115 lines
2.8 KiB
Go
115 lines
2.8 KiB
Go
package hash
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import (
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"errors"
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"github.com/nspcc-dev/neo-go/pkg/util"
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)
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// MerkleTree implementation.
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type MerkleTree struct {
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root *MerkleTreeNode
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depth int
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}
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// NewMerkleTree returns a new MerkleTree object.
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func NewMerkleTree(hashes []util.Uint256) (*MerkleTree, error) {
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if len(hashes) == 0 {
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return nil, errors.New("length of the hashes cannot be zero")
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}
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nodes := make([]*MerkleTreeNode, len(hashes))
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for i := 0; i < len(hashes); i++ {
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nodes[i] = &MerkleTreeNode{
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hash: hashes[i],
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}
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}
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return &MerkleTree{
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root: buildMerkleTree(nodes),
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depth: 1,
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}, nil
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}
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// Root returns the computed root hash of the MerkleTree.
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func (t *MerkleTree) Root() util.Uint256 {
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return t.root.hash
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}
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func buildMerkleTree(leaves []*MerkleTreeNode) *MerkleTreeNode {
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if len(leaves) == 0 {
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panic("length of leaves cannot be zero")
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}
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if len(leaves) == 1 {
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return leaves[0]
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}
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parents := make([]*MerkleTreeNode, (len(leaves)+1)/2)
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for i := 0; i < len(parents); i++ {
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parents[i] = &MerkleTreeNode{}
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parents[i].leftChild = leaves[i*2]
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leaves[i*2].parent = parents[i]
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if i*2+1 == len(leaves) {
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parents[i].rightChild = parents[i].leftChild
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} else {
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parents[i].rightChild = leaves[i*2+1]
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leaves[i*2+1].parent = parents[i]
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}
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b1 := parents[i].leftChild.hash.BytesBE()
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b2 := parents[i].rightChild.hash.BytesBE()
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b1 = append(b1, b2...)
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parents[i].hash = DoubleSha256(b1)
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}
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return buildMerkleTree(parents)
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}
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// CalcMerkleRoot calculates the Merkle root hash value for the given slice of hashes.
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// It doesn't create a full MerkleTree structure and it uses the given slice as a
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// scratchpad, so it will destroy its contents in the process. But it's much more
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// memory efficient if you only need a root hash value. While NewMerkleTree would
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// make 3*N allocations for N hashes, this function will only make 4.
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func CalcMerkleRoot(hashes []util.Uint256) util.Uint256 {
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if len(hashes) == 0 {
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return util.Uint256{}
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}
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if len(hashes) == 1 {
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return hashes[0]
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}
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scratch := make([]byte, 64)
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parents := hashes[:(len(hashes)+1)/2]
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for i := 0; i < len(parents); i++ {
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copy(scratch, hashes[i*2].BytesBE())
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if i*2+1 == len(hashes) {
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copy(scratch[32:], hashes[i*2].BytesBE())
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} else {
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copy(scratch[32:], hashes[i*2+1].BytesBE())
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}
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parents[i] = DoubleSha256(scratch)
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}
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return CalcMerkleRoot(parents)
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}
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// MerkleTreeNode represents a node in the MerkleTree.
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type MerkleTreeNode struct {
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hash util.Uint256
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parent *MerkleTreeNode
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leftChild *MerkleTreeNode
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rightChild *MerkleTreeNode
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}
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// IsLeaf returns whether this node is a leaf node or not.
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func (n *MerkleTreeNode) IsLeaf() bool {
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return n.leftChild == nil && n.rightChild == nil
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}
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// IsRoot returns whether this node is a root node or not.
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func (n *MerkleTreeNode) IsRoot() bool {
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return n.parent == nil
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}
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