func (b *Backup) Step(p int) (bool, error) {
	ret := C.sqlite3_backup_step(b.b, C.int(p))
	if ret == C.SQLITE_DONE {
		return true, nil
	} else if ret != 0 {
		return false, Error{Code: ErrNo(ret)}
	}
	return false, nil
}
Backs up for one step. Calls the underlying `sqlite3_backup_step` function.
This function returns a boolean indicating if the backup is done and
an error signalling any other error. Done is returned if the underlying C
function returns SQLITE_DONE (Code 101)
package sqlite3
import "C"
import (
	"unsafe"
)
type Backup struct {
	b *C.sqlite3_backup
}
func (c *SQLiteConn) Backup(dest string, conn *SQLiteConn, src string) (*Backup, error) {
	destptr := C.CString(dest)
	defer C.free(unsafe.Pointer(destptr))
	srcptr := C.CString(src)
	defer C.free(unsafe.Pointer(srcptr))
	if b := C.sqlite3_backup_init(c.db, destptr, conn.db, srcptr); b != nil {
		return &Backup{b: b}, nil
	}
	return nil, c.lastError()
}