这里相关代码，没有使用上。

/* this file implements the  merkle tree hash
 * this is used to build a a hash of sorted Tips
 * this is also used build merkle hash of transactions within hash
 */
// this merkle is not compatible with treehash that exists in block package
// reason for using this version, as it has been battle tested in bitcoin, cryptonote  treehash on the otherhand is less tested

nextPowerOfTwo

// nextPowerOfTwo returns the next highest power of two from a given number if
// it is not already a power of two.  This is a helper function used during the
// calculation of a merkle tree.

HashMerkleBranches

// HashMerkleBranches takes two hashes, treated as the left and right tree
// nodes, and returns the hash of their concatenation.  This is a helper
// function used to aid in the generation of a merkle tree.

BuildMerkleTreeStore

// BuildMerkleTreeStore creates a merkle tree from a slice of transaction hashes or tips hashes,
// stores it using a linear array, and returns a slice of the backing array.  A
// linear array was chosen as opposed to an actual tree structure since it uses
// about half as much memory.  The following describes a merkle tree and how it
// is stored in a linear array.
//
// A merkle tree is a tree in which every non-leaf node is the hash of its
// children nodes.  A diagram depicting how this works for Decred transactions
// where h(x) is a blake256 hash follows:
//
//             root = h1234 = h(h12 + h34)
//            /                           \
//      h12 = h(h1 + h2)            h34 = h(h3 + h4)
//       /            \              /            \
//    h1 = h(tx1)  h2 = h(tx2)    h3 = h(tx3)  h4 = h(tx4)
//
// The above stored as a linear array is as follows:
//
//     [h1 h2 h3 h4 h12 h34 root]
//
// As the above shows, the merkle root is always the last element in the array.
//
// The number of inputs is not always a power of two which results in a
// balanced tree structure as above.  In that case, parent nodes with no
// children are also zero and parent nodes with only a single left node
// are calculated by concatenating the left node with itself before hashing.
// Since this function uses nodes that are pointers to the hashes, empty nodes
// will be nil.

MerkleRoot

在这里，就是 BuildMerkleTreeStore.