restic: Unify code to load Index/Lock/Snapshot

internal/index/index_parallel.go

@@ -5,9 +5,7 @@ import (
 	"runtime"
 	"sync"
 
-	"github.com/restic/restic/internal/debug"
 	"github.com/restic/restic/internal/restic"
-	"golang.org/x/sync/errgroup"
 )
 
 // ForAllIndexes loads all index files in parallel and calls the given callback.
@@ -16,68 +14,23 @@ import (
 func ForAllIndexes(ctx context.Context, repo restic.Repository,
 	fn func(id restic.ID, index *Index, oldFormat bool, err error) error) error {
 
-	debug.Log("Start")
-
-	type FileInfo struct {
-		restic.ID
-		Size int64
-	}
-
-	var m sync.Mutex
-
-	// track spawned goroutines using wg, create a new context which is
-	// cancelled as soon as an error occurs.
-	wg, ctx := errgroup.WithContext(ctx)
-
-	ch := make(chan FileInfo)
-	// send list of index files through ch, which is closed afterwards
-	wg.Go(func() error {
-		defer close(ch)
-		return repo.List(ctx, restic.IndexFile, func(id restic.ID, size int64) error {
-			select {
-			case <-ctx.Done():
-				return ctx.Err()
-			case ch <- FileInfo{id, size}:
-			}
-			return nil
-		})
-	})
-
-	// a worker receives an index ID from ch, loads the index, and sends it to indexCh
-	worker := func() error {
-		var buf []byte
-		for fi := range ch {
-			debug.Log("worker got file %v", fi.ID.Str())
-			var err error
-			var idx *Index
-			oldFormat := false
-
-			if cap(buf) < int(fi.Size) {
-				// overallocate a bit
-				buf = make([]byte, fi.Size+128*1024)
-			}
-			buf, err = repo.LoadUnpacked(ctx, restic.IndexFile, fi.ID, buf[:0])
-			if err == nil {
-				idx, oldFormat, err = DecodeIndex(buf, fi.ID)
-			}
-
-			m.Lock()
-			err = fn(fi.ID, idx, oldFormat, err)
-			m.Unlock()
-			if err != nil {
-				return err
-			}
-		}
-		return nil
-	}
-
 	// decoding an index can take quite some time such that this can be both CPU- or IO-bound
 	// as the whole index is kept in memory anyways, a few workers too much don't matter
-	workerCount := int(repo.Connections()) + runtime.GOMAXPROCS(0)
-	// run workers on ch
-	for i := 0; i < workerCount; i++ {
-		wg.Go(worker)
-	}
+	workerCount := repo.Connections() + uint(runtime.GOMAXPROCS(0))
 
-	return wg.Wait()
+	var m sync.Mutex
+	return restic.ParallelList(ctx, repo.Backend(), restic.IndexFile, workerCount, func(ctx context.Context, id restic.ID, size int64) error {
+		var err error
+		var idx *Index
+		oldFormat := false
+
+		buf, err := repo.LoadUnpacked(ctx, restic.IndexFile, id, nil)
+		if err == nil {
+			idx, oldFormat, err = DecodeIndex(buf, id)
+		}
+
+		m.Lock()
+		defer m.Unlock()
+		return fn(id, idx, oldFormat, err)
+	})
 }