From 66efa425bf8b2d88b7a3b7ef1d1805e1cea0c023 Mon Sep 17 00:00:00 2001
From: Alexander Neumann <alexander@bumpern.de>
Date: Sun, 24 Mar 2019 22:12:38 +0100
Subject: [PATCH] Reuse buffer in worker functions

---
 internal/checker/checker.go       |  7 +++++--
 internal/repository/index.go      | 12 ++++++------
 internal/repository/repository.go | 15 +++++++++------
 3 files changed, 20 insertions(+), 14 deletions(-)

diff --git a/internal/checker/checker.go b/internal/checker/checker.go
index 79b3cb4b9..c5bee4bef 100644
--- a/internal/checker/checker.go
+++ b/internal/checker/checker.go
@@ -108,14 +108,17 @@ func (c *Checker) LoadIndex(ctx context.Context) (hints []error, errs []error) {
 
 	// 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())
-			idx, err := repository.LoadIndexWithDecoder(ctx, c.repo, fi.ID, repository.DecodeIndex)
+			var err error
+			var idx *repository.Index
+			idx, buf, err = repository.LoadIndexWithDecoder(ctx, c.repo, buf[:0], fi.ID, repository.DecodeIndex)
 			if errors.Cause(err) == repository.ErrOldIndexFormat {
 				debug.Log("index %v has old format", fi.ID.Str())
 				hints = append(hints, ErrOldIndexFormat{fi.ID})
 
-				idx, err = repository.LoadIndexWithDecoder(ctx, c.repo, fi.ID, repository.DecodeOldIndex)
+				idx, buf, err = repository.LoadIndexWithDecoder(ctx, c.repo, buf[:0], fi.ID, repository.DecodeOldIndex)
 			}
 
 			err = errors.Wrapf(err, "error loading index %v", fi.ID.Str())
diff --git a/internal/repository/index.go b/internal/repository/index.go
index ef6661dfc..32d00882a 100644
--- a/internal/repository/index.go
+++ b/internal/repository/index.go
@@ -549,21 +549,21 @@ func DecodeOldIndex(buf []byte) (idx *Index, err error) {
 }
 
 // LoadIndexWithDecoder loads the index and decodes it with fn.
-func LoadIndexWithDecoder(ctx context.Context, repo restic.Repository, id restic.ID, fn func([]byte) (*Index, error)) (idx *Index, err error) {
+func LoadIndexWithDecoder(ctx context.Context, repo restic.Repository, buf []byte, id restic.ID, fn func([]byte) (*Index, error)) (*Index, []byte, error) {
 	debug.Log("Loading index %v", id)
 
-	buf, err := repo.LoadAndDecrypt(ctx, nil, restic.IndexFile, id)
+	buf, err := repo.LoadAndDecrypt(ctx, buf[:0], restic.IndexFile, id)
 	if err != nil {
-		return nil, err
+		return nil, buf[:0], err
 	}
 
-	idx, err = fn(buf)
+	idx, err := fn(buf)
 	if err != nil {
 		debug.Log("error while decoding index %v: %v", id, err)
-		return nil, err
+		return nil, buf[:0], err
 	}
 
 	idx.id = id
 
-	return idx, nil
+	return idx, buf, nil
 }
diff --git a/internal/repository/repository.go b/internal/repository/repository.go
index 6ab8ca595..cb78c25c1 100644
--- a/internal/repository/repository.go
+++ b/internal/repository/repository.go
@@ -431,11 +431,13 @@ func (r *Repository) LoadIndex(ctx context.Context) error {
 
 	// 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 {
-			idx, err := LoadIndex(ctx, r, fi.ID)
-			if err != nil {
-				fmt.Fprintf(os.Stderr, "%v, ignoring\n", err)
-				return nil
+			var err error
+			var idx *Index
+			idx, buf, err = LoadIndexWithDecoder(ctx, r, buf[:0], fi.ID, DecodeIndex)
+			if err != nil && errors.Cause(err) == ErrOldIndexFormat {
+				idx, buf, err = LoadIndexWithDecoder(ctx, r, buf[:0], fi.ID, DecodeOldIndex)
 			}
 
 			select {
@@ -548,14 +550,15 @@ func (r *Repository) PrepareCache(indexIDs restic.IDSet) error {
 
 // LoadIndex loads the index id from backend and returns it.
 func LoadIndex(ctx context.Context, repo restic.Repository, id restic.ID) (*Index, error) {
-	idx, err := LoadIndexWithDecoder(ctx, repo, id, DecodeIndex)
+	idx, _, err := LoadIndexWithDecoder(ctx, repo, nil, id, DecodeIndex)
 	if err == nil {
 		return idx, nil
 	}
 
 	if errors.Cause(err) == ErrOldIndexFormat {
 		fmt.Fprintf(os.Stderr, "index %v has old format\n", id.Str())
-		return LoadIndexWithDecoder(ctx, repo, id, DecodeOldIndex)
+		idx, _, err := LoadIndexWithDecoder(ctx, repo, nil, id, DecodeOldIndex)
+		return idx, err
 	}
 
 	return nil, err