程嶏清单 17-10.txt

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程序清单17-10：disconnect.pl
sub _rcv {                     
    my ($conn, $rcv_now) = @_; 
    my ($msg, $offset, $bytes_to_read, $bytes_read);
    my $sock = $conn->{sock};
    return unless defined($sock);
    if (exists $conn->{msg}) {
        $msg           = $conn->{msg};
        delete $conn->{'msg'};              
        $offset        = length($msg) - 1;  
        $bytes_to_read = $conn->{bytes_to_read};
    } else {
        # 这是典型的情况
        $msg           = "";
        $offset        = 0 ;
        $bytes_to_read = 0 ;                # Will get set soon
    }
#  以阻塞模式来读取消息的长度信息，这里假设在读取四个字节信息的时间内时不
#  会阻塞的
    if (!$bytes_to_read)  {                 # 获取新的长度信息 
        my $buf;
        $conn->set_blocking();
        $bytes_read = sysread($sock, $buf, 4);
        if ($! || ($bytes_read != 4)) {
            goto FINISH;
        }
        $bytes_to_read = unpack ('N', $buf);
    }
    $conn->set_non_blocking() unless $rcv_now;
    while ($bytes_to_read) {
        $bytes_read = sysread ($sock, $msg, $bytes_to_read, $offset);
        if (defined ($bytes_read)) {
            if ($bytes_read == 0) {
                last;
            }
            $bytes_to_read -= $bytes_read;
            $offset        += $bytes_read;
        } else {
            if (_err_will_block($!)) {
                # 只能以非阻塞模式运行到这里
                $conn->{msg}           = $msg;
                $conn->{bytes_to_read} = $bytes_to_read;
                return ; # 返回事件循环，当套接字再次可以读时，_rcv将会被调用
            } else {
                last;
            }
        }
    }
    # 消息成功读取
  FINISH:
    if (length($msg) == 0) {
        $conn->disconnect();
    }
    if ($rcv_now) {
        return ($msg, $!);
    } else {
        &{$conn->{rcvd_notification_proc}}($conn, $msg, $!);
    }
}