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/* 
 * Licensed to the soi-toolkit project under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The soi-toolkit project licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.soitoolkit.commons.mule.util;

import java.io.IOException;
import java.io.InputStream;
import java.io.PushbackInputStream;

/**
 * Removes BOM chars from an input-stream if any.
 * Based on code published at: http://forums.sun.com/thread.jspa?threadID=5310966
 * 
 * @author Magnus Larsson
 *
 */
public class BOMStripperInputStream extends PushbackInputStream {

    public static final int[][] BOMS =
    {

        {
            0x00, 0x00, 0xFE, 0xFF
        },
        {
            0xFF, 0xFE, 0x00, 0x00
        },

        {
            0x2B, 0x2F, 0x76, 0x38
        },
        {
            0x2B, 0x2F, 0x76, 0x39
        },

        {
            0x2B, 0x2F, 0x76, 0x2B
        },
        {
            0x2B, 0x2F, 0x76, 0x2F
        },

        {
            0xDD, 0x73, 0x66, 0x73
        },
        {
            0xEF, 0xBB, 0xBF
        },

        {
            0x0E, 0xFE, 0xFF
        },
        {
            0xFB, 0xEE, 0x28
        },

        {
            0xFE, 0xFF
        },
        {
            0xFF, 0xFE
        }
    };

 
    static private int testForBOM(int[] bom, int[] bytes)

    {
        for (int index = 0; index < bom.length; index++)
        {
            if (bom[index] != bytes[index])

                return 0;
        }
        return bom.length;
    }
 
    public BOMStripperInputStream(InputStream is) throws IOException

    {
        super(is, 4);
 
        final int[] bytes =
        {

            read(), read(), read(), read()
        };
        int count = 0;
        for (int[] bom : BOMS)

        {
            count = testForBOM(bom, bytes);
            if (count != 0)
                break;
        }

        for (int index = bytes.length - 1; index >= count; index--)
        {
            if (bytes[index] != -1)

                unread(bytes[index]);
        }
    }
}