = self;
37 *st
38 }
39 }
40 }
41}
42
43IdxNewtype!(
44 /// A type specifically for rule indices.
45 ///
46 /// It is guaranteed that `RIdx` can be converted, without loss of precision, to `usize` with
47 /// the idiom `usize::from(...)`.
48 RIdx
49);
50IdxNewtype!(
51 /// A type specifically for production indices (e.g. a rule `E::=A|B` would
52 /// have two productions for the single rule `E`).
53 ///
54 /// It is guaranteed that `PIdx` can be converted, without loss of precision, to `usize` with
55 /// the idiom `usize::from(...)`.
56 PIdx
57);
58IdxNewtype!(
59 /// A type specifically for symbol indices (within a production).
60 ///
61 /// It is guaranteed that `SIdx` can be converted, without loss of precision, to `usize` with
62 /// the idiom `usize::from(...)`.
63 SIdx
64);
65IdxNewtype!(
66 /// A type specifically for token indices.
67 ///
68 /// It is guaranteed that `TIdx` can be converted, without loss of precision, to `usize` with
69 /// the idiom `usize::from(...)`.
70 TIdx
71);