Add cursor functionality to walletdb.

walletdb/bdb/db.go

@@ -167,6 +167,76 @@ func (b *bucket) Delete(key []byte) error {
 	return convertErr((*bolt.Bucket)(b).Delete(key))
 }
 
+// Cursor returns a new cursor, allowing for iteration over the bucket's
+// key/value pairs and nested buckets in forward or backward order.
+//
+// This function is part of the walletdb.Bucket interface implementation.
+func (b *bucket) Cursor() walletdb.Cursor {
+	return (*cursor)((*bolt.Bucket)(b).Cursor())
+}
+
+// cursor represents a cursor over key/value pairs and nested buckets of a
+// bucket.
+//
+// Note that open cursors are not tracked on bucket changes and any
+// modifications to the bucket, with the exception of cursor.Delete, invalidate
+// the cursor. After invalidation, the cursor must be repositioned, or the keys
+// and values returned may be unpredictable.
+type cursor bolt.Cursor
+
+// Bucket returns the bucket the cursor was created for.
+//
+// This function is part of the walletdb.Cursor interface implementation.
+func (c *cursor) Bucket() walletdb.Bucket {
+	return (*bucket)((*bolt.Cursor)(c).Bucket())
+}
+
+// Delete removes the current key/value pair the cursor is at without
+// invalidating the cursor. Returns ErrTxNotWritable if attempted on a read-only
+// transaction, or ErrIncompatibleValue if attempted when the cursor points to a
+// nested bucket.
+//
+// This function is part of the walletdb.Cursor interface implementation.
+func (c *cursor) Delete() error {
+	return convertErr((*bolt.Cursor)(c).Delete())
+}
+
+// First positions the cursor at the first key/value pair and returns the pair.
+//
+// This function is part of the walletdb.Cursor interface implementation.
+func (c *cursor) First() (key, value []byte) {
+	return (*bolt.Cursor)(c).First()
+}
+
+// Last positions the cursor at the last key/value pair and returns the pair.
+//
+// This function is part of the walletdb.Cursor interface implementation.
+func (c *cursor) Last() (key, value []byte) {
+	return (*bolt.Cursor)(c).Last()
+}
+
+// Next moves the cursor one key/value pair forward and returns the new pair.
+//
+// This function is part of the walletdb.Cursor interface implementation.
+func (c *cursor) Next() (key, value []byte) {
+	return (*bolt.Cursor)(c).Next()
+}
+
+// Prev moves the cursor one key/value pair backward and returns the new pair.
+//
+// This function is part of the walletdb.Cursor interface implementation.
+func (c *cursor) Prev() (key, value []byte) {
+	return (*bolt.Cursor)(c).Prev()
+}
+
+// Seek positions the cursor at the passed seek key. If the key does not exist,
+// the cursor is moved to the next key after seek. Returns the new pair.
+//
+// This function is part of the walletdb.Cursor interface implementation.
+func (c *cursor) Seek(seek []byte) (key, value []byte) {
+	return (*bolt.Cursor)(c).Seek(seek)
+}
+
 // transaction represents a database transaction.  It can either by read-only or
 // read-write and implements the walletdb.Bucket interface.  The transaction
 // provides a root bucket against which all read and writes occur.

walletdb/interface.go

@@ -82,6 +82,49 @@ type Bucket interface {
 	// that does not exist does not return an error.  Returns
 	// ErrTxNotWritable if attempted against a read-only transaction.
 	Delete(key []byte) error
+
+	// Cursor returns a new cursor, allowing for iteration over the bucket's
+	// key/value pairs and nested buckets in forward or backward order.
+	Cursor() Cursor
+}
+
+// Cursor represents a cursor over key/value pairs and nested buckets of a
+// bucket.
+//
+// Note that open cursors are not tracked on bucket changes and any
+// modifications to the bucket, with the exception of Cursor.Delete, invalidate
+// the cursor.  After invalidation, the cursor must be repositioned, or the keys
+// and values returned may be unpredictable.
+type Cursor interface {
+	// Bucket returns the bucket the cursor was created for.
+	Bucket() Bucket
+
+	// Delete removes the current key/value pair the cursor is at without
+	// invalidating the cursor.  Returns ErrTxNotWritable if attempted on a
+	// read-only transaction, or ErrIncompatibleValue if attempted when the
+	// cursor points to a nested bucket.
+	Delete() error
+
+	// First positions the cursor at the first key/value pair and returns
+	// the pair.
+	First() (key, value []byte)
+
+	// Last positions the cursor at the last key/value pair and returns the
+	// pair.
+	Last() (key, value []byte)
+
+	// Next moves the cursor one key/value pair forward and returns the new
+	// pair.
+	Next() (key, value []byte)
+
+	// Prev moves the cursor one key/value pair backward and returns the new
+	// pair.
+	Prev() (key, value []byte)
+
+	// Seek positions the cursor at the passed seek key.  If the key does
+	// not exist, the cursor is moved to the next key after seek.  Returns
+	// the new pair.
+	Seek(seek []byte) (key, value []byte)
 }
 
 // Tx represents a database transaction.  It can either by read-only or