From 1f0e7ca09c9d7c5787c218156fa5096a1bdf2ea8 Mon Sep 17 00:00:00 2001
From: Pieter Wuille <pieter.wuille@gmail.com>
Date: Wed, 27 Sep 2017 18:50:31 -0700
Subject: Use SHA256D64 in Merkle root computation

---
 src/consensus/merkle.cpp | 25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

(limited to 'src/consensus/merkle.cpp')

diff --git a/src/consensus/merkle.cpp b/src/consensus/merkle.cpp
index 74a9ebb2e3..a23dd00144 100644
--- a/src/consensus/merkle.cpp
+++ b/src/consensus/merkle.cpp
@@ -130,10 +130,23 @@ static void MerkleComputation(const std::vector<uint256>& leaves, uint256* proot
     if (proot) *proot = h;
 }
 
-uint256 ComputeMerkleRoot(const std::vector<uint256>& leaves, bool* mutated) {
-    uint256 hash;
-    MerkleComputation(leaves, &hash, mutated, -1, nullptr);
-    return hash;
+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;
+            }
+        }
+        if (hashes.size() & 1) {
+            hashes.push_back(hashes.back());
+        }
+        SHA256D64(hashes[0].begin(), hashes[0].begin(), hashes.size() / 2);
+        hashes.resize(hashes.size() / 2);
+    }
+    if (mutated) *mutated = mutation;
+    if (hashes.size() == 0) return uint256();
+    return hashes[0];
 }
 
 std::vector<uint256> ComputeMerkleBranch(const std::vector<uint256>& leaves, uint32_t position) {
@@ -162,7 +175,7 @@ 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)
@@ -173,7 +186,7 @@ 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)
-- 
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