Bug 519391: avoid iterating and copying large lists

The BuildConsolePartitioner used to compute partitions from offsets
by iterating over the list of partitions. This strategy is fine
for small build outputs. But outputs in the 100,000+ line range
can have huge number of partitions. This commit updates the logic
to take advantage of the fact that the partitions are sorted
and contiguous to do binary searches to find the partition, and
uses a new method (computePartitioningAsList) to use a view onto
the original partitions list instead of significant copying.

Change-Id: I4395df36431a6ae45e6b77d6f76fd29532347ac5

core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/buildconsole/BuildConsolePartitioner.java

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2002, 2017 QNX Software Systems and others.
+ * Copyright (c) 2002, 2018 QNX Software Systems and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
@@ -19,6 +19,7 @@ import java.io.IOException;
 import java.io.OutputStream;
 import java.net.URI;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 import java.util.concurrent.atomic.AtomicBoolean;
 
@@ -61,9 +62,13 @@ public class BuildConsolePartitioner
 
 	/**
 	 * Active list of partitions, must only be accessed form UI thread which
-	 * provides implicit lock
+	 * provides implicit lock.
+	 * 
+	 * The partitions are required to be sorted, and the partitions must not have
+	 * any gaps. (The Offset + Length of partition N must equals the Offset of
+	 * partition N + 1.)
 	 */
-	List<ITypedRegion> fPartitions = new ArrayList<ITypedRegion>();
+	List<BuildConsolePartition> fPartitions = new ArrayList<>();
 	/**
 	 * Active document, must only be accessed form UI thread which provides
 	 * implicit lock
@@ -365,39 +370,70 @@ public class BuildConsolePartitioner
 	 */
 	@Override
 	public ITypedRegion[] computePartitioning(int offset, int length) {
-		if (offset == 0 && length == fDocument.getLength()) {
-			return fPartitions.toArray(new ITypedRegion[fPartitions.size()]);
-		}
-		int end = offset + length;
-		List<ITypedRegion> list = new ArrayList<ITypedRegion>();
-		for (int i = 0; i < fPartitions.size(); i++) {
-			ITypedRegion partition = fPartitions.get(i);
-			int partitionStart = partition.getOffset();
-			int partitionEnd = partitionStart + partition.getLength();
-			if ((offset >= partitionStart && offset <= partitionEnd)
-					|| (offset < partitionStart && end >= partitionStart)) {
-				list.add(partition);
-			}
-		}
+		List<BuildConsolePartition> list = computePartitioningAsList(offset, length);
 		return list.toArray(new ITypedRegion[list.size()]);
 	}
 
+	public List<BuildConsolePartition> computePartitioningAsList(int offset, int length) {
+		List<BuildConsolePartition> list;
+		if (offset == 0 && length == fDocument.getLength()) {
+			list = fPartitions;
+		} else {
+			int fromIndex = getPartitionIndex(offset);
+			int toIndex = getPartitionIndex(offset + length - 1);
+			if (fromIndex < 0 && toIndex < 0) {
+				// entire range falls outside, should be unreachable
+				return Collections.emptyList();
+			} else if (fromIndex < 0) {
+				fromIndex = 0;
+			} else if (toIndex < 0) {
+				toIndex = fPartitions.size() - 1;
+			}
+			list = fPartitions.subList(fromIndex, toIndex + 1);
+		}
+		return list;
+	}
+
 	/**
 	 * @see org.eclipse.jface.text.IDocumentPartitioner#getPartition(int)
 	 */
 	@Override
-	public ITypedRegion getPartition(int offset) {
-		for (int i = 0; i < fPartitions.size(); i++) {
-			ITypedRegion partition = fPartitions.get(i);
-			int start = partition.getOffset();
-			int end = start + partition.getLength();
-			if (offset >= start && offset < end) {
-				return partition;
-			}
+	public BuildConsolePartition getPartition(int offset) {
+		int partitionIndex = getPartitionIndex(offset);
+		if (partitionIndex >= 0) {
+			return fPartitions.get(partitionIndex);
 		}
 		return null;
 	}
 
+	private int getPartitionIndex(int offset) {
+		BuildConsolePartition searchTerm = new BuildConsolePartition(null, offset, 0, null, null, 0);
+		int index = Collections.binarySearch(fPartitions, searchTerm,
+				(a, b) -> Integer.compare(a.getOffset(), b.getOffset()));
+		if (index >= 0) {
+			// exact match to beginning of a partition
+			return index;
+		} else if (index == -1) {
+			// before first partition
+			return -1;
+		} else if (index == -(fPartitions.size() + 1)) {
+			// either in or after last partition
+			BuildConsolePartition lastPartition = fPartitions.get(fPartitions.size() - 1);
+			int lastPartitionEnd = lastPartition.getOffset() + lastPartition.getLength();
+			assert offset >= lastPartition.getOffset();
+			if (offset < lastPartitionEnd) {
+				// within last partition
+				return fPartitions.size() - 1;
+			} else {
+				// after last partition
+				return -1;
+			}
+		} else {
+			// within a partition
+			return -(index + 1) - 1;
+		}
+	}
+
 	@Override
 	public IRegion documentChanged2(DocumentEvent event) {
 		String text = event.getText();
@@ -407,20 +443,19 @@ public class BuildConsolePartitioner
 			fEditData.clear();
 			return new Region(0, 0);
 		}
-		ITypedRegion[] affectedRegions = computePartitioning(event.getOffset(), text.length());
-		if (affectedRegions.length == 0) {
+		List<BuildConsolePartition> affectedRegions = computePartitioningAsList(event.getOffset(), text.length());
+		if (affectedRegions.size() == 0) {
 			return null;
 		}
-		if (affectedRegions.length == 1) {
-			return affectedRegions[0];
+		if (affectedRegions.size() == 1) {
+			return affectedRegions.get(0);
 		}
-		int affectedLength = affectedRegions[0].getLength();
-		for (int i = 1; i < affectedRegions.length; i++) {
-			ITypedRegion region = affectedRegions[i];
+		int affectedLength = 0;
+		for (BuildConsolePartition region : affectedRegions) {
 			affectedLength += region.getLength();
 		}
 
-		return new Region(affectedRegions[0].getOffset(), affectedLength);
+		return new Region(affectedRegions.get(0).getOffset(), affectedLength);
 	}
 
 	public IConsole getConsole() {

core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/buildconsole/BuildConsolePartitionerEditData.java

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2016, 2017 Kichwa Coders and others.
+ * Copyright (c) 2016, 2018 Kichwa Coders and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
@@ -49,7 +49,7 @@ public class BuildConsolePartitionerEditData {
 		/**
 		 * New partitions that match the new contents.
 		 */
-		List<ITypedRegion> getNewPartitions();
+		List<BuildConsolePartition> getNewPartitions();
 
 		/**
 		 * All the streams that have been written to since the last update.
@@ -73,7 +73,7 @@ public class BuildConsolePartitionerEditData {
 	 * Editable partitions, all modifications are made to this copy of the
 	 * partitions, then the UI thread occasionally gets these updates
 	 */
-	private List<BuildConsolePartition> fEditPartitions = new ArrayList<BuildConsolePartition>();
+	private List<BuildConsolePartition> fEditPartitions = new ArrayList<>();
 
 	/**
 	 * Set to true when an edit causes the document marker manager to need to be
@@ -318,7 +318,7 @@ public class BuildConsolePartitionerEditData {
 		boolean problemsAdded;
 		long newOffset;
 		String newConents;
-		List<ITypedRegion> newPartitions;
+		List<BuildConsolePartition> newPartitions;
 		List<IBuildConsoleStreamDecorator> streamsNeedingNotifcation;
 
 		synchronized (this) {
@@ -346,7 +346,7 @@ public class BuildConsolePartitionerEditData {
 			}
 
 			@Override
-			public List<ITypedRegion> getNewPartitions() {
+			public List<BuildConsolePartition> getNewPartitions() {
 				return newPartitions;
 			}
 

core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/buildconsole/BuildConsoleViewer.java

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2002, 2013 QNX Software Systems and others.
+ * Copyright (c) 2002, 2018 QNX Software Systems and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
@@ -11,11 +11,12 @@
  *******************************************************************************/
 package org.eclipse.cdt.internal.ui.buildconsole;
 
+import java.util.List;
+
 import org.eclipse.jface.text.BadLocationException;
 import org.eclipse.jface.text.DocumentEvent;
 import org.eclipse.jface.text.IDocument;
 import org.eclipse.jface.text.IDocumentListener;
-import org.eclipse.jface.text.ITypedRegion;
 import org.eclipse.jface.text.TextViewer;
 import org.eclipse.swt.SWT;
 import org.eclipse.swt.custom.LineBackgroundEvent;
@@ -163,10 +164,10 @@ public class BuildConsoleViewer extends TextViewer
 
 		// Note, computePartitioning actually doesn't change anything in partitioning,
 		// but only computes number of affected regions.
-		ITypedRegion[] regions = partitioner.computePartitioning(event.lineOffset, event.lineText.length());
-		StyleRange[] styles = new StyleRange[regions.length];
-		for (int i = 0; i < regions.length; i++) {
-			BuildConsolePartition partition = (BuildConsolePartition) regions[i];
+		List<BuildConsolePartition> regions = partitioner.computePartitioningAsList(event.lineOffset, event.lineText.length());
+		StyleRange[] styles = new StyleRange[regions.size()];
+		for (int i = 0; i < regions.size(); i++) {
+			BuildConsolePartition partition = regions.get(i);
 			if (partition.getStream()== null) return;
 
 			Color colorFG = partition.getStream().getColor();

core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/buildconsole/DocumentMarkerManager.java

@@ -111,7 +111,7 @@ class DocumentMarkerManager {
 	BuildConsolePartition getCurrentPartition() {
 		if ( 0 <= highlightedPartitionIndex && 	
 				highlightedPartitionIndex < fPartitioner.fPartitions.size() ) {
-			BuildConsolePartition p = (BuildConsolePartition)fPartitioner.fPartitions.get(highlightedPartitionIndex);
+			BuildConsolePartition p = fPartitioner.fPartitions.get(highlightedPartitionIndex);
 			return p;
 		}
 		return null;