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refactor: port upstream changes for merkle
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@div72
div72 committed Mar 5, 2024
1 parent 2c233c1 commit 8be8771
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130 changes: 14 additions & 116 deletions src/consensus/merkle.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -37,118 +37,25 @@
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]).Write(h).Finalize(h);
}
// Store the resulting hash at inner position level.
inner[level] = h;
if (matchh) {
matchlevel = level;
}
}
// 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).Write(h).Finalize(h);
// 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]).Write(h).Finalize(h);
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);
}
// Return result.
if (pmutated) *pmutated = mutated;
if (proot) *proot = h;
}

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;
if (mutated) *mutated = mutation;
if (hashes.size() == 0) return uint256();
return hashes[0];
}

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(*it, hash);
} else {
hash = Hash(hash, *it);
}
nIndex >>= 1;
}
return hash;
}

uint256 BlockMerkleRoot(const CBlock& block, bool* mutated)
{
Expand All @@ -157,15 +64,6 @@ 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);
}

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);
}
12 changes: 1 addition & 11 deletions src/consensus/merkle.h
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Original file line number Diff line number Diff line change
Expand Up @@ -5,27 +5,17 @@
#ifndef BITCOIN_CONSENSUS_MERKLE_H
#define BITCOIN_CONSENSUS_MERKLE_H

#include <stdint.h>
#include <vector>

#include "main.h"
#include <uint256.h>

uint256 ComputeMerkleRoot(const std::vector<uint256>& leaves, bool* mutated = nullptr);
std::vector<uint256> ComputeMerkleBranch(const std::vector<uint256>& leaves, uint32_t position);
uint256 ComputeMerkleRootFromBranch(const uint256& leaf, const std::vector<uint256>& branch, uint32_t position);
uint256 ComputeMerkleRoot(std::vector<uint256> leaves, bool* mutated = nullptr);

/*
* Compute the Merkle root of the transactions in a block.
* *mutated is set to true if a duplicated subtree was found.
*/
uint256 BlockMerkleRoot(const CBlock& block, bool* mutated = nullptr);

/*
* Compute the Merkle branch for the tree of transactions in a block, for a
* given position.
* This can be verified using ComputeMerkleRootFromBranch.
*/
std::vector<uint256> BlockMerkleBranch(const CBlock& block, uint32_t position);

#endif // BITCOIN_CONSENSUS_MERKLE_H
123 changes: 123 additions & 0 deletions src/test/merkle_tests.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,129 @@

BOOST_AUTO_TEST_SUITE(merkle_tests)

/* 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;
}
}
mutated |= (inner[level] == h);
CHash256().Write(inner[level]).Write(h).Finalize(h);
}
// Store the resulting hash at inner position level.
inner[level] = h;
if (matchh) {
matchlevel = level;
}
}
// 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).Write(h).Finalize(h);
// 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]).Write(h).Finalize(h);
level++;
}
}
// Return result.
if (pmutated) *pmutated = mutated;
if (proot) *proot = h;
}

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(*it, hash);
} else {
hash = Hash(hash, *it);
}
nIndex >>= 1;
}
return hash;
}

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);
}

// Older version of the merkle root computation code, for comparison.
static uint256 BlockBuildMerkleTree(const CBlock& block, std::vector<uint256>& vMerkleTree)
{
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