backend: Deduplicate sanity checks for parameters of Load() method

The check is now handled by backend.DefaultLoad. This also guarantees
consistent behavior across all backends.

internal/backend/azure/azure.go

@@ -300,17 +300,6 @@ func (be *Backend) Load(ctx context.Context, h restic.Handle, length int, offset
 
 func (be *Backend) openReader(ctx context.Context, h restic.Handle, length int, offset int64) (io.ReadCloser, error) {
 	debug.Log("Load %v, length %v, offset %v from %v", h, length, offset, be.Filename(h))
-	if err := h.Valid(); err != nil {
-		return nil, backoff.Permanent(err)
-	}
-
-	if offset < 0 {
-		return nil, errors.New("offset is negative")
-	}
-
-	if length < 0 {
-		return nil, errors.Errorf("invalid length %d", length)
-	}
 
 	objName := be.Filename(h)
 	blockBlobClient := be.container.NewBlobClient(objName)

internal/backend/b2/b2.go

@@ -207,17 +207,6 @@ func (be *b2Backend) Load(ctx context.Context, h restic.Handle, length int, offs
 
 func (be *b2Backend) openReader(ctx context.Context, h restic.Handle, length int, offset int64) (io.ReadCloser, error) {
 	debug.Log("Load %v, length %v, offset %v from %v", h, length, offset, be.Filename(h))
-	if err := h.Valid(); err != nil {
-		return nil, backoff.Permanent(err)
-	}
-
-	if offset < 0 {
-		return nil, errors.New("offset is negative")
-	}
-
-	if length < 0 {
-		return nil, errors.Errorf("invalid length %d", length)
-	}
 
 	ctx, cancel := context.WithCancel(ctx)
 

internal/backend/gs/gs.go

@@ -273,17 +273,7 @@ func (be *Backend) Load(ctx context.Context, h restic.Handle, length int, offset
 
 func (be *Backend) openReader(ctx context.Context, h restic.Handle, length int, offset int64) (io.ReadCloser, error) {
 	debug.Log("Load %v, length %v, offset %v from %v", h, length, offset, be.Filename(h))
-	if err := h.Valid(); err != nil {
-		return nil, err
-	}
 
-	if offset < 0 {
-		return nil, errors.New("offset is negative")
-	}
-
-	if length < 0 {
-		return nil, errors.Errorf("invalid length %d", length)
-	}
 	if length == 0 {
 		// negative length indicates read till end to GCS lib
 		length = -1

internal/backend/local/local.go

@@ -218,13 +218,6 @@ func (b *Local) Load(ctx context.Context, h restic.Handle, length int, offset in
 
 func (b *Local) openReader(ctx context.Context, h restic.Handle, length int, offset int64) (io.ReadCloser, error) {
 	debug.Log("Load %v, length %v, offset %v", h, length, offset)
-	if err := h.Valid(); err != nil {
-		return nil, backoff.Permanent(err)
-	}
-
-	if offset < 0 {
-		return nil, errors.New("offset is negative")
-	}
 
 	b.sem.GetToken()
 	f, err := fs.Open(b.Filename(h))

internal/backend/mem/mem_backend.go

@@ -114,9 +114,6 @@ func (be *MemoryBackend) Load(ctx context.Context, h restic.Handle, length int,
 }
 
 func (be *MemoryBackend) openReader(ctx context.Context, h restic.Handle, length int, offset int64) (io.ReadCloser, error) {
-	if err := h.Valid(); err != nil {
-		return nil, backoff.Permanent(err)
-	}
 
 	be.sem.GetToken()
 	be.m.Lock()

internal/backend/s3/s3.go

@@ -312,17 +312,6 @@ func (be *Backend) Load(ctx context.Context, h restic.Handle, length int, offset
 
 func (be *Backend) openReader(ctx context.Context, h restic.Handle, length int, offset int64) (io.ReadCloser, error) {
 	debug.Log("Load %v, length %v, offset %v from %v", h, length, offset, be.Filename(h))
-	if err := h.Valid(); err != nil {
-		return nil, backoff.Permanent(err)
-	}
-
-	if offset < 0 {
-		return nil, errors.New("offset is negative")
-	}
-
-	if length < 0 {
-		return nil, errors.Errorf("invalid length %d", length)
-	}
 
 	objName := be.Filename(h)
 	opts := minio.GetObjectOptions{}

internal/backend/sftp/sftp.go

@@ -430,13 +430,6 @@ func (wr *wrapReader) Close() error {
 
 func (r *SFTP) openReader(ctx context.Context, h restic.Handle, length int, offset int64) (io.ReadCloser, error) {
 	debug.Log("Load %v, length %v, offset %v", h, length, offset)
-	if err := h.Valid(); err != nil {
-		return nil, backoff.Permanent(err)
-	}
-
-	if offset < 0 {
-		return nil, errors.New("offset is negative")
-	}
 
 	r.sem.GetToken()
 	f, err := r.c.Open(r.Filename(h))

internal/backend/swift/swift.go

@@ -144,17 +144,6 @@ func (be *beSwift) Load(ctx context.Context, h restic.Handle, length int, offset
 
 func (be *beSwift) openReader(ctx context.Context, h restic.Handle, length int, offset int64) (io.ReadCloser, error) {
 	debug.Log("Load %v, length %v, offset %v", h, length, offset)
-	if err := h.Valid(); err != nil {
-		return nil, backoff.Permanent(err)
-	}
-
-	if offset < 0 {
-		return nil, errors.New("offset is negative")
-	}
-
-	if length < 0 {
-		return nil, errors.Errorf("invalid length %d", length)
-	}
 
 	objName := be.Filename(h)
 

internal/backend/utils.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"io"
 
+	"github.com/cenkalti/backoff/v4"
 	"github.com/restic/restic/internal/debug"
 	"github.com/restic/restic/internal/errors"
 	"github.com/restic/restic/internal/restic"
@@ -62,6 +63,15 @@ func LimitReadCloser(r io.ReadCloser, n int64) *LimitedReadCloser {
 func DefaultLoad(ctx context.Context, h restic.Handle, length int, offset int64,
 	openReader func(ctx context.Context, h restic.Handle, length int, offset int64) (io.ReadCloser, error),
 	fn func(rd io.Reader) error) error {
+	if err := h.Valid(); err != nil {
+		return backoff.Permanent(err)
+	}
+	if offset < 0 {
+		return errors.New("offset is negative")
+	}
+	if length < 0 {
+		return errors.Errorf("invalid length %d", length)
+	}
 	rd, err := openReader(ctx, h, length, offset)
 	if err != nil {
 		return err