From a123a1997f3ab527ab83b44ca18bec94883f46d0 Mon Sep 17 00:00:00 2001
From: metamuffin <metamuffin@disroot.org>
Date: Fri, 18 Apr 2025 23:33:29 +0200
Subject: use impl Hash for cache key instead of string

---
 base/src/cache.rs | 57 +++++++++++++++++++++++++++++++++++++------------------
 1 file changed, 39 insertions(+), 18 deletions(-)

(limited to 'base/src')

diff --git a/base/src/cache.rs b/base/src/cache.rs
index 0b28e1b..40c6e7b 100644
--- a/base/src/cache.rs
+++ b/base/src/cache.rs
@@ -10,11 +10,13 @@ use bincode::{Decode, Encode};
 use log::{info, warn};
 use rand::random;
 use serde::Serialize;
+use sha2::Sha512;
 use std::{
     any::Any,
     collections::{BTreeMap, HashMap},
     fs::rename,
     future::Future,
+    hash::{Hash, Hasher},
     io::Seek,
     path::PathBuf,
     sync::{
@@ -36,19 +38,28 @@ impl CachePath {
     }
 }
 
-pub fn cache_location(seed: &[&str]) -> (usize, CachePath) {
+pub fn cache_location(kind: &str, key: impl Hash) -> (usize, CachePath) {
     use sha2::Digest;
-    let mut d = sha2::Sha512::new();
-    for s in seed {
-        d.update(s.as_bytes());
-        d.update(b"\0");
+    struct ShaHasher(Sha512);
+    impl Hasher for ShaHasher {
+        fn finish(&self) -> u64 {
+            unreachable!()
+        }
+        fn write(&mut self, bytes: &[u8]) {
+            self.0.update(bytes);
+        }
     }
-    let d = d.finalize();
+    let mut d = ShaHasher(sha2::Sha512::new());
+    d.0.update(kind);
+    d.0.update(b"\0");
+    key.hash(&mut d);
+
+    let d = d.0.finalize();
     let n =
         d[0] as usize | ((d[1] as usize) << 8) | ((d[2] as usize) << 16) | ((d[3] as usize) << 24);
     let fname = base64::engine::general_purpose::URL_SAFE.encode(d);
-    let fname = &fname[..22];
-    let fname = format!("{}-{}", seed[0], fname); // about 128 bits
+    let fname = &fname[..30]; // 180 bits
+    let fname = format!("{}-{}", kind, fname);
     (n, CachePath(fname.into()))
 }
 
@@ -57,14 +68,15 @@ pub static CACHE_GENERATION_LOCKS: LazyLock<[Mutex<()>; CACHE_GENERATION_BUCKET_
     LazyLock::new(|| [(); CACHE_GENERATION_BUCKET_COUNT].map(|_| Mutex::new(())));
 
 pub async fn async_cache_file<Fun, Fut>(
-    seed: &[&str],
+    kind: &str,
+    key: impl Hash,
     generate: Fun,
 ) -> Result<CachePath, anyhow::Error>
 where
     Fun: FnOnce(tokio::fs::File) -> Fut,
     Fut: Future<Output = Result<(), anyhow::Error>>,
 {
-    let (bucket, location) = cache_location(seed);
+    let (bucket, location) = cache_location(kind, key);
     // we need a lock even if it exists since somebody might be still in the process of writing.
     let _guard = CACHE_GENERATION_LOCKS[bucket % CACHE_GENERATION_BUCKET_COUNT]
         .lock()
@@ -95,11 +107,15 @@ where
 
 thread_local! { pub static WITHIN_CACHE_FILE: AtomicBool = const { AtomicBool::new(false) }; }
 
-pub fn cache_file<Fun>(seed: &[&str], mut generate: Fun) -> Result<CachePath, anyhow::Error>
+pub fn cache_file<Fun>(
+    kind: &str,
+    key: impl Hash,
+    mut generate: Fun,
+) -> Result<CachePath, anyhow::Error>
 where
     Fun: FnMut(std::fs::File) -> Result<(), anyhow::Error>,
 {
-    let (bucket, location) = cache_location(seed);
+    let (bucket, location) = cache_location(kind, key);
     // we need a lock even if it exists since somebody might be still in the process of writing.
     let already_within = WITHIN_CACHE_FILE.with(|a| a.swap(true, Ordering::Relaxed));
     let _guard = if already_within {
@@ -139,12 +155,16 @@ pub static CACHE_IN_MEMORY_OBJECTS: LazyLock<RwLock<HashMap<PathBuf, InMemoryCac
     LazyLock::new(|| RwLock::new(HashMap::new()));
 pub static CACHE_IN_MEMORY_SIZE: AtomicUsize = AtomicUsize::new(0);
 
-pub fn cache_memory<Fun, T>(seed: &[&str], mut generate: Fun) -> Result<Arc<T>, anyhow::Error>
+pub fn cache_memory<Fun, T>(
+    kind: &str,
+    key: impl Hash,
+    mut generate: Fun,
+) -> Result<Arc<T>, anyhow::Error>
 where
     Fun: FnMut() -> Result<T, anyhow::Error>,
     T: Encode + Decode + Send + Sync + 'static,
 {
-    let (_, location) = cache_location(seed);
+    let (_, location) = cache_location(kind, &key);
     {
         let mut g = CACHE_IN_MEMORY_OBJECTS.write().unwrap();
         if let Some(entry) = g.get_mut(&location.abs()) {
@@ -158,7 +178,7 @@ where
         }
     }
 
-    let location = cache_file(seed, move |mut file| {
+    let location = cache_file(kind, &key, move |mut file| {
         let object = generate()?;
         bincode::encode_into_std_write(&object, &mut file, bincode::config::standard())
             .context("encoding cache object")?;
@@ -189,7 +209,8 @@ where
 }
 
 pub async fn async_cache_memory<Fun, Fut, T>(
-    seed: &[&str],
+    kind: &str,
+    key: impl Hash,
     generate: Fun,
 ) -> Result<Arc<T>, anyhow::Error>
 where
@@ -197,7 +218,7 @@ where
     Fut: Future<Output = Result<T, anyhow::Error>>,
     T: Encode + Decode + Send + Sync + 'static,
 {
-    let (_, location) = cache_location(seed);
+    let (_, location) = cache_location(kind, &key);
     {
         let mut g = CACHE_IN_MEMORY_OBJECTS.write().unwrap();
         if let Some(entry) = g.get_mut(&location.abs()) {
@@ -211,7 +232,7 @@ where
         }
     }
 
-    let location = async_cache_file(seed, move |mut file| async move {
+    let location = async_cache_file(kind, &key, move |mut file| async move {
         let object = generate().await?;
         let data = bincode::encode_to_vec(&object, bincode::config::standard())
             .context("encoding cache object")?;
-- 
cgit v1.2.3-70-g09d2