chain.cpp raw
1 // Copyright (c) 2009-2010 Satoshi Nakamoto
2 // Copyright (c) 2009-2022 The Limenka developers
3 // Distributed under the MIT software license, see the accompanying
4 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
5
6 #include <chain.h>
7 #include <tinyformat.h>
8 #include <util/time.h>
9
10 std::string CBlockFileInfo::ToString() const
11 {
12 return strprintf("CBlockFileInfo(blocks=%u, size=%u, heights=%u...%u, time=%s...%s)", nBlocks, nSize, nHeightFirst, nHeightLast, FormatISO8601Date(nTimeFirst), FormatISO8601Date(nTimeLast));
13 }
14
15 std::string CBlockIndex::ToString() const
16 {
17 return strprintf("CBlockIndex(pprev=%p, nHeight=%d, merkle=%s, hashBlock=%s)",
18 pprev, nHeight, hashMerkleRoot.ToString(), GetBlockHash().ToString());
19 }
20
21 void CChain::SetTip(CBlockIndex& block)
22 {
23 CBlockIndex* pindex = █
24 vChain.resize(pindex->nHeight + 1);
25 while (pindex && vChain[pindex->nHeight] != pindex) {
26 vChain[pindex->nHeight] = pindex;
27 pindex = pindex->pprev;
28 }
29 }
30
31 std::vector<uint256> LocatorEntries(const CBlockIndex* index)
32 {
33 int step = 1;
34 std::vector<uint256> have;
35 if (index == nullptr) return have;
36
37 have.reserve(32);
38 while (index) {
39 have.emplace_back(index->GetBlockHash());
40 if (index->nHeight == 0) break;
41 // Exponentially larger steps back, plus the genesis block.
42 int height = std::max(index->nHeight - step, 0);
43 // Use skiplist.
44 index = index->GetAncestor(height);
45 if (have.size() > 10) step *= 2;
46 }
47 return have;
48 }
49
50 CBlockLocator GetLocator(const CBlockIndex* index)
51 {
52 return CBlockLocator{LocatorEntries(index)};
53 }
54
55 CBlockLocator CChain::GetLocator() const
56 {
57 return ::GetLocator(Tip());
58 }
59
60 const CBlockIndex *CChain::FindFork(const CBlockIndex *pindex) const {
61 if (pindex == nullptr) {
62 return nullptr;
63 }
64 if (pindex->nHeight > Height())
65 pindex = pindex->GetAncestor(Height());
66 while (pindex && !Contains(pindex))
67 pindex = pindex->pprev;
68 return pindex;
69 }
70
71 CBlockIndex* CChain::FindEarliestAtLeast(int64_t nTime, int height) const
72 {
73 std::pair<int64_t, int> blockparams = std::make_pair(nTime, height);
74 std::vector<CBlockIndex*>::const_iterator lower = std::lower_bound(vChain.begin(), vChain.end(), blockparams,
75 [](CBlockIndex* pBlock, const std::pair<int64_t, int>& blockparams) -> bool { return pBlock->GetBlockTimeMax() < blockparams.first || pBlock->nHeight < blockparams.second; });
76 return (lower == vChain.end() ? nullptr : *lower);
77 }
78
79 /** Turn the lowest '1' bit in the binary representation of a number into a '0'. */
80 int static inline InvertLowestOne(int n) { return n & (n - 1); }
81
82 /** Compute what height to jump back to with the CBlockIndex::pskip pointer. */
83 int static inline GetSkipHeight(int height) {
84 if (height < 2)
85 return 0;
86
87 // Determine which height to jump back to. Any number strictly lower than height is acceptable,
88 // but the following expression seems to perform well in simulations (max 110 steps to go back
89 // up to 2**18 blocks).
90 return (height & 1) ? InvertLowestOne(InvertLowestOne(height - 1)) + 1 : InvertLowestOne(height);
91 }
92
93 const CBlockIndex* CBlockIndex::GetAncestor(int height) const
94 {
95 if (height > nHeight || height < 0) {
96 return nullptr;
97 }
98
99 const CBlockIndex* pindexWalk = this;
100 int heightWalk = nHeight;
101 while (heightWalk > height) {
102 int heightSkip = GetSkipHeight(heightWalk);
103 int heightSkipPrev = GetSkipHeight(heightWalk - 1);
104 if (pindexWalk->pskip != nullptr &&
105 (heightSkip == height ||
106 (heightSkip > height && !(heightSkipPrev < heightSkip - 2 &&
107 heightSkipPrev >= height)))) {
108 // Only follow pskip if pprev->pskip isn't better than pskip->pprev.
109 pindexWalk = pindexWalk->pskip;
110 heightWalk = heightSkip;
111 } else {
112 assert(pindexWalk->pprev);
113 pindexWalk = pindexWalk->pprev;
114 heightWalk--;
115 }
116 }
117 return pindexWalk;
118 }
119
120 CBlockIndex* CBlockIndex::GetAncestor(int height)
121 {
122 return const_cast<CBlockIndex*>(static_cast<const CBlockIndex*>(this)->GetAncestor(height));
123 }
124
125 void CBlockIndex::BuildSkip()
126 {
127 if (pprev)
128 pskip = pprev->GetAncestor(GetSkipHeight(nHeight));
129 }
130
131 arith_uint256 GetBlockProof(const CBlockIndex& block)
132 {
133 arith_uint256 bnTarget;
134 bool fNegative;
135 bool fOverflow;
136 bnTarget.SetCompact(block.nBits, &fNegative, &fOverflow);
137 if (fNegative || fOverflow || bnTarget == 0)
138 return 0;
139 // We need to compute 2**256 / (bnTarget+1), but we can't represent 2**256
140 // as it's too large for an arith_uint256. However, as 2**256 is at least as large
141 // as bnTarget+1, it is equal to ((2**256 - bnTarget - 1) / (bnTarget+1)) + 1,
142 // or ~bnTarget / (bnTarget+1) + 1.
143 return (~bnTarget / (bnTarget + 1)) + 1;
144 }
145
146 int64_t GetBlockProofEquivalentTime(const CBlockIndex& to, const CBlockIndex& from, const CBlockIndex& tip, const Consensus::Params& params)
147 {
148 arith_uint256 r;
149 int sign = 1;
150 if (to.nChainWork > from.nChainWork) {
151 r = to.nChainWork - from.nChainWork;
152 } else {
153 r = from.nChainWork - to.nChainWork;
154 sign = -1;
155 }
156 r = r * arith_uint256(params.nPowTargetSpacing) / GetBlockProof(tip);
157 if (r.bits() > 63) {
158 return sign * std::numeric_limits<int64_t>::max();
159 }
160 return sign * int64_t(r.GetLow64());
161 }
162
163 /** Find the last common ancestor two blocks have.
164 * Both pa and pb must be non-nullptr. */
165 const CBlockIndex* LastCommonAncestor(const CBlockIndex* pa, const CBlockIndex* pb) {
166 if (pa->nHeight > pb->nHeight) {
167 pa = pa->GetAncestor(pb->nHeight);
168 } else if (pb->nHeight > pa->nHeight) {
169 pb = pb->GetAncestor(pa->nHeight);
170 }
171
172 while (pa != pb && pa && pb) {
173 pa = pa->pprev;
174 pb = pb->pprev;
175 }
176
177 // Eventually all chain branches meet at the genesis block.
178 assert(pa == pb);
179 return pa;
180 }
181