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The DSI utilities are a mishmash of classes accumulated during the last twenty years in projects developed at the DSI (Dipartimento di Scienze dell'Informazione, i.e., Information Sciences Department), now DI (Dipartimento di Informatica, i.e., Informatics Department), of the Universita` degli Studi di Milano.

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/*
 * DSI utilities
 *
 * Copyright (C) 2010-2020 Sebastiano Vigna
 *
 *  This library is free software; you can redistribute it and/or modify it
 *  under the terms of the GNU Lesser General Public License as published by the Free
 *  Software Foundation; either version 3 of the License, or (at your option)
 *  any later version.
 *
 *  This library is distributed in the hope that it will be useful, but
 *  WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 *  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License
 *  for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public License
 *  along with this program; if not, see .
 *
 */

package it.unimi.dsi.io;

import static org.junit.Assert.assertEquals;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.channels.FileChannel;
import java.nio.channels.FileChannel.MapMode;
import java.util.Random;

import org.junit.Test;

import it.unimi.dsi.util.SplitMix64Random;

/** Note: this test has little meaning unless you change ByteBufferInputStream.FIRST_SHIFT to 16.
 */

@SuppressWarnings("resource")
public class ByteBufferInputStreamTest {

	private static final boolean DEBUG = false;

	@Test
	public void testStream() throws FileNotFoundException, IOException {
		final File f = File.createTempFile(ByteBufferInputStreamTest.class.getName(), "tmp");
		f.deleteOnExit();
		final int l = 100000;
		final long seed = System.currentTimeMillis();
		if (DEBUG) System.err.println("Seed: " + seed);
		final Random random = new SplitMix64Random(seed);

		for(int n = 1; n < 8; n++) {
			final FileOutputStream fos = new FileOutputStream(f);
			for(int i = 0; i < l * n; i++) fos.write(random.nextInt() & 0xFF);
			fos.close();

			final FileChannel channel = new FileInputStream(f).getChannel();
			ByteBufferInputStream bis = ByteBufferInputStream.map(channel, MapMode.READ_ONLY);
			if (n % 2 == 0) bis = bis.copy();

			FileInputStream test = new FileInputStream(f);
			FileChannel fc = test.getChannel();
			int a1, a2, off, len, pos;
			final byte b1[] = new byte[32768];
			final byte b2[] = new byte[32768];

			for(int k = 0; k < l / 10; k++) {

				switch (random.nextInt(6)) {

				case 0:
					if (DEBUG) System.err.println("read()");
					a1 = bis.read();
					a2 = test.read();
					assertEquals(a2, a1);
					break;

				case 1:
					off = random.nextInt(b1.length);
					len = random.nextInt(b1.length - off + 1);
					a1 = bis.read(b1, off, len);
					a2 = test.read(b2, off, len);
					if (DEBUG) System.err.println("read(b, " + off + ", " + len + ")");

					assertEquals(a2, a1);

					for (int i = off; i < off + len; i++)
						assertEquals(b2[i], b1[i]);
					break;

				case 2:
					if (DEBUG) System.err.println("available()");
					assertEquals(test.available(), bis.available());
					break;

				case 3:
					pos = (int)bis.position();
					if (DEBUG) System.err.println("position()=" + pos);
					assertEquals((int)fc.position(), pos);
					break;

				case 4:
					pos = random.nextInt(l * n);
					bis.position(pos);
					if (DEBUG) System.err.println("position(" + pos + ")");
					(test = new FileInputStream(f)).skip(pos);
					fc = test.getChannel();
					break;

				case 5:
					pos = random.nextInt((int)(l * n - bis.position() + 1));
					if (DEBUG) System.err.println("skip(" + pos + ")");
					a1 = (int)bis.skip(pos);
					a2 = (int)test.skip(pos);
					assertEquals(a2, a1);
					break;
				}
			}

			test.close();
			bis = null;
			System.gc(); // Try to get rid of mapped buffers.
			channel.close();
		}
	}
}