#[must_use]
pub fn hex_bytes(bytes: &[u8]) -> String {
const HEX: &[u8; 16] = b"0123456789abcdef";
let mut out = String::with_capacity(bytes.len() * 2);
for byte in bytes {
out.push(HEX[usize::from(byte >> 4)] as char);
out.push(HEX[usize::from(byte & 0x0f)] as char);
}
out
}
#[must_use]
#[cfg(feature = "host")]
pub fn is_lowercase_hex(value: &str) -> bool {
value
.bytes()
.all(|byte| byte.is_ascii_digit() || matches!(byte, b'a'..=b'f'))
}
#[must_use]
#[cfg(feature = "host")]
pub fn is_canonical_lowercase_hex(value: &str) -> bool {
!value.is_empty() && value.len().is_multiple_of(2) && is_lowercase_hex(value)
}
#[cfg(all(test, feature = "host"))]
mod tests {
use super::*;
#[test]
fn lowercase_hex_predicates_distinguish_alphabet_and_canonical_length() {
for (value, lowercase, canonical) in [
("", true, false),
("0", true, false),
("00", true, true),
("0a", true, true),
("0A", false, false),
("0g", false, false),
("é", false, false),
] {
assert_eq!(is_lowercase_hex(value), lowercase, "{value:?}");
assert_eq!(is_canonical_lowercase_hex(value), canonical, "{value:?}");
}
}
}