Class LineDisciplineTerminal

  • All Implemented Interfaces:
    java.io.Closeable, java.io.Flushable, java.lang.AutoCloseable, TerminalExt, Terminal
    Direct Known Subclasses:
    ExternalTerminal

    public class LineDisciplineTerminal
    extends AbstractTerminal
    Abstract terminal with support for line discipline. The Terminal interface represents the slave side of a PTY, but implementations derived from this class will handle both the slave and master side of things. In order to correctly handle line discipline, the terminal needs to read the input in advance in order to raise the signals as fast as possible. For example, when the user hits Ctrl+C, we can't wait until the application consumes all the read events. The same applies to echoing, when enabled, as the echoing has to happen as soon as the user hit the keyboard, and not only when the application running in the terminal processes the input.

    The LineDisciplineTerminal class provides a terminal implementation that emulates the line discipline functionality typically provided by the operating system's terminal driver. Line discipline refers to the processing of input and output characters according to various modes and settings, such as canonical mode, echo, and special character handling.

    This terminal implementation is particularly useful in environments where:

    • The underlying system does not provide native terminal capabilities
    • The application needs precise control over terminal behavior
    • The terminal is being used in a non-standard environment (e.g., embedded systems)

    Key features of this implementation include:

    • Emulation of canonical and non-canonical input modes
    • Support for character echoing
    • Special character handling (e.g., interrupt, erase, kill)
    • Input and output processing according to terminal attributes

    This terminal implementation works with any input and output streams, making it highly flexible and adaptable to various environments.

    See Also:
    Attributes, AbstractTerminal
    • Field Detail

      • masterOutput

        protected final java.io.OutputStream masterOutput
      • slaveInputPipe

        protected final java.io.OutputStream slaveInputPipe
      • slaveWriter

        protected final java.io.PrintWriter slaveWriter
      • slaveOutput

        protected final java.io.OutputStream slaveOutput
      • attributes

        protected final Attributes attributes
        Console data
      • size

        protected final Size size
      • skipNextLf

        protected boolean skipNextLf
    • Constructor Detail

      • LineDisciplineTerminal

        public LineDisciplineTerminal​(java.lang.String name,
                                      java.lang.String type,
                                      java.io.OutputStream masterOutput,
                                      java.nio.charset.Charset encoding)
                               throws java.io.IOException
        Throws:
        java.io.IOException
      • LineDisciplineTerminal

        public LineDisciplineTerminal​(java.lang.String name,
                                      java.lang.String type,
                                      java.io.OutputStream masterOutput,
                                      java.nio.charset.Charset encoding,
                                      Terminal.SignalHandler signalHandler)
                               throws java.io.IOException
        Throws:
        java.io.IOException
      • LineDisciplineTerminal

        public LineDisciplineTerminal​(java.lang.String name,
                                      java.lang.String type,
                                      java.io.OutputStream masterOutput,
                                      java.nio.charset.Charset encoding,
                                      java.nio.charset.Charset stdinEncoding,
                                      java.nio.charset.Charset stdoutEncoding,
                                      java.nio.charset.Charset stderrEncoding,
                                      Terminal.SignalHandler signalHandler)
                               throws java.io.IOException
        Throws:
        java.io.IOException
    • Method Detail

      • reader

        public NonBlockingReader reader()
        Description copied from interface: Terminal
        Retrieve the Reader for this terminal. This is the standard way to read input from this terminal. The reader is non blocking.
        Returns:
        The non blocking reader
      • writer

        public java.io.PrintWriter writer()
        Description copied from interface: Terminal
        Retrieve the Writer for this terminal. This is the standard way to write to this terminal.
        Returns:
        The writer
      • input

        public java.io.InputStream input()
        Description copied from interface: Terminal
        Retrieve the input stream for this terminal. In some rare cases, there may be a need to access the terminal input stream directly. In the usual cases, use the Terminal.reader() instead.
        Returns:
        The input stream
        See Also:
        Terminal.reader()
      • output

        public java.io.OutputStream output()
        Description copied from interface: Terminal
        Retrieve the output stream for this terminal. In some rare cases, there may be a need to access the terminal output stream directly. In the usual cases, use the Terminal.writer() instead.
        Returns:
        The output stream
        See Also:
        Terminal.writer()
      • getAttributes

        public Attributes getAttributes()
        Description copied from interface: Terminal
        Returns the current terminal attributes.

        Terminal attributes control various aspects of terminal behavior, including:

        • Input processing - How input characters are processed (e.g., character mapping, parity checking)
        • Output processing - How output characters are processed (e.g., newline translation)
        • Control settings - Hardware settings like baud rate and character size
        • Local settings - Terminal behavior settings like echo, canonical mode, and signal generation
        • Control characters - Special characters like EOF, interrupt, and erase

        The returned Attributes object is a copy of the terminal's current attributes and can be safely modified without affecting the terminal until it is applied using Terminal.setAttributes(Attributes). This allows for making multiple changes to the attributes before applying them all at once.

        Example usage:

         Terminal terminal = TerminalBuilder.terminal();
        
         // Get current attributes
         Attributes attrs = terminal.getAttributes();
        
         // Modify attributes
         attrs.setLocalFlag(LocalFlag.ECHO, false);      // Disable echo
         attrs.setInputFlag(InputFlag.ICRNL, false);     // Disable CR to NL mapping
         attrs.setControlChar(ControlChar.VMIN, 1);      // Set minimum input to 1 character
         attrs.setControlChar(ControlChar.VTIME, 0);     // Set timeout to 0 deciseconds
        
         // Apply modified attributes
         terminal.setAttributes(attrs);
         
        Returns:
        a copy of the terminal's current attributes
        See Also:
        Terminal.setAttributes(Attributes), Attributes, Terminal.enterRawMode()
      • setAttributes

        public void setAttributes​(Attributes attr)
        Description copied from interface: Terminal
        Sets the terminal attributes to the specified values.

        This method applies the specified attributes to the terminal, changing its behavior according to the settings in the Attributes object. The terminal makes a copy of the provided attributes, so further modifications to the attr object will not affect the terminal until this method is called again.

        Terminal attributes control various aspects of terminal behavior, including input and output processing, control settings, local settings, and special control characters. Changing these attributes allows for fine-grained control over how the terminal processes input and output.

        Common attribute modifications include:

        • Disabling echo for password input
        • Enabling/disabling canonical mode for line-by-line or character-by-character input
        • Disabling signal generation for custom handling of Ctrl+C and other control sequences
        • Changing control characters like the interrupt character or end-of-file character

        For convenience, the Terminal.enterRawMode() method provides a pre-configured set of attributes suitable for full-screen interactive applications.

        Example usage:

         Terminal terminal = TerminalBuilder.terminal();
        
         // Save original attributes for later restoration
         Attributes originalAttrs = terminal.getAttributes();
        
         try {
             // Create and configure new attributes
             Attributes attrs = new Attributes(originalAttrs);
             attrs.setLocalFlag(LocalFlag.ECHO, false);      // Disable echo for password input
             attrs.setLocalFlag(LocalFlag.ICANON, false);    // Disable canonical mode
        
             // Apply the new attributes
             terminal.setAttributes(attrs);
        
             // Use terminal with modified attributes...
         } finally {
             // Restore original attributes
             terminal.setAttributes(originalAttrs);
         }
         
        Parameters:
        attr - the attributes to apply to the terminal
        See Also:
        Terminal.getAttributes(), Attributes, Terminal.enterRawMode()
      • getSize

        public Size getSize()
        Description copied from interface: Terminal
        Retrieve the size of the visible window
        Returns:
        the visible terminal size
        See Also:
        Terminal.getBufferSize()
      • setSize

        public void setSize​(Size sz)
        Description copied from interface: Terminal
        Sets the size of the terminal.

        This method attempts to resize the terminal to the specified dimensions. Note that not all terminals support resizing, and the actual size after this operation may differ from the requested size depending on terminal capabilities and constraints.

        For virtual terminals or terminal emulators, this may update the internal size representation. For physical terminals, this may send appropriate escape sequences to adjust the viewable area.

        Parameters:
        sz - the new terminal size (columns and rows)
        See Also:
        Terminal.getSize()
      • processInputByte

        public void processInputByte​(int c)
                              throws java.io.IOException
        Master input processing. All data coming to the terminal should be provided using this method.
        Parameters:
        c - the input byte
        Throws:
        java.io.IOException - if anything wrong happens
      • processInputBytes

        public void processInputBytes​(byte[] input)
                               throws java.io.IOException
        Throws:
        java.io.IOException
      • processInputBytes

        public void processInputBytes​(byte[] input,
                                      int offset,
                                      int length)
                               throws java.io.IOException
        Throws:
        java.io.IOException
      • doProcessInputByte

        protected boolean doProcessInputByte​(int c)
                                      throws java.io.IOException
        Throws:
        java.io.IOException
      • processOutputByte

        protected void processOutputByte​(int c)
                                  throws java.io.IOException
        Master output processing. All data going to the master should be provided by this method.
        Parameters:
        c - the output byte
        Throws:
        java.io.IOException - if anything wrong happens
      • processIOException

        protected void processIOException​(java.io.IOException ioException)
      • doClose

        protected void doClose()
                        throws java.io.IOException
        Overrides:
        doClose in class AbstractTerminal
        Throws:
        java.io.IOException
      • getProvider

        public TerminalProvider getProvider()
        Description copied from interface: TerminalExt
        Returns the terminal provider that created this terminal.

        The terminal provider is responsible for creating and managing terminal instances on a specific platform. This method allows access to the provider that created this terminal, which can be useful for accessing provider-specific functionality or for creating additional terminals with the same provider.

        Returns:
        the TerminalProvider that created this terminal, or null if the terminal was created with no provider
        See Also:
        TerminalProvider
      • getSystemStream

        public SystemStream getSystemStream()
        Description copied from interface: TerminalExt
        Returns the system stream associated with this terminal, if any.

        This method indicates whether the terminal is bound to a standard system stream (standard input, standard output, or standard error). Terminals that are connected to system streams typically represent the actual terminal window or console that the application is running in.

        Returns:
        the underlying system stream, which may be SystemStream.Input, SystemStream.Output, SystemStream.Error, or null if this terminal is not bound to a system stream
        See Also:
        SystemStream