feat(storage): support signed read options and local byte ranges

storage/local/local.go

@@ -151,14 +151,31 @@ func (s *Store) Get(ctx context.Context, key string) (storage.Object, error) {
 	}
 	info.ModifiedAt = stat.ModTime()
 	ok = true
-	return storage.Object{Info: info, Body: &body{Reader: storage.ContextReader{Context: ctx, Reader: io.LimitReader(f, info.Size)}, Closer: f}}, nil
+	// Expose only the payload as a seekable section. Seeks are relative to the
+	// object, never to our private metadata header or other disk bytes.
+	return storage.Object{Info: info, Body: &body{section: io.NewSectionReader(f, int64(length)+4, info.Size), file: f, ctx: ctx}}, nil
 }
 
 type body struct {
-	io.Reader
-	io.Closer
+	section *io.SectionReader
+	file    *os.File
+	ctx     context.Context
 }
 
+func (b *body) Read(p []byte) (int, error) {
+	if err := b.ctx.Err(); err != nil {
+		return 0, err
+	}
+	return b.section.Read(p)
+}
+func (b *body) Seek(offset int64, whence int) (int64, error) {
+	if err := b.ctx.Err(); err != nil {
+		return 0, err
+	}
+	return b.section.Seek(offset, whence)
+}
+func (b *body) Close() error { return b.file.Close() }
+
 func (s *Store) Delete(ctx context.Context, key string) error {
 	if err := storage.Check(ctx, key); err != nil {
 		return err