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use crate::{NodeId, UUID};
impl UUID {
#[must_use]
pub const fn get_node_id(&self) -> Option<NodeId> {
match self.get_version() {
Some(1 | 2 | 6) => {
let [_, _, _, _, _, _, _, _, _, _, b1, b2, b3, b4, b5, b6] = self.bytes;
let node_id = NodeId {
bytes: [b1, b2, b3, b4, b5, b6],
};
Some(node_id)
}
_ => None,
}
}
}
#[allow(clippy::unwrap_used)]
#[cfg(test)]
mod tests {
use super::*;
/// Helper that fabricates a UUID with a specific version *and* node ID.
///
/// - `version` is written into the high nibble of byte 6
/// (see RFC 4122 §4.1.3).
/// - The RFC 4122 “variant 1” bits (`10xx_xxxx`) are written
/// into byte 8, but the variant is irrelevant for `node_id()`.
fn make_uuid(version: u8, node: [u8; 6]) -> UUID {
let mut bytes = [0u8; 16];
// Any arbitrary values for the time / clock sequence fields:
for (i, item) in bytes.iter_mut().enumerate() {
*item = i.try_into().unwrap();
}
// Embed the requested version.
bytes[6] = (version << 4) | (bytes[6] & 0x0F);
// Embed RFC-4122 variant 1 (“10xx_xxxx”).
bytes[8] = 0b1000_0000;
// Copy the node identifier into the last six bytes.
bytes[10..16].copy_from_slice(&node);
UUID { bytes }
}
#[test]
fn node_id_returns_some_for_versions_1_2_and_6() {
let node = [0x11, 0x22, 0x33, 0x44, 0x55, 0x66];
for &v in &[1u8, 2, 6] {
let uuid = make_uuid(v, node);
assert_eq!(
uuid.get_node_id(),
Some(NodeId { bytes: node }),
"unexpected result for version {v}"
);
}
}
#[test]
fn node_id_returns_none_for_all_other_versions() {
let unwanted = [0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff];
// All versions that must *not* yield a node ID.
for &v in &[0u8, 3, 4, 5, 7, 8, 9, 0xF] {
let uuid = make_uuid(v, unwanted);
assert_eq!(
uuid.get_node_id(),
None,
"version {v} incorrectly returned Some(..)"
);
}
}
// -----------------------------------------------------------------------
// Compile-time proof: `UUID::node_id` is const-compatible
// -----------------------------------------------------------------------
// Build a UUID and compute its node ID entirely at compile time.
const SAMPLE_UUID: UUID = {
let mut bytes = [0u8; 16];
bytes[6] = 0x10; // version 1
bytes[8] = 0x80; // variant 1
// node_id
bytes[10] = 1;
bytes[11] = 2;
bytes[12] = 3;
bytes[13] = 4;
bytes[14] = 5;
bytes[15] = 6;
UUID { bytes }
};
const SAMPLE_NODE_ID: Option<NodeId> = SAMPLE_UUID.get_node_id();
#[test]
fn const_evaluation_matches_runtime_result() {
assert_eq!(
SAMPLE_NODE_ID,
Some(NodeId {
bytes: [1, 2, 3, 4, 5, 6]
})
);
}
}