// Based on CPartialMerkleTree::TraverseAndBuild in Neoscoin Core.
private static void traverseAndBuild(
int height,
int pos,
List<Sha256Hash> allLeafHashes,
byte[] includeBits,
List<Boolean> matchedChildBits,
List<Sha256Hash> resultHashes) {
boolean parentOfMatch = false;
// Is this node a parent of at least one matched hash?
for (int p = pos << height; p < (pos + 1) << height && p < allLeafHashes.size(); p++) {
if (Utils.checkBitLE(includeBits, p)) {
parentOfMatch = true;
break;
}
}
// Store as a flag bit.
matchedChildBits.add(parentOfMatch);
if (height == 0 || !parentOfMatch) {
// If at height 0, or nothing interesting below, store hash and stop.
resultHashes.add(calcHash(height, pos, allLeafHashes));
} else {
// Otherwise descend into the subtrees.
int h = height - 1;
int p = pos * 2;
traverseAndBuild(h, p, allLeafHashes, includeBits, matchedChildBits, resultHashes);
if (p + 1 < getTreeWidth(allLeafHashes.size(), h))
traverseAndBuild(h, p + 1, allLeafHashes, includeBits, matchedChildBits, resultHashes);
}
}
/**
* Calculates a PMT given the list of leaf hashes and which leaves need to be included. The
* relevant interior hashes are calculated and a new PMT returned.
*/
public static PartialMerkleTree buildFromLeaves(
NetworkParameters params, byte[] includeBits, List<Sha256Hash> allLeafHashes) {
// Calculate height of the tree.
int height = 0;
while (getTreeWidth(allLeafHashes.size(), height) > 1) height++;
List<Boolean> bitList = new ArrayList<Boolean>();
List<Sha256Hash> hashes = new ArrayList<Sha256Hash>();
traverseAndBuild(height, 0, allLeafHashes, includeBits, bitList, hashes);
byte[] bits = new byte[(int) Math.ceil(bitList.size() / 8.0)];
for (int i = 0; i < bitList.size(); i++) if (bitList.get(i)) Utils.setBitLE(bits, i);
return new PartialMerkleTree(params, bits, hashes, allLeafHashes.size());
}