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.QualifiedName;
import org.eclipse.core.runtime.content.IContentDescription;
import org.eclipse.core.runtime.content.ITextContentDescriber;

/**
 * A content interpreter for XML files. 
 * This class provides internal basis for XML-based content describers.
 * <p>
 * Note: do not add protected/public members to this class if you don't intend to 
 * make them public API.
 * </p>
 *
 * @see org.eclipse.core.runtime.content.XMLRootElementContentDescriber 
 * @see "http://www.w3.org/TR/REC-xml *"
 */
public class XMLContentDescriber extends TextContentDescriber implements ITextContentDescriber {
	private static final QualifiedName[] SUPPORTED_OPTIONS = new QualifiedName[] {IContentDescription.CHARSET, IContentDescription.BYTE_ORDER_MARK};
	private static final String ENCODING = "encoding=\""; //$NON-NLS-1$
	private static final String XML_PREFIX = "<?xml "; //$NON-NLS-1$

	public int describe(InputStream input, IContentDescription description) throws IOException {
		byte[] bom = getByteOrderMark(input);
		String xmlDeclEncoding = "UTF-8"; //$NON-NLS-1$
		input.reset();
		if (bom != null) {
			if (bom == IContentDescription.BOM_UTF_16BE)
				xmlDeclEncoding = "UTF-16BE"; //$NON-NLS-1$
			else if (bom == IContentDescription.BOM_UTF_16LE)
				xmlDeclEncoding = "UTF-16LE"; //$NON-NLS-1$
			// skip BOM to make comparison simpler
			input.skip(bom.length);
			// set the BOM in the description if requested
			if (description != null && description.isRequested(IContentDescription.BYTE_ORDER_MARK))
				description.setProperty(IContentDescription.BYTE_ORDER_MARK, bom);
		}
		byte[] xmlPrefixBytes = XML_PREFIX.getBytes(xmlDeclEncoding);
		byte[] prefix = new byte[xmlPrefixBytes.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] != xmlPrefixBytes[i])
				// we don't have a XMLDecl... there is not enough info to say anything
				return INDETERMINATE;
		if (description == null)
			return VALID;
		// describe charset if requested
		if (description.isRequested(IContentDescription.CHARSET)) {
			String fullXMLDecl = readFullXMLDecl(input, xmlDeclEncoding);
			if (fullXMLDecl != null)
				description.setProperty(IContentDescription.CHARSET, getCharset(fullXMLDecl));
		}
		return VALID;
	}

	private String readFullXMLDecl(InputStream input, String unicodeEncoding) throws IOException {
		byte[] xmlDecl = new byte[100];
		int c = 0;
		// looks for XMLDecl ending char (?)
		int read = 0;
		while (read < xmlDecl.length && (c = input.read()) != -1 && c != '?')
			xmlDecl[read++] = (byte) c;
		return c == '?' ? new String(xmlDecl, 0, read, unicodeEncoding) : null;
	}

	public int describe(Reader input, IContentDescription description) 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;
		if (description == null)
			return VALID;		
		// describe charset if requested
		if ((description.isRequested(IContentDescription.CHARSET)))
			description.setProperty(IContentDescription.CHARSET, getCharset(line));
		return VALID;
	}

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

	public QualifiedName[] getSupportedOptions() {
		return SUPPORTED_OPTIONS;
	}
}