From 731549ac1d08df6c956be672353e11c4aac1716f Mon Sep 17 00:00:00 2001
From: Matthias Beyer <mail@beyermatthias.de>
Date: Mon, 5 Apr 2021 11:53:29 +0200
Subject: Add AsyncDag::load()

Signed-off-by: Matthias Beyer <mail@beyermatthias.de>
---
 src/async_dag.rs | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/src/async_dag.rs b/src/async_dag.rs
index 0da6e2c..88a839e 100644
--- a/src/async_dag.rs
+++ b/src/async_dag.rs
@@ -47,6 +47,24 @@ impl<Id, N, Backend> AsyncDag<Id, N, Backend>
             })
     }
 
+    /// Load a AsyncDag object using `head` as HEAD node.
+    ///
+    /// # Warning
+    ///
+    /// This fails if backend.get(head) fails.
+    pub async fn load(backend: Backend, head: Id) -> Result<Self> {
+        backend.get(head)
+            .await?
+            .map(|(id, _)| {
+                AsyncDag {
+                    head: id,
+                    backend: backend,
+                    _node: std::marker::PhantomData,
+                }
+            })
+            .ok_or_else(|| anyhow!("Node not found"))
+    }
+
     /// Check whether an `id` is in the DAG.
     pub async fn has_id(&self, id: &Id) -> Result<bool> {
         self.stream()
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