Mitigated Serial Monitor resource exhaustion when the connected device sends a lot of data

Fixes #2233

Author: cmaglie

app/src/processing/app/SerialMonitor.java

@@ -19,27 +19,29 @@
 package processing.app;
 
 import processing.app.debug.MessageConsumer;
+import processing.app.debug.TextAreaFIFO;
 import processing.core.*;
 import static processing.app.I18n._;
 
 import java.awt.*;
 import java.awt.event.*;
 import javax.swing.*;
 import javax.swing.border.*;
-import javax.swing.event.*;
 import javax.swing.text.*;
 
-public class SerialMonitor extends JFrame implements MessageConsumer {
+public class SerialMonitor extends JFrame implements MessageConsumer,ActionListener {
   private Serial serial;
   private String port;
-  private JTextArea textArea;
+  private TextAreaFIFO textArea;
   private JScrollPane scrollPane;
   private JTextField textField;
   private JButton sendButton;
   private JCheckBox autoscrollBox;
   private JComboBox lineEndings;
   private JComboBox serialRates;
   private int serialRate;
+  private javax.swing.Timer updateTimer;
+  private StringBuffer updateBuffer;
 
   public SerialMonitor(String port) {
     super(port);
@@ -67,7 +69,9 @@ public void actionPerformed(ActionEvent e) {
     Font editorFont = Preferences.getFont("editor.font");
     Font font = new Font(consoleFont.getName(), consoleFont.getStyle(), editorFont.getSize());
 
-    textArea = new JTextArea(16, 40);
+    textArea = new TextAreaFIFO(4000000);
+    textArea.setRows(16);
+    textArea.setColumns(40);
     textArea.setEditable(false);    
     textArea.setFont(font);
 
@@ -171,6 +175,9 @@ public void actionPerformed(ActionEvent event) {
         }
       }
     }
+
+    updateBuffer = new StringBuffer(1048576);
+    updateTimer = new javax.swing.Timer(33, this);  // redraw serial monitor at 30 Hz
   }
 
   protected void setPlacement(int[] location) {
@@ -203,9 +210,9 @@ private void send(String s) {
 
   public void openSerialPort() throws SerialException {
     if (serial != null) return;
-  
     serial = new Serial(port, serialRate);
     serial.addListener(this);
+    updateTimer.start();
   }
 
   public void closeSerialPort() {
@@ -219,13 +226,32 @@ public void closeSerialPort() {
     }
   }
 
-  public void message(final String s) {
-    SwingUtilities.invokeLater(new Runnable() {
-      public void run() {
-        textArea.append(s);
-        if (autoscrollBox.isSelected()) {
-        	textArea.setCaretPosition(textArea.getDocument().getLength());
-        }
-      }});
+  public void message(String s) {
+    // TODO: can we pass a byte array, to avoid overhead of String
+    addToUpdateBuffer(s);
   }
+
+  private synchronized void addToUpdateBuffer(String s) {
+    updateBuffer.append(s);
+  }
+
+  private synchronized String consumeUpdateBuffer() {
+    String s = updateBuffer.toString();
+    updateBuffer.setLength(0);
+    return s;
+  }
+
+  public void actionPerformed(ActionEvent e) {
+    final String s = consumeUpdateBuffer();
+    if (s.length() > 0) {
+      //System.out.println("gui append " + s.length());
+      boolean scroll = autoscrollBox.isSelected();
+      textArea.allowTrim(scroll);
+      textArea.append(s);
+      if (scroll) {
+        textArea.setCaretPosition(textArea.getDocument().getLength());
+      }
+    }
+  }
+
 }

app/src/processing/app/debug/TextAreaFIFO.java

@@ -0,0 +1,78 @@
+/*
+  Copyright (c) 2014 Paul Stoffregen <paul@pjrc.com>
+
+  This program is free software; you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation; either version 2 of the License, or
+  (at your option) any later version.
+
+  This program is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program; if not, write to the Free Software Foundation,
+  Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+  
+  $Id$
+*/
+
+// adapted from https://community.oracle.com/thread/1479784
+
+package processing.app.debug;
+
+import javax.swing.JTextArea;
+import javax.swing.SwingUtilities;
+import javax.swing.event.DocumentEvent;
+import javax.swing.event.DocumentListener;
+import javax.swing.text.BadLocationException;
+
+public class TextAreaFIFO extends JTextArea implements DocumentListener {
+  private int maxChars;
+
+  private int updateCount; // limit how often we trim the document
+
+  private boolean doTrim;
+
+  public TextAreaFIFO(int max) {
+    maxChars = max;
+    updateCount = 0;
+    doTrim = true;
+    getDocument().addDocumentListener(this);
+  }
+
+  public void allowTrim(boolean trim) {
+    doTrim = trim;
+  }
+
+  public void insertUpdate(DocumentEvent e) {
+    if (++updateCount > 150 && doTrim) {
+      updateCount = 0;
+      SwingUtilities.invokeLater(new Runnable() {
+        public void run() {
+          trimDocument();
+        }
+      });
+    }
+  }
+
+  public void removeUpdate(DocumentEvent e) {
+  }
+
+  public void changedUpdate(DocumentEvent e) {
+  }
+
+  public void trimDocument() {
+    int len = 0;
+    len = getDocument().getLength();
+    if (len > maxChars) {
+      int n = len - maxChars;
+      System.out.println("trimDocument: remove " + n + " chars");
+      try {
+        getDocument().remove(0, n);
+      } catch (BadLocationException ble) {
+      }
+    }
+  }
+}

build/shared/revisions.txt

@@ -13,6 +13,9 @@ ARDUINO 1.0.7
 * Fixed missing NOT_AN_INTERRUPT constant in digitalPinToInterrupt() macro
 * Fixed performance regression in HardwareSerial::available() introduced with https://github.com/arduino/Arduino/pull/2057
 
+[ide]
+* Mitigated Serial Monitor resource exhaustion when the connected device sends a lot of data (Paul Stoffregen)
+
 ARDUINO 1.0.6 - 2014.09.16
 
 [core]