JarEntryReader.java

package mandelbrot.ocamljava_maven_plugin.util;

import java.io.BufferedInputStream;
import java.io.ByteArrayOutputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Collection;
import java.util.Set;
import java.util.jar.JarEntry;
import java.util.jar.JarInputStream;
import java.util.jar.Manifest;

import org.apache.maven.plugin.AbstractMojo;
import org.codehaus.plexus.util.FileUtils;

import com.google.common.base.Optional;
import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableList;

public class JarEntryReader {

	private volatile Optional<Manifest> manifest;

	public Optional<Manifest> getManifest() {
		return manifest == null ? Optional.<Manifest> absent() : manifest;
	}

	@SuppressWarnings("unused")
	private final AbstractMojo abstractMojo;

	public JarEntryReader(final AbstractMojo abstractMojo) {
		this.abstractMojo = Preconditions.checkNotNull(abstractMojo);
	}

	private static final int BUFFER_SIZE = 16384;

	public Collection<EntryInfo> readEntries(final String archiveFile) throws IOException {
		return readEntries(archiveFile, null, null);
	}
	
	public Collection<EntryInfo> readEntries(final String archiveFile, final byte[] optionalBuffer) throws IOException {
		return readEntries(archiveFile, optionalBuffer, null);
	}
	

	public Collection<EntryInfo> readEntries(final String archiveFile,
			final Set<String> allowedExtensions) throws IOException {
		return readEntries(archiveFile, null, allowedExtensions);
	}

	public Collection<EntryInfo> readEntries(final String archiveFile,
			final byte[] optionalBuffer, final Set<String> allowedExtensions)
			throws IOException {

		final byte[] buffer = optionalBuffer == null ? new byte[BUFFER_SIZE]
				: optionalBuffer;

		final FileInputStream in = new FileInputStream(archiveFile);
		final BufferedInputStream bufferedInputStream = new BufferedInputStream(
				in);
		final JarInputStream jarInputStream = new JarInputStream(
				bufferedInputStream);
		this.manifest = Optional.fromNullable(jarInputStream.getManifest());

		final ImmutableList.Builder<EntryInfo> builder = ImmutableList
				.builder();

		JarEntry nextEntry = null;

		while ((nextEntry = jarInputStream.getNextJarEntry()) != null) {
			if (allowedExtensions == null || allowedExtensions.contains(FileUtils.getExtension(nextEntry.getName()).toLowerCase())) {
				builder.add(getEntryInfo(nextEntry, jarInputStream, buffer));
			}
		}

		return builder.build();
	}

	private EntryInfo getEntryInfo(final JarEntry nextEntry,
			final JarInputStream in, final byte[] buffer) throws IOException {

		final ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();

		pipe(byteArrayOutputStream, buffer, in);

		return EntryInfo.builder()
				.setBytes(byteArrayOutputStream.toByteArray())
				.setEntry(nextEntry).build();

	}

	private void pipe(final OutputStream out, final byte[] buffer,
			final InputStream in) throws IOException {
		while (true) {
			final int nRead = in.read(buffer, 0, buffer.length);
			if (nRead <= 0)
				break;
			out.write(buffer, 0, nRead);
		}
	}
}