Release v0.3.0

vendor/github.com/btcsuite/btcwallet/walletdb/interface.go

@@ -7,7 +7,10 @@
 
 package walletdb
 
-import "io"
+import (
+	"fmt"
+	"io"
+)
 
 // ReadTx represents a database transaction that can only be used for reads.  If
 // a database update must occur, use a ReadWriteTx.
@@ -126,6 +129,16 @@ type ReadWriteBucket interface {
 
 	// Tx returns the bucket's transaction.
 	Tx() ReadWriteTx
+
+	// NextSequence returns an autoincrementing integer for the bucket.
+	NextSequence() (uint64, error)
+
+	// SetSequence updates the sequence number for the bucket.
+	SetSequence(v uint64) error
+
+	// Sequence returns the current integer for the bucket without
+	// incrementing it.
+	Sequence() uint64
 }
 
 // ReadCursor represents a bucket cursor that can be positioned at the start or
@@ -191,6 +204,18 @@ type DB interface {
 	Close() error
 }
 
+// BatchDB is a special version of the main DB interface that allos the caller
+// to specify write transactions that should be combine dtoegether if multiple
+// goroutines are calling the Batch method.
+type BatchDB interface {
+	DB
+
+	// Batch is similar to the package-level Update method, but it will
+	// attempt to optismitcally combine the invocation of several
+	// transaction functions into a single db write transaction.
+	Batch(func(tx ReadWriteTx) error) error
+}
+
 // View opens a database read transaction and executes the function f with the
 // transaction passed as a parameter.  After f exits, the transaction is rolled
 // back.  If f errors, its error is returned, not a rollback error (if any
@@ -200,11 +225,20 @@ func View(db DB, f func(tx ReadTx) error) error {
 	if err != nil {
 		return err
 	}
+
+	// Make sure the transaction rolls back in the event of a panic.
+	defer func() {
+		if tx != nil {
+			tx.Rollback()
+		}
+	}()
+
 	err = f(tx)
 	rollbackErr := tx.Rollback()
 	if err != nil {
 		return err
 	}
+
 	if rollbackErr != nil {
 		return rollbackErr
 	}
@@ -222,6 +256,14 @@ func Update(db DB, f func(tx ReadWriteTx) error) error {
 	if err != nil {
 		return err
 	}
+
+	// Make sure the transaction rolls back in the event of a panic.
+	defer func() {
+		if tx != nil {
+			tx.Rollback()
+		}
+	}()
+
 	err = f(tx)
 	if err != nil {
 		// Want to return the original error, not a rollback error if
@@ -229,9 +271,27 @@ func Update(db DB, f func(tx ReadWriteTx) error) error {
 		_ = tx.Rollback()
 		return err
 	}
+
 	return tx.Commit()
 }
 
+// Batch opens a database read/write transaction and executes the function f
+// with the transaction passed as a parameter.  After f exits, if f did not
+// error, the transaction is committed.  Otherwise, if f did error, the
+// transaction is rolled back.  If the rollback fails, the original error
+// returned by f is still returned.  If the commit fails, the commit error is
+// returned.
+//
+// Batch is only useful when there are multiple goroutines calling it.
+func Batch(db DB, f func(tx ReadWriteTx) error) error {
+	batchDB, ok := db.(BatchDB)
+	if !ok {
+		return fmt.Errorf("need batch")
+	}
+
+	return batchDB.Batch(f)
+}
+
 // Driver defines a structure for backend drivers to use when they registered
 // themselves as a backend which implements the Db interface.
 type Driver struct {