perl - 这段使用 Switch.pm 的代码安全吗？

Question

在我们公司，我们使用这个代码(最后给出)大约 10 年，它运行良好。

前几天我们遇到了一些问题，我们不得不重新编写完整的包，我们决定用 Damian 的 Switch 模块替换这段代码(以提高代码的可读性)。

一切对我们来说都很好。

后来我在 Perlmonks 上找到了达米安把这个模块放在下面

Damian modules you shouldn't use in production because their purpose is to explore and prototype future core language features.

但它对我们来说很好，因为我们没有达到这个模块的限制(我猜)。

现在我请你们看看这两种实现(嵌套 if else vs switch)，让我知道在较新的实现中使用 Switch 是否很好，或者我们是否会为我们创造一些 future 的问题？在下面给出的代码中使用 Switch 是否正常，或者是否存在任何隐藏的错误/问题？

我已经在 CPAN 和 Perlmonks 上阅读了这个模块的错误和评论，我想我们的代码离遇到这些错误还很远(我认为是这样)。

我们正在使用 Perl 5.8.5 .

PS:我知道 Switch 的替代品，我们有 given/when在 Perl 5.10 中，我们可以使用 dispatch table和其他指定的解决方案 here ，但现在我们只想比较使用 Switch 的新实现。

使用嵌套 if else

if ($command =~ /^enter$/) {
    $self->show_main_frames();
}       
elsif ($command =~ /^XYZ_MENU/i) {
    $self->show_main_menu($manual, $dbot);
}
elsif ($command =~ /^DBOT/i) {
    $dbot->process();
}
# XML is used for the reminders-history: Request 2666
elsif ($command =~ /^XML_DBOT/i) {
    $dbot->process();
}
elsif ($command =~ /^UGS/i) {
    $ugsui->process();
}
elsif ($command eq "kill") {
    my $login = $self->{COMMON_HASH}{login} || "";
    my $su_login = $self->{CONF}->get("start", "SU_LOGIN");
    if ($login eq $su_login) {      
            # usually only certain user with certain permission will be
            # able to do this. 
            $self->do_error("Daemon was killed by ".$login);
            $self->db_connection->disconnect();
            $self->{LOG}->write("User $login killed the daemon", 0);
            exit; # this 'exit' actually kill the daemon
    }
    else {
            $self->do_error("User $login tried to kill the daemon. ".
            "This incident will be reported");
            $self->{LOG}->write("User $login tried to kill the daemon", 2);
    }
}
elsif ($command eq "logout") {
    # check if we should delete the password cookie
    my $forget_me = $self->{CGI}->param("forget_me") || 0;
    if ($forget_me) {
            $self->{DB_PASSWORD_COOKIE}->delete_cookie();
    }

    $ugsui->do_logout();
    # Cliff edit remove id from logged_in
    $session->remove_session($session->login());
    # delete the session of the user
    delete $self->{SESSIONS}{$session->id()};
    if ($self->{CACHE_TO_FILE}) {
            my $session_data_path = 
                XYZ_DIR
            ."/code/cache/session_data"
        .$session->id();
            unlink($session_data_path);
    }
}
# if we just login we should create all the main frames        
elsif ($command eq "login") {
    # if extra_param holds "command*XXX" the XXX will be placed instead of
    # the command. extra_param holds pairs that are astrics-separated
    my $extra_param = $cgi->param("extra_param");
    $extra_param = "" if (!defined($extra_param));
    $extra_param =~ /command\*([^\*]+)/i;
    my $other_command = defined($1) ? $1 : "";
    if ($other_command =~ /^dbot/i) { # meanwhile - works only on dbot 
                                  # commands
        $command = $other_command;
            # now we will get the other parameters from the extra_param 
            # (actually including the command that is still in the 
            # $extra_param)         
            while ($extra_param =~ /^\*?([^\*]+)\*([^\*]+)(.*)/) {
            $extra_param = $3;
            my $name = $1;
            my $value = $2;     
            $cgi->param(-name => $name,
                 -value => $value);
            }#end while
    }#end if
    else{
    $self->show_main_frames();
    }
}#end elsif
else {
    $self->show_main_frames();
}#end outer else

使用开关

switch ($command) 
{
    case /^enter$/      { $self->show_main_frames() }
    case /^XYZ_MENU/i   { $self->show_main_menu($manual, $dbot) }
    case /^DBOT/i       { $dbot->process() }
        case /^XML_DBOT/i   { $dbot->process() }
        case /^UGS/i        { $ugsui->process() }
        case "kill"     {
                my $login = $self->{COMMON_HASH}{login} || "";
                    my $su_login = $self->{CONF}->get("start", "SU_LOGIN");
                if ($login eq $su_login) {      
                        # usually only certain user with certain permission will be
                        # able to do this. 
                        $self->do_error("Daemon was killed by ".$login);
                        $self->db_connection->disconnect();
                        $self->{LOG}->write("User $login killed the daemon", 0);
                        exit; # this 'exit' actually kill the daemon
                    }
                else    {
                        $self->do_error("User $login tried to kill the daemon. ".
                            "This incident will be reported");
                        $self->{LOG}->write("User $login tried to kill the daemon", 2);
                    }
                    }
        case "logout"       {
                    # check if we should delete the password cookie
                    my $forget_me = $self->{CGI}->param("forget_me") || 0;
                    if ($forget_me) {
                            $self->{DB_PASSWORD_COOKIE}->delete_cookie();
                    }

                $ugsui->do_logout();
                # Cliff edit remove id from logged_in
                $session->remove_session($session->login());
                # delete the session of the user
                delete $self->{SESSIONS}{$session->id()};
                    if ($self->{CACHE_TO_FILE}) {
                            my $session_data_path = 
                                XYZ_DIR
                        ."/code/cache/session_data"
                        .$session->id();
                    unlink($session_data_path);
                    }
                    }
        case "login"        {
                # if extra_param holds "command*XXX" the XXX will be placed instead of
                # the command. extra_param holds pairs that are astrics-separated
                my $extra_param = $cgi->param("extra_param");
                $extra_param = "" if (!defined($extra_param));
                $extra_param =~ /command\*([^\*]+)/i;
                my $other_command = defined($1) ? $1 : "";
                if ($other_command =~ /^dbot/i) 
                    { # meanwhile - works only on dbot 
                                       # commands
                    $command = $other_command;
                        # now we will get the other parameters from the extra_param 
                        # (actually including the command that is still in the 
                        # $extra_param)         
                        while ($extra_param =~ /^\*?([^\*]+)\*([^\*]+)(.*)/) {
                        $extra_param = $3;
                        my $name = $1;
                        my $value = $2;     
                        $cgi->param(-name => $name,
                             -value => $value);
                            }#end while
                    }#end if
                else {$self->show_main_frames();}
                }
    else            {$self->show_main_frames();}
} # end switch

Answer 1

Switch 自己解析源代码。这可能导致难以诊断直接使用它的代码中的错误。 Switch 产生的问题不是间歇性的，因此如果您的代码有效，您无需担心。

但实际上，它并没有增加太多。

带开关:

switch ($command) {
    case /^enter$/      { $self->show_main_frames() }
    case /^XYZ_MENU/i   { $self->show_main_menu($manual, $dbot) }
    case /^DBOT/i       { $dbot->process() }
    case /^XML_DBOT/i   { $dbot->process() }
    case /^UGS/i        { $ugsui->process() }
    case "kill"         {
        my $login = $self->{COMMON_HASH}{login} || "";

不带开关:

for ($command) {
    if    (/^enter$/)      { $self->show_main_frames() }
    elsif (/^XYZ_MENU/i)   { $self->show_main_menu($manual, $dbot) }
    elsif (/^DBOT/i)       { $dbot->process() }
    elsif (/^XML_DBOT/i)   { $dbot->process() }
    elsif (/^UGS/i)        { $ugsui->process() }
    elsif ($_ eq "kill")   {
        my $login = $self->{COMMON_HASH}{login} || "";

( elsif (/^kill\z/) 也可以。)