com.jaromin.alfresco.extractor.AbstractBitmapExtractor.java Source code

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Here is the source code for com.jaromin.alfresco.extractor.AbstractBitmapExtractor.java

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/**
 * Copyright 2012 Patrick Jaromin
 *
 * Licensed 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 com.jaromin.alfresco.extractor;

import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.InputStream;

import org.apache.commons.lang.ArrayUtils;

/**
 * 
 * @author pjaromin
 *
 */
public abstract class AbstractBitmapExtractor implements BitmapExtractor {

    /**
     * Reads through the file sequentially searching for the sequence. If found it reads that 
     * header fully, positioning the next read for the byte immediately following the header
     * and returns true. If none found, the file will be entirely consumed and method returns false.
     * @param in
     * @return
     * @throws IOException
     */
    protected boolean nextMatch(byte[] seq, InputStream in) throws IOException {
        in = buffer(in);
        int b = 0;
        while ((b = in.read()) != -1) {
            if (matches(seq, in, b)) {
                return true;
            }
        }

        return false;
    }

    /**
     * Check if the next series of bytes from the stream matches the sequence.
     * The int 'b' is the most recently-read byte and the input stream is positioned
     * to read the byte immediately following 'b'.
     * If the match fails, the stream is reset. If it matches, the stream is NOT reset.
     * @param seq
     * @param in
     * @param b
     * @return
     * @throws IOException
     */
    protected boolean matches(byte[] seq, InputStream in, int b) throws IOException {
        if (((byte) b) == seq[0]) {
            // potential match, read next 7 bytes
            byte[] buf = new byte[seq.length - 1];
            in.mark(buf.length);
            if (in.read(buf) == -1) {
                in.reset();
                return false;
            } else {
                if (ArrayUtils.isEquals(buf, ArrayUtils.subarray(seq, 1, seq.length))) { // last 7 bytes
                    return true;
                }
                in.reset(); // rewind
            }
        }
        return false;
    }

    protected InputStream buffer(InputStream in) {
        // Wrap with buffer if needed...
        if (!(in instanceof BufferedInputStream)) {
            in = new BufferedInputStream(in);
        }
        return in;
    }
}