3 files changed, 59 insertions, 1 deletions
diff --git a/src/util/Cargo.toml b/src/util/Cargo.toml
index 57c70ffb..7d79f21a 100644
--- a/src/util/Cargo.toml
+++ b/src/util/Cargo.toml
@@ -18,12 +18,14 @@ garage_db = { version = "0.8.0", path = "../db" }
 
 async-trait = "0.1"
 blake2 = "0.9"
+bytes = "1.0"
+digest = "0.10"
 err-derive = "0.3"
 xxhash-rust = { version = "0.8", default-features = false, features = ["xxh3"] }
 hex = "0.4"
 tracing = "0.1.30"
 rand = "0.8"
-sha2 = "0.9"
+sha2 = "0.10"
 
 chrono = "0.4"
 rmp-serde = "0.15"
diff --git a/src/util/async_hash.rs b/src/util/async_hash.rs
new file mode 100644
index 00000000..67776eb9
--- /dev/null
+++ b/src/util/async_hash.rs
@@ -0,0 +1,55 @@
+use bytes::Bytes;
+use digest::Digest;
+
+use tokio::sync::mpsc;
+use tokio::task::JoinHandle;
+
+use crate::data::*;
+
+/// Compute the sha256 of a slice,
+/// spawning on a tokio thread for CPU-intensive processing
+/// The argument has to be an owned Bytes, as it is moved out to a new thread.
+pub async fn async_sha256sum(data: Bytes) -> Hash {
+	tokio::task::spawn_blocking(move || sha256sum(&data))
+		.await
+		.unwrap()
+}
+
+/// Compute the blake2sum of a slice,
+/// spawning on a tokio thread for CPU-intensive processing.
+/// The argument has to be an owned Bytes, as it is moved out to a new thread.
+pub async fn async_blake2sum(data: Bytes) -> Hash {
+	tokio::task::spawn_blocking(move || blake2sum(&data))
+		.await
+		.unwrap()
+}
+
+// ----
+
+pub struct AsyncHasher<D: Digest> {
+	sendblk: mpsc::UnboundedSender<Bytes>,
+	task: JoinHandle<digest::Output<D>>,
+}
+
+impl<D: Digest> AsyncHasher<D> {
+	pub fn new() -> Self {
+		let (sendblk, mut recvblk) = mpsc::unbounded_channel::<Bytes>();
+		let task = tokio::task::spawn_blocking(move || {
+			let mut digest = D::new();
+			while let Some(blk) = recvblk.blocking_recv() {
+				digest.update(&blk[..]);
+			}
+			digest.finalize()
+		});
+		Self { sendblk, task }
+	}
+
+	pub fn update(&self, b: Bytes) {
+		self.sendblk.send(b).unwrap()
+	}
+
+	pub async fn finalize(self) -> digest::Output<D> {
+		drop(self.sendblk);
+		self.task.await.unwrap()
+	}
+}
diff --git a/src/util/lib.rs b/src/util/lib.rs
index fce151af..7152f92a 100644
--- a/src/util/lib.rs
+++ b/src/util/lib.rs
@@ -3,6 +3,7 @@
 #[macro_use]
 extern crate tracing;
 
+pub mod async_hash;
 pub mod background;
 pub mod config;
 pub mod crdt;