Add AbstractCompressedHandle: an abstract superclass for compressed h…

…andles

src/main/java/org/scijava/io/location/AbstractCompressedHandle.java

@@ -0,0 +1,133 @@
+/*
+ * #%L
+ * SciJava Common shared library for SciJava software.
+ * %%
+ * Copyright (C) 2009 - 2017 Board of Regents of the University of
+ * Wisconsin-Madison, Broad Institute of MIT and Harvard, and Max Planck
+ * Institute of Molecular Cell Biology and Genetics.
+ * %%
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ * #L%
+ */
+
+package org.scijava.io.location;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+
+import org.scijava.io.handle.AbstractStreamHandle;
+import org.scijava.io.handle.DataHandle;
+import org.scijava.io.handle.DataHandleService;
+import org.scijava.io.handle.ResettableStreamHandle;
+import org.scijava.plugin.Parameter;
+
+/**
+ * Abstract superclass for {@link DataHandle}s that operate on compressed data.
+ *
+ * @author Gabriel Einsdorf
+ */
+public abstract class AbstractCompressedHandle<L extends AbstractHigherOrderLocation>
+	extends AbstractStreamHandle<L> implements ResettableStreamHandle<L>
+{
+
+	private DataHandle<Location> rawHandle;
+	protected InputStream inputStream;
+
+	@Parameter
+	private DataHandleService dataHandleService;
+
+	public AbstractCompressedHandle() {
+		super();
+	}
+
+	@Override
+	public void resetStream() throws IOException {
+
+		if (raw() instanceof ResettableStreamHandle<?>) {
+			((ResettableStreamHandle<Location>) rawHandle).resetStream();
+		}
+		else {
+			rawHandle.seek(0);
+		}
+		initInputStream();
+	}
+
+	@Override
+	public InputStream in() throws IOException {
+		if (inputStream == null) {
+			initInputStream();
+		}
+		return inputStream;
+	}
+
+	@Override
+	public long skip(long n) throws IOException {
+		long skipped = in().skip(n);
+		setOffset(offset() + skipped);
+		return skipped; 
+	}
+
+	protected abstract void initInputStream() throws IOException;
+
+	@Override
+	public OutputStream out() throws IOException {
+		return null;
+	}
+
+	@Override
+	public boolean isWritable() {
+		return false;
+	}
+
+	@Override
+	public boolean isReadable() {
+		return true;
+	}
+
+	@Override
+	public long length() throws IOException {
+		return raw().length();
+	}
+
+	@Override
+	public boolean exists() throws IOException {
+		return raw().exists();
+	}
+
+	@Override
+	public void setLength(long length) throws IOException {
+		throw new IOException("This handle " + this.getClass().getSimpleName() +
+			" is read-only!");
+	}
+
+	/**
+	 * @return the raw underlying DataHandle (not decompressed)
+	 */
+	protected DataHandle<Location> raw() {
+		if (rawHandle == null) {
+			rawHandle = dataHandleService.create(get().getBaseLocation());
+		}
+		return rawHandle;
+	}
+
+}