datacite.oai.provider.util.BOMUtil.java Source code

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Here is the source code for datacite.oai.provider.util.BOMUtil.java

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package datacite.oai.provider.util;

/*******************************************************************************
* Copyright (c) 2011 DataCite
*
* All rights reserved. This program and the accompanying 
* materials are made available under the terms of the 
* Apache License, Version 2.0 which accompanies 
* this distribution, and is available at 
* http://www.apache.org/licenses/LICENSE-2.0
*
*******************************************************************************/

import java.io.UnsupportedEncodingException;
import java.util.HashMap;

import org.apache.commons.lang.ArrayUtils;

/**
 * Encapsulates utils for BOM removal. Currently only UTF-8/16/32 supported.
 * @author PaluchM
 *
 */
public class BOMUtil {

    /**UTF-8 Byte Order Mark **/
    public static final byte[] UTF8_BOM = { (byte) 0xEF, (byte) 0xBB, (byte) 0xBF };
    /**UTF-16 Big Endian Byte Order Mark **/
    public static final byte[] UTF16BE_BOM = { (byte) 0xFE, (byte) 0xFF };
    /**UTF-16 Little Endian Byte Order Mark **/
    public static final byte[] UTF16LE_BOM = { (byte) 0xFF, (byte) 0xFE };
    /**UTF-32 Big Endian Byte Order Mark **/
    public static final byte[] UTF32BE_BOM = { (byte) 0x00, (byte) 0x00, (byte) 0xFE, (byte) 0xFF };
    /**UTF-32 Little Endian Byte Order Mark **/
    public static final byte[] UTF32LE_BOM = { (byte) 0xFF, (byte) 0xFE, (byte) 0xFE, (byte) 0xFF };

    /** Mapping of encoding string (alphanumeric only) to BOM **/
    private static final HashMap<String, byte[]> BOM_MAP = new HashMap<String, byte[]>();
    static {
        BOM_MAP.put("UTF8", UTF8_BOM);
        BOM_MAP.put("UTF16LE", UTF16LE_BOM);
        BOM_MAP.put("UTF16BE", UTF16BE_BOM);
        BOM_MAP.put("UTF32BE", UTF32BE_BOM);
        BOM_MAP.put("UTF32LE", UTF32LE_BOM);
    }

    /**Hidden constructor**/
    private BOMUtil() {
    }

    /**
     * Remove a Byte Order Mark from the beginning of a byte[].
     * @param array The byte[] to remove a BOM from.
     * @param encoding The character encoding to remove the BOM for.
     * @return The original byte[] without BOM.
     */
    public static byte[] removeBOM(byte[] array, String encoding) throws UnsupportedEncodingException {
        if (encoding == null || encoding.trim().length() == 0) {
            throw new UnsupportedEncodingException("Unsupported encoding: " + encoding);
        } else {
            encoding = encoding.toUpperCase().replaceAll("[^A-Z0-9]", "");
            byte[] bom = BOMUtil.BOM_MAP.get(encoding);
            if (bom == null) {
                throw new UnsupportedEncodingException("Unsupported encoding: " + encoding);
            } else {
                return BOMUtil.removeBOM(array, bom);
            }
        }
    }

    /**
      * Remove a Byte Order Mark from the beginning of a byte[].
      * @param array The byte[] to remove a BOM from.
      * @param BOM The byte[] BOM to remove.
      * @return The original byte[] without BOM.
      */
    public static byte[] removeBOM(byte[] array, byte[] BOM) {
        int i;
        boolean hasBOM = true;
        for (i = 0; (i < BOM.length) && hasBOM; i++) {
            if ((byte) array[i] != (byte) BOM[i]) {
                hasBOM = false;
            }
        }
        if (hasBOM) {
            return ArrayUtils.subarray(array, BOM.length, array.length);
        } else {
            return array;
        }
    }
}