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1295969 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 | //! LMDB-backed ZK proof cache (heed 0.20).
//!
//! Key: hex(band_byte ‖ SHA-256(n_artists ‖ total_btt ‖ splits_bps)) = 66 hex chars
//! Value: hex-encoded ZK proof bytes (stored as JSON string in LMDB)
//!
//! Eviction policy: none (proofs are deterministic — same inputs always produce
//! the same proof, so stale entries are never harmful, only wasteful).
use sha2::{Digest, Sha256};
pub struct ZkProofCache {
db: crate::persist::LmdbStore,
}
impl ZkProofCache {
pub fn open(path: &str) -> anyhow::Result<Self> {
Ok(Self {
db: crate::persist::LmdbStore::open(path, "zk_proofs")?,
})
}
/// Build the 33-byte cache key (band byte ‖ SHA-256 of inputs).
pub fn cache_key(band: u8, n_artists: u32, total_btt: u64, splits_bps: &[u16]) -> [u8; 33] {
let mut h = Sha256::new();
h.update(n_artists.to_le_bytes());
h.update(total_btt.to_le_bytes());
for bps in splits_bps {
h.update(bps.to_le_bytes());
}
let hash: [u8; 32] = h.finalize().into();
let mut key = [0u8; 33];
key[0] = band;
key[1..].copy_from_slice(&hash);
key
}
fn key_str(band: u8, n_artists: u32, total_btt: u64, splits_bps: &[u16]) -> String {
hex::encode(Self::cache_key(band, n_artists, total_btt, splits_bps))
}
/// Retrieve a cached proof. Returns `None` on miss.
pub fn get(
&self,
band: u8,
n_artists: u32,
total_btt: u64,
splits_bps: &[u16],
) -> Option<Vec<u8>> {
let key = Self::key_str(band, n_artists, total_btt, splits_bps);
let hex_str: String = self.db.get(&key).ok().flatten()?;
hex::decode(hex_str).ok()
}
/// Store a proof. The proof bytes are hex-encoded to stay JSON-compatible.
pub fn put(
&self,
band: u8,
n_artists: u32,
total_btt: u64,
splits_bps: &[u16],
proof: Vec<u8>,
) {
let key = Self::key_str(band, n_artists, total_btt, splits_bps);
let hex_proof = hex::encode(&proof);
if let Err(e) = self.db.put(&key, &hex_proof) {
tracing::error!(err=%e, "ZK proof cache write error");
}
}
/// Prometheus-compatible metrics line.
pub fn metrics_text(&self) -> String {
let count = self.db.all_values::<String>().map(|v| v.len()).unwrap_or(0);
format!("retrosync_zk_cache_entries {count}\n")
}
}
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