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    #[inline]
26    fn top_decode_or_handle_err<I, H>(input: I, h: H) -> Result<Self, H::HandledErr>
27    where
28        I: TopDecodeInput,
29        H: DecodeErrorHandler,
30    {
31        if input.byte_len() == 0 {
32            Ok(Empty)
33        } else {
34            Err(h.handle_error(DecodeError::INPUT_TOO_LONG))
35        }
36    }
37}
38
39impl NestedEncode for Empty {
40    #[inline]
41    fn dep_encode_or_handle_err<O, H>(&self, _dest: &mut O, _h: H) -> Result<(), H::HandledErr>
42    where
43        O: NestedEncodeOutput,
44        H: EncodeErrorHandler,
45    {
46        Ok(())
47    }
48}
49
50impl NestedDecode for Empty {
51    #[inline]
52    fn dep_decode_or_handle_err<I, H>(_input: &mut I, _h: H) -> Result<Self, H::HandledErr>
53    where
54        I: NestedDecodeInput,
55        H: DecodeErrorHandler,
56    {
57        Ok(Empty)
58    }
59}
60
61#[cfg(test)]
62pub mod tests {
63    use crate::test_util::{check_dep_encode_decode, check_top_encode_decode};
64    use alloc::vec::Vec;
65
66    #[test]
67    fn test_top_empty() {
68        check_top_encode_decode(super::Empty, &[]);
69    }
70
71    #[test]
72    fn test_dep_empty() {
73        check_dep_encode_decode(super::Empty, &[]);
74    }
75
76    #[test]
77    fn test_dep_unit() {
78        check_dep_encode_decode((), &[]);
79    }
80
81    #[test]
82    fn test_empty_vec_compacted() {
83        check_top_encode_decode(Vec::<u8>::new(), &[]);
84    }
85}
multiversx_sc_codec/impl_for_types/impl_empty.rs

multiversx_sc_codec/impl_for_types/
impl_empty.rs
