TargetSourceRangeComputer.java

/*******************************************************************************
 * Copyright (c) 2005, 2009 IBM Corporation 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
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.jdt.core.dom.rewrite;

import org.eclipse.jdt.core.dom.ASTNode;
import org.eclipse.jdt.core.dom.CompilationUnit;

/**
 * An object for computing adjusted source ranges for AST nodes that are being replaced or deleted.
 * <p>
 * For example, a refactoring like inline method may choose to replace calls to the method but leave
 * intact any comments immediately preceding the calls. On the other hand, a refactoring like
 * extract method may choose to extract not only the nodes for the selected code but also any
 * comments preceding or following them.
 * </p>
 * <p>
 * Clients should subclass if they need to influence the the source range to be affected when
 * replacing or deleting a particular node. An instance of the subclass should be registered with
 * {@link ASTRewrite#setTargetSourceRangeComputer(TargetSourceRangeComputer)}. During a call to
 * {@link ASTRewrite#rewriteAST(org.eclipse.jface.text.IDocument, java.util.Map)}, the
 * {@link #computeSourceRange(ASTNode)} method on this object will be used to compute the source
 * range for a node being deleted or replaced.
 * </p>
 * 
 * @since 3.1
 */
public class TargetSourceRangeComputer {

	/**
	 * Reified source range. Instances are "value" object (cannot be modified).
	 * 
	 * @since 3.1
	 */
	public static final class SourceRange {
		/**
		 * 0-based character index, or <code>-1</code> if no source position information is known.
		 */
		private int startPosition;

		/**
		 * (possibly 0) length, or <code>0</code> if no source position information is known.
		 */
		private int length;

		/**
		 * Creates a new source range.
		 * 
		 * @param startPosition the 0-based character index, or <code>-1</code> if no source
		 *            position information is known
		 * @param length the (possibly 0) length, or <code>0</code> if no source position
		 *            information is known
		 */
		public SourceRange(int startPosition, int length) {
			this.startPosition= startPosition;
			this.length= length;
		}

		/**
		 * Returns the start position.
		 * 
		 * @return the 0-based character index, or <code>-1</code> if no source position information
		 *         is known
		 */
		public int getStartPosition() {
			return this.startPosition;
		}

		/**
		 * Returns the source length.
		 * 
		 * @return a (possibly 0) length, or <code>0</code> if no source position information is
		 *         known
		 */
		public int getLength() {
			return this.length;
		}
	}

	/**
	 * Creates a new target source range computer.
	 */
	public TargetSourceRangeComputer() {
		// do nothing
	}

	/**
	 * Returns the target source range of the given node. Unlike {@link ASTNode#getStartPosition()}
	 * and {@link ASTNode#getLength()}, the extended source range may include comments and
	 * whitespace immediately before or after the normal source range for the node.
	 * <p>
	 * The returned source ranges must satisfy the following conditions:
	 * <dl>
	 * <li>no two source ranges in an AST may be overlapping</li>
	 * <li>a source range of a parent node must fully cover the source ranges of its children</li>
	 * </dl>
	 * </p>
	 * <p>
	 * The default implementation uses {@link CompilationUnit#getExtendedStartPosition(ASTNode)} and
	 * {@link CompilationUnit#getExtendedLength(ASTNode)} to compute the target source range.
	 * Clients may override or extend this method to expand or contract the source range of the
	 * given node. The resulting source range must cover at least the original source range of the
	 * node.
	 * </p>
	 * 
	 * @param node the node with a known source range in the compilation unit being rewritten
	 * @return the exact source range in the compilation unit being rewritten that should be
	 *         replaced (or deleted)
	 */
	public SourceRange computeSourceRange(ASTNode node) {
		ASTNode root= node.getRoot();
		if (root instanceof CompilationUnit) {
			CompilationUnit cu= (CompilationUnit)root;
			return new SourceRange(cu.getExtendedStartPosition(node), cu.getExtendedLength(node));
		}
		return new SourceRange(node.getStartPosition(), node.getLength());
	}
}