bring in merkle from tmlibs

merkle/simple_proof.go

@@ -0,0 +1,144 @@
+package merkle
+
+import (
+	"bytes"
+	"fmt"
+)
+
+type SimpleProof struct {
+	Aunts [][]byte `json:"aunts"` // Hashes from leaf's sibling to a root's child.
+}
+
+// proofs[0] is the proof for items[0].
+func SimpleProofsFromHashers(items []Hasher) (rootHash []byte, proofs []*SimpleProof) {
+	trails, rootSPN := trailsFromHashers(items)
+	rootHash = rootSPN.Hash
+	proofs = make([]*SimpleProof, len(items))
+	for i, trail := range trails {
+		proofs[i] = &SimpleProof{
+			Aunts: trail.FlattenAunts(),
+		}
+	}
+	return
+}
+
+func SimpleProofsFromMap(m map[string]Hasher) (rootHash []byte, proofs []*SimpleProof) {
+	sm := NewSimpleMap()
+	for k, v := range m {
+		sm.Set(k, v)
+	}
+	sm.Sort()
+	kvs := sm.kvs
+	kvsH := make([]Hasher, 0, len(kvs))
+	for _, kvp := range kvs {
+		kvsH = append(kvsH, KVPair(kvp))
+	}
+	return SimpleProofsFromHashers(kvsH)
+}
+
+// Verify that leafHash is a leaf hash of the simple-merkle-tree
+// which hashes to rootHash.
+func (sp *SimpleProof) Verify(index int, total int, leafHash []byte, rootHash []byte) bool {
+	computedHash := computeHashFromAunts(index, total, leafHash, sp.Aunts)
+	return computedHash != nil && bytes.Equal(computedHash, rootHash)
+}
+
+func (sp *SimpleProof) String() string {
+	return sp.StringIndented("")
+}
+
+func (sp *SimpleProof) StringIndented(indent string) string {
+	return fmt.Sprintf(`SimpleProof{
+%s  Aunts: %X
+%s}`,
+		indent, sp.Aunts,
+		indent)
+}
+
+// Use the leafHash and innerHashes to get the root merkle hash.
+// If the length of the innerHashes slice isn't exactly correct, the result is nil.
+// Recursive impl.
+func computeHashFromAunts(index int, total int, leafHash []byte, innerHashes [][]byte) []byte {
+	if index >= total || index < 0 || total <= 0 {
+		return nil
+	}
+	switch total {
+	case 0:
+		panic("Cannot call computeHashFromAunts() with 0 total")
+	case 1:
+		if len(innerHashes) != 0 {
+			return nil
+		}
+		return leafHash
+	default:
+		if len(innerHashes) == 0 {
+			return nil
+		}
+		numLeft := (total + 1) / 2
+		if index < numLeft {
+			leftHash := computeHashFromAunts(index, numLeft, leafHash, innerHashes[:len(innerHashes)-1])
+			if leftHash == nil {
+				return nil
+			}
+			return SimpleHashFromTwoHashes(leftHash, innerHashes[len(innerHashes)-1])
+		}
+		rightHash := computeHashFromAunts(index-numLeft, total-numLeft, leafHash, innerHashes[:len(innerHashes)-1])
+		if rightHash == nil {
+			return nil
+		}
+		return SimpleHashFromTwoHashes(innerHashes[len(innerHashes)-1], rightHash)
+	}
+}
+
+// Helper structure to construct merkle proof.
+// The node and the tree is thrown away afterwards.
+// Exactly one of node.Left and node.Right is nil, unless node is the root, in which case both are nil.
+// node.Parent.Hash = hash(node.Hash, node.Right.Hash) or
+// hash(node.Left.Hash, node.Hash), depending on whether node is a left/right child.
+type SimpleProofNode struct {
+	Hash   []byte
+	Parent *SimpleProofNode
+	Left   *SimpleProofNode // Left sibling  (only one of Left,Right is set)
+	Right  *SimpleProofNode // Right sibling (only one of Left,Right is set)
+}
+
+// Starting from a leaf SimpleProofNode, FlattenAunts() will return
+// the inner hashes for the item corresponding to the leaf.
+func (spn *SimpleProofNode) FlattenAunts() [][]byte {
+	// Nonrecursive impl.
+	innerHashes := [][]byte{}
+	for spn != nil {
+		if spn.Left != nil {
+			innerHashes = append(innerHashes, spn.Left.Hash)
+		} else if spn.Right != nil {
+			innerHashes = append(innerHashes, spn.Right.Hash)
+		} else {
+			break
+		}
+		spn = spn.Parent
+	}
+	return innerHashes
+}
+
+// trails[0].Hash is the leaf hash for items[0].
+// trails[i].Parent.Parent....Parent == root for all i.
+func trailsFromHashers(items []Hasher) (trails []*SimpleProofNode, root *SimpleProofNode) {
+	// Recursive impl.
+	switch len(items) {
+	case 0:
+		return nil, nil
+	case 1:
+		trail := &SimpleProofNode{items[0].Hash(), nil, nil, nil}
+		return []*SimpleProofNode{trail}, trail
+	default:
+		lefts, leftRoot := trailsFromHashers(items[:(len(items)+1)/2])
+		rights, rightRoot := trailsFromHashers(items[(len(items)+1)/2:])
+		rootHash := SimpleHashFromTwoHashes(leftRoot.Hash, rightRoot.Hash)
+		root := &SimpleProofNode{rootHash, nil, nil, nil}
+		leftRoot.Parent = root
+		leftRoot.Right = rightRoot
+		rightRoot.Parent = root
+		rightRoot.Left = leftRoot
+		return append(lefts, rights...), root
+	}
+}