Mega Code Archive
Returns the offset of the bracket matching the one at the specified offset of the document
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/*
* TextUtilities.java - Utility functions used by the text area classes
* Copyright (C) 1999 Slava Pestov
*
* You may use and modify this package for any purpose. Redistribution is
* permitted, in both source and binary form, provided that this notice
* remains intact in all source distributions of this package.
*/
import javax.swing.text.BadLocationException;
import javax.swing.text.Document;
/**
* Class with several utility functions used by the text area component.
*
* @author Slava Pestov
* @version $Id$
*/
public class TextUtilities
{
/**
* Returns the offset of the bracket matching the one at the specified offset
* of the document, or -1 if the bracket is unmatched (or if the character is
* not a bracket).
*
* @param doc
* The document
* @param offset
* The offset
* @exception BadLocationException
* If an out-of-bounds access was attempted on the document
* text
*/
public static int findMatchingBracket( Document doc, int offset ) throws BadLocationException
{
if( doc.getLength() == 0 )
return -1;
char c = doc.getText( offset, 1 ).charAt( 0 );
char cprime; // c` - corresponding character
boolean direction; // true = back, false = forward
switch( c )
{
case '(' :
cprime = ')';
direction = false;
break;
case ')' :
cprime = '(';
direction = true;
break;
case '[' :
cprime = ']';
direction = false;
break;
case ']' :
cprime = '[';
direction = true;
break;
case '{' :
cprime = '}';
direction = false;
break;
case '}' :
cprime = '{';
direction = true;
break;
default :
return -1;
}
int count;
// How to merge these two cases is left as an exercise
// for the reader.
// Go back or forward
if( direction )
{
// Count is 1 initially because we have already
// `found' one closing bracket
count = 1;
// Get text[0,offset-1];
String text = doc.getText( 0, offset );
// Scan backwards
for( int i = offset - 1; i >= 0; i-- )
{
// If text[i] == c, we have found another
// closing bracket, therefore we will need
// two opening brackets to complete the
// match.
char x = text.charAt( i );
if( x == c )
count++ ;
// If text[i] == cprime, we have found a
// opening bracket, so we return i if
// --count == 0
else if( x == cprime )
{
if( --count == 0 )
return i;
}
}
}
else
{
// Count is 1 initially because we have already
// `found' one opening bracket
count = 1;
// So we don't have to + 1 in every loop
offset++ ;
// Number of characters to check
int len = doc.getLength() - offset;
// Get text[offset+1,len];
String text = doc.getText( offset, len );
// Scan forwards
for( int i = 0; i < len; i++ )
{
// If text[i] == c, we have found another
// opening bracket, therefore we will need
// two closing brackets to complete the
// match.
char x = text.charAt( i );
if( x == c )
count++ ;
// If text[i] == cprime, we have found an
// closing bracket, so we return i if
// --count == 0
else if( x == cprime )
{
if( --count == 0 )
return i + offset;
}
}
}
// Nothing found
return -1;
}
}
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