Add []byte to repo.LoadAndDecrypt and utils.LoadAll

This commit changes the signatures for repository.LoadAndDecrypt and
utils.LoadAll to allow passing in a []byte as the buffer to use. This
buffer is enlarged as needed, and returned back to the caller for
further use.

In later commits, this allows reducing allocations by reusing a buffer
for multiple calls, e.g. in a worker function.

cmd/restic/cmd_cat.go

@@ -74,7 +74,7 @@ func runCat(gopts GlobalOptions, args []string) error {
 		fmt.Println(string(buf))
 		return nil
 	case "index":
-		buf, err := repo.LoadAndDecrypt(gopts.ctx, restic.IndexFile, id)
+		buf, err := repo.LoadAndDecrypt(gopts.ctx, nil, restic.IndexFile, id)
 		if err != nil {
 			return err
 		}
@@ -99,7 +99,7 @@ func runCat(gopts GlobalOptions, args []string) error {
 		return nil
 	case "key":
 		h := restic.Handle{Type: restic.KeyFile, Name: id.String()}
-		buf, err := backend.LoadAll(gopts.ctx, repo.Backend(), h)
+		buf, err := backend.LoadAll(gopts.ctx, nil, repo.Backend(), h)
 		if err != nil {
 			return err
 		}
@@ -150,7 +150,7 @@ func runCat(gopts GlobalOptions, args []string) error {
 	switch tpe {
 	case "pack":
 		h := restic.Handle{Type: restic.DataFile, Name: id.String()}
-		buf, err := backend.LoadAll(gopts.ctx, repo.Backend(), h)
+		buf, err := backend.LoadAll(gopts.ctx, nil, repo.Backend(), h)
 		if err != nil {
 			return err
 		}

internal/backend/test/tests.go

@@ -79,7 +79,7 @@ func (s *Suite) TestConfig(t *testing.T) {
 	var testString = "Config"
 
 	// create config and read it back
-	_, err := backend.LoadAll(context.TODO(), b, restic.Handle{Type: restic.ConfigFile})
+	_, err := backend.LoadAll(context.TODO(), nil, b, restic.Handle{Type: restic.ConfigFile})
 	if err == nil {
 		t.Fatalf("did not get expected error for non-existing config")
 	}
@@ -93,7 +93,7 @@ func (s *Suite) TestConfig(t *testing.T) {
 	// same config
 	for _, name := range []string{"", "foo", "bar", "0000000000000000000000000000000000000000000000000000000000000000"} {
 		h := restic.Handle{Type: restic.ConfigFile, Name: name}
-		buf, err := backend.LoadAll(context.TODO(), b, h)
+		buf, err := backend.LoadAll(context.TODO(), nil, b, h)
 		if err != nil {
 			t.Fatalf("unable to read config with name %q: %+v", name, err)
 		}
@@ -491,7 +491,7 @@ func (s *Suite) TestSave(t *testing.T) {
 		err := b.Save(context.TODO(), h, restic.NewByteReader(data))
 		test.OK(t, err)
 
-		buf, err := backend.LoadAll(context.TODO(), b, h)
+		buf, err := backend.LoadAll(context.TODO(), nil, b, h)
 		test.OK(t, err)
 		if len(buf) != len(data) {
 			t.Fatalf("number of bytes does not match, want %v, got %v", len(data), len(buf))
@@ -584,7 +584,7 @@ func (s *Suite) TestSaveFilenames(t *testing.T) {
 			continue
 		}
 
-		buf, err := backend.LoadAll(context.TODO(), b, h)
+		buf, err := backend.LoadAll(context.TODO(), nil, b, h)
 		if err != nil {
 			t.Errorf("test %d failed: Load() returned %+v", i, err)
 			continue
@@ -734,7 +734,7 @@ func (s *Suite) TestBackend(t *testing.T) {
 
 			// test Load()
 			h := restic.Handle{Type: tpe, Name: ts.id}
-			buf, err := backend.LoadAll(context.TODO(), b, h)
+			buf, err := backend.LoadAll(context.TODO(), nil, b, h)
 			test.OK(t, err)
 			test.Equals(t, ts.data, string(buf))
 

internal/backend/utils.go

@@ -1,20 +1,33 @@
 package backend
 
 import (
+	"bytes"
 	"context"
 	"io"
-	"io/ioutil"
 
 	"github.com/restic/restic/internal/restic"
 )
 
-// LoadAll reads all data stored in the backend for the handle.
+// LoadAll reads all data stored in the backend for the handle into the given
-func LoadAll(ctx context.Context, be restic.Backend, h restic.Handle) (buf []byte, err error) {
+// buffer, which is truncated. If the buffer is not large enough or nil, a new
-	err = be.Load(ctx, h, 0, 0, func(rd io.Reader) (ierr error) {
+// one is allocated.
-		buf, ierr = ioutil.ReadAll(rd)
+func LoadAll(ctx context.Context, buf []byte, be restic.Backend, h restic.Handle) ([]byte, error) {
-		return ierr
+	err := be.Load(ctx, h, 0, 0, func(rd io.Reader) error {
+		// make sure this is idempotent, in case an error occurs this function may be called multiple times!
+		wr := bytes.NewBuffer(buf[:0])
+		_, cerr := io.Copy(wr, rd)
+		if cerr != nil {
+			return cerr
+		}
+		buf = wr.Bytes()
+		return nil
 	})
-	return buf, err
+
+	if err != nil {
+		return nil, err
+	}
+
+	return buf, nil
 }
 
 // LimitedReadCloser wraps io.LimitedReader and exposes the Close() method.

internal/backend/utils_test.go

@@ -19,6 +19,7 @@ const MiB = 1 << 20
 
 func TestLoadAll(t *testing.T) {
 	b := mem.New()
+	var buf []byte
 
 	for i := 0; i < 20; i++ {
 		data := rtest.Random(23+i, rand.Intn(MiB)+500*KiB)
@@ -28,7 +29,7 @@ func TestLoadAll(t *testing.T) {
 		err := b.Save(context.TODO(), h, restic.NewByteReader(data))
 		rtest.OK(t, err)
 
-		buf, err := backend.LoadAll(context.TODO(), b, restic.Handle{Type: restic.DataFile, Name: id.String()})
+		buf, err := backend.LoadAll(context.TODO(), buf, b, restic.Handle{Type: restic.DataFile, Name: id.String()})
 		rtest.OK(t, err)
 
 		if len(buf) != len(data) {
@@ -43,55 +44,66 @@ func TestLoadAll(t *testing.T) {
 	}
 }
 
-func TestLoadSmallBuffer(t *testing.T) {
+func save(t testing.TB, be restic.Backend, buf []byte) restic.Handle {
+	id := restic.Hash(buf)
+	h := restic.Handle{Name: id.String(), Type: restic.DataFile}
+	err := be.Save(context.TODO(), h, restic.NewByteReader(buf))
+	if err != nil {
+		t.Fatal(err)
+	}
+	return h
+}
+
+func TestLoadAllAppend(t *testing.T) {
 	b := mem.New()
 
-	for i := 0; i < 20; i++ {
+	h1 := save(t, b, []byte("foobar test string"))
-		data := rtest.Random(23+i, rand.Intn(MiB)+500*KiB)
+	randomData := rtest.Random(23, rand.Intn(MiB)+500*KiB)
+	h2 := save(t, b, randomData)
 
-		id := restic.Hash(data)
+	var tests = []struct {
-		h := restic.Handle{Name: id.String(), Type: restic.DataFile}
+		handle restic.Handle
-		err := b.Save(context.TODO(), h, restic.NewByteReader(data))
+		buf    []byte
-		rtest.OK(t, err)
+		want   []byte
-
+	}{
-		buf, err := backend.LoadAll(context.TODO(), b, restic.Handle{Type: restic.DataFile, Name: id.String()})
+		{
-		rtest.OK(t, err)
+			handle: h1,
-
+			buf:    nil,
-		if len(buf) != len(data) {
+			want:   []byte("foobar test string"),
-			t.Errorf("length of returned buffer does not match, want %d, got %d", len(data), len(buf))
+		},
-			continue
+		{
+			handle: h1,
+			buf:    []byte("xxx"),
+			want:   []byte("foobar test string"),
+		},
+		{
+			handle: h2,
+			buf:    nil,
+			want:   randomData,
+		},
+		{
+			handle: h2,
+			buf:    make([]byte, 0, 200),
+			want:   randomData,
+		},
+		{
+			handle: h2,
+			buf:    []byte("foobarbaz"),
+			want:   randomData,
+		},
 	}
 
-		if !bytes.Equal(buf, data) {
+	for _, test := range tests {
-			t.Errorf("wrong data returned")
+		t.Run("", func(t *testing.T) {
-			continue
+			buf, err := backend.LoadAll(context.TODO(), test.buf, b, test.handle)
-		}
+			if err != nil {
-	}
+				t.Fatal(err)
 			}
 
-func TestLoadLargeBuffer(t *testing.T) {
+			if !bytes.Equal(buf, test.want) {
-	b := mem.New()
+				t.Errorf("wrong data returned, want %q, got %q", test.want, buf)
-
-	for i := 0; i < 20; i++ {
-		data := rtest.Random(23+i, rand.Intn(MiB)+500*KiB)
-
-		id := restic.Hash(data)
-		h := restic.Handle{Name: id.String(), Type: restic.DataFile}
-		err := b.Save(context.TODO(), h, restic.NewByteReader(data))
-		rtest.OK(t, err)
-
-		buf, err := backend.LoadAll(context.TODO(), b, restic.Handle{Type: restic.DataFile, Name: id.String()})
-		rtest.OK(t, err)
-
-		if len(buf) != len(data) {
-			t.Errorf("length of returned buffer does not match, want %d, got %d", len(data), len(buf))
-			continue
-		}
-
-		if !bytes.Equal(buf, data) {
-			t.Errorf("wrong data returned")
-			continue
 			}
+		})
 	}
 }
 

internal/cache/backend_test.go

@@ -17,7 +17,7 @@ import (
 )
 
 func loadAndCompare(t testing.TB, be restic.Backend, h restic.Handle, data []byte) {
-	buf, err := backend.LoadAll(context.TODO(), be, h)
+	buf, err := backend.LoadAll(context.TODO(), nil, be, h)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -147,7 +147,7 @@ func TestErrorBackend(t *testing.T) {
 	loadTest := func(wg *sync.WaitGroup, be restic.Backend) {
 		defer wg.Done()
 
-		buf, err := backend.LoadAll(context.TODO(), be, h)
+		buf, err := backend.LoadAll(context.TODO(), nil, be, h)
 		if err == testErr {
 			return
 		}

internal/repository/index.go

@@ -552,7 +552,7 @@ func DecodeOldIndex(buf []byte) (idx *Index, err error) {
 func LoadIndexWithDecoder(ctx context.Context, repo restic.Repository, id restic.ID, fn func([]byte) (*Index, error)) (idx *Index, err error) {
 	debug.Log("Loading index %v", id)
 
-	buf, err := repo.LoadAndDecrypt(ctx, restic.IndexFile, id)
+	buf, err := repo.LoadAndDecrypt(ctx, nil, restic.IndexFile, id)
 	if err != nil {
 		return nil, err
 	}

internal/repository/key.go

@@ -184,7 +184,7 @@ func SearchKey(ctx context.Context, s *Repository, password string, maxKeys int,
 // LoadKey loads a key from the backend.
 func LoadKey(ctx context.Context, s *Repository, name string) (k *Key, err error) {
 	h := restic.Handle{Type: restic.KeyFile, Name: name}
-	data, err := backend.LoadAll(ctx, s.be, h)
+	data, err := backend.LoadAll(ctx, nil, s.be, h)
 	if err != nil {
 		return nil, err
 	}

internal/repository/repository.go

@@ -9,7 +9,6 @@ import (
 	"io"
 	"os"
 
-	"github.com/restic/restic/internal/backend"
 	"github.com/restic/restic/internal/cache"
 	"github.com/restic/restic/internal/crypto"
 	"github.com/restic/restic/internal/debug"
@@ -67,15 +66,29 @@ func (r *Repository) PrefixLength(t restic.FileType) (int, error) {
 	return restic.PrefixLength(r.be, t)
 }
 
-// LoadAndDecrypt loads and decrypts data identified by t and id from the
+// LoadAndDecrypt loads and decrypts the file with the given type and ID, using
-// backend.
+// the supplied buffer (which must be empty). If the buffer is nil, a new
-func (r *Repository) LoadAndDecrypt(ctx context.Context, t restic.FileType, id restic.ID) (buf []byte, err error) {
+// buffer will be allocated and returned.
+func (r *Repository) LoadAndDecrypt(ctx context.Context, buf []byte, t restic.FileType, id restic.ID) ([]byte, error) {
+	if len(buf) != 0 {
+		panic("buf is not empty")
+	}
+
 	debug.Log("load %v with id %v", t, id)
 
 	h := restic.Handle{Type: t, Name: id.String()}
-	buf, err = backend.LoadAll(ctx, r.be, h)
+	err := r.be.Load(ctx, h, 0, 0, func(rd io.Reader) error {
+		// make sure this call is idempotent, in case an error occurs
+		wr := bytes.NewBuffer(buf[:0])
+		_, cerr := io.Copy(wr, rd)
+		if cerr != nil {
+			return cerr
+		}
+		buf = wr.Bytes()
+		return nil
+	})
+
 	if err != nil {
-		debug.Log("error loading %v: %v", h, err)
 		return nil, err
 	}
 
@@ -188,7 +201,7 @@ func (r *Repository) loadBlob(ctx context.Context, id restic.ID, t restic.BlobTy
 // LoadJSONUnpacked decrypts the data and afterwards calls json.Unmarshal on
 // the item.
 func (r *Repository) LoadJSONUnpacked(ctx context.Context, t restic.FileType, id restic.ID, item interface{}) (err error) {
-	buf, err := r.LoadAndDecrypt(ctx, t, id)
+	buf, err := r.LoadAndDecrypt(ctx, nil, t, id)
 	if err != nil {
 		return err
 	}

internal/repository/repository_test.go

@@ -244,7 +244,7 @@ func BenchmarkLoadAndDecrypt(b *testing.B) {
 	b.SetBytes(int64(length))
 
 	for i := 0; i < b.N; i++ {
-		data, err := repo.LoadAndDecrypt(context.TODO(), restic.DataFile, storageID)
+		data, err := repo.LoadAndDecrypt(context.TODO(), nil, restic.DataFile, storageID)
 		rtest.OK(b, err)
 		if len(data) != length {
 			b.Errorf("wanted %d bytes, got %d", length, len(data))

internal/restic/repository.go

@@ -39,8 +39,11 @@ type Repository interface {
 	SaveUnpacked(context.Context, FileType, []byte) (ID, error)
 	SaveJSONUnpacked(context.Context, FileType, interface{}) (ID, error)
 
-	LoadJSONUnpacked(context.Context, FileType, ID, interface{}) error
+	LoadJSONUnpacked(ctx context.Context, t FileType, id ID, dest interface{}) error
-	LoadAndDecrypt(context.Context, FileType, ID) ([]byte, error)
+	// LoadAndDecrypt loads and decrypts the file with the given type and ID,
+	// using the supplied buffer (which must be empty). If the buffer is nil, a
+	// new buffer will be allocated and returned.
+	LoadAndDecrypt(ctx context.Context, buf []byte, t FileType, id ID) (data []byte, err error)
 
 	LoadBlob(context.Context, BlobType, ID, []byte) (int, error)
 	SaveBlob(context.Context, BlobType, []byte, ID) (ID, error)