From 3b88cd1725bdded57c2ff845db5d471d2da63e6a Mon Sep 17 00:00:00 2001
From: Justus Winter <justus@sequoia-pgp.org>
Date: Tue, 17 Nov 2020 15:20:48 +0100
Subject: openpgp: Require Write for impl Digest.

---
 openpgp/src/crypto/backend/cng/hash.rs | 12 ++++++++++++
 openpgp/src/crypto/hash.rs             | 12 +++++++++++-
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/openpgp/src/crypto/backend/cng/hash.rs b/openpgp/src/crypto/backend/cng/hash.rs
index 1f58d4cc..8d3bbb0f 100644
--- a/openpgp/src/crypto/backend/cng/hash.rs
+++ b/openpgp/src/crypto/backend/cng/hash.rs
@@ -1,4 +1,5 @@
 use core::convert::{TryFrom, TryInto};
+use std::io;
 use std::sync::Mutex;
 
 use crate::crypto::hash::Digest;
@@ -61,6 +62,17 @@ impl Digest for Hash {
     }
 }
 
+impl io::Write for Hash {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        self.update(buf);
+        Ok(buf.len())
+    }
+    fn flush(&mut self) -> io::Result<()> {
+        // Do nothing.
+        Ok(())
+    }
+}
+
 impl TryFrom<HashAlgorithm> for cng::HashAlgorithmId {
     type Error = Error;
 
diff --git a/openpgp/src/crypto/hash.rs b/openpgp/src/crypto/hash.rs
index 410d9eae..27641429 100644
--- a/openpgp/src/crypto/hash.rs
+++ b/openpgp/src/crypto/hash.rs
@@ -31,7 +31,7 @@ use std::io::{self, Write};
 const DUMP_HASHED_VALUES: Option<&str> = None;
 
 /// Hasher capable of calculating a digest for the input byte stream.
-pub(crate) trait Digest: DynClone  + Send + Sync {
+pub(crate) trait Digest: DynClone + Write + Send + Sync {
     /// Returns the algorithm.
     fn algo(&self) -> HashAlgorithm;
 
@@ -229,6 +229,16 @@ impl Digest for HashDumper {
     }
 }
 
+impl io::Write for HashDumper {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        self.hasher.write(buf)
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        self.hasher.flush()
+    }
+}
+
 /// Hashes OpenPGP packets and related types.
 ///
 /// Some OpenPGP data structures need to be hashed to be covered by
-- 
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