From 35984c2c884ddcb676abd142e58c8b80301398b8 Mon Sep 17 00:00:00 2001
From: Steven Allen <steven@stebalien.com>
Date: Tue, 11 Jul 2017 20:27:22 -0700
Subject: [PATCH] Change IPFS to use the new pluggable Block to IPLD decoding
 framework.

Later, we should:

1. Pull the other node formats out of IPFS (at least the raw one).
2. Pull out the decoder registration/management into a `go-ipld` library.

License: MIT
Signed-off-by: Steven Allen <steven@stebalien.com>
---
 merkledag/coding.go    | 27 +++++++++++++++++++++++++++
 merkledag/merkledag.go | 41 ++++++++++++-----------------------------
 merkledag/raw.go       | 12 ++++++++++++
 3 files changed, 51 insertions(+), 29 deletions(-)

diff --git a/merkledag/coding.go b/merkledag/coding.go
index c66bb889a47..39da14a099d 100644
--- a/merkledag/coding.go
+++ b/merkledag/coding.go
@@ -3,6 +3,9 @@ package merkledag
 import (
 	"fmt"
 	"sort"
+	"strings"
+
+	"gx/ipfs/QmVA4mafxbfH5aEvNz8fyoxC6J1xhAtw88B4GerPznSZBg/go-block-format"
 
 	pb "github.com/ipfs/go-ipfs/merkledag/pb"
 
@@ -108,3 +111,27 @@ func DecodeProtobuf(encoded []byte) (*ProtoNode, error) {
 	}
 	return n, nil
 }
+
+// DecodeProtobufBlock is a block decoder for protobuf IPLD nodes conforming to
+// node.DecodeBlockFunc
+func DecodeProtobufBlock(b blocks.Block) (node.Node, error) {
+	c := b.Cid()
+	if c.Type() != cid.DagProtobuf {
+		return nil, fmt.Errorf("this function can only decode protobuf nodes")
+	}
+
+	decnd, err := DecodeProtobuf(b.RawData())
+	if err != nil {
+		if strings.Contains(err.Error(), "Unmarshal failed") {
+			return nil, fmt.Errorf("The block referred to by '%s' was not a valid merkledag node", c)
+		}
+		return nil, fmt.Errorf("Failed to decode Protocol Buffers: %v", err)
+	}
+
+	decnd.cached = c
+	decnd.Prefix = c.Prefix()
+	return decnd, nil
+}
+
+// Type assertion
+var _ node.DecodeBlockFunc = DecodeProtobufBlock
diff --git a/merkledag/merkledag.go b/merkledag/merkledag.go
index b033af405f8..82b1693ae6c 100644
--- a/merkledag/merkledag.go
+++ b/merkledag/merkledag.go
@@ -4,7 +4,6 @@ package merkledag
 import (
 	"context"
 	"fmt"
-	"strings"
 	"sync"
 
 	bserv "github.com/ipfs/go-ipfs/blockservice"
@@ -16,6 +15,15 @@ import (
 	ipldcbor "gx/ipfs/QmemYymP73eVdTUUMZEiSpiHeZQKNJdT5dP2iuHssZh1sR/go-ipld-cbor"
 )
 
+// TODO: We should move these registrations elsewhere. Really, most of the IPLD
+// functionality should go in a `go-ipld` repo but that will take a lot of work
+// and design.
+func init() {
+	node.Register(cid.DagProtobuf, DecodeProtobufBlock)
+	node.Register(cid.Raw, DecodeRawBlock)
+	node.Register(cid.DagCBOR, ipldcbor.DecodeBlock)
+}
+
 var ErrNotFound = fmt.Errorf("merkledag: not found")
 
 // DAGService is an IPFS Merkle DAG service.
@@ -94,32 +102,7 @@ func (n *dagService) Get(ctx context.Context, c *cid.Cid) (node.Node, error) {
 		return nil, fmt.Errorf("Failed to get block for %s: %v", c, err)
 	}
 
-	return decodeBlock(b)
-}
-
-func decodeBlock(b blocks.Block) (node.Node, error) {
-	c := b.Cid()
-
-	switch c.Type() {
-	case cid.DagProtobuf:
-		decnd, err := DecodeProtobuf(b.RawData())
-		if err != nil {
-			if strings.Contains(err.Error(), "Unmarshal failed") {
-				return nil, fmt.Errorf("The block referred to by '%s' was not a valid merkledag node", c)
-			}
-			return nil, fmt.Errorf("Failed to decode Protocol Buffers: %v", err)
-		}
-
-		decnd.cached = b.Cid()
-		decnd.Prefix = b.Cid().Prefix()
-		return decnd, nil
-	case cid.Raw:
-		return NewRawNodeWPrefix(b.RawData(), b.Cid().Prefix())
-	case cid.DagCBOR:
-		return ipldcbor.Decode(b.RawData())
-	default:
-		return nil, fmt.Errorf("unrecognized object type: %s", c.Type())
-	}
+	return node.Decode(b)
 }
 
 // GetLinks return the links for the node, the node doesn't necessarily have
@@ -174,7 +157,7 @@ func (sg *sesGetter) Get(ctx context.Context, c *cid.Cid) (node.Node, error) {
 		return nil, err
 	}
 
-	return decodeBlock(blk)
+	return node.Decode(blk)
 }
 
 // FetchGraph fetches all nodes that are children of the given node
@@ -235,7 +218,7 @@ func (ds *dagService) GetMany(ctx context.Context, keys []*cid.Cid) <-chan *Node
 					return
 				}
 
-				nd, err := decodeBlock(b)
+				nd, err := node.Decode(b)
 				if err != nil {
 					out <- &NodeOption{Err: err}
 					return
diff --git a/merkledag/raw.go b/merkledag/raw.go
index 9d1e18671e3..856a407fccc 100644
--- a/merkledag/raw.go
+++ b/merkledag/raw.go
@@ -1,6 +1,7 @@
 package merkledag
 
 import (
+	"fmt"
 	"gx/ipfs/QmVA4mafxbfH5aEvNz8fyoxC6J1xhAtw88B4GerPznSZBg/go-block-format"
 
 	u "gx/ipfs/QmSU6eubNdhXjFBJBSksTp8kv8YRub8mGAPv8tVJHmL2EU/go-ipfs-util"
@@ -22,6 +23,17 @@ func NewRawNode(data []byte) *RawNode {
 	return &RawNode{blk}
 }
 
+// DecodeRawBlock is a block decoder for raw IPLD nodes conforming to `node.DecodeBlockFunc`.
+func DecodeRawBlock(block blocks.Block) (node.Node, error) {
+	if block.Cid().Type() != cid.Raw {
+		return nil, fmt.Errorf("raw nodes cannot be decoded from non-raw blocks: %d", block.Cid().Type())
+	}
+	// Once you "share" a block, it should be immutable. Therefore, we can just use this block as-is.
+	return &RawNode{block}, nil
+}
+
+var _ node.DecodeBlockFunc = DecodeRawBlock
+
 // NewRawNodeWPrefix creates a RawNode with the hash function
 // specified in prefix.
 func NewRawNodeWPrefix(data []byte, prefix cid.Prefix) (*RawNode, error) {