lighthouse/eth2/utils/serde_hex/src/lib.rs

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use hex;
use hex::ToHex;
use serde::de::{self, Visitor};
use std::fmt;
pub fn encode<T: AsRef<[u8]>>(data: T) -> String {
let mut hex = String::with_capacity(data.as_ref().len() * 2);
// Writing to a string never errors, so we can unwrap here.
data.write_hex(&mut hex).unwrap();
let mut s = "0x".to_string();
s.push_str(hex.as_str());
s
}
pub struct PrefixedHexVisitor;
impl<'de> Visitor<'de> for PrefixedHexVisitor {
type Value = Vec<u8>;
fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
formatter.write_str("a hex string with 0x prefix")
}
fn visit_str<E>(self, value: &str) -> Result<Self::Value, E>
where
E: de::Error,
{
if value.starts_with("0x") {
Ok(hex::decode(&value[2..])
.map_err(|e| de::Error::custom(format!("invalid hex ({:?})", e)))?)
} else {
Err(de::Error::custom("missing 0x prefix"))
}
}
}
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pub struct HexVisitor;
impl<'de> Visitor<'de> for HexVisitor {
type Value = Vec<u8>;
fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
formatter.write_str("a hex string (irrelevant of prefix)")
}
fn visit_str<E>(self, value: &str) -> Result<Self::Value, E>
where
E: de::Error,
{
Ok(hex::decode(value.trim_start_matches("0x"))
.map_err(|e| de::Error::custom(format!("invalid hex ({:?})", e)))?)
}
}
#[cfg(test)]
mod test {
use super::*;
#[test]
fn encoding() {
let bytes = vec![0, 255];
let hex = encode(&bytes);
assert_eq!(hex.as_str(), "0x00ff");
let bytes = vec![];
let hex = encode(&bytes);
assert_eq!(hex.as_str(), "0x");
let bytes = vec![1, 2, 3];
let hex = encode(&bytes);
assert_eq!(hex.as_str(), "0x010203");
}
}