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use std::fmt;
/// Wrapper for [`ua::EUInformation::unit_id`](crate::ua::EUInformation::unit_id).
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct UnitId(i32);
impl UnitId {
#[must_use]
pub(crate) const fn new(unit_id: i32) -> Self {
Self(unit_id)
}
/// The common UNECE code.
///
/// Decoded from the wrapped integer value according to the
/// [mapping defined by OPC UA](https://reference.opcfoundation.org/Core/Part8/v104/docs/5.6.3).
///
/// Returns an ASCII alphanumeric string with a minimum length of 1 and
/// a maximum length of 3. All other strings are discarded as invalid.
/// `unit_id`s where the most significant byte is not `0x00` are rejected
/// as invalid.
///
/// Returns `None` if the value could not be decoded or is invalid.
///
/// The returned string is not guaranteed to represent a valid _Common Code_
/// as defined by the [UNECE documents] or the [OPC UA specification].
///
/// [UNECE documents]: <https://unece.org/trade/documents/session-documents/revision-6>
/// [OPC UA specification]: <http://www.opcfoundation.org/UA/EngineeringUnits/UNECE/UNECE_to_OPCUA.csv>
#[must_use]
pub fn to_unece_code(&self) -> Option<String> {
let Self(unit_id) = self;
let ascii_chars = unit_id
.to_be_bytes()
.iter()
.copied()
.skip_while(|c| *c == 0x00)
.map(|c| {
// TODO: Are lowercase ASCII characters allowed? Probably not.
c.is_ascii_alphanumeric().then_some(c)
})
.collect::<Option<Vec<_>>>()?;
// TODO: Restrict minimum length to 2?
if !(1..=3).contains(&ascii_chars.len()) {
return None;
}
let code = String::from_utf8(ascii_chars);
debug_assert!(code.is_ok(), "never fails for ASCII character codes");
code.ok()
}
}
impl fmt::Display for UnitId {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
self.0.fmt(f)
}
}
#[cfg(test)]
mod tests {
use crate::ua::UnitId;
#[test]
fn unece_code_from_unit_id() {
assert_eq!(UnitId::new(12_592).to_unece_code().unwrap(), "10"); // group
assert_eq!(UnitId::new(12_851).to_unece_code().unwrap(), "23"); // gram per cubic centimetre
assert_eq!(UnitId::new(17_476).to_unece_code().unwrap(), "DD"); // degree [unit of angle]
assert_eq!(UnitId::new(23_130).to_unece_code().unwrap(), "ZZ"); // mutually defined
assert_eq!(UnitId::new(4_405_297).to_unece_code().unwrap(), "C81"); // radian
assert_eq!(UnitId::new(5_910_833).to_unece_code().unwrap(), "Z11"); // hanging container
// Allow only codes with expected length.
assert!(UnitId::new(0x0000_0000).to_unece_code().is_none());
assert!(UnitId::new(0x3000_0000).to_unece_code().is_none());
assert!(
UnitId::new(0x0000_0030).to_unece_code().is_some(),
"valid code of 1 ASCII character"
);
assert!(UnitId::new(0x3000_0030).to_unece_code().is_none());
assert!(
UnitId::new(0x0000_3030).to_unece_code().is_some(),
"valid code of 2 ASCII characters"
);
assert!(UnitId::new(0x3000_3030).to_unece_code().is_none());
assert!(
UnitId::new(0x0030_3030).to_unece_code().is_some(),
"valid code of 3 ASCII characters"
);
assert!(UnitId::new(0x3030_3030).to_unece_code().is_none());
}
}