Class NonBlockingInputStream

java.lang.Object
java.io.InputStream
org.jline.utils.NonBlockingInputStream
All Implemented Interfaces:
Closeable, AutoCloseable
Direct Known Subclasses:
NonBlockingInputStreamImpl, NonBlockingPumpInputStream
public abstract class NonBlockingInputStream extends InputStream
An input stream that supports non-blocking read operations with timeouts.

The NonBlockingInputStream class extends InputStream to provide non-blocking read operations. Unlike standard input streams, which block indefinitely until data is available or the end of the stream is reached, non-blocking input streams can be configured to return immediately or after a specified timeout if no data is available.

This class defines two special return values:

  • EOF (-1) - Indicates that the end of the stream has been reached
  • READ_EXPIRED (-2) - Indicates that the read operation timed out

This abstract class provides the framework for non-blocking input operations, with concrete implementations handling the details of how the non-blocking behavior is achieved (e.g., through NIO, separate threads, or native methods).

Non-blocking input streams are particularly useful for terminal applications that need to perform other tasks while waiting for user input, or that need to implement features like input timeouts or polling.

  • Field Details

    • EOF

      public static final int EOF
      See Also:

    • READ_EXPIRED

      public static final int READ_EXPIRED
      See Also:

    • closed

      protected volatile boolean closed
      Flag indicating whether this input stream has been closed. Marked as volatile to ensure visibility across threads.

  • Constructor Details

    • NonBlockingInputStream

      public NonBlockingInputStream()
      Default constructor. Initializes close mode based on the current value of the system property.

  • Method Details

    • checkClosed

      protected void checkClosed() throws IOException
      Checks if this input stream has been closed.

      In JLine 3.x, warn mode is enabled by default: when a closed input stream is accessed, it logs a WARNING instead of throwing an exception. This allows existing code to continue working while alerting developers to the issue.

      The behavior can be controlled via the system property PROP_CLOSE_MODE:

      • "strict" - Throw ClosedException
      • "warn" - Log a warning but continue (default in JLine 3.x)
      • "lenient" - Silently allow access (no warning, no exception)
      Throws:
      ClosedException - if this input stream has been closed and strict mode is enabled
      IOException

    • read

      public int read() throws IOException
      Reads the next byte of data from the input stream. The value byte is returned as an int in the range 0 to 255. If no byte is available because the end of the stream has been reached, the value -1 is returned. This method blocks until input data is available, the end of the stream is detected, or an exception is thrown.
      Specified by:
      read in class InputStream
      Returns:
      the next byte of data, or -1 if the end of the stream is reached.
      Throws:
      IOException - if an I/O error occurs.

    • peek

      public int peek(long timeout) throws IOException
      Peeks to see if there is a byte waiting in the input stream without actually consuming the byte.
      Parameters:
      timeout - The amount of time to wait, 0 == forever
      Returns:
      -1 on eof, -2 if the timeout expired with no available input or the character that was read (without consuming it).
      Throws:
      IOException - if an I/O error occurs.

    • read

      public int read(long timeout) throws IOException
      Attempts to read a character from the input stream for a specific period of time.
      Parameters:
      timeout - The amount of time to wait for the character
      Returns:
      The character read, -1 if EOF is reached, or -2 if the read timed out.
      Throws:
      IOException - if an I/O error occurs.

    • read

      public int read(byte[] b, int off, int len) throws IOException
      Overrides:
      read in class InputStream
      Throws:
      IOException

    • readBuffered

      public int readBuffered(byte[] b) throws IOException
      Throws:
      IOException

    • readBuffered

      public int readBuffered(byte[] b, long timeout) throws IOException
      Throws:
      IOException

    • readBuffered

      public int readBuffered(byte[] b, int off, int len, long timeout) throws IOException
      Throws:
      IOException

    • shutdown

      public void shutdown()
      Shuts down the thread that is handling blocking I/O if any. Note that if the thread is currently blocked waiting for I/O it may not actually shut down until the I/O is received.

    • read

      public abstract int read(long timeout, boolean isPeek) throws IOException
      Throws:
      IOException

    • close

      public void close() throws IOException
      Closes this input stream and marks it as closed.

      Subsequent read operations behavior depends on the PROP_CLOSE_MODE setting:

      • "strict" - Throw ClosedException
      • "warn" - Log a warning but continue (default in JLine 3.x)
      • "lenient" - Silently allow access
      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface Closeable
      Overrides:
      close in class InputStream
      Throws:
      IOException - if an I/O error occurs