Repository: bitcoin/bitcoin
File: src/validation.cpp (C++)

Code before:
            // Find which child we just visited.
            std::pair<std::multimap<CBlockIndex*,CBlockIndex*>::iterator,std::multimap<CBlockIndex*,CBlockIndex*>::iterator> rangePar = forward.equal_range(pindexPar);
            while (rangePar.first->second != pindex) {
                assert(rangePar.first != rangePar.second); // Our parent must have at least the node we're coming from as child.
                rangePar.first++;
            }
            // Proceed to the next one.
            rangePar.first++;
            if (rangePar.first != rangePar.second) {
                // Move to the sibling.
                pindex = rangePar.first->second;
                break;
            } else {
                // Move up further.
                pindex = pindexPar;
                nHeight--;
                continue;
            }
        }
    }

    // Check that we actually traversed the entire map.
    assert(nNodes == forward.size());
}

std::string Chainstate::ToString()
{
    AssertLockHeld(::cs_main);
    CBlockIndex* tip = m_chain.Tip();
    return strprintf("Chainstate [%s] @ height %d (%s)",
                     m_from_snapshot_blockhash ? "snapshot" : "ibd",
                     tip ? tip->nHeight : -1, tip ? tip->GetBlockHash().ToString() : "null");
}

bool Chainstate::ResizeCoinsCaches(size_t coinstip_size, size_t coinsdb_size)
{
    AssertLockHeld(::cs_main);
    if (coinstip_size == m_coinstip_cache_size_bytes &&
            coinsdb_size == m_coinsdb_cache_size_bytes) {
        // Cache sizes are unchanged, no need to continue.
        return true;
    }
    size_t old_coinstip_size = m_coinstip_cache_size_bytes;
    m_coinstip_cache_size_bytes = coinstip_size;
    m_coinsdb_cache_size_bytes = coinsdb_size;
    CoinsDB().ResizeCache(coinsdb_size);

    LogPrintf("[%s] resized coinsdb cache to %.1f MiB\n",
        this->ToString(), coinsdb_size * (1.0 / 1024 / 1024));
    LogPrintf("[%s] resized coinstip cache to %.1f MiB\n",
        this->ToString(), coinstip_size * (1.0 / 1024 / 1024));

Review comment (bug):
In commit "validation: improve performance of CheckBlockIndex" (4b05c654c1a5df294fa32a94c38001ac2b4ff2de)

I think this assert might be a little clearer if it replaced `m_best_header` with `best_hdr_chain.Tip()`. Both values should be identical but latter doesn't require remembering how the `best_hdr_chain` tip was assigned ~300 lines earlier in the code. Also I think the check could be stricter because if `pindex` is not null, `pindexPar` cannot be the best header. Would suggest:

```c++
// There will not be a next block if (and only if) parent block is the best header.
assert((pindex == nullptr) == (pindexPar == best_hdr_chain.Tip()));
```

Code after:
            nHeight++;
            pindex = best_hdr_chain[nHeight];
            if (!pindex) break; // we are finished, since the best header chain is always processed last
            continue;
        }
        // This is a leaf node.
        // Move upwards until we reach a node of which we have not yet visited the last child.
        while (pindex) {
            // We are going to either move to a parent or a sibling of pindex.
            snap_update_firsts();
            // If pindex was the first with a certain property, unset the corresponding variable.
            if (pindex == pindexFirstInvalid) pindexFirstInvalid = nullptr;
            if (pindex == pindexFirstMissing) pindexFirstMissing = nullptr;
            if (pindex == pindexFirstNeverProcessed) pindexFirstNeverProcessed = nullptr;
            if (pindex == pindexFirstNotTreeValid) pindexFirstNotTreeValid = nullptr;
            if (pindex == pindexFirstNotTransactionsValid) pindexFirstNotTransactionsValid = nullptr;
            if (pindex == pindexFirstNotChainValid) pindexFirstNotChainValid = nullptr;
            if (pindex == pindexFirstNotScriptsValid) pindexFirstNotScriptsValid = nullptr;
            // Find our parent.
            CBlockIndex* pindexPar = pindex->pprev;
            // Find which child we just visited.
            std::pair<std::multimap<CBlockIndex*,CBlockIndex*>::iterator,std::multimap<CBlockIndex*,CBlockIndex*>::iterator> rangePar = forward.equal_range(pindexPar);
            while (rangePar.first->second != pindex) {
                assert(rangePar.first != rangePar.second); // Our parent must have at least the node we're coming from as child.
                rangePar.first++;
            }
            // Proceed to the next one.
            rangePar.first++;
            if (rangePar.first != rangePar.second) {
                // Move to a sibling not part of the best header chain.
                pindex = rangePar.first->second;
                break;
            } else if (pindexPar == best_hdr_chain[nHeight - 1]) {
                // Move to pindex's sibling on the best-chain, if it has one.
                pindex = best_hdr_chain[nHeight];
                // There will not be a next block if (and only if) parent block is the best header.
                assert((pindex == nullptr) == (pindexPar == best_hdr_chain.Tip()));
                break;
            } else {
                // Move up further.
                pindex = pindexPar;
                nHeight--;
                continue;
            }
        }
    }

    // Check that we actually traversed the entire block index.
    assert(nNodes == forward.size() + best_hdr_chain.Height() + 1);
}