1 files changed, 16 insertions, 117 deletions

diff --git a/src/consensus/merkle.cpp b/src/consensus/merkle.cpp
index 74a9ebb2e3..07cd109cc1 100644
--- a/src/consensus/merkle.cpp
+++ b/src/consensus/merkle.cpp
@@ -42,118 +42,26 @@
        root.
 */
 
-/* This implements a constant-space merkle root/path calculator, limited to 2^32 leaves. */
-static void MerkleComputation(const std::vector<uint256>& leaves, uint256* proot, bool* pmutated, uint32_t branchpos, std::vector<uint256>* pbranch) {
-    if (pbranch) pbranch->clear();
-    if (leaves.size() == 0) {
-        if (pmutated) *pmutated = false;
-        if (proot) *proot = uint256();
-        return;
-    }
-    bool mutated = false;
-    // count is the number of leaves processed so far.
-    uint32_t count = 0;
-    // inner is an array of eagerly computed subtree hashes, indexed by tree
-    // level (0 being the leaves).
-    // For example, when count is 25 (11001 in binary), inner[4] is the hash of
-    // the first 16 leaves, inner[3] of the next 8 leaves, and inner[0] equal to
-    // the last leaf. The other inner entries are undefined.
-    uint256 inner[32];
-    // Which position in inner is a hash that depends on the matching leaf.
-    int matchlevel = -1;
-    // First process all leaves into 'inner' values.
-    while (count < leaves.size()) {
-        uint256 h = leaves[count];
-        bool matchh = count == branchpos;
-        count++;
-        int level;
-        // For each of the lower bits in count that are 0, do 1 step. Each
-        // corresponds to an inner value that existed before processing the
-        // current leaf, and each needs a hash to combine it.
-        for (level = 0; !(count & (((uint32_t)1) << level)); level++) {
-            if (pbranch) {
-                if (matchh) {
-                    pbranch->push_back(inner[level]);
-                } else if (matchlevel == level) {
-                    pbranch->push_back(h);
-                    matchh = true;
-                }
+
+uint256 ComputeMerkleRoot(std::vector<uint256> hashes, bool* mutated) {
+    bool mutation = false;
+    while (hashes.size() > 1) {
+        if (mutated) {
+            for (size_t pos = 0; pos + 1 < hashes.size(); pos += 2) {
+                if (hashes[pos] == hashes[pos + 1]) mutation = true;
             }
-            mutated |= (inner[level] == h);
-            CHash256().Write(inner[level].begin(), 32).Write(h.begin(), 32).Finalize(h.begin());
         }
-        // Store the resulting hash at inner position level.
-        inner[level] = h;
-        if (matchh) {
-            matchlevel = level;
+        if (hashes.size() & 1) {
+            hashes.push_back(hashes.back());
         }
+        SHA256D64(hashes[0].begin(), hashes[0].begin(), hashes.size() / 2);
+        hashes.resize(hashes.size() / 2);
     }
-    // Do a final 'sweep' over the rightmost branch of the tree to process
-    // odd levels, and reduce everything to a single top value.
-    // Level is the level (counted from the bottom) up to which we've sweeped.
-    int level = 0;
-    // As long as bit number level in count is zero, skip it. It means there
-    // is nothing left at this level.
-    while (!(count & (((uint32_t)1) << level))) {
-        level++;
-    }
-    uint256 h = inner[level];
-    bool matchh = matchlevel == level;
-    while (count != (((uint32_t)1) << level)) {
-        // If we reach this point, h is an inner value that is not the top.
-        // We combine it with itself (Bitcoin's special rule for odd levels in
-        // the tree) to produce a higher level one.
-        if (pbranch && matchh) {
-            pbranch->push_back(h);
-        }
-        CHash256().Write(h.begin(), 32).Write(h.begin(), 32).Finalize(h.begin());
-        // Increment count to the value it would have if two entries at this
-        // level had existed.
-        count += (((uint32_t)1) << level);
-        level++;
-        // And propagate the result upwards accordingly.
-        while (!(count & (((uint32_t)1) << level))) {
-            if (pbranch) {
-                if (matchh) {
-                    pbranch->push_back(inner[level]);
-                } else if (matchlevel == level) {
-                    pbranch->push_back(h);
-                    matchh = true;
-                }
-            }
-            CHash256().Write(inner[level].begin(), 32).Write(h.begin(), 32).Finalize(h.begin());
-            level++;
-        }
-    }
-    // Return result.
-    if (pmutated) *pmutated = mutated;
-    if (proot) *proot = h;
+    if (mutated) *mutated = mutation;
+    if (hashes.size() == 0) return uint256();
+    return hashes[0];
 }
 
-uint256 ComputeMerkleRoot(const std::vector<uint256>& leaves, bool* mutated) {
-    uint256 hash;
-    MerkleComputation(leaves, &hash, mutated, -1, nullptr);
-    return hash;
-}
-
-std::vector<uint256> ComputeMerkleBranch(const std::vector<uint256>& leaves, uint32_t position) {
-    std::vector<uint256> ret;
-    MerkleComputation(leaves, nullptr, nullptr, position, &ret);
-    return ret;
-}
-
-uint256 ComputeMerkleRootFromBranch(const uint256& leaf, const std::vector<uint256>& vMerkleBranch, uint32_t nIndex) {
-    uint256 hash = leaf;
-    for (std::vector<uint256>::const_iterator it = vMerkleBranch.begin(); it != vMerkleBranch.end(); ++it) {
-        if (nIndex & 1) {
-            hash = Hash(BEGIN(*it), END(*it), BEGIN(hash), END(hash));
-        } else {
-            hash = Hash(BEGIN(hash), END(hash), BEGIN(*it), END(*it));
-        }
-        nIndex >>= 1;
-    }
-    return hash;
-}
 
 uint256 BlockMerkleRoot(const CBlock& block, bool* mutated)
 {
@@ -162,7 +70,7 @@ uint256 BlockMerkleRoot(const CBlock& block, bool* mutated)
     for (size_t s = 0; s < block.vtx.size(); s++) {
         leaves[s] = block.vtx[s]->GetHash();
     }
-    return ComputeMerkleRoot(leaves, mutated);
+    return ComputeMerkleRoot(std::move(leaves), mutated);
 }
 
 uint256 BlockWitnessMerkleRoot(const CBlock& block, bool* mutated)
@@ -173,15 +81,6 @@ uint256 BlockWitnessMerkleRoot(const CBlock& block, bool* mutated)
     for (size_t s = 1; s < block.vtx.size(); s++) {
         leaves[s] = block.vtx[s]->GetWitnessHash();
     }
-    return ComputeMerkleRoot(leaves, mutated);
+    return ComputeMerkleRoot(std::move(leaves), mutated);
 }
 
-std::vector<uint256> BlockMerkleBranch(const CBlock& block, uint32_t position)
-{
-    std::vector<uint256> leaves;
-    leaves.resize(block.vtx.size());
-    for (size_t s = 0; s < block.vtx.size(); s++) {
-        leaves[s] = block.vtx[s]->GetHash();
-    }
-    return ComputeMerkleBranch(leaves, position);
-}