Add NewHashFromBytes & update comments

merkletree.go

@@ -15,8 +15,8 @@ import (
 )
 
 const (
-	// proofFlagsLen is the byte length of the flags in the proof header (first 32
-	// bytes).
+	// proofFlagsLen is the byte length of the flags in the proof header
+	// (first 32 bytes).
 	proofFlagsLen = 2
 	// ElemBytesLen is the length of the Hash byte array
 	ElemBytesLen = 32
@@ -45,9 +45,11 @@ var (
 	// ErrEntryIndexAlreadyExists is used when the entry index already
 	// exists in the tree.
 	ErrEntryIndexAlreadyExists = errors.New("the entry index already exists in the tree")
-	// ErrNotWritable is used when the MerkleTree is not writable and a write function is called
+	// ErrNotWritable is used when the MerkleTree is not writable and a
+	// write function is called
 	ErrNotWritable = errors.New("Merkle Tree not writable")
-	rootNodeValue  = []byte("currentroot")
+
+	rootNodeValue = []byte("currentroot")
 	// HashZero is used at Empty nodes
 	HashZero = Hash{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
 )
@@ -77,7 +79,8 @@ func (h *Hash) BigInt() *big.Int {
 	return new(big.Int).SetBytes(common.SwapEndianness(h[:]))
 }
 
-// Bytes returns the []byte representation of the *Hash
+// Bytes returns the []byte representation of the *Hash, which always is 32
+// bytes length.
 func (h *Hash) Bytes() []byte {
 	bi := new(big.Int).SetBytes(common.SwapEndianness(h[:])).Bytes()
 	b := [32]byte{}
@@ -85,7 +88,10 @@ func (h *Hash) Bytes() []byte {
 	return b[:]
 }
 
-// NewBigIntFromBytes returns a *big.Int from a byte array, swapping the endianness in the process. This is the intended method to get a *big.Int from a byte array that previously has ben generated by the Hash.Bytes() method.
+// NewBigIntFromBytes returns a *big.Int from a byte array, swapping the
+// endianness in the process. This is the intended method to get a *big.Int
+// from a byte array that previously has ben generated by the Hash.Bytes()
+// method.
 func NewBigIntFromBytes(b []byte) (*big.Int, error) {
 	if len(b) != 32 {
 		return nil, fmt.Errorf("Expected 32 bytes, found %d bytes", len(b))
@@ -100,6 +106,18 @@ func NewHashFromBigInt(b *big.Int) *Hash {
 	return r
 }
 
+// NewHashFromBytes returns a *Hash from a byte array, swapping the endianness
+// in the process. This is the intended method to get a *Hash from a byte array
+// that previously has ben generated by the Hash.Bytes() method.
+func NewHashFromBytes(b []byte) (*Hash, error) {
+	if len(b) != 32 {
+		return nil, fmt.Errorf("Expected 32 bytes, found %d bytes", len(b))
+	}
+	var h Hash
+	copy(h[:], common.SwapEndianness(b))
+	return &h, nil
+}
+
 // MerkleTree is the struct with the main elements of the MerkleTree
 type MerkleTree struct {
 	sync.RWMutex
@@ -109,7 +127,8 @@ type MerkleTree struct {
 	maxLevels int
 }
 
-// NewMerkleTree loads a new Merkletree. If in the sotrage already exists one will open that one, if not, will create a new one.
+// NewMerkleTree loads a new Merkletree. If in the sotrage already exists one
+// will open that one, if not, will create a new one.
 func NewMerkleTree(storage db.Storage, maxLevels int) (*MerkleTree, error) {
 	mt := MerkleTree{db: storage, maxLevels: maxLevels, writable: true}
 
@@ -158,7 +177,8 @@ func (mt *MerkleTree) Snapshot(rootKey *Hash) (*MerkleTree, error) {
 	return &MerkleTree{db: mt.db, maxLevels: mt.maxLevels, rootKey: rootKey, writable: false}, nil
 }
 
-// Add adds a Key & Value into the MerkleTree. Where the `k` determines the path from the Root to the Leaf.
+// Add adds a Key & Value into the MerkleTree. Where the `k` determines the
+// path from the Root to the Leaf.
 func (mt *MerkleTree) Add(k, v *big.Int) error {
 	// verify that the MerkleTree is writable
 	if !mt.writable {

merkletree_test.go

@@ -7,6 +7,7 @@ import (
 	"math/big"
 	"testing"
 
+	"github.com/iden3/go-iden3-core/common"
 	"github.com/iden3/go-merkletree/db/memory"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -46,6 +47,14 @@ func TestHashParsers(t *testing.T) {
 	assert.Equal(t, "4932297968297298434239270129193057052722409868268166443802652458940273154854", h.BigInt().String())
 	assert.Equal(t, "49322979...", h.String())
 	assert.Equal(t, "0ae794eb9c3d8bbb9002e993fc2ed301dcbd2af5508ed072c375e861f1aa5b26", h.Hex())
+
+	b1, err := NewBigIntFromBytes(b.Bytes())
+	assert.Nil(t, err)
+	assert.Equal(t, new(big.Int).SetBytes(common.SwapEndianness(b.Bytes())).String(), b1.String())
+
+	b2, err := NewHashFromBytes(b.Bytes())
+	assert.Nil(t, err)
+	assert.Equal(t, b.String(), b2.BigInt().String())
 }
 
 func TestNewTree(t *testing.T) {

node.go

@@ -11,12 +11,14 @@ type NodeType byte
 const (
 	// NodeTypeMiddle indicates the type of middle Node that has children.
 	NodeTypeMiddle NodeType = 0
-	// NodeTypeLeaf indicates the type of a leaf Node that contains a key & value.
+	// NodeTypeLeaf indicates the type of a leaf Node that contains a key &
+	// value.
 	NodeTypeLeaf NodeType = 1
 	// NodeTypeEmpty indicates the type of an empty Node.
 	NodeTypeEmpty NodeType = 2
 
-	// DBEntryTypeRoot indicates the type of a DB entry that indicates the current Root of a MerkleTree
+	// DBEntryTypeRoot indicates the type of a DB entry that indicates the
+	// current Root of a MerkleTree
 	DBEntryTypeRoot NodeType = 3
 )
 
@@ -114,7 +116,8 @@ func (n *Node) Key() (*Hash, error) {
 	return n.key, nil
 }
 
-// Value returns the value of the node.  This is the content that is stored in the backend database.
+// Value returns the value of the node.  This is the content that is stored in
+// the backend database.
 func (n *Node) Value() []byte {
 	switch n.Type {
 	case NodeTypeMiddle: // {Type || ChildL || ChildR}