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use std::collections::BTreeMap;
use std::convert::TryInto;
use serde::{Deserialize, Serialize};
use garage_util::data::*;
/// Node IDs used in K2V are u64 integers that are the abbreviation
/// of full Garage node IDs which are 256-bit UUIDs.
pub type K2VNodeId = u64;
pub fn make_node_id(node_id: Uuid) -> K2VNodeId {
let mut tmp = [0u8; 8];
tmp.copy_from_slice(&node_id.as_slice()[..8]);
u64::from_be_bytes(tmp)
}
#[derive(PartialEq, Eq, Debug, Serialize, Deserialize)]
pub struct CausalContext {
pub vector_clock: BTreeMap<K2VNodeId, u64>,
}
impl CausalContext {
/// Empty causality context
pub fn new_empty() -> Self {
Self {
vector_clock: BTreeMap::new(),
}
}
/// Make binary representation and encode in base64
pub fn serialize(&self) -> String {
let mut ints = Vec::with_capacity(2 * self.vector_clock.len());
for (node, time) in self.vector_clock.iter() {
ints.push(*node);
ints.push(*time);
}
let checksum = ints.iter().fold(0, |acc, v| acc ^ *v);
let mut bytes = u64::to_be_bytes(checksum).to_vec();
for i in ints {
bytes.extend(u64::to_be_bytes(i));
}
base64::encode_config(bytes, base64::URL_SAFE_NO_PAD)
}
/// Parse from base64-encoded binary representation
pub fn parse(s: &str) -> Result<Self, String> {
let bytes = base64::decode_config(s, base64::URL_SAFE_NO_PAD)
.map_err(|e| format!("bad causality token base64: {}", e))?;
if bytes.len() % 16 != 8 || bytes.len() < 8 {
return Err("bad causality token length".into());
}
let checksum = u64::from_be_bytes(bytes[..8].try_into().unwrap());
let mut ret = CausalContext {
vector_clock: BTreeMap::new(),
};
for i in 0..(bytes.len() / 16) {
let node_id = u64::from_be_bytes(bytes[8 + i * 16..16 + i * 16].try_into().unwrap());
let time = u64::from_be_bytes(bytes[16 + i * 16..24 + i * 16].try_into().unwrap());
ret.vector_clock.insert(node_id, time);
}
let check = ret.vector_clock.iter().fold(0, |acc, (n, t)| acc ^ *n ^ *t);
if check != checksum {
return Err("bad causality token checksum".into());
}
Ok(ret)
}
/// Check if this causal context contains newer items than another one
pub fn is_newer_than(&self, other: &Self) -> bool {
self.vector_clock
.iter()
.any(|(k, v)| v > other.vector_clock.get(k).unwrap_or(&0))
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_causality_token_serialization() {
let ct = CausalContext {
vector_clock: [(4, 42), (1928131023, 76), (0xefc0c1c47f9de433, 2)]
.iter()
.cloned()
.collect(),
};
assert_eq!(CausalContext::parse(&ct.serialize()).unwrap(), ct);
}
}
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