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Move BlockMerkleBranch back to merkle.{h,cpp}
The Mining interface uses this function in the next commit to calculate the coinbase merkle path. Stratum v2 uses this to send a compact work template. This partially undoes the change in 4defdfa, but is not a revert, because the implementation changed in the meantime. This commit also documents the function.
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+113
-104
lines changed

3 files changed

+113
-104
lines changed

‎src/consensus/merkle.cpp

Lines changed: 103 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -83,3 +83,106 @@ uint256 BlockWitnessMerkleRoot(const CBlock& block, bool* mutated)
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return ComputeMerkleRoot(std::move(leaves), mutated);
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}
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/* This implements a constant-space merkle root/path calculator, limited to 2^32 leaves. */
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static void MerkleComputation(const std::vector<uint256>& leaves, uint256* proot, bool* pmutated, uint32_t branchpos, std::vector<uint256>* pbranch) {
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if (pbranch) pbranch->clear();
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if (leaves.size() == 0) {
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if (pmutated) *pmutated = false;
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if (proot) *proot = uint256();
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return;
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}
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bool mutated = false;
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// count is the number of leaves processed so far.
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uint32_t count = 0;
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// inner is an array of eagerly computed subtree hashes, indexed by tree
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// level (0 being the leaves).
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// For example, when count is 25 (11001 in binary), inner[4] is the hash of
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// the first 16 leaves, inner[3] of the next 8 leaves, and inner[0] equal to
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// the last leaf. The other inner entries are undefined.
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uint256 inner[32];
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// Which position in inner is a hash that depends on the matching leaf.
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int matchlevel = -1;
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// First process all leaves into 'inner' values.
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while (count < leaves.size()) {
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uint256 h = leaves[count];
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bool matchh = count == branchpos;
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count++;
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int level;
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// For each of the lower bits in count that are 0, do 1 step. Each
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// corresponds to an inner value that existed before processing the
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// current leaf, and each needs a hash to combine it.
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for (level = 0; !(count & ((uint32_t{1}) << level)); level++) {
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if (pbranch) {
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if (matchh) {
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pbranch->push_back(inner[level]);
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} else if (matchlevel == level) {
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pbranch->push_back(h);
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matchh = true;
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}
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}
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mutated |= (inner[level] == h);
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h = Hash(inner[level], h);
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}
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// Store the resulting hash at inner position level.
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inner[level] = h;
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if (matchh) {
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matchlevel = level;
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}
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}
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// Do a final 'sweep' over the rightmost branch of the tree to process
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// odd levels, and reduce everything to a single top value.
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// Level is the level (counted from the bottom) up to which we've sweeped.
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int level = 0;
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// As long as bit number level in count is zero, skip it. It means there
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// is nothing left at this level.
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while (!(count & ((uint32_t{1}) << level))) {
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level++;
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}
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uint256 h = inner[level];
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bool matchh = matchlevel == level;
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while (count != ((uint32_t{1}) << level)) {
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// If we reach this point, h is an inner value that is not the top.
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// We combine it with itself (Bitcoin's special rule for odd levels in
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// the tree) to produce a higher level one.
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if (pbranch && matchh) {
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pbranch->push_back(h);
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}
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h = Hash(h, h);
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// Increment count to the value it would have if two entries at this
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// level had existed.
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count += ((uint32_t{1}) << level);
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level++;
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// And propagate the result upwards accordingly.
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while (!(count & ((uint32_t{1}) << level))) {
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if (pbranch) {
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if (matchh) {
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pbranch->push_back(inner[level]);
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} else if (matchlevel == level) {
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pbranch->push_back(h);
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matchh = true;
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}
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}
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h = Hash(inner[level], h);
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level++;
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}
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}
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// Return result.
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if (pmutated) *pmutated = mutated;
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if (proot) *proot = h;
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}
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static std::vector<uint256> ComputeMerkleBranch(const std::vector<uint256>& leaves, uint32_t position) {
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std::vector<uint256> ret;
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MerkleComputation(leaves, nullptr, nullptr, position, &ret);
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return ret;
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}
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std::vector<uint256> BlockMerkleBranch(const CBlock& block, uint32_t position)
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{
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std::vector<uint256> leaves;
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leaves.resize(block.vtx.size());
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for (size_t s = 0; s < block.vtx.size(); s++) {
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leaves[s] = block.vtx[s]->GetHash();
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}
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return ComputeMerkleBranch(leaves, position);
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}

‎src/consensus/merkle.h

Lines changed: 10 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -24,4 +24,14 @@ uint256 BlockMerkleRoot(const CBlock& block, bool* mutated = nullptr);
2424
*/
2525
uint256 BlockWitnessMerkleRoot(const CBlock& block, bool* mutated = nullptr);
2626

27+
/**
28+
* Compute merkle path to the specified transaction
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*
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* @param[in] block the block
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* @param[in] position transaction for which to calculate the merkle path, defaults to coinbase
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*
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* @return merkle path ordered from the deepest
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*/
35+
std::vector<uint256> BlockMerkleBranch(const CBlock& block, uint32_t position = 0);
36+
2737
#endif // BITCOIN_CONSENSUS_MERKLE_H

‎src/test/merkle_tests.cpp

Lines changed: 0 additions & 104 deletions
Original file line numberDiff line numberDiff line change
@@ -23,110 +23,6 @@ static uint256 ComputeMerkleRootFromBranch(const uint256& leaf, const std::vecto
2323
return hash;
2424
}
2525

26-
/* This implements a constant-space merkle root/path calculator, limited to 2^32 leaves. */
27-
static void MerkleComputation(const std::vector<uint256>& leaves, uint256* proot, bool* pmutated, uint32_t branchpos, std::vector<uint256>* pbranch) {
28-
if (pbranch) pbranch->clear();
29-
if (leaves.size() == 0) {
30-
if (pmutated) *pmutated = false;
31-
if (proot) *proot = uint256();
32-
return;
33-
}
34-
bool mutated = false;
35-
// count is the number of leaves processed so far.
36-
uint32_t count = 0;
37-
// inner is an array of eagerly computed subtree hashes, indexed by tree
38-
// level (0 being the leaves).
39-
// For example, when count is 25 (11001 in binary), inner[4] is the hash of
40-
// the first 16 leaves, inner[3] of the next 8 leaves, and inner[0] equal to
41-
// the last leaf. The other inner entries are undefined.
42-
uint256 inner[32];
43-
// Which position in inner is a hash that depends on the matching leaf.
44-
int matchlevel = -1;
45-
// First process all leaves into 'inner' values.
46-
while (count < leaves.size()) {
47-
uint256 h = leaves[count];
48-
bool matchh = count == branchpos;
49-
count++;
50-
int level;
51-
// For each of the lower bits in count that are 0, do 1 step. Each
52-
// corresponds to an inner value that existed before processing the
53-
// current leaf, and each needs a hash to combine it.
54-
for (level = 0; !(count & ((uint32_t{1}) << level)); level++) {
55-
if (pbranch) {
56-
if (matchh) {
57-
pbranch->push_back(inner[level]);
58-
} else if (matchlevel == level) {
59-
pbranch->push_back(h);
60-
matchh = true;
61-
}
62-
}
63-
mutated |= (inner[level] == h);
64-
h = Hash(inner[level], h);
65-
}
66-
// Store the resulting hash at inner position level.
67-
inner[level] = h;
68-
if (matchh) {
69-
matchlevel = level;
70-
}
71-
}
72-
// Do a final 'sweep' over the rightmost branch of the tree to process
73-
// odd levels, and reduce everything to a single top value.
74-
// Level is the level (counted from the bottom) up to which we've sweeped.
75-
int level = 0;
76-
// As long as bit number level in count is zero, skip it. It means there
77-
// is nothing left at this level.
78-
while (!(count & ((uint32_t{1}) << level))) {
79-
level++;
80-
}
81-
uint256 h = inner[level];
82-
bool matchh = matchlevel == level;
83-
while (count != ((uint32_t{1}) << level)) {
84-
// If we reach this point, h is an inner value that is not the top.
85-
// We combine it with itself (Bitcoin's special rule for odd levels in
86-
// the tree) to produce a higher level one.
87-
if (pbranch && matchh) {
88-
pbranch->push_back(h);
89-
}
90-
h = Hash(h, h);
91-
// Increment count to the value it would have if two entries at this
92-
// level had existed.
93-
count += ((uint32_t{1}) << level);
94-
level++;
95-
// And propagate the result upwards accordingly.
96-
while (!(count & ((uint32_t{1}) << level))) {
97-
if (pbranch) {
98-
if (matchh) {
99-
pbranch->push_back(inner[level]);
100-
} else if (matchlevel == level) {
101-
pbranch->push_back(h);
102-
matchh = true;
103-
}
104-
}
105-
h = Hash(inner[level], h);
106-
level++;
107-
}
108-
}
109-
// Return result.
110-
if (pmutated) *pmutated = mutated;
111-
if (proot) *proot = h;
112-
}
113-
114-
static std::vector<uint256> ComputeMerkleBranch(const std::vector<uint256>& leaves, uint32_t position) {
115-
std::vector<uint256> ret;
116-
MerkleComputation(leaves, nullptr, nullptr, position, &ret);
117-
return ret;
118-
}
119-
120-
static std::vector<uint256> BlockMerkleBranch(const CBlock& block, uint32_t position)
121-
{
122-
std::vector<uint256> leaves;
123-
leaves.resize(block.vtx.size());
124-
for (size_t s = 0; s < block.vtx.size(); s++) {
125-
leaves[s] = block.vtx[s]->GetHash();
126-
}
127-
return ComputeMerkleBranch(leaves, position);
128-
}
129-
13026
// Older version of the merkle root computation code, for comparison.
13127
static uint256 BlockBuildMerkleTree(const CBlock& block, bool* fMutated, std::vector<uint256>& vMerkleTree)
13228
{

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