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: mounter_freebsd.go
    path of file: ./repos/docker-ce/components/engine/vendor/github.com/moby/sys/mount
    
    the code of the file until where you have to start completion: //go:build freebsd && cgo
// +build freebsd,cgo

package mount

/*
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <sys/_iovec.h>
#include <sys/mount.h>
#include <sys/param.h>
*/
import "C"

import (
	"strings"
	"syscall"
	"unsafe"
)

func allocateIOVecs(options []string) []C.struct_iovec {
	out := make([]C.struct_iovec, len(options))
	for i, option := range options {
		out[i].iov_base = unsafe.Pointer(C.CString(option))
		out[i].iov_len = C.size_
    
func mount(device, target, mType string, flag uintptr, data string) error {
	isNullFS := false

	xs := strings.Split(data, ",")
	for _, x := range xs {
		if x == "bind" {
			isNullFS = true
		}
	}

	options := []string{"fspath", target}
	if isNullFS {
		options = append(options, "fstype", "nullfs", "target", device)
	} else {
		options = append(options, "fstype", mType, "from", device)
	}
	rawOptions := allocateIOVecs(options)
	for _, rawOption := range rawOptions {
		defer C.free(rawOption.iov_base)
	}

	if errno := C.nmount(&rawOptions[0], C.uint(len(options)), C.int(flag)); errno != 0 {
		return &mountError{
			op:     "mount",
			source: device,
			target: target,
			flags:  flag,
			err:    syscall.Errno(errno),
		}
	}
	return nil
}