1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
|
// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2016 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#include "merkleblock.h"
#include "hash.h"
#include "consensus/consensus.h"
#include "utilstrencodings.h"
CMerkleBlock::CMerkleBlock(const CBlock& block, CBloomFilter& filter)
{
header = block.GetBlockHeader();
std::vector<bool> vMatch;
std::vector<uint256> vHashes;
vMatch.reserve(block.vtx.size());
vHashes.reserve(block.vtx.size());
for (unsigned int i = 0; i < block.vtx.size(); i++)
{
const uint256& hash = block.vtx[i]->GetHash();
if (filter.IsRelevantAndUpdate(*block.vtx[i]))
{
vMatch.push_back(true);
vMatchedTxn.push_back(std::make_pair(i, hash));
}
else
vMatch.push_back(false);
vHashes.push_back(hash);
}
txn = CPartialMerkleTree(vHashes, vMatch);
}
CMerkleBlock::CMerkleBlock(const CBlock& block, const std::set<uint256>& txids)
{
header = block.GetBlockHeader();
std::vector<bool> vMatch;
std::vector<uint256> vHashes;
vMatch.reserve(block.vtx.size());
vHashes.reserve(block.vtx.size());
for (unsigned int i = 0; i < block.vtx.size(); i++)
{
const uint256& hash = block.vtx[i]->GetHash();
if (txids.count(hash))
vMatch.push_back(true);
else
vMatch.push_back(false);
vHashes.push_back(hash);
}
txn = CPartialMerkleTree(vHashes, vMatch);
}
uint256 CPartialMerkleTree::CalcHash(int height, unsigned int pos, const std::vector<uint256> &vTxid) {
//we can never have zero txs in a merkle block, we always need the coinbase tx
//if we do not have this assert, we can hit a memory access violation when indexing into vTxid
assert(vTxid.size() != 0);
if (height == 0) {
// hash at height 0 is the txids themself
return vTxid[pos];
} else {
// calculate left hash
uint256 left = CalcHash(height-1, pos*2, vTxid), right;
// calculate right hash if not beyond the end of the array - copy left hash otherwise
if (pos*2+1 < CalcTreeWidth(height-1))
right = CalcHash(height-1, pos*2+1, vTxid);
else
right = left;
// combine subhashes
return Hash(BEGIN(left), END(left), BEGIN(right), END(right));
}
}
void CPartialMerkleTree::TraverseAndBuild(int height, unsigned int pos, const std::vector<uint256> &vTxid, const std::vector<bool> &vMatch) {
// determine whether this node is the parent of at least one matched txid
bool fParentOfMatch = false;
for (unsigned int p = pos << height; p < (pos+1) << height && p < nTransactions; p++)
fParentOfMatch |= vMatch[p];
// store as flag bit
vBits.push_back(fParentOfMatch);
if (height==0 || !fParentOfMatch) {
// if at height 0, or nothing interesting below, store hash and stop
vHash.push_back(CalcHash(height, pos, vTxid));
} else {
// otherwise, don't store any hash, but descend into the subtrees
TraverseAndBuild(height-1, pos*2, vTxid, vMatch);
if (pos*2+1 < CalcTreeWidth(height-1))
TraverseAndBuild(height-1, pos*2+1, vTxid, vMatch);
}
}
uint256 CPartialMerkleTree::TraverseAndExtract(int height, unsigned int pos, unsigned int &nBitsUsed, unsigned int &nHashUsed, std::vector<uint256> &vMatch, std::vector<unsigned int> &vnIndex) {
if (nBitsUsed >= vBits.size()) {
// overflowed the bits array - failure
fBad = true;
return uint256();
}
bool fParentOfMatch = vBits[nBitsUsed++];
if (height==0 || !fParentOfMatch) {
// if at height 0, or nothing interesting below, use stored hash and do not descend
if (nHashUsed >= vHash.size()) {
// overflowed the hash array - failure
fBad = true;
return uint256();
}
const uint256 &hash = vHash[nHashUsed++];
if (height==0 && fParentOfMatch) { // in case of height 0, we have a matched txid
vMatch.push_back(hash);
vnIndex.push_back(pos);
}
return hash;
} else {
// otherwise, descend into the subtrees to extract matched txids and hashes
uint256 left = TraverseAndExtract(height-1, pos*2, nBitsUsed, nHashUsed, vMatch, vnIndex), right;
if (pos*2+1 < CalcTreeWidth(height-1)) {
right = TraverseAndExtract(height-1, pos*2+1, nBitsUsed, nHashUsed, vMatch, vnIndex);
if (right == left) {
// The left and right branches should never be identical, as the transaction
// hashes covered by them must each be unique.
fBad = true;
}
} else {
right = left;
}
// and combine them before returning
return Hash(BEGIN(left), END(left), BEGIN(right), END(right));
}
}
CPartialMerkleTree::CPartialMerkleTree(const std::vector<uint256> &vTxid, const std::vector<bool> &vMatch) : nTransactions(vTxid.size()), fBad(false) {
// reset state
vBits.clear();
vHash.clear();
// calculate height of tree
int nHeight = 0;
while (CalcTreeWidth(nHeight) > 1)
nHeight++;
// traverse the partial tree
TraverseAndBuild(nHeight, 0, vTxid, vMatch);
}
CPartialMerkleTree::CPartialMerkleTree() : nTransactions(0), fBad(true) {}
uint256 CPartialMerkleTree::ExtractMatches(std::vector<uint256> &vMatch, std::vector<unsigned int> &vnIndex) {
vMatch.clear();
// An empty set will not work
if (nTransactions == 0)
return uint256();
// check for excessively high numbers of transactions
if (nTransactions > MAX_BLOCK_WEIGHT / MIN_TRANSACTION_WEIGHT)
return uint256();
// there can never be more hashes provided than one for every txid
if (vHash.size() > nTransactions)
return uint256();
// there must be at least one bit per node in the partial tree, and at least one node per hash
if (vBits.size() < vHash.size())
return uint256();
// calculate height of tree
int nHeight = 0;
while (CalcTreeWidth(nHeight) > 1)
nHeight++;
// traverse the partial tree
unsigned int nBitsUsed = 0, nHashUsed = 0;
uint256 hashMerkleRoot = TraverseAndExtract(nHeight, 0, nBitsUsed, nHashUsed, vMatch, vnIndex);
// verify that no problems occurred during the tree traversal
if (fBad)
return uint256();
// verify that all bits were consumed (except for the padding caused by serializing it as a byte sequence)
if ((nBitsUsed+7)/8 != (vBits.size()+7)/8)
return uint256();
// verify that all hashes were consumed
if (nHashUsed != vHash.size())
return uint256();
return hashMerkleRoot;
}
|
