org.codehaus.mojo.mrm.impl.digest.MD5DigestFileEntry.java Source code

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Here is the source code for org.codehaus.mojo.mrm.impl.digest.MD5DigestFileEntry.java

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/*
 * Copyright 2011 Stephen Connolly
 *
 * 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 org.codehaus.mojo.mrm.impl.digest;

import org.apache.commons.io.IOUtils;
import org.apache.commons.lang.StringUtils;
import org.codehaus.mojo.mrm.api.BaseFileEntry;
import org.codehaus.mojo.mrm.api.DirectoryEntry;
import org.codehaus.mojo.mrm.api.FileEntry;
import org.codehaus.mojo.mrm.api.FileSystem;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.math.BigInteger;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * A {@link FileEntry} that corresponds to the MD5 digest of another file entry.
 */
public class MD5DigestFileEntry extends BaseFileEntry {

    /**
     * Ensure consistent serialization.
     *
     * @since 1.0
     */
    private static final long serialVersionUID = 1L;

    /**
     * The entry we will calculate the digest of.
     *
     * @since 1.0
     */
    private final FileEntry entry;

    /**
     * Creates an instance in the specified directory of the specified file system that will calculate the
     * digest of the specified file entry.
     *
     * @param fileSystem the file system.
     * @param parent     the parent directory.
     * @param entry      the entry to digest.
     * @since 1.0
     */
    public MD5DigestFileEntry(FileSystem fileSystem, DirectoryEntry parent, FileEntry entry) {
        super(fileSystem, parent, entry.getName() + ".md5");
        this.entry = entry;
    }

    /**
     * {@inheritDoc}
     */
    public long getLastModified() throws IOException {
        return entry.getLastModified();
    }

    /**
     * {@inheritDoc}
     */
    public long getSize() throws IOException {
        return 32;
    }

    /**
     * {@inheritDoc}
     */
    public InputStream getInputStream() throws IOException {
        return new ByteArrayInputStream(getContent());
    }

    /**
     * Generates the digest.
     *
     * @return the digest.
     * @throws IOException if the backing entry could not be read.
     * @since 1.0
     */
    private byte[] getContent() throws IOException {
        InputStream is = null;
        try {
            MessageDigest digest = MessageDigest.getInstance("MD5");
            digest.reset();
            byte[] buffer = new byte[8192];
            int read;
            try {
                is = entry.getInputStream();
                while ((read = is.read(buffer)) > 0) {
                    digest.update(buffer, 0, read);
                }
            } catch (IOException e) {
                if (is != null) {
                    throw e;
                }
            }
            final String md5 = StringUtils.leftPad(new BigInteger(1, digest.digest()).toString(16), 32, "0");
            return md5.getBytes();
        } catch (NoSuchAlgorithmException e) {
            IOException ioe = new IOException("Unable to calculate hash");
            ioe.initCause(e);
            throw ioe;
        } finally {
            IOUtils.closeQuietly(is);
        }
    }

    /**
     * A {@link org.codehaus.mojo.mrm.impl.digest.DigestFileEntryFactory} that creates MD5 digest entries.
     *
     * @since 1.0
     */
    public static class Factory extends BaseDigestFileEntryFactory {
        /**
         * {@inheritDoc}
         */
        public String getType() {
            return ".md5";
        }

        /**
         * {@inheritDoc}
         */
        public FileEntry create(FileSystem fileSystem, DirectoryEntry parent, FileEntry entry) {
            return new MD5DigestFileEntry(fileSystem, parent, entry);
        }
    }
}