multiversx_sc_codec/impl_for_types/
impl_empty.rs

1use crate::{
2    DecodeError, DecodeErrorHandler, EncodeErrorHandler, NestedDecode, NestedDecodeInput,
3    NestedEncode, NestedEncodeOutput, TopDecode, TopDecodeInput, TopEncode, TopEncodeOutput,
4};
5
6/// Empty structure with an empty bytes representation. Equivalent to `false`, `0` or `[u8; 0]`, but more explicit.
7///
8/// Note: the unit type `()` would have naturally fit this role, but we decided to make the unit type multi-value only.
9#[derive(Debug, PartialEq, Eq)]
10pub struct Empty;
11
12impl TopEncode for Empty {
13    #[inline]
14    fn top_encode_or_handle_err<O, H>(&self, output: O, _h: H) -> Result<(), H::HandledErr>
15    where
16        O: TopEncodeOutput,
17        H: EncodeErrorHandler,
18    {
19        output.set_slice_u8(&[]);
20        Ok(())
21    }
22}
23
24impl TopDecode for Empty {
25    fn top_decode_or_handle_err<I, H>(input: I, h: H) -> Result<Self, H::HandledErr>
26    where
27        I: TopDecodeInput,
28        H: DecodeErrorHandler,
29    {
30        if input.byte_len() == 0 {
31            Ok(Empty)
32        } else {
33            Err(h.handle_error(DecodeError::INPUT_TOO_LONG))
34        }
35    }
36}
37
38impl NestedEncode for Empty {
39    #[inline]
40    fn dep_encode_or_handle_err<O, H>(&self, _dest: &mut O, _h: H) -> Result<(), H::HandledErr>
41    where
42        O: NestedEncodeOutput,
43        H: EncodeErrorHandler,
44    {
45        Ok(())
46    }
47}
48
49impl NestedDecode for Empty {
50    #[inline]
51    fn dep_decode_or_handle_err<I, H>(_input: &mut I, _h: H) -> Result<Self, H::HandledErr>
52    where
53        I: NestedDecodeInput,
54        H: DecodeErrorHandler,
55    {
56        Ok(Empty)
57    }
58}
59
60#[cfg(test)]
61pub mod tests {
62    use crate::test_util::{check_dep_encode_decode, check_top_encode_decode};
63    use alloc::vec::Vec;
64
65    #[test]
66    fn test_top_empty() {
67        check_top_encode_decode(super::Empty, &[]);
68    }
69
70    #[test]
71    fn test_dep_empty() {
72        check_dep_encode_decode(super::Empty, &[]);
73    }
74
75    #[test]
76    fn test_dep_unit() {
77        check_dep_encode_decode((), &[]);
78    }
79
80    #[test]
81    fn test_empty_vec_compacted() {
82        check_top_encode_decode(Vec::<u8>::new(), &[]);
83    }
84}
multiversx_sc_codec/impl_for_types/impl_empty.rs

multiversx_sc_codec/impl_for_types/
impl_empty.rs
