core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/text/CWordFinder.java

package org.eclipse.cdt.internal.ui.text;

/*
 * (c) Copyright QNX Software Systems Ltd. 2002.
 * All Rights Reserved.
 */

import org.eclipse.jface.text.BadLocationException;
import org.eclipse.jface.text.IDocument;
import org.eclipse.jface.text.IRegion;
import org.eclipse.jface.text.Region;

/**
 * This is a helper class for the text editor to be able to determine,
 * given a particular offset in a document, various candidates segments
 * for things like context help, proposals and hovering.
 */
public class CWordFinder 
{
	/**
	 * This method determines for a given offset into a given document
	 * what the region is which defines the current word.  A word is
	 * defined as the set of non "C" identifiers.  So assuming that !
	 * indicated the current cursor postion:
	 *  !afunction(int a, int b) --> word = length 0
	 *  afunc!tion(int a, int b) --> word = afunction
	 *  afunction!(int a, int b) --> word = afunction
	 *  afunction(!int a, int b) --> word = length 0
	 *  afunction(int a,! int b) --> word = length 0
	 *  afunction(!)			 --> word = length 0
	 * @param document The document to be examined
	 * @param offset The offset into the document where a word should 
	 * be idendified.
	 * @return The region defining the current word, which may be a 
	 * region of length 0 if the offset is not in a word, or null if
	 * there is an error accessing the docment data.
	 */
	public static IRegion findWord( IDocument document, int offset ) 
	{
		int start = -1;
		int end = -1;
				
		try 
		{	
			int pos = offset;
			char c;
			
			while( pos >= 0 ) 
			{
				c = document.getChar( pos );
				if ( !Character.isJavaIdentifierPart( c ) )
					break;
				--pos;
			}
			
			start = pos;
			
			pos = offset;
			int length = document.getLength();
			
			while( pos < length ) 
			{
				c = document.getChar( pos );
				if ( !Character.isJavaIdentifierPart( c ) )
					break;
				++pos;
			}
			
			end = pos;
			
		} 
		catch( BadLocationException x ) 
		{
		}
		
		if ( start > -1 && end > -1 ) 
		{
			if ( start == offset && end == offset )
				return new Region( offset, 0 );
			else if ( start == offset )
				return new Region( start, end - start );
			else
				return new Region( start + 1, end - start - 1 );
		}
		
		return null;
	}
	
	/**
	 * This method will determine the region for the name of the function 
	 * within which the current offset is contained.
	 * @param document The document to be examined
	 * @param offset The offset into the document where a word should 
	 * be idendified.
	 * @return The region defining the current word, which may be a 
	 * region of length 0 if the offset is not in a function, or null if
	 * there is an error accessing the docment data.
	 */
	public static IRegion findFunction( IDocument document, int offset ) 
	{
		int leftbracket = -1;
		int leftbracketcount = 0;
		int rightbracket = -1;
		int rightbracketcount = 0;
		int functionstart = -1;
		int functionend = -1;
				
				
		try 
		{	
			int length = document.getLength();
			int pos;
			char c;

			//Find most relevant right bracket from our position
			pos = offset;
			rightbracketcount = leftbracketcount = 0;
			while(pos < length) {
				c = document.getChar( pos );

				if( c == ')') {
					rightbracketcount++;
					if(rightbracketcount >= leftbracketcount) {
						rightbracket = pos;
						break;
					}
				}
				
				if(c == '(') {			
					leftbracketcount++;
				}
				
				if(c == ';') {
					break;
				}
				
				pos++;
			}
			
			if ( rightbracket == -1 ) {
				return new Region(offset, 0);
			}

			//Now backtrack our way from the rightbracket to the left
			pos = rightbracket;
			rightbracketcount = leftbracketcount = 0;
			while(pos >= 0) {
				c = document.getChar( pos );

				if( c == ')') {
					rightbracketcount++;
				}
				
				if(c == '(') {			
					leftbracketcount++;
					if(leftbracketcount >= rightbracketcount) {
						leftbracket = pos;
						break;
					}
				}
				
				if(c == ';') {
					break;
				}
				
				pos--;
			}

			if ( leftbracket == -1 ) {
				return new Region(offset, 0);
			}
			
			//Now work our way to the function name
			pos = leftbracket - 1;
			while(pos >= 0) {
				c = document.getChar( pos );
				if(functionend == -1 && c == ' ' ) {
					pos--;
					continue;
				}
				
				if(!Character.isJavaIdentifierPart(c)) {
					break;
				}
				
				functionstart = pos;
				if(functionend == -1) {
					functionend = pos;
				}

				pos--;
			}
		} catch( BadLocationException x ) {
			/* Ignore */
		}
		
		if (functionstart > -1 && functionend > -1) {
			return new Region(functionstart, functionend - functionstart + 1);
		}
		
		return null;
	}
	
}