// newBlockImporter returns a new importer for the provided file reader seeker
// and database.
func newBlockImporter(db database.Db, r io.ReadSeeker) *blockImporter {
return &blockImporter{
db: db,
r: r,
processQueue: make(chan []byte, 2),
doneChan: make(chan bool),
errChan: make(chan error),
quit: make(chan struct{}),
chain: blockchain.New(db, activeNetParams, nil),
medianTime: blockchain.NewMedianTime(),
lastLogTime: time.Now(),
}
}
// This example demonstrates how to create a new chain instance and use
// ProcessBlock to attempt to attempt add a block to the chain. As the package
// overview documentation describes, this includes all of the Bitcoin consensus
// rules. This example intentionally attempts to insert a duplicate genesis
// block to illustrate how an invalid block is handled.
func ExampleBlockChain_ProcessBlock() {
// Create a new database to store the accepted blocks into. Typically
// this would be opening an existing database and would not use memdb
// which is a memory-only database backend, but we create a new db
// here so this is a complete working example.
db, err := database.CreateDB("memdb")
if err != nil {
fmt.Printf("Failed to create database: %v\n", err)
return
}
defer db.Close()
// Insert the main network genesis block. This is part of the initial
// database setup. Like above, this typically would not be needed when
// opening an existing database.
genesisBlock := btcutil.NewBlock(chaincfg.MainNetParams.GenesisBlock)
_, err = db.InsertBlock(genesisBlock)
if err != nil {
fmt.Printf("Failed to insert genesis block: %v\n", err)
return
}
// Create a new BlockChain instance using the underlying database for
// the main bitcoin network and ignore notifications.
chain := blockchain.New(db, &chaincfg.MainNetParams, nil)
// Create a new median time source that is required by the upcoming
// call to ProcessBlock. Ordinarily this would also add time values
// obtained from other peers on the network so the local time is
// adjusted to be in agreement with other peers.
timeSource := blockchain.NewMedianTime()
// Process a block. For this example, we are going to intentionally
// cause an error by trying to process the genesis block which already
// exists.
isOrphan, err := chain.ProcessBlock(genesisBlock, timeSource, blockchain.BFNone)
if err != nil {
fmt.Printf("Failed to process block: %v\n", err)
return
}
fmt.Printf("Block accepted. Is it an orphan?: %v", isOrphan)
// Output:
// Failed to process block: already have block 000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f
}
// findCandidates searches the chain backwards for checkpoint candidates and
// returns a slice of found candidates, if any. It also stops searching for
// candidates at the last checkpoint that is already hard coded into btcchain
// since there is no point in finding candidates before already existing
// checkpoints.
func findCandidates(db database.Db, latestHash *wire.ShaHash) ([]*chaincfg.Checkpoint, error) {
// Start with the latest block of the main chain.
block, err := db.FetchBlockBySha(latestHash)
if err != nil {
return nil, err
}
// Setup chain and get the latest checkpoint. Ignore notifications
// since they aren't needed for this util.
chain := blockchain.New(db, activeNetParams, nil)
latestCheckpoint := chain.LatestCheckpoint()
if latestCheckpoint == nil {
return nil, fmt.Errorf("unable to retrieve latest checkpoint")
}
// The latest known block must be at least the last known checkpoint
// plus required checkpoint confirmations.
checkpointConfirmations := int32(blockchain.CheckpointConfirmations)
requiredHeight := latestCheckpoint.Height + checkpointConfirmations
if block.Height() < requiredHeight {
return nil, fmt.Errorf("the block database is only at height "+
"%d which is less than the latest checkpoint height "+
"of %d plus required confirmations of %d",
block.Height(), latestCheckpoint.Height,
checkpointConfirmations)
}
// Indeterminate progress setup.
numBlocksToTest := block.Height() - requiredHeight
progressInterval := (numBlocksToTest / 100) + 1 // min 1
fmt.Print("Searching for candidates")
defer fmt.Println()
// Loop backwards through the chain to find checkpoint candidates.
candidates := make([]*chaincfg.Checkpoint, 0, cfg.NumCandidates)
numTested := int32(0)
for len(candidates) < cfg.NumCandidates && block.Height() > requiredHeight {
// Display progress.
if numTested%progressInterval == 0 {
fmt.Print(".")
}
// Determine if this block is a checkpoint candidate.
isCandidate, err := chain.IsCheckpointCandidate(block)
if err != nil {
return nil, err
}
// All checks passed, so this node seems like a reasonable
// checkpoint candidate.
if isCandidate {
checkpoint := chaincfg.Checkpoint{
Height: block.Height(),
Hash: block.Sha(),
}
candidates = append(candidates, &checkpoint)
}
prevHash := &block.MsgBlock().Header.PrevBlock
block, err = db.FetchBlockBySha(prevHash)
if err != nil {
return nil, err
}
numTested++
}
return candidates, nil
}