Add Graphviz methods

merkletree.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"errors"
 	"fmt"
+	"io"
 	"math/big"
 	"sync"
 
@@ -491,3 +492,95 @@ func RootFromProof(proof *Proof, k, v *big.Int) (*Hash, error) {
 	}
 	return midKey, nil
 }
+
+// walk is a helper recursive function to iterate over all tree branches
+func (mt *MerkleTree) walk(key *Hash, f func(*Node)) error {
+	n, err := mt.GetNode(key)
+	if err != nil {
+		return err
+	}
+	switch n.Type {
+	case NodeTypeEmpty:
+		f(n)
+	case NodeTypeLeaf:
+		f(n)
+	case NodeTypeMiddle:
+		f(n)
+		if err := mt.walk(n.ChildL, f); err != nil {
+			return err
+		}
+		if err := mt.walk(n.ChildR, f); err != nil {
+			return err
+		}
+	default:
+		return ErrInvalidNodeFound
+	}
+	return nil
+}
+
+// Walk iterates over all the branches of a MerkleTree with the given rootKey
+// if rootKey is nil, it will get the current RootKey of the current state of the MerkleTree.
+// For each node, it calls the f function given in the parameters.
+// See some examples of the Walk function usage in the merkletree_test.go
+// test functions: TestMTWalk, TestMTWalkGraphViz, TestMTWalkDumpClaims
+func (mt *MerkleTree) Walk(rootKey *Hash, f func(*Node)) error {
+	if rootKey == nil {
+		rootKey = mt.Root()
+	}
+	err := mt.walk(rootKey, f)
+	return err
+}
+
+// GraphViz uses Walk function to generate a string GraphViz representation of the
+// tree and writes it to w
+func (mt *MerkleTree) GraphViz(w io.Writer, rootKey *Hash) error {
+	fmt.Fprintf(w, `digraph hierarchy {
+node [fontname=Monospace,fontsize=10,shape=box]
+`)
+	cnt := 0
+	var errIn error
+	err := mt.Walk(rootKey, func(n *Node) {
+		k, err := n.Key()
+		if err != nil {
+			errIn = err
+		}
+		switch n.Type {
+		case NodeTypeEmpty:
+		case NodeTypeLeaf:
+			fmt.Fprintf(w, "\"%v\" [style=filled];\n", k.BigInt().String())
+		case NodeTypeMiddle:
+			lr := [2]string{n.ChildL.BigInt().String(), n.ChildR.BigInt().String()}
+			for i := range lr {
+				if lr[i] == "0" {
+					lr[i] = fmt.Sprintf("empty%v", cnt)
+					fmt.Fprintf(w, "\"%v\" [style=dashed,label=0];\n", lr[i])
+					cnt++
+				}
+			}
+			fmt.Fprintf(w, "\"%v\" -> {\"%v\" \"%v\"}\n", k.BigInt().String(), lr[0], lr[1])
+		default:
+		}
+	})
+	fmt.Fprintf(w, "}\n")
+	if errIn != nil {
+		return errIn
+	}
+	return err
+}
+
+// PrintGraphViz prints directly the GraphViz() output
+func (mt *MerkleTree) PrintGraphViz(rootKey *Hash) error {
+	if rootKey == nil {
+		rootKey = mt.Root()
+	}
+	w := bytes.NewBufferString("")
+	fmt.Fprintf(w, "--------\nGraphViz of the MerkleTree with RootKey "+rootKey.BigInt().String()+"\n")
+	err := mt.GraphViz(w, nil)
+	if err != nil {
+		return err
+	}
+	fmt.Fprintf(w, "End of GraphViz of the MerkleTree with RootKey "+rootKey.BigInt().String()+"\n--------\n")
+
+	fmt.Println(w)
+	return nil
+}