Index: src/main/java/org/apache/commons/compress/utils/SeekableInMemoryByteChannel.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>ISO-8859-1
===================================================================
--- src/main/java/org/apache/commons/compress/utils/SeekableInMemoryByteChannel.java	(revision d9fe818eef0003afe295e6e6df112257cffbc88f)
+++ src/main/java/org/apache/commons/compress/utils/SeekableInMemoryByteChannel.java	(revision )
@@ -21,7 +21,6 @@
 import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.nio.channels.ClosedChannelException;
-import java.nio.channels.NonWritableChannelException;
 import java.nio.channels.SeekableByteChannel;
 import java.util.Arrays;
 
@@ -50,9 +49,10 @@
     }
 
     @Override
-    public SeekableByteChannel position(long newPosition) {
-        if (newPosition > Integer.MAX_VALUE) {
-            throw new IllegalArgumentException("Position cannot exceed " + Integer.MAX_VALUE);
+    public SeekableByteChannel position(long newPosition) throws IOException {
+        ensureOpen();
+        if (newPosition < 0L || newPosition > Integer.MAX_VALUE) {
+            throw new IllegalArgumentException("Position has to be in range 0.. " + Integer.MAX_VALUE);
         }
         position = (int) newPosition;
         return this;
@@ -76,8 +76,9 @@
 
     @Override
     public int read(ByteBuffer buf) throws IOException {
-        if (!isOpen()) {
-            throw new ClosedChannelException();
+        ensureOpen();
+        if (position > size) {
+            position = size;
         }
         int pos = position;
         int sz = size;
@@ -103,9 +104,7 @@
 
     @Override
     public int write(ByteBuffer b) throws IOException {
-        if (!isOpen()) {
-            throw new ClosedChannelException();
-        }
+        ensureOpen();
         int pos = position;
         int sz = data.length;
         int wanted = b.remaining();
@@ -137,6 +136,12 @@
             len <<= 1;
         }
         data = Arrays.copyOf(data, len);
+    }
+
+    private void ensureOpen() throws ClosedChannelException {
+        if (closed) {
+            throw new ClosedChannelException();
+        }
     }
 
 }
Index: src/test/java/org/apache/commons/compress/utils/SeekableInMemoryByteChannelTest.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>ISO-8859-1
===================================================================
--- src/test/java/org/apache/commons/compress/utils/SeekableInMemoryByteChannelTest.java	(revision )
+++ src/test/java/org/apache/commons/compress/utils/SeekableInMemoryByteChannelTest.java	(revision )
@@ -0,0 +1,174 @@
+package org.apache.commons.compress.utils;
+
+import org.junit.Test;
+
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.nio.channels.ClosedChannelException;
+import java.nio.charset.Charset;
+import java.util.Arrays;
+
+import static org.apache.commons.compress.utils.CharsetNames.UTF_8;
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+
+public class SeekableInMemoryByteChannelTest {
+
+    private final byte[] testData = "Some data".getBytes(Charset.forName(UTF_8));
+
+    @Test
+    public void shouldReadContentsProperly() throws IOException {
+        //given
+        SeekableInMemoryByteChannel c = new SeekableInMemoryByteChannel(testData);
+        ByteBuffer readBuffer = ByteBuffer.allocate(testData.length);
+        //when
+        int readCount = c.read(readBuffer);
+        //then
+        assertEquals(testData.length, readCount);
+        assertArrayEquals(testData, readBuffer.array());
+        assertEquals(testData.length, c.position());
+    }
+
+    @Test
+    public void shouldReadContentsWhenBiggerBufferSupplied() throws IOException {
+        //given
+        SeekableInMemoryByteChannel c = new SeekableInMemoryByteChannel(testData);
+        ByteBuffer readBuffer = ByteBuffer.allocate(testData.length + 1);
+        //when
+        int readCount = c.read(readBuffer);
+        //then
+        assertEquals(testData.length, readCount);
+        assertArrayEquals(testData, Arrays.copyOf(readBuffer.array(), testData.length));
+        assertEquals(testData.length, c.position());
+    }
+
+    @Test
+    public void shouldReadDataFromSetPosition() throws IOException {
+        //given
+        SeekableInMemoryByteChannel c = new SeekableInMemoryByteChannel(testData);
+        ByteBuffer readBuffer = ByteBuffer.allocate(4);
+        //when
+        c.position(5L);
+        int readCount = c.read(readBuffer);
+        //then
+        assertEquals(4L, readCount);
+        assertEquals("data", new String(readBuffer.array(), Charset.forName(UTF_8)));
+        assertEquals(testData.length, c.position());
+    }
+
+    @Test
+    public void shouldReadNoDataWhenPositionAtTheEnd() throws IOException {
+        //given
+        SeekableInMemoryByteChannel c = new SeekableInMemoryByteChannel(testData);
+        ByteBuffer readBuffer = ByteBuffer.allocate(testData.length);
+        //when
+        c.position(testData.length + 1);
+        int readCount = c.read(readBuffer);
+        //then
+        assertEquals(0L, readBuffer.position());
+        assertEquals(0, readCount);
+    }
+
+    @Test(expected = ClosedChannelException.class)
+    public void shouldThrowExceptionOnReadingClosedChannel() throws IOException {
+        //given
+        SeekableInMemoryByteChannel c = new SeekableInMemoryByteChannel();
+        //when
+        c.close();
+        c.read(ByteBuffer.allocate(1));
+    }
+
+    @Test
+    public void shouldWriteDataProperly() throws IOException {
+        //given
+        SeekableInMemoryByteChannel c = new SeekableInMemoryByteChannel();
+        ByteBuffer inData = ByteBuffer.wrap(testData);
+        //when
+        int writeCount = c.write(inData);
+        //then
+        assertEquals(testData.length, writeCount);
+        assertArrayEquals(testData, Arrays.copyOf(c.array(), (int) c.size()));
+        assertEquals(testData.length, c.position());
+    }
+
+    @Test
+    public void shouldWriteDataProperlyAfterPositionSet() throws IOException {
+        //given
+        SeekableInMemoryByteChannel c = new SeekableInMemoryByteChannel(testData);
+        ByteBuffer inData = ByteBuffer.wrap(testData);
+        ByteBuffer expectedData = ByteBuffer.allocate(testData.length + 5).put(testData, 0, 5).put(testData);
+        //when
+        c.position(5L);
+        int writeCount = c.write(inData);
+
+        //then
+        assertEquals(testData.length, writeCount);
+        assertArrayEquals(expectedData.array(), Arrays.copyOf(c.array(), (int) c.size()));
+        assertEquals(testData.length + 5, c.position());
+    }
+
+
+    @Test(expected = ClosedChannelException.class)
+    public void shouldThrowExceptionOnWritingToClosedChannel() throws IOException {
+        //given
+        SeekableInMemoryByteChannel c = new SeekableInMemoryByteChannel();
+        //when
+        c.close();
+        c.write(ByteBuffer.allocate(1));
+    }
+
+    @Test
+    public void shouldTruncateContentsProperly() throws IOException {
+        //given
+        SeekableInMemoryByteChannel c = new SeekableInMemoryByteChannel(testData);
+        //when
+        c.truncate(4);
+        //then
+        byte[] bytes = Arrays.copyOf(c.array(), (int) c.size());
+        assertEquals("Some", new String(bytes, Charset.forName(UTF_8)));
+    }
+
+    @Test
+    public void shouldSetProperPositionOnTruncate() throws IOException {
+        //given
+        SeekableInMemoryByteChannel c = new SeekableInMemoryByteChannel(testData);
+        //when
+        c.position(testData.length);
+        c.truncate(4L);
+        //then
+        assertEquals(4L, c.position());
+        assertEquals(4L, c.size());
+    }
+
+    @Test
+    public void shouldSetProperPosition() throws IOException {
+        //given
+        SeekableInMemoryByteChannel c = new SeekableInMemoryByteChannel(testData);
+        //when
+        long posAtFour = c.position(4L).position();
+        long posAtTheEnd = c.position(testData.length).position();
+        long posPastTheEnd = c.position(testData.length + 1L).position();
+        //then
+        assertEquals(4L, posAtFour);
+        assertEquals(c.size(), posAtTheEnd);
+        assertEquals(posPastTheEnd, posPastTheEnd);
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void shouldThrowExceptionWhenSettingIncorrectPosition() throws IOException {
+        //given
+        SeekableInMemoryByteChannel c = new SeekableInMemoryByteChannel();
+        //when
+        c.position((long) Integer.MAX_VALUE + 1);
+    }
+
+    @Test(expected = ClosedChannelException.class)
+    public void shouldThrowExceptionWhenSettingPositionOnClosedChannel() throws IOException {
+        //given
+        SeekableInMemoryByteChannel c = new SeekableInMemoryByteChannel();
+        //when
+        c.close();
+        c.position(1L);
+    }
+
+}
\ No newline at end of file