From b3e74fabb5be473969d71adbc2ec72becc502134 Mon Sep 17 00:00:00 2001
From: Jeromy <jeromyj@gmail.com>
Date: Sun, 1 Feb 2015 21:48:26 +0000
Subject: [PATCH] implement trickledag for faster unixfs operations

---
 importer/importer_test.go | 63 +++++++++++++++++++++++++++
 importer/trickledag.go    | 91 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 154 insertions(+)
 create mode 100644 importer/trickledag.go

diff --git a/importer/importer_test.go b/importer/importer_test.go
index 8a70cec93..b0c3bf62f 100644
--- a/importer/importer_test.go
+++ b/importer/importer_test.go
@@ -96,6 +96,32 @@ func TestBuilderConsistency(t *testing.T) {
 	}
 }
 
+func TestTrickleBuilderConsistency(t *testing.T) {
+	nbytes := 100000
+	buf := new(bytes.Buffer)
+	io.CopyN(buf, u.NewTimeSeededRand(), int64(nbytes))
+	should := dup(buf.Bytes())
+	dagserv := merkledag.Mock(t)
+	nd, err := BuildTrickleDagFromReader(buf, dagserv, nil, chunk.DefaultSplitter)
+	if err != nil {
+		t.Fatal(err)
+	}
+	r, err := uio.NewDagReader(context.Background(), nd, dagserv)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	out, err := ioutil.ReadAll(r)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = arrComp(out, should)
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
 func arrComp(a, b []byte) error {
 	if len(a) != len(b) {
 		return fmt.Errorf("Arrays differ in length. %d != %d", len(a), len(b))
@@ -220,6 +246,43 @@ func TestSeekingBasic(t *testing.T) {
 	}
 }
 
+func TestTrickleSeekingBasic(t *testing.T) {
+	nbytes := int64(10 * 1024)
+	should := make([]byte, nbytes)
+	u.NewTimeSeededRand().Read(should)
+
+	read := bytes.NewReader(should)
+	dnp := getDagservAndPinner(t)
+	nd, err := BuildDagFromReader(read, dnp.ds, dnp.mp, &chunk.SizeSplitter{500})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	rs, err := uio.NewDagReader(context.Background(), nd, dnp.ds)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	start := int64(4000)
+	n, err := rs.Seek(start, os.SEEK_SET)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if n != start {
+		t.Fatal("Failed to seek to correct offset")
+	}
+
+	out, err := ioutil.ReadAll(rs)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = arrComp(out, should[start:])
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
 func TestSeekToBegin(t *testing.T) {
 	nbytes := int64(10 * 1024)
 	should := make([]byte, nbytes)
diff --git a/importer/trickledag.go b/importer/trickledag.go
new file mode 100644
index 000000000..d37dc6161
--- /dev/null
+++ b/importer/trickledag.go
@@ -0,0 +1,91 @@
+package importer
+
+import (
+	"io"
+
+	"github.com/jbenet/go-ipfs/importer/chunk"
+	dag "github.com/jbenet/go-ipfs/merkledag"
+	"github.com/jbenet/go-ipfs/pin"
+)
+
+// layerRepeat specifies how many times to append a child tree of a
+// given depth. Higher values increase the width of a given node, which
+// improves seek speeds.
+const layerRepeat = 4
+
+func BuildTrickleDagFromReader(r io.Reader, ds dag.DAGService, mp pin.ManualPinner, spl chunk.BlockSplitter) (*dag.Node, error) {
+	// Start the splitter
+	blkch := spl.Split(r)
+
+	// Create our builder helper
+	db := &dagBuilderHelper{
+		dserv:    ds,
+		mp:       mp,
+		in:       blkch,
+		maxlinks: DefaultLinksPerBlock,
+		indrSize: defaultIndirectBlockDataSize(),
+	}
+
+	root := newUnixfsNode()
+	err := db.fillNodeRec(root, 1)
+	if err != nil {
+		return nil, err
+	}
+	for level := 1; !db.done(); level++ {
+		for i := 0; i < layerRepeat && !db.done(); i++ {
+			next := newUnixfsNode()
+			err := db.fillTrickleRec(next, level)
+			if err != nil {
+				return nil, err
+			}
+			err = root.addChild(next, db)
+			if err != nil {
+				return nil, err
+			}
+		}
+	}
+
+	rootnode, err := root.getDagNode()
+	if err != nil {
+		return nil, err
+	}
+
+	rootkey, err := ds.Add(rootnode)
+	if err != nil {
+		return nil, err
+	}
+
+	if mp != nil {
+		mp.PinWithMode(rootkey, pin.Recursive)
+		err := mp.Flush()
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	return root.getDagNode()
+}
+
+func (db *dagBuilderHelper) fillTrickleRec(node *unixfsNode, depth int) error {
+	// Always do this, even in the base case
+	err := db.fillNodeRec(node, 1)
+	if err != nil {
+		return err
+	}
+
+	for i := 1; i < depth && !db.done(); i++ {
+		for j := 0; j < layerRepeat; j++ {
+			next := newUnixfsNode()
+			err := db.fillTrickleRec(next, i)
+			if err != nil {
+				return err
+			}
+
+			err = node.addChild(next, db)
+			if err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}