feat: load model from oci image

vendor/oras.land/oras-go/v2/internal/copyutil/stack.go

@@ -0,0 +1,55 @@
+/*
+Copyright The ORAS Authors.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package copyutil
+
+import (
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+)
+
+// NodeInfo represents information of a node that is being visited in
+// ExtendedCopy.
+type NodeInfo struct {
+	// Node represents a node in the graph.
+	Node ocispec.Descriptor
+	// Depth represents the depth of the node in the graph.
+	Depth int
+}
+
+// Stack represents a stack data structure that is used in ExtendedCopy for
+// storing node information.
+type Stack []NodeInfo
+
+// IsEmpty returns true if the stack is empty, otherwise returns false.
+func (s *Stack) IsEmpty() bool {
+	return len(*s) == 0
+}
+
+// Push pushes an item to the stack.
+func (s *Stack) Push(i NodeInfo) {
+	*s = append(*s, i)
+}
+
+// Pop pops the top item out of the stack.
+func (s *Stack) Pop() (NodeInfo, bool) {
+	if s.IsEmpty() {
+		return NodeInfo{}, false
+	}
+
+	last := len(*s) - 1
+	top := (*s)[last]
+	*s = (*s)[:last]
+	return top, true
+}