btcd中database代码详解

     在btcd.go文件中，函数loadBlockDB根据配置初始化了相应的数据库

func loadBlockDB() (database.DB, error) {
	// The memdb backend does not have a file path associated with it, so
	// handle it uniquely.  We also don't want to worry about the multiple
	// database type warnings when running with the memory database.
	if cfg.DbType == "memdb" {
		btcdLog.Infof("Creating block database in memory.")
		db, err := database.Create(cfg.DbType)
		if err != nil {
			return nil, err
		}
		return db, nil
	}

	warnMultipleDBs()

	// The database name is based on the database type.
	dbPath := blockDbPath(cfg.DbType)

	// The regression test is special in that it needs a clean database for
	// each run, so remove it now if it already exists.
	removeRegressionDB(dbPath)

	btcdLog.Infof("Loading block database from '%s'", dbPath)
	db, err := database.Open(cfg.DbType, dbPath, activeNetParams.Net)
	if err != nil {
		// Return the error if it's not because the database doesn't
		// exist.
		if dbErr, ok := err.(database.Error); !ok || dbErr.ErrorCode !=
			database.ErrDbDoesNotExist {

			return nil, err
		}

		// Create the db if it does not exist.
		err = os.MkdirAll(cfg.DataDir, 0700)
		if err != nil {
			return nil, err
		}
		db, err = database.Create(cfg.DbType, dbPath, activeNetParams.Net)
		if err != nil {
			return nil, err
		}
	}

	btcdLog.Info("Block database loaded")
	return db, nil
}

　　在btcdMain函数中，调用loadBlockDB()获得数据库的句柄，通过newservre配置blockchain对象

server, err := newServer(cfg.Listeners, db, activeNetParams.Params,interrupt)

　　   loadBlockDB()返回的是btcd中定义的数据库的接口，接口的定义如下：

// DB provides a generic interface that is used to store bitcoin blocks and
// related metadata.  This interface is intended to be agnostic to the actual
// mechanism used for backend data storage.  The RegisterDriver function can be
// used to add a new backend data storage method.
//
// This interface is divided into two distinct categories of functionality.
//
// The first category is atomic metadata storage with bucket support.  This is
// accomplished through the use of database transactions.
//
// The second category is generic block storage.  This functionality is
// intentionally separate because the mechanism used for block storage may or
// may not be the same mechanism used for metadata storage.  For example, it is
// often more efficient to store the block data as flat files while the metadata
// is kept in a database.  However, this interface aims to be generic enough to
// support blocks in the database too, if needed by a particular backend.
type DB interface {
	// Type returns the database driver type the current database instance
	// was created with.
	Type() string

	// Begin starts a transaction which is either read-only or read-write
	// depending on the specified flag.  Multiple read-only transactions
	// can be started simultaneously while only a single read-write
	// transaction can be started at a time.  The call will block when
	// starting a read-write transaction when one is already open.
	//
	// NOTE: The transaction must be closed by calling Rollback or Commit on
	// it when it is no longer needed.  Failure to do so can result in
	// unclaimed memory and/or inablity to close the database due to locks
	// depending on the specific database implementation.
	Begin(writable bool) (Tx, error)

	// View invokes the passed function in the context of a managed
	// read-only transaction.  Any errors returned from the user-supplied
	// function are returned from this function.
	//
	// Calling Rollback or Commit on the transaction passed to the
	// user-supplied function will result in a panic.
	View(fn func(tx Tx) error) error

	// Update invokes the passed function in the context of a managed
	// read-write transaction.  Any errors returned from the user-supplied
	// function will cause the transaction to be rolled back and are
	// returned from this function.  Otherwise, the transaction is committed
	// when the user-supplied function returns a nil error.
	//
	// Calling Rollback or Commit on the transaction passed to the
	// user-supplied function will result in a panic.
	Update(fn func(tx Tx) error) error

	// Close cleanly shuts down the database and syncs all data.  It will
	// block until all database transactions have been finalized (rolled
	// back or committed).
	Close() error
}　　

     函数处理收到的block

 

func (b *BlockChain) ProcessBlock(block *btcutil.Block, flags BehaviorFlags) (bool, bool, error)

　　该函数会检查block的合法性，并且确认该block和该block之前的block是否也存在在数据库中。如果都满足要求则写入到数据库，写入数据库的代码函数如下：

func (b *BlockChain) maybeAcceptBlock(block *btcutil.Block, flags BehaviorFlags) (bool, error)

　　

      函数dbStoreBlock把block信息放入pendingBlockData数组，

   

在transaction的commit方法中，把block信息写进数据库，一个transaction可以存放多个block，然后一次写入文件。

在transcation的writePendingAndCommit()方法中，把数据写入数据库

在这个函数中打开leveldb数据库

func openDB(dbPath string, network wire.BitcoinNet, create bool) (database.DB, error) {

　　

     transcation 的commit方法

   

   在writePendingAndCommit()中有写数据库

最后调用到这个函数