data: split node and snapshot code from restic package

internal/data/find.go

@@ -0,0 +1,49 @@
+package data
+
+import (
+	"context"
+	"sync"
+
+	"github.com/restic/restic/internal/restic"
+	"github.com/restic/restic/internal/ui/progress"
+	"golang.org/x/sync/errgroup"
+)
+
+// FindUsedBlobs traverses the tree ID and adds all seen blobs (trees and data
+// blobs) to the set blobs. Already seen tree blobs will not be visited again.
+func FindUsedBlobs(ctx context.Context, repo restic.Loader, treeIDs restic.IDs, blobs restic.FindBlobSet, p *progress.Counter) error {
+	var lock sync.Mutex
+
+	wg, ctx := errgroup.WithContext(ctx)
+	treeStream := StreamTrees(ctx, wg, repo, treeIDs, func(treeID restic.ID) bool {
+		// locking is necessary the goroutine below concurrently adds data blobs
+		lock.Lock()
+		h := restic.BlobHandle{ID: treeID, Type: restic.TreeBlob}
+		blobReferenced := blobs.Has(h)
+		// noop if already referenced
+		blobs.Insert(h)
+		lock.Unlock()
+		return blobReferenced
+	}, p)
+
+	wg.Go(func() error {
+		for tree := range treeStream {
+			if tree.Error != nil {
+				return tree.Error
+			}
+
+			lock.Lock()
+			for _, node := range tree.Nodes {
+				switch node.Type {
+				case NodeTypeFile:
+					for _, blob := range node.Content {
+						blobs.Insert(restic.BlobHandle{ID: blob, Type: restic.DataBlob})
+					}
+				}
+			}
+			lock.Unlock()
+		}
+		return nil
+	})
+	return wg.Wait()
+}