kvdb: move channeldb/kvdb to top level

kvdb/etcd/readwrite_cursor.go

@@ -0,0 +1,143 @@
+// +build kvdb_etcd
+
+package etcd
+
+// readWriteCursor holds a reference to the cursors bucket, the value
+// prefix and the current key used while iterating.
+type readWriteCursor struct {
+	// bucket holds the reference to the parent bucket.
+	bucket *readWriteBucket
+
+	// prefix holds the value prefix which is in front of each
+	// value key in the bucket.
+	prefix string
+
+	// currKey holds the current key of the cursor.
+	currKey string
+}
+
+func newReadWriteCursor(bucket *readWriteBucket) *readWriteCursor {
+	return &readWriteCursor{
+		bucket: bucket,
+		prefix: string(bucket.id),
+	}
+}
+
+// First positions the cursor at the first key/value pair and returns
+// the pair.
+func (c *readWriteCursor) First() (key, value []byte) {
+	// Get the first key with the value prefix.
+	kv, err := c.bucket.tx.stm.First(c.prefix)
+	if err != nil {
+		// TODO: revise this once kvdb interface supports errors
+		return nil, nil
+	}
+
+	if kv != nil {
+		c.currKey = kv.key
+		return getKeyVal(kv)
+	}
+
+	return nil, nil
+}
+
+// Last positions the cursor at the last key/value pair and returns the
+// pair.
+func (c *readWriteCursor) Last() (key, value []byte) {
+	kv, err := c.bucket.tx.stm.Last(c.prefix)
+	if err != nil {
+		// TODO: revise this once kvdb interface supports errors
+		return nil, nil
+	}
+
+	if kv != nil {
+		c.currKey = kv.key
+		return getKeyVal(kv)
+	}
+
+	return nil, nil
+}
+
+// Next moves the cursor one key/value pair forward and returns the new
+// pair.
+func (c *readWriteCursor) Next() (key, value []byte) {
+	kv, err := c.bucket.tx.stm.Next(c.prefix, c.currKey)
+	if err != nil {
+		// TODO: revise this once kvdb interface supports errors
+		return nil, nil
+	}
+
+	if kv != nil {
+		c.currKey = kv.key
+		return getKeyVal(kv)
+	}
+
+	return nil, nil
+}
+
+// Prev moves the cursor one key/value pair backward and returns the new
+// pair.
+func (c *readWriteCursor) Prev() (key, value []byte) {
+	kv, err := c.bucket.tx.stm.Prev(c.prefix, c.currKey)
+	if err != nil {
+		// TODO: revise this once kvdb interface supports errors
+		return nil, nil
+	}
+
+	if kv != nil {
+		c.currKey = kv.key
+		return getKeyVal(kv)
+	}
+
+	return nil, nil
+}
+
+// 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.
+func (c *readWriteCursor) Seek(seek []byte) (key, value []byte) {
+	// Return nil if trying to seek to an empty key.
+	if seek == nil {
+		return nil, nil
+	}
+
+	// Seek to the first key with prefix + seek. If that key is not present
+	// STM will seek to the next matching key with prefix.
+	kv, err := c.bucket.tx.stm.Seek(c.prefix, c.prefix+string(seek))
+	if err != nil {
+		// TODO: revise this once kvdb interface supports errors
+		return nil, nil
+	}
+
+	if kv != nil {
+		c.currKey = kv.key
+		return getKeyVal(kv)
+	}
+
+	return nil, nil
+}
+
+// Delete removes the current key/value pair the cursor is at without
+// invalidating the cursor.  Returns ErrIncompatibleValue if attempted
+// when the cursor points to a nested bucket.
+func (c *readWriteCursor) Delete() error {
+	// Get the next key after the current one. We could do this
+	// after deletion too but it's one step more efficient here.
+	nextKey, err := c.bucket.tx.stm.Next(c.prefix, c.currKey)
+	if err != nil {
+		return err
+	}
+
+	if isBucketKey(c.currKey) {
+		c.bucket.DeleteNestedBucket(getKey(c.currKey))
+	} else {
+		c.bucket.Delete(getKey(c.currKey))
+	}
+
+	if nextKey != nil {
+		// Set current key to the next one.
+		c.currKey = nextKey.key
+	}
+
+	return nil
+}