bundles/org.eclipse.core.runtime/src/org/eclipse/core/internal/content/XMLContentDescriber.java

/*******************************************************************************
 * Copyright (c) 2004 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials 
 * are made available under the terms of the Common Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/cpl-v10.html
 * 
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.core.internal.content;

import java.io.*;
import org.eclipse.core.runtime.content.IContentDescriber;
import org.eclipse.core.runtime.content.IContentDescription;

/**
 * A content interpreter for XML files. 
 * 
 * @see "http://www.w3.org/TR/REC-xml *"
 */
public class XMLContentDescriber implements IContentDescriber {
	private static final String ENCODING = "encoding=\""; //$NON-NLS-1$
	private static final String XML_PREFIX = "<?xml "; //$NON-NLS-1$
	private static final byte[] XML_PREFIX_BYTES = new byte[] {'<', '?', 'x', 'm', 'l', ' '}; //$NON-NLS-1$

	public int describe(InputStream input, IContentDescription description, int flags) throws IOException {
		//TODO: support BOM
		byte[] prefix = new byte[XML_PREFIX.length()];
		if (input.read(prefix) < prefix.length)
			// there is not enough info to say anything
			return INDETERMINATE;
		for (int i = 0; i < prefix.length; i++)
			if (prefix[i] != XML_PREFIX_BYTES[i])
				// we don't have a XMLDecl... there is not enough info to say anything
				return INDETERMINATE;
		// describe charset if requested
		if ((flags & IContentDescription.CHARSET) != 0) {
			String fullXMLDecl = readFullXMLDecl(input);
			if (fullXMLDecl != null)
				description.setCharset(getCharset(fullXMLDecl));
		}
		return VALID;
	}

	private String readFullXMLDecl(InputStream input) throws IOException {
		StringBuffer xmlDecl = new StringBuffer(50);
		int c;
		// looks for XMLDecl ending char (?)
		while (((c = input.read()) != -1 && c != '?'))
			xmlDecl.append((char) c);
		return c == '?' ? xmlDecl.toString() : null;
	}

	public int describe(Reader input, IContentDescription description, int flags) throws IOException {
		BufferedReader reader = new BufferedReader(input);
		String line = reader.readLine();
		// end of stream
		if (line == null)
			return INDETERMINATE;
		// XMLDecl should be the first string (no blanks allowed)
		if (!line.startsWith(XML_PREFIX))
			return INDETERMINATE;
		// describe charset if requested
		if ((flags & IContentDescription.CHARSET) != 0)
			description.setCharset(getCharset(line));
		return VALID;
	}

	private String getCharset(String firstLine) {
		int encodingPos = firstLine.indexOf(ENCODING);
		if (encodingPos == -1)
			return null;
		int firstQuote = firstLine.indexOf('"', encodingPos);
		if (firstQuote == -1 || firstLine.length() == firstQuote - 1)
			return null;
		int secondQuote = firstLine.indexOf('"', firstQuote + 1);
		if (secondQuote == -1)
			return null;
		return firstLine.substring(firstQuote + 1, secondQuote);
	}

	public int getSupportedOptions() {
		return IContentDescription.CHARSET;
	}
}