src/dedo.go: Introduce snapshotT type

1 files changed, 31 insertions, 0 deletions

diff --git a/src/dedo.go b/src/dedo.go
index 2bb805e..580e6a6 100644
--- a/src/dedo.go
+++ b/src/dedo.go
@@ -91,6 +91,13 @@ type DatabaseI interface{
 	Path() string
 }
 
+type snapshotT struct{
+	db    *DB
+	meta  *meta
+	root  roBucketT
+	pages map[pgid]*page
+}
+
 /// transactionT represents a read-only or read/write transaction on the
 /// database.  Read-only transactions can be used for retrieving values for keys
 /// and creating cursors.  Read/write transactions can create and remove buckets
@@ -582,6 +589,16 @@ func newBucket(tx *transactionT) Bucket {
 	return b
 }
 
+/// newBucket() returns a new bucket associated with a transaction.
+func newSnapshotBucket(snapshot *snapshotT) Bucket {
+	return Bucket{tx: &transactionT{
+		db:       snapshot.db,
+		meta:     snapshot.meta,
+		root:     snapshot.root,
+		pages:    snapshot.pages,
+	}}
+}
+
 /// Bucket.Cursor() creates a cursor associated with the bucket.  The cursor is
 /// only valid as long as the transaction is open.  Do not use a cursor after
 /// the transaction is closed.
@@ -3458,6 +3475,20 @@ func mergepgids(dst, a, b pgids) {
 	_ = append(merged, follow...)
 }
 
+func (snapshot *snapshotT) init(db *DB) {
+	snapshot.db = db
+	snapshot.pages = nil
+
+	// Copy the meta page since it can be changed by the writer.
+	snapshot.meta = &meta{}
+	db.meta().copy(snapshot.meta)
+
+	// Copy over the root bucket.
+	snapshot.root = newSnapshotBucket(snapshot)
+	snapshot.root.ref = &bucket{}
+	*snapshot.root.ref = snapshot.meta.root
+}
+
 /// transactionT.init() initializes the transaction.
 func (tx *transactionT) init(db *DB) {
 	tx.db = db