You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: packer.go
    path of file: ./repos/sealer/vendor/github.com/vbatts/tar-split/tar/storage
    
    the code of the file until where you have to start completion: package storage

import (
	"encoding/json"
	"errors"
	"io"
	"path/filepath"
	"unicode/utf8"
)

// ErrDuplicatePath occurs when a tar archive has more than one entry for the
// same file path
var ErrDuplicatePath = er
    
func (jup *jsonUnpacker) Next() (*Entry, error) {
	var e Entry
	err := jup.dec.Decode(&e)
	if err != nil {
		return nil, err
	}

	// check for dup name
	if e.Type == FileType {
		cName := filepath.Clean(e.GetName())
		if _, ok := jup.seen[cName]; ok {
			return nil, ErrDuplicatePath
		}
		jup.seen[cName] = struct{}{}
	}

	return &e, err
}