From cd6d2d24f475dfac5001b46cde23c52cd15a8175 Mon Sep 17 00:00:00 2001
From: Jeromy <why@ipfs.io>
Date: Tue, 29 Nov 2016 10:15:40 -0800
Subject: [PATCH] merkledag: retain cid types when roundtripping through a
 ProtoNode

License: MIT
Signed-off-by: Jeromy <why@ipfs.io>
---
 merkledag/coding.go    | 15 +++++++++++++--
 merkledag/merkledag.go |  1 +
 merkledag/node.go      |  3 +++
 3 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/merkledag/coding.go b/merkledag/coding.go
index 3b43e4c95..2bd88265b 100644
--- a/merkledag/coding.go
+++ b/merkledag/coding.go
@@ -7,7 +7,7 @@ import (
 	pb "github.com/ipfs/go-ipfs/merkledag/pb"
 
 	node "gx/ipfs/QmRSU5EqqWVZSNdbU51yXmVoF1uNw3JgTNB6RaiL7DZM16/go-ipld-node"
-	u "gx/ipfs/Qmb912gdngC1UWwTkhuW8knyRbcWeu5kqkxBpveLmW8bSr/go-ipfs-util"
+	mh "gx/ipfs/QmYDds3421prZgqKbLpEK7T9Aa2eVdQ7o3YarX1LVLdP2J/go-multihash"
 	cid "gx/ipfs/QmcTcsTvfaeEBRFo1TkFgT8sRmgi1n1LTZpecfVP8fzpGD/go-cid"
 )
 
@@ -84,7 +84,18 @@ func (n *ProtoNode) EncodeProtobuf(force bool) ([]byte, error) {
 	}
 
 	if n.cached == nil {
-		n.cached = cid.NewCidV0(u.Hash(n.encoded))
+		if n.prefix.MhType == 0 { // unset
+			n.prefix.Codec = cid.DagProtobuf
+			n.prefix.MhLength = -1
+			n.prefix.MhType = mh.SHA2_256
+			n.prefix.Version = 0
+		}
+		c, err := n.prefix.Sum(n.encoded)
+		if err != nil {
+			return nil, err
+		}
+
+		n.cached = c
 	}
 
 	return n.encoded, nil
diff --git a/merkledag/merkledag.go b/merkledag/merkledag.go
index 10ff5fb58..67169ed05 100644
--- a/merkledag/merkledag.go
+++ b/merkledag/merkledag.go
@@ -103,6 +103,7 @@ func decodeBlock(b blocks.Block) (node.Node, error) {
 		}
 
 		decnd.cached = b.Cid()
+		decnd.prefix = b.Cid().Prefix()
 		return decnd, nil
 	case cid.Raw:
 		return NewRawNode(b.RawData()), nil
diff --git a/merkledag/node.go b/merkledag/node.go
index 16d6941a2..6c89947ab 100644
--- a/merkledag/node.go
+++ b/merkledag/node.go
@@ -22,6 +22,9 @@ type ProtoNode struct {
 	encoded []byte
 
 	cached *cid.Cid
+
+	// prefix specifies cid version and hashing function
+	prefix cid.Prefix
 }
 
 type LinkSlice []*node.Link