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: file_header.go
    path of file: ./repos/gocryptfs/internal/contentenc
    
    the code of the file until where you have to start completion: package contentenc

// Per-file header
//
// Format: [ "Version" uint16 big endian ] [ "Id" 16 random bytes ]

import (
	"bytes"
	"encoding/binary"
	"encoding/hex"
	"fmt"
	"log"

	"github.com/rfjakob/gocryptfs/v2/internal/cryptocore"
)

const (
	// CurrentVersion is the current On-Disk-Format version
	CurrentVersion = 2


    
func ParseHeader(buf []byte) (*FileHeader, error) {
	if len(buf) != HeaderLen {
		return nil, fmt.Errorf("ParseHeader: invalid length, want=%d have=%d", HeaderLen, len(buf))
	}
	if bytes.Equal(buf, allZeroHeader) {
		return nil, fmt.Errorf("ParseHeader: header is all-zero. Header hexdump: %s", hex.EncodeToString(buf))
	}
	var h FileHeader
	h.Version = binary.BigEndian.Uint16(buf[0:headerVersionLen])
	if h.Version != CurrentVersion {
		return nil, fmt.Errorf("ParseHeader: invalid version, want=%d have=%d. Header hexdump: %s",
			CurrentVersion, h.Version, hex.EncodeToString(buf))
	}
	h.ID = buf[headerVersionLen:]
	if bytes.Equal(h.ID, allZeroFileID) {
		return nil, fmt.Errorf("ParseHeader: file id is all-zero. Header hexdump: %s",
			hex.EncodeToString(buf))
	}
	return &h, nil
}