kvdb: move channeldb/kvdb to top level

kvdb/etcd/readwrite_tx.go

@@ -0,0 +1,99 @@
+// +build kvdb_etcd
+
+package etcd
+
+import (
+	"github.com/btcsuite/btcwallet/walletdb"
+)
+
+// readWriteTx holds a reference to the STM transaction.
+type readWriteTx struct {
+	// stm is the reference to the parent STM.
+	stm STM
+
+	// rootBucketID holds the sha256 hash of the root bucket id, which is used
+	// for key space spearation.
+	rootBucketID [bucketIDLength]byte
+
+	// active is true if the transaction hasn't been committed yet.
+	active bool
+}
+
+// newReadWriteTx creates an rw transaction with the passed STM.
+func newReadWriteTx(stm STM, prefix string) *readWriteTx {
+	return &readWriteTx{
+		stm:          stm,
+		active:       true,
+		rootBucketID: makeBucketID([]byte(prefix)),
+	}
+}
+
+// rooBucket is a helper function to return the always present
+// pseudo root bucket.
+func rootBucket(tx *readWriteTx) *readWriteBucket {
+	return newReadWriteBucket(tx, tx.rootBucketID[:], tx.rootBucketID[:])
+}
+
+// ReadBucket opens the root bucket for read only access.  If the bucket
+// described by the key does not exist, nil is returned.
+func (tx *readWriteTx) ReadBucket(key []byte) walletdb.ReadBucket {
+	return rootBucket(tx).NestedReadWriteBucket(key)
+}
+
+// Rollback closes the transaction, discarding changes (if any) if the
+// database was modified by a write transaction.
+func (tx *readWriteTx) Rollback() error {
+	// If the transaction has been closed roolback will fail.
+	if !tx.active {
+		return walletdb.ErrTxClosed
+	}
+
+	// Rollback the STM and set the tx to inactive.
+	tx.stm.Rollback()
+	tx.active = false
+
+	return nil
+}
+
+// ReadWriteBucket opens the root bucket for read/write access.  If the
+// bucket described by the key does not exist, nil is returned.
+func (tx *readWriteTx) ReadWriteBucket(key []byte) walletdb.ReadWriteBucket {
+	return rootBucket(tx).NestedReadWriteBucket(key)
+}
+
+// CreateTopLevelBucket creates the top level bucket for a key if it
+// does not exist.  The newly-created bucket it returned.
+func (tx *readWriteTx) CreateTopLevelBucket(key []byte) (walletdb.ReadWriteBucket, error) {
+	return rootBucket(tx).CreateBucketIfNotExists(key)
+}
+
+// DeleteTopLevelBucket deletes the top level bucket for a key.  This
+// errors if the bucket can not be found or the key keys a single value
+// instead of a bucket.
+func (tx *readWriteTx) DeleteTopLevelBucket(key []byte) error {
+	return rootBucket(tx).DeleteNestedBucket(key)
+}
+
+// Commit commits the transaction if not already committed. Will return
+// error if the underlying STM fails.
+func (tx *readWriteTx) Commit() error {
+	// Commit will fail if the transaction is already committed.
+	if !tx.active {
+		return walletdb.ErrTxClosed
+	}
+
+	// Try committing the transaction.
+	if err := tx.stm.Commit(); err != nil {
+		return err
+	}
+
+	// Mark the transaction as not active after commit.
+	tx.active = false
+
+	return nil
+}
+
+// OnCommit sets the commit callback (overriding if already set).
+func (tx *readWriteTx) OnCommit(cb func()) {
+	tx.stm.OnCommit(cb)
+}