From 95c85c127a8c646591069df8ca92247529f5afe6 Mon Sep 17 00:00:00 2001
From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Mon, 3 May 2021 22:42:04 +0100
Subject: [PATCH] provide DigestWrite::of

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
---
 src/bin/otter.rs | 7 ++-----
 src/utils.rs     | 7 +++++++
 2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/src/bin/otter.rs b/src/bin/otter.rs
index b8553adf..f9c9457f 100644
--- a/src/bin/otter.rs
+++ b/src/bin/otter.rs
@@ -1341,11 +1341,8 @@ mod upload_bundle {
       .with_context(|| args.bundle_file.clone())
       .context("open bundle file")?;
     let mut f = BufReader::new(f);
-    let hash = {
-      let mut dw = bundles::DigestWrite::sink();
-      io::copy(&mut f, &mut dw).context("read bundle file (for hash)")?;
-      dw.finish().0
-    };
+    let hash = bundles::DigestWrite::of(&mut f)
+      .context("read bundle file (for hash)")?;
     let kind = bundles::Kind::only();
     f.rewind().context("rewind bundle file")?;
     let cmd = MC::UploadBundle {
diff --git a/src/utils.rs b/src/utils.rs
index 438984ff..00f3c836 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -584,6 +584,13 @@ impl<D: Digest, W: Write> DigestWrite<D, W> {
 }
 impl<D: Digest> DigestWrite<D, io::Sink> {
   pub fn sink() -> Self { DigestWrite::new(io::sink()) }
+
+  #[throws(io::Error)]
+  pub fn of<R>(r: &mut R) -> digest::Output<D> where R: Read {
+    let mut dw = DigestWrite::<D,_>::sink();
+    io::copy(r, &mut dw)?;
+    dw.finish().0
+  }
 }
 
 impl<D: Digest, W: Write> Write for DigestWrite<D, W> {
-- 
2.30.2