org.alfresco.encoding.BomCharactersetFinder.java Source code

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Here is the source code for org.alfresco.encoding.BomCharactersetFinder.java

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/*
 * Copyright (C) 2005-2010 Alfresco Software Limited.
 *
 * This file is part of Alfresco
 *
 * Alfresco is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Alfresco is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with Alfresco. If not, see <http://www.gnu.org/licenses/>.
 */
package org.alfresco.encoding;

import java.io.ByteArrayInputStream;
import java.io.InputStreamReader;
import java.nio.charset.Charset;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * Byte Order Marker encoding detection.
 * 
 * @since 2.1
 * @author Pacific Northwest National Lab
 * @author Derek Hulley
 */
public class BomCharactersetFinder extends AbstractCharactersetFinder {
    private static Log logger = LogFactory.getLog(BomCharactersetFinder.class);

    @Override
    public void setBufferSize(int bufferSize) {
        logger.warn("Setting the buffersize has no effect for charset finder: "
                + BomCharactersetFinder.class.getName());
    }

    /**
     * @return          Returns 64
     */
    @Override
    protected int getBufferSize() {
        return 64;
    }

    /**
     * Just searches the Byte Order Marker, i.e. the first three characters for a sign of
     * the encoding.
     */
    protected Charset detectCharsetImpl(byte[] buffer) throws Exception {
        Charset charset = null;
        ByteArrayInputStream bis = null;
        try {
            bis = new ByteArrayInputStream(buffer);
            bis.mark(3);
            char[] byteHeader = new char[3];
            InputStreamReader in = new InputStreamReader(bis);
            int bytesRead = in.read(byteHeader);
            bis.reset();

            if (bytesRead < 2) {
                // ASCII
                charset = Charset.forName("Cp1252");
            } else if (byteHeader[0] == 0xFE && byteHeader[1] == 0xFF) {
                // UCS-2 Big Endian
                charset = Charset.forName("UTF-16BE");
            } else if (byteHeader[0] == 0xFF && byteHeader[1] == 0xFE) {
                // UCS-2 Little Endian
                charset = Charset.forName("UTF-16LE");
            } else if (bytesRead >= 3 && byteHeader[0] == 0xEF && byteHeader[1] == 0xBB && byteHeader[2] == 0xBF) {
                // UTF-8
                charset = Charset.forName("UTF-8");
            } else {
                // No idea
                charset = null;
            }
            // Done
            return charset;
        } finally {
            if (bis != null) {
                try {
                    bis.close();
                } catch (Throwable e) {
                }
            }
        }
    }
}