feat: load model from oci image

vendor/oras.land/oras-go/v2/internal/graph/memory.go

@@ -0,0 +1,134 @@
+/*
+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 graph
+
+import (
+	"context"
+	"errors"
+	"sync"
+
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+	"oras.land/oras-go/v2/content"
+	"oras.land/oras-go/v2/errdef"
+	"oras.land/oras-go/v2/internal/descriptor"
+	"oras.land/oras-go/v2/internal/status"
+	"oras.land/oras-go/v2/internal/syncutil"
+)
+
+// Memory is a memory based PredecessorFinder.
+type Memory struct {
+	predecessors sync.Map // map[descriptor.Descriptor]map[descriptor.Descriptor]ocispec.Descriptor
+	indexed      sync.Map // map[descriptor.Descriptor]any
+}
+
+// NewMemory creates a new memory PredecessorFinder.
+func NewMemory() *Memory {
+	return &Memory{}
+}
+
+// Index indexes predecessors for each direct successor of the given node.
+// There is no data consistency issue as long as deletion is not implemented
+// for the underlying storage.
+func (m *Memory) Index(ctx context.Context, fetcher content.Fetcher, node ocispec.Descriptor) error {
+	successors, err := content.Successors(ctx, fetcher, node)
+	if err != nil {
+		return err
+	}
+
+	m.index(ctx, node, successors)
+	return nil
+}
+
+// Index indexes predecessors for all the successors of the given node.
+// There is no data consistency issue as long as deletion is not implemented
+// for the underlying storage.
+func (m *Memory) IndexAll(ctx context.Context, fetcher content.Fetcher, node ocispec.Descriptor) error {
+	// track content status
+	tracker := status.NewTracker()
+
+	var fn syncutil.GoFunc[ocispec.Descriptor]
+	fn = func(ctx context.Context, region *syncutil.LimitedRegion, desc ocispec.Descriptor) error {
+		// skip the node if other go routine is working on it
+		_, committed := tracker.TryCommit(desc)
+		if !committed {
+			return nil
+		}
+
+		// skip the node if it has been indexed
+		key := descriptor.FromOCI(desc)
+		_, exists := m.indexed.Load(key)
+		if exists {
+			return nil
+		}
+
+		successors, err := content.Successors(ctx, fetcher, desc)
+		if err != nil {
+			if errors.Is(err, errdef.ErrNotFound) {
+				// skip the node if it does not exist
+				return nil
+			}
+			return err
+		}
+		m.index(ctx, desc, successors)
+		m.indexed.Store(key, nil)
+
+		if len(successors) > 0 {
+			// traverse and index successors
+			return syncutil.Go(ctx, nil, fn, successors...)
+		}
+		return nil
+	}
+	return syncutil.Go(ctx, nil, fn, node)
+}
+
+// Predecessors returns the nodes directly pointing to the current node.
+// Predecessors returns nil without error if the node does not exists in the
+// store.
+// Like other operations, calling Predecessors() is go-routine safe. However,
+// it does not necessarily correspond to any consistent snapshot of the stored
+// contents.
+func (m *Memory) Predecessors(_ context.Context, node ocispec.Descriptor) ([]ocispec.Descriptor, error) {
+	key := descriptor.FromOCI(node)
+	value, exists := m.predecessors.Load(key)
+	if !exists {
+		return nil, nil
+	}
+	predecessors := value.(*sync.Map)
+
+	var res []ocispec.Descriptor
+	predecessors.Range(func(key, value interface{}) bool {
+		res = append(res, value.(ocispec.Descriptor))
+		return true
+	})
+	return res, nil
+}
+
+// index indexes predecessors for each direct successor of the given node.
+// There is no data consistency issue as long as deletion is not implemented
+// for the underlying storage.
+func (m *Memory) index(ctx context.Context, node ocispec.Descriptor, successors []ocispec.Descriptor) {
+	if len(successors) == 0 {
+		return
+	}
+
+	predecessorKey := descriptor.FromOCI(node)
+	for _, successor := range successors {
+		successorKey := descriptor.FromOCI(successor)
+		value, _ := m.predecessors.LoadOrStore(successorKey, &sync.Map{})
+		predecessors := value.(*sync.Map)
+		predecessors.Store(predecessorKey, node)
+	}
+}