fix: reduce calls to MinNamespace & MaxNamespace

hasher.go

@@ -154,9 +154,9 @@ func (n *NmtHasher) BlockSize() int {
 
 func (n *NmtHasher) EmptyRoot() []byte {
 	n.baseHasher.Reset()
-	emptyNs := bytes.Repeat([]byte{0}, int(n.NamespaceLen))
+	emptyNs := bytes.Repeat([]byte{0}, int(n.NamespaceLen)*2)
 	h := n.baseHasher.Sum(nil)
-	digest := append(append(emptyNs, emptyNs...), h...)
+	digest := append(emptyNs, h...)
 
 	return digest
 }
@@ -212,56 +212,68 @@ func (n *NmtHasher) MustHashLeaf(ndata []byte) []byte {
 	return res
 }
 
-// ValidateNodeFormat checks whether the supplied node conforms to the
-// namespaced hash format and returns ErrInvalidNodeLen if not.
-func (n *NmtHasher) ValidateNodeFormat(node []byte) (err error) {
+type nsIDRange struct {
+	Min, Max namespace.ID
+}
+
+// tryFetchNodeNSRange attempts to return the min and max namespace ids.
+// It will return an ErrInvalidNodeLen | ErrInvalidNodeNamespaceOrder
+// if the supplied node does not conform to the namespaced hash format.
+func (n *NmtHasher) tryFetchNodeNSRange(node []byte) (nsIDRange, error) {
 	expectedNodeLen := n.Size()
 	nodeLen := len(node)
 	if nodeLen != expectedNodeLen {
-		return fmt.Errorf("%w: got: %v, want %v", ErrInvalidNodeLen, nodeLen, expectedNodeLen)
+		return nsIDRange{}, fmt.Errorf("%w: got: %v, want %v", ErrInvalidNodeLen, nodeLen, expectedNodeLen)
 	}
 	// check the namespace order
 	minNID := namespace.ID(MinNamespace(node, n.NamespaceSize()))
 	maxNID := namespace.ID(MaxNamespace(node, n.NamespaceSize()))
 	if maxNID.Less(minNID) {
-		return fmt.Errorf("%w: max namespace ID %d is less than min namespace ID %d ", ErrInvalidNodeNamespaceOrder, maxNID, minNID)
+		return nsIDRange{}, fmt.Errorf("%w: max namespace ID %d is less than min namespace ID %d ", ErrInvalidNodeNamespaceOrder, maxNID, minNID)
 	}
-	return nil
+	return nsIDRange{Min: minNID, Max: maxNID}, nil
+}
+
+// ValidateNodeFormat checks whether the supplied node conforms to the
+// namespaced hash format and returns ErrInvalidNodeLen if not.
+func (n *NmtHasher) ValidateNodeFormat(node []byte) (err error) {
+	_, err = n.tryFetchNodeNSRange(node)
+	return
 }
 
-// validateSiblingsNamespaceOrder checks whether left and right as two sibling
-// nodes in an NMT have correct namespace IDs relative to each other, more
-// specifically, the maximum namespace ID of the left sibling should not exceed
-// the minimum namespace ID of the right sibling. It returns ErrUnorderedSiblings error if the check fails.
-func (n *NmtHasher) validateSiblingsNamespaceOrder(left, right []byte) (err error) {
-	if err := n.ValidateNodeFormat(left); err != nil {
-		return fmt.Errorf("%w: left node does not match the namesapce hash format", err)
+// tryFetchLeftAndRightNSRange attempts to return the min/max namespace ids of both
+// the left and right nodes. It verifies whether left
+// and right comply by the namespace hash format, and are correctly ordered
+// according to their namespace IDs.
+func (n *NmtHasher) tryFetchLeftAndRightNSRanges(left, right []byte) (
+	lNsRange nsIDRange,
+	rNsRange nsIDRange,
+	err error,
+) {
+	lNsRange, err = n.tryFetchNodeNSRange(left)
+	if err != nil {
+		return
 	}
-	if err := n.ValidateNodeFormat(right); err != nil {
-		return fmt.Errorf("%w: right node does not match the namesapce hash format", err)
+	rNsRange, err = n.tryFetchNodeNSRange(right)
+	if err != nil {
+		return
 	}
-	leftMaxNs := namespace.ID(MaxNamespace(left, n.NamespaceSize()))
-	rightMinNs := namespace.ID(MinNamespace(right, n.NamespaceSize()))
 
 	// check the namespace range of the left and right children
-	if rightMinNs.Less(leftMaxNs) {
-		return fmt.Errorf("%w: the maximum namespace of the left child %x is greater than the min namespace of the right child %x", ErrUnorderedSiblings, leftMaxNs, rightMinNs)
+	if rNsRange.Min.Less(lNsRange.Max) {
+		err = fmt.Errorf("%w: the maximum namespace of the left child %x is greater than the min namespace of the right child %x", ErrUnorderedSiblings, lNsRange.Max, rNsRange.Min)
+		return
 	}
-	return nil
+	return
 }
 
 // ValidateNodes is a helper function  to verify the
 // validity of the inputs of HashNode. It verifies whether left
 // and right comply by the namespace hash format, and are correctly ordered
 // according to their namespace IDs.
 func (n *NmtHasher) ValidateNodes(left, right []byte) error {
-	if err := n.ValidateNodeFormat(left); err != nil {
-		return err
-	}
-	if err := n.ValidateNodeFormat(right); err != nil {
-		return err
-	}
-	return n.validateSiblingsNamespaceOrder(left, right)
+	_, _, err := n.tryFetchLeftAndRightNSRanges(left, right)
+	return err
 }
 
 // HashNode calculates a namespaced hash of a node using the supplied left and
@@ -278,21 +290,19 @@ func (n *NmtHasher) ValidateNodes(left, right []byte) error {
 // If the namespace range of the right child is start=end=MAXNID, indicating that it represents the root of a subtree whose leaves all have the namespace ID of `MAXNID`, then exclude the right child from the namespace range calculation. Instead,
 // assign the namespace range of the left child as the parent's namespace range.
 func (n *NmtHasher) HashNode(left, right []byte) ([]byte, error) {
-	// validate the inputs
-	if err := n.ValidateNodes(left, right); err != nil {
+	// validate the inputs & fetch the namespace ranges
+	lRange, rRange, err := n.tryFetchLeftAndRightNSRanges(left, right)
+	if err != nil {
 		return nil, err
 	}
 
 	h := n.baseHasher
 	h.Reset()
 
-	leftMinNs, leftMaxNs := MinNamespace(left, n.NamespaceLen), MaxNamespace(left, n.NamespaceLen)
-	rightMinNs, rightMaxNs := MinNamespace(right, n.NamespaceLen), MaxNamespace(right, n.NamespaceLen)
-
 	// compute the namespace range of the parent node
-	minNs, maxNs := computeNsRange(leftMinNs, leftMaxNs, rightMinNs, rightMaxNs, n.ignoreMaxNs, n.precomputedMaxNs)
+	minNs, maxNs := computeNsRange(lRange.Min, lRange.Max, rRange.Min, rRange.Max, n.ignoreMaxNs, n.precomputedMaxNs)
 
-	res := make([]byte, 0)
+	res := make([]byte, 0, len(minNs)*2)
 	res = append(res, minNs...)
 	res = append(res, maxNs...)
 

hasher_test.go

@@ -283,56 +283,6 @@ func TestHashNode_Error(t *testing.T) {
 	}
 }
 
-func TestValidateSiblings(t *testing.T) {
-	// create a dummy hash to use as the digest of the left and right child
-	randHash := createByteSlice(sha256.Size, 0x01)
-
-	type children struct {
-		l []byte // namespace hash of the left child with the format of MinNs||MaxNs||h
-		r []byte // namespace hash of the right child with the format of MinNs||MaxNs||h
-	}
-
-	tests := []struct {
-		name     string
-		nidLen   namespace.IDSize
-		children children
-		wantErr  bool
-	}{
-		{
-			"wrong left node format", 2,
-			children{concat([]byte{0, 0, 1, 1}, randHash[:len(randHash)-1]), concat([]byte{0, 0, 1, 1}, randHash)},
-			true,
-		},
-		{
-			"wrong right node format", 2,
-			children{concat([]byte{0, 0, 1, 1}, randHash), concat([]byte{0, 0, 1, 1}, randHash[:len(randHash)-1])},
-			true,
-		},
-		{
-			"left.maxNs>right.minNs", 2,
-			children{concat([]byte{0, 0, 1, 1}, randHash), concat([]byte{0, 0, 1, 1}, randHash)},
-			true,
-		},
-		{
-			"left.maxNs=right.minNs", 2,
-			children{concat([]byte{0, 0, 1, 1}, randHash), concat([]byte{1, 1, 2, 2}, randHash)},
-			false,
-		},
-		{
-			"left.maxNs<right.minNs", 2,
-			children{concat([]byte{0, 0, 1, 1}, randHash), concat([]byte{2, 2, 3, 3}, randHash)},
-			false,
-		},
-	}
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			n := NewNmtHasher(sha256.New(), tt.nidLen, false)
-			err := n.validateSiblingsNamespaceOrder(tt.children.l, tt.children.r)
-			assert.Equal(t, tt.wantErr, err != nil)
-		})
-	}
-}
-
 func TestValidateNodeFormat(t *testing.T) {
 	hashValue := createByteSlice(sha256.Size, 0x01)
 	minNID := createByteSlice(2, 0x00)

nmt.go

@@ -682,16 +682,14 @@ type LeafRange struct {
 // which is formatted as: minimum namespace ID || maximum namespace ID || hash
 // digest.
 func MinNamespace(hash []byte, size namespace.IDSize) []byte {
-	min := make([]byte, 0, size)
-	return append(min, hash[:size]...)
+	return hash[:size:size]
 }
 
 // MaxNamespace extracts the maximum namespace ID from a given namespace hash,
 // which is formatted as: minimum namespace ID || maximum namespace ID || hash
 // digest.
 func MaxNamespace(hash []byte, size namespace.IDSize) []byte {
-	max := make([]byte, 0, size)
-	return append(max, hash[size:size*2]...)
+	return hash[size : size*2 : size*2]
 }
 
 // Size returns the number of leaves in the tree.

nmt_test.go

@@ -704,6 +704,7 @@ func BenchmarkComputeRoot(b *testing.B) {
 		{"64-leaves", 64, 8, 256},
 		{"128-leaves", 128, 8, 256},
 		{"256-leaves", 256, 8, 256},
+		//{"20k-leaves", 20000, 8, 512},
 	}
 
 	for _, tt := range tests {