UnionInputStream: combines sequential InputStreams into one

The UnionInputStream utility class combines multiple sequential
InputStreams so they appear to the caller as a single stream with
no gaps.  This can be used to concentate streams coming from multiple
independent HTTP connections (for example).

The companion unit test covers the class's full functionality.

Change-Id: I0676c7b5e082a5886bf0e8f43f9fd6c46a666228
Signed-off-by: Shawn O. Pearce <sop@google.com>

1 files changed, 217 insertions, 0 deletions

diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/util/io/UnionInputStreamTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/util/io/UnionInputStreamTest.java
new file mode 100644
index 0000000000..2bcd134c66
--- /dev/null
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/util/io/UnionInputStreamTest.java
@@ -0,0 +1,217 @@
+/*
+ * Copyright (C) 2009, Google Inc.
+ * and other copyright owners as documented in the project's IP log.
+ *
+ * This program and the accompanying materials are made available
+ * under the terms of the Eclipse Distribution License v1.0 which
+ * accompanies this distribution, is reproduced below, and is
+ * available at http://www.eclipse.org/org/documents/edl-v10.php
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * - 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.
+ *
+ * - Neither the name of the Eclipse Foundation, Inc. nor the
+ *   names of its contributors may be used to endorse or promote
+ *   products derived from this software without specific prior
+ *   written permission.
+ *
+ * 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 OWNER 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.
+ */
+
+package org.eclipse.jgit.util.io;
+
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+import java.util.Arrays;
+
+import junit.framework.TestCase;
+
+public class UnionInputStreamTest extends TestCase {
+	public void testEmptyStream() throws IOException {
+		final UnionInputStream u = new UnionInputStream();
+		assertTrue(u.isEmpty());
+		assertEquals(-1, u.read());
+		assertEquals(-1, u.read(new byte[1], 0, 1));
+		assertEquals(0, u.available());
+		assertEquals(0, u.skip(1));
+		u.close();
+	}
+
+	public void testReadSingleBytes() throws IOException {
+		final UnionInputStream u = new UnionInputStream();
+
+		assertTrue(u.isEmpty());
+		u.add(new ByteArrayInputStream(new byte[] { 1, 0, 2 }));
+		u.add(new ByteArrayInputStream(new byte[] { 3 }));
+		u.add(new ByteArrayInputStream(new byte[] { 4, 5 }));
+
+		assertFalse(u.isEmpty());
+		assertEquals(3, u.available());
+		assertEquals(1, u.read());
+		assertEquals(0, u.read());
+		assertEquals(2, u.read());
+		assertEquals(0, u.available());
+
+		assertEquals(3, u.read());
+		assertEquals(0, u.available());
+
+		assertEquals(4, u.read());
+		assertEquals(1, u.available());
+		assertEquals(5, u.read());
+		assertEquals(0, u.available());
+		assertEquals(-1, u.read());
+
+		assertTrue(u.isEmpty());
+		u.add(new ByteArrayInputStream(new byte[] { (byte) 255 }));
+		assertEquals(255, u.read());
+		assertEquals(-1, u.read());
+		assertTrue(u.isEmpty());
+	}
+
+	public void testReadByteBlocks() throws IOException {
+		final UnionInputStream u = new UnionInputStream();
+		u.add(new ByteArrayInputStream(new byte[] { 1, 0, 2 }));
+		u.add(new ByteArrayInputStream(new byte[] { 3 }));
+		u.add(new ByteArrayInputStream(new byte[] { 4, 5 }));
+
+		final byte[] r = new byte[5];
+		assertEquals(5, u.read(r, 0, 5));
+		assertTrue(Arrays.equals(new byte[] { 1, 0, 2, 3, 4 }, r));
+		assertEquals(1, u.read(r, 0, 5));
+		assertEquals(5, r[0]);
+		assertEquals(-1, u.read(r, 0, 5));
+	}
+
+	public void testArrayConstructor() throws IOException {
+		final UnionInputStream u = new UnionInputStream(
+				new ByteArrayInputStream(new byte[] { 1, 0, 2 }),
+				new ByteArrayInputStream(new byte[] { 3 }),
+				new ByteArrayInputStream(new byte[] { 4, 5 }));
+
+		final byte[] r = new byte[5];
+		assertEquals(5, u.read(r, 0, 5));
+		assertTrue(Arrays.equals(new byte[] { 1, 0, 2, 3, 4 }, r));
+		assertEquals(1, u.read(r, 0, 5));
+		assertEquals(5, r[0]);
+		assertEquals(-1, u.read(r, 0, 5));
+	}
+
+	public void testMarkSupported() {
+		final UnionInputStream u = new UnionInputStream();
+		assertFalse(u.markSupported());
+		u.add(new ByteArrayInputStream(new byte[] { 1, 0, 2 }));
+		assertFalse(u.markSupported());
+	}
+
+	public void testSkip() throws IOException {
+		final UnionInputStream u = new UnionInputStream();
+		u.add(new ByteArrayInputStream(new byte[] { 1, 0, 2 }));
+		u.add(new ByteArrayInputStream(new byte[] { 3 }));
+		u.add(new ByteArrayInputStream(new byte[] { 4, 5 }));
+		assertEquals(0, u.skip(0));
+		assertEquals(4, u.skip(4));
+		assertEquals(4, u.read());
+		assertEquals(1, u.skip(5));
+		assertEquals(0, u.skip(5));
+		assertEquals(-1, u.read());
+
+		u.add(new ByteArrayInputStream(new byte[] { 20, 30 }) {
+			public long skip(long n) {
+				return 0;
+			}
+		});
+		assertEquals(2, u.skip(8));
+		assertEquals(-1, u.read());
+	}
+
+	public void testAutoCloseDuringRead() throws IOException {
+		final UnionInputStream u = new UnionInputStream();
+		final boolean closed[] = new boolean[2];
+		u.add(new ByteArrayInputStream(new byte[] { 1 }) {
+			public void close() {
+				closed[0] = true;
+			}
+		});
+		u.add(new ByteArrayInputStream(new byte[] { 2 }) {
+			public void close() {
+				closed[1] = true;
+			}
+		});
+
+		assertFalse(closed[0]);
+		assertFalse(closed[1]);
+
+		assertEquals(1, u.read());
+		assertFalse(closed[0]);
+		assertFalse(closed[1]);
+
+		assertEquals(2, u.read());
+		assertTrue(closed[0]);
+		assertFalse(closed[1]);
+
+		assertEquals(-1, u.read());
+		assertTrue(closed[0]);
+		assertTrue(closed[1]);
+	}
+
+	public void testCloseDuringClose() throws IOException {
+		final UnionInputStream u = new UnionInputStream();
+		final boolean closed[] = new boolean[2];
+		u.add(new ByteArrayInputStream(new byte[] { 1 }) {
+			public void close() {
+				closed[0] = true;
+			}
+		});
+		u.add(new ByteArrayInputStream(new byte[] { 2 }) {
+			public void close() {
+				closed[1] = true;
+			}
+		});
+
+		assertFalse(closed[0]);
+		assertFalse(closed[1]);
+
+		u.close();
+
+		assertTrue(closed[0]);
+		assertTrue(closed[1]);
+	}
+
+	public void testExceptionDuringClose() {
+		final UnionInputStream u = new UnionInputStream();
+		u.add(new ByteArrayInputStream(new byte[] { 1 }) {
+			public void close() throws IOException {
+				throw new IOException("I AM A TEST");
+			}
+		});
+		try {
+			u.close();
+			fail("close ignored inner stream exception");
+		} catch (IOException e) {
+			assertEquals("I AM A TEST", e.getMessage());
+		}
+	}
+}