bitcoin core write block to disk

WriteBlockToDisk.cpp

// validation.cpp

/** Store block on disk. If dbp is non-nullptr, the file is known to already reside on disk */
static bool AcceptBlock(const std::shared_ptr<const CBlock>& pblock, CValidationState& state, const CChainParams& chainparams, CBlockIndex** ppindex, bool fRequested, const CDiskBlockPos* dbp, bool* fNewBlock)
{
  // ...
  // Header is valid/has work, merkle tree and segwit merkle tree are good...RELAY NOW
  // (but if it does not build on our best tip, let the SendMessages loop relay it)
  if (!IsInitialBlockDownload() && chainActive.Tip() == pindex->pprev)
    GetMainSignals().NewPoWValidBlock(pindex, pblock);

  int nHeight = pindex->nHeight;

  // Write block to history file
  try {
    unsigned int nBlockSize = ::GetSerializeSize(block, SER_DISK, CLIENT_VERSION);
    CDiskBlockPos blockPos;
    if (dbp != nullptr)
      blockPos = *dbp;
    if (!FindBlockPos(state, blockPos, nBlockSize+8, nHeight, block.GetBlockTime(), dbp != nullptr))
      return error("AcceptBlock(): FindBlockPos failed");
    if (dbp == nullptr)
      if (!WriteBlockToDisk(block, blockPos, chainparams.MessageStart()))
        AbortNode(state, "Failed to write block");
    if (!ReceivedBlockTransactions(block, state, pindex, blockPos, chainparams.GetConsensus()))
      return error("AcceptBlock(): ReceivedBlockTransactions failed");
  } catch (const std::runtime_error& e) {
    return AbortNode(state, std::string("System error: ") + e.what());
  }

  if (fCheckForPruning)
    FlushStateToDisk(chainparams, state, FLUSH_STATE_NONE); // we just allocated more disk space for block files

  return true;
}

static bool FindBlockPos(CValidationState &state, CDiskBlockPos &pos, unsigned int nAddSize, unsigned int nHeight, uint64_t nTime, bool fKnown = false)
{
  // ...
  unsigned int nFile = fKnown ? pos.nFile : nLastBlockFile;
  if (vinfoBlockFile.size() <= nFile) {
    vinfoBlockFile.resize(nFile + 1);
  }

  if (!fKnown) {
    while (vinfoBlockFile[nFile].nSize + nAddSize >= MAX_BLOCKFILE_SIZE) {
      nFile++;
      if (vinfoBlockFile.size() <= nFile) {
        vinfoBlockFile.resize(nFile + 1);
      }
    }
    pos.nFile = nFile;
    pos.nPos = vinfoBlockFile[nFile].nSize;
  }

  if ((int)nFile != nLastBlockFile) {
    if (!fKnown) {
      LogPrintf("Leaving block file %i: %s\n", nLastBlockFile, vinfoBlockFile[nLastBlockFile].ToString());
    }
    FlushBlockFile(!fKnown);
    nLastBlockFile = nFile;
  }

  vinfoBlockFile[nFile].AddBlock(nHeight, nTime);
  if (fKnown)
    vinfoBlockFile[nFile].nSize = std::max(pos.nPos + nAddSize, vinfoBlockFile[nFile].nSize);
  else
    vinfoBlockFile[nFile].nSize += nAddSize;

  if (!fKnown) {
    unsigned int nOldChunks = (pos.nPos + BLOCKFILE_CHUNK_SIZE - 1) / BLOCKFILE_CHUNK_SIZE;
    unsigned int nNewChunks = (vinfoBlockFile[nFile].nSize + BLOCKFILE_CHUNK_SIZE - 1) / BLOCKFILE_CHUNK_SIZE;
    if (nNewChunks > nOldChunks) {
      if (fPruneMode)
        fCheckForPruning = true;
      if (CheckDiskSpace(nNewChunks * BLOCKFILE_CHUNK_SIZE - pos.nPos)) {
        FILE *file = OpenBlockFile(pos);
        if (file) {
          LogPrintf("Pre-allocating up to position 0x%x in blk%05u.dat\n", nNewChunks * BLOCKFILE_CHUNK_SIZE, pos.nFile);
          AllocateFileRange(file, pos.nPos, nNewChunks * BLOCKFILE_CHUNK_SIZE - pos.nPos);
          fclose(file);
        }
      }
      else
        return state.Error("out of disk space");
    }
  }

  setDirtyFileInfo.insert(nFile);
  return true;
}

static bool WriteBlockToDisk(const CBlock& block, CDiskBlockPos& pos, const CMessageHeader::MessageStartChars& messageStart)
{
  // Open history file to append
  CAutoFile fileout(OpenBlockFile(pos), SER_DISK, CLIENT_VERSION);
  if (fileout.IsNull())
    return error("WriteBlockToDisk: OpenBlockFile failed");

  // Write index header
  unsigned int nSize = GetSerializeSize(fileout, block);
  fileout << FLATDATA(messageStart) << nSize;

  // Write block
  long fileOutPos = ftell(fileout.Get());
  if (fileOutPos < 0)
    return error("WriteBlockToDisk: ftell failed");
  pos.nPos = (unsigned int)fileOutPos;
  fileout << block;

  return true;
}