serde_utils/
hex.rs

1//! Provides utilities for parsing 0x-prefixed hex strings.
2
3use serde::de::{self, Visitor};
4use std::fmt;
5
6/// Encode `data` as a 0x-prefixed hex string.
7pub fn encode<T: AsRef<[u8]>>(data: T) -> String {
8    let hex = hex::encode(data);
9
10    let mut s = "0x".to_string();
11    s.push_str(hex.as_str());
12    s
13}
14
15/// Decode `data` from a 0x-prefixed hex string.
16pub fn decode(s: &str) -> Result<Vec<u8>, String> {
17    if let Some(stripped) = s.strip_prefix("0x") {
18        hex::decode(stripped).map_err(|e| format!("invalid hex: {:?}", e))
19    } else {
20        Err("hex must have 0x prefix".to_string())
21    }
22}
23
24pub struct PrefixedHexVisitor;
25
26impl<'de> Visitor<'de> for PrefixedHexVisitor {
27    type Value = Vec<u8>;
28
29    fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
30        formatter.write_str("a hex string with 0x prefix")
31    }
32
33    fn visit_str<E>(self, value: &str) -> Result<Self::Value, E>
34    where
35        E: de::Error,
36    {
37        decode(value).map_err(de::Error::custom)
38    }
39}
40
41pub struct HexVisitor;
42
43impl<'de> Visitor<'de> for HexVisitor {
44    type Value = Vec<u8>;
45
46    fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
47        formatter.write_str("a hex string (irrelevant of prefix)")
48    }
49
50    fn visit_str<E>(self, value: &str) -> Result<Self::Value, E>
51    where
52        E: de::Error,
53    {
54        hex::decode(value.trim_start_matches("0x"))
55            .map_err(|e| de::Error::custom(format!("invalid hex ({:?})", e)))
56    }
57}
58
59#[cfg(test)]
60mod test {
61    use super::*;
62
63    #[test]
64    fn encoding() {
65        let bytes = vec![0, 255];
66        let hex = encode(bytes);
67        assert_eq!(hex.as_str(), "0x00ff");
68
69        let bytes = vec![];
70        let hex = encode(bytes);
71        assert_eq!(hex.as_str(), "0x");
72
73        let bytes = vec![1, 2, 3];
74        let hex = encode(bytes);
75        assert_eq!(hex.as_str(), "0x010203");
76    }
77}
serde_utils/hex.rs

serde_utils/
hex.rs
