Add Blockstore Blockstreamer and fix Walk func

blockstreamer.go

@@ -2,11 +2,65 @@ package blockstream
 
 import (
 	"context"
+	blockstore "github.com/ipfs/go-ipfs-blockstore"
 
 	blocks "github.com/ipfs/go-block-format"
 	"github.com/ipfs/go-cid"
 )
 
+// TODO Implementation distributing requests between multiple streamers by some abstract characteristic.
 type BlockStreamer interface {
+
+	// Stream initiates ordered stream of Blocks from implementation defined source.
+	//
+	// Err chan returns BlockError for requested blocks skipped on the response stream with reasonable error.
+	// It has two purposes: obvious error handling and overcoming congestions.
+	// If err chan returns any other error, the stream is terminated for some internal issue described by the error.
 	Stream(context.Context, <-chan []cid.Cid) (<-chan blocks.Block, <-chan error)
 }
+
+type BlockstoreStreamer struct {
+	bs blockstore.Blockstore
+}
+
+func NewBlockstoreStreamer(bs blockstore.Blockstore) BlockStreamer {
+	return &BlockstoreStreamer{
+		bs: bs,
+	}
+}
+
+func (b *BlockstoreStreamer) Stream(ctx context.Context, in <-chan []cid.Cid) (<-chan blocks.Block, <-chan error) {
+	outB, outErr := make(chan blocks.Block, len(in)), make(chan error, 1)
+
+	// TODO Spawn multiple routines to accelerate Stream for case when more Ps are available.
+	go func() {
+		select {
+		case ids, ok := <-in:
+			if !ok {
+				return
+			}
+
+			for _, id := range ids {
+				b, err := b.bs.Get(id)
+				if err != nil {
+					select {
+					case outErr <- &BlockError{Cid: id, Err: err}:
+					case <-ctx.Done():
+						return
+					}
+				}
+
+				select {
+				case outB <- b:
+				case <-ctx.Done():
+					return
+				}
+			}
+
+		case <-ctx.Done():
+			return
+		}
+	}()
+
+	return outB, outErr
+}

error.go

@@ -0,0 +1,19 @@
+package blockstream
+
+import (
+	"fmt"
+	"github.com/ipfs/go-cid"
+)
+
+type BlockError struct {
+	Cid cid.Cid
+	Err error
+}
+
+func (br *BlockError) Error() string {
+	return fmt.Sprintf("blockstream: failed to process block %s: %s", br.Cid, br.Err)
+}
+
+func (br *BlockError) Unwrap() error {
+	return br.Err
+}

go.mod

@@ -3,19 +3,20 @@ module github.com/Wondertan/go-blockstream
 go 1.14
 
 require (
-	github.com/Wondertan/go-libp2p-access v0.0.2
+	github.com/Wondertan/go-libp2p-access v0.1.0
 	github.com/Wondertan/go-serde v1.0.1
+	github.com/davidlazar/go-crypto v0.0.0-20190912175916-7055855a373f // indirect
 	github.com/gogo/protobuf v1.3.1
 	github.com/ipfs/go-block-format v0.0.2
-	github.com/ipfs/go-cid v0.0.6
-	github.com/ipfs/go-datastore v0.4.4
-	github.com/ipfs/go-ipfs-blockstore v1.0.0
-	github.com/ipfs/go-ipfs-ds-help v1.0.0
+	github.com/ipfs/go-cid v0.0.7
+	github.com/ipfs/go-datastore v0.4.5
+	github.com/ipfs/go-ipfs-blockstore v1.0.2
 	github.com/ipfs/go-ipfs-exchange-interface v0.0.1
 	github.com/ipfs/go-ipld-format v0.2.0
 	github.com/ipfs/go-log/v2 v2.1.1
 	github.com/ipfs/go-merkledag v0.3.2
-	github.com/libp2p/go-libp2p v0.10.0
-	github.com/libp2p/go-libp2p-core v0.6.0
+	github.com/libp2p/go-libp2p v0.11.0
+	github.com/libp2p/go-libp2p-core v0.6.1
+	github.com/libp2p/go-sockaddr v0.1.0 // indirect
 	github.com/stretchr/testify v1.6.1
 )