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: structhash.go
    path of file: ./repos/scan4all/vendor/github.com/cnf/structhash
    
    the code of the file until where you have to start completion: package structhash

import (
	"bytes"
	"crypto/md5"
	"crypto/sha1"
	"fmt"
	"reflect"
	"sort"
	"strconv"
	"strings"
)

// Version returns the version of the supplied hash as an integer
// or -1 on failure
func Version(h string) int {
	if h == "" {
		return -1
	}
	if h[0] != 'v' {
		return -1
	}
	if spos := strings.IndexRune(h[1:], '_'); spos >= 0 {
		n, e := strconv.Atoi(h[1 : spos+1])
		if e != nil {
			return -1
		}
		return n
	}
	return -1
}

// Hash takes a data structure and returns a hash string of that data structure
// at the version asked.
//
// This function uses md5 hashing function and default formatter. See also Dump()
// function.
func Hash(c interface{}, version int) (string, error) {
	return fmt.Sprintf("v%d_%x", version, Md5(c, version)), nil
}

// Dump takes a data structure and returns its byte representation. This can be
// useful if you need to use your own h
    
func filterField(f reflect.StructField, i *item, version int) (bool, error) {
	var err error
	ver := 0
	lastver := -1
	if str := f.Tag.Get("hash"); str != "" {
		if str == "-" {
			return false, nil
		}
		for _, tag := range strings.Split(str, " ") {
			args := strings.Split(strings.TrimSpace(tag), ":")
			if len(args) != 2 {
				return false, tagError(tag)
			}
			switch args[0] {
			case "name":
				i.name = args[1]
			case "version":
				if ver, err = strconv.Atoi(args[1]); err != nil {
					return false, tagError(tag)
				}
			case "lastversion":
				if lastver, err = strconv.Atoi(args[1]); err != nil {
					return false, tagError(tag)
				}
			case "method":
				property, found := f.Type.MethodByName(strings.TrimSpace(args[1]))
				if !found || property.Type.NumOut() != 1 {
					return false, tagError(tag)
				}
				i.value = property.Func.Call([]reflect.Value{i.value})[0]
			}
		}
	} else {
		if str := f.Tag.Get("lastversion"); str != "" {
			if lastver, err = strconv.Atoi(str); err != nil {
				return false, tagError(str)
			}
		}
		if str := f.Tag.Get("version"); str != "" {
			if ver, err = strconv.Atoi(str); err != nil {
				return false, tagError(str)
			}
		}
	}
	if lastver != -1 && lastver < version {
		return false, nil
	}
	if ver > version {
		return false, nil
	}
	return true, nil
}