Bug 1080 - Add read support for memory mapped big file I/O via specialized InputStream impl., incl. mark/reset

- ByteBufferInputStream simply impl. InputStream for an arbitrary 2MiB restricted ByteBuffer
  - Users may only need a smaller implementation for 'smaller' file sizes
    or for streaming a [native] ByteBuffer.

- MappedByteBufferInputStream impl. InputStream for any file size,
  while slicing the total size to memory mapped buffers via the given FileChannel.
  The latter are mapped lazily and diff. flush/cache methods are supported
  to ease virtual memory usage.

- TestByteBufferInputStream: Basic unit test for basic functionality and perf. stats.

2 files changed, 670 insertions, 0 deletions

diff --git a/src/java/com/jogamp/common/nio/ByteBufferInputStream.java b/src/java/com/jogamp/common/nio/ByteBufferInputStream.java
new file mode 100644
index 0000000..5b6f121
--- /dev/null
+++ b/src/java/com/jogamp/common/nio/ByteBufferInputStream.java
@@ -0,0 +1,183 @@
+/**
+ * Copyright 2014 JogAmp Community. All rights reserved.
+ *
+ * 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 JogAmp Community ``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 JogAmp Community 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.
+ *
+ * The views and conclusions contained in the software and documentation are those of the
+ * authors and should not be interpreted as representing official policies, either expressed
+ * or implied, of JogAmp Community.
+ */
+package com.jogamp.common.nio;
+
+import java.io.BufferedInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.nio.ByteBuffer;
+import java.nio.MappedByteBuffer;
+import java.nio.channels.FileChannel;
+import java.nio.channels.FileChannel.MapMode;
+
+/**
+ * An {@link InputStream} implementation based on an underlying {@link ByteBuffer}
+ * supporting {@link #markSupported() mark}.
+ * <p>
+ * May be utilized as well with a {@link MappedByteBuffer memory-mapped} {@link FileChannel#map(MapMode, long, long) FileChannel}
+ * using a size &le; {@link Integer#MAX_VALUE}.<br>
+ * This becomes efficient with files &ge; 10 MiB, depending on the platform
+ * and whether the traditional method uses a {@link BufferedInputStream} supporting {@code mark} incl. it's buffer size.<br>
+ * See test case {@code com.jogamp.common.nio.TestByteBufferInputStream}.
+ * </p>
+ * @since 2.3.0
+ */
+public class ByteBufferInputStream extends InputStream {
+    private final ByteBuffer buf;
+    private int mark;
+
+    /**
+     * Creates a new byte-buffer input stream.
+     *
+     * @param buf the underlying byte buffer.
+     */
+    public ByteBufferInputStream(final ByteBuffer buf) {
+        this.buf = buf;
+        this.mark = -1;
+    }
+
+    @Override
+    public final int available() {
+        return buf.remaining();
+    }
+
+    /**
+     * <i>This implementation supports {@code mark}.</i>
+     * <p>
+     * {@inheritDoc}
+     * </p>
+     */
+    @Override
+    public final boolean markSupported() {
+        return true;
+    }
+
+    /**
+     * <i>This implementation supports {@code mark}.</i>
+     * <p>
+     * {@inheritDoc}
+     * </p>
+     * @see #markSupported()
+     */
+    @Override
+    public final synchronized void mark(final int unused) {
+        mark = buf.position();
+    }
+
+    /**
+     * <i>This implementation supports {@code mark}.</i>
+     * <p>
+     * {@inheritDoc}
+     * </p>
+     * @see #markSupported()
+     */
+    @Override
+    public final synchronized void reset() throws IOException {
+        if ( mark == -1 ) {
+            throw new IOException();
+        }
+        buf.position(mark);
+    }
+
+    @Override
+    public final long skip(final long n) throws IOException {
+        if( 0 > n ) {
+            return 0;
+        }
+        final int s = (int) Math.min( buf.remaining(), n );
+        buf.position(buf.position() + s);
+        return s;
+    }
+
+    @Override
+    public final int read() {
+        if ( ! buf.hasRemaining() ) {
+            return -1;
+        }
+        return buf.get() & 0xFF;
+    }
+
+    @Override
+    public final int read(final byte[] b, final int off, final int len) {
+        if (b == null) {
+            throw new NullPointerException();
+        } else if (off < 0 || len < 0 || len > b.length - off) {
+            throw new IndexOutOfBoundsException("offset "+off+", length "+len+", b.length "+b.length);
+        }
+        if ( 0 == len ) {
+            return 0;
+        }
+        final int totalRem = buf.remaining();
+        if ( 0 == totalRem ) {
+            return -1;
+        }
+        final int maxLen = Math.min(totalRem, len);
+        if( buf.hasArray() ) {
+            System.arraycopy(buf.array(), buf.arrayOffset() + buf.position(), b, off, maxLen);
+            buf.position( buf.position() + maxLen );
+        } else {
+            buf.get(b, off, maxLen);
+        }
+        return maxLen;
+    }
+
+    // @Override
+    public final int read(final ByteBuffer b, final int len) {
+        if (b == null) {
+            throw new NullPointerException();
+        } else if (len < 0 || len > b.remaining()) {
+            throw new IndexOutOfBoundsException("length "+len+", b "+b);
+        }
+        if ( 0 == len ) {
+            return 0;
+        }
+        final int remaining = buf.remaining();
+        if ( 0 == remaining ) {
+            return -1;
+        }
+        final int maxLen = Math.min(remaining, len);
+        if( buf.hasArray() && b.hasArray() ) {
+            System.arraycopy(buf.array(), buf.arrayOffset() + buf.position(), b.array(), b.arrayOffset() + b.position(), maxLen);
+            buf.position( buf.position() + maxLen );
+            b.position( b.position() + maxLen );
+        } else if( maxLen == remaining ) {
+            b.put(buf);
+        } else {
+            final int _limit = buf.limit();
+            buf.limit(maxLen);
+            try {
+                b.put(buf);
+            } finally {
+                buf.limit(_limit);
+            }
+        }
+        return maxLen;
+    }
+
+    public final ByteBuffer getBuffer() { return buf; }
+}
diff --git a/src/java/com/jogamp/common/nio/MappedByteBufferInputStream.java b/src/java/com/jogamp/common/nio/MappedByteBufferInputStream.java
new file mode 100644
index 0000000..52f5b5a
--- /dev/null
+++ b/src/java/com/jogamp/common/nio/MappedByteBufferInputStream.java
@@ -0,0 +1,487 @@
+/**
+ * Copyright 2014 JogAmp Community. All rights reserved.
+ *
+ * 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 JogAmp Community ``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 JogAmp Community 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.
+ *
+ * The views and conclusions contained in the software and documentation are those of the
+ * authors and should not be interpreted as representing official policies, either expressed
+ * or implied, of JogAmp Community.
+ */
+package com.jogamp.common.nio;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.lang.ref.WeakReference;
+import java.lang.reflect.Method;
+import java.nio.ByteBuffer;
+import java.nio.MappedByteBuffer;
+import java.nio.channels.FileChannel;
+import java.security.AccessController;
+import java.security.PrivilegedAction;
+
+import jogamp.common.Debug;
+
+import com.jogamp.common.os.Platform;
+
+/**
+ * An {@link InputStream} implementation based on an underlying {@link MappedByteBuffer}
+ * supporting {@link #markSupported() mark}.
+ * <p>
+ * Intended to be utilized with a {@link MappedByteBuffer memory-mapped} {@link FileChannel#map(MapMode, long, long) FileChannel}
+ * beyond its size limitation of {@link Integer#MAX_VALUE}.<br>
+ * </p>
+ * @since 2.3.0
+ */
+public class MappedByteBufferInputStream extends InputStream {
+    public static enum CacheMode {
+        /**
+         * Keep all previous lazily cached buffer slices alive, useful for hopping readers,
+         * i.e. random access via {@link MappedByteBufferInputStream#position(long) position(p)}
+         * or {@link MappedByteBufferInputStream#reset() reset()}.
+         */
+        FLUSH_NONE,
+        /**
+         * Soft flush the previous lazily cached buffer slice when caching the next buffer slice,
+         * useful for sequential forward readers, as well as for hopping readers like {@link #FLUSH_NONE}
+         * in case of relatively short periods between hopping across slices.
+         * <p>
+         * Implementation clears the buffer slice reference
+         * while preserving a {@link WeakReference} to allow its resurrection if not yet
+         * {@link System#gc() garbage collected}.
+         * </p>
+         * <p>
+         * This is the default.
+         * </p>
+         */
+        FLUSH_PRE_SOFT,
+        /**
+         * Hard flush the previous lazily cached buffer slice when caching the next buffer slice,
+         * useful for sequential forward readers.
+         * <p>
+         * Besides clearing the buffer slice reference,
+         * implementation attempts to hard flush the mapped buffer
+         * using a {@code sun.misc.Cleaner} by reflection.
+         * In case such method does not exist nor works, implementation falls back to {@link #FLUSH_PRE_SOFT}.
+         * </p>
+         */
+        FLUSH_PRE_HARD
+    };
+
+    /**
+     * Default slice shift, i.e. 1L << shift, denoting slice size in MiB:
+     * <ul>
+     *   <li>{@link Platform#is64Bit() 64bit machines} -> 30 = 1024 MiB</li>
+     *   <li>{@link Platform#is32Bit() 32bit machines} -> 29 = 512 MiB</li>
+     * </ul>
+     * <p>
+     * In case the default is too much of-used up address-space, one may choose other values:
+     * <ul>
+     *   <li>29 ->  512 MiB</li>
+     *   <li>28 ->  256 MiB</li>
+     *   <li>27 ->  128 MiB</li>
+     *   <li>26 ->   64 MiB</li>
+     * </ul>
+     * </p>
+     */
+    public static final int DEFAULT_SLICE_SHIFT;
+
+    private static final boolean DEBUG;
+
+    static {
+        Platform.initSingleton();
+        if( Platform.is32Bit() ) {
+            DEFAULT_SLICE_SHIFT = 29;
+        } else {
+            DEFAULT_SLICE_SHIFT = 30;
+        }
+
+        DEBUG = Debug.debug("ByteBufferInputStream");
+    }
+
+    private final int sliceShift;
+    private final FileChannel fc;
+    private final FileChannel.MapMode mmode;
+    private final MappedByteBuffer[] slices;
+    private final WeakReference<MappedByteBuffer>[] slices2GC;
+    private final int sliceCount;
+    private final long totalSize;
+
+    private Method mbbCleaner;
+    private Method cClean;
+    private boolean cleanerInit;
+    private boolean hasCleaner;
+    private CacheMode cmode;
+
+    private int currSlice;
+    private long mark;
+
+    @SuppressWarnings("unchecked")
+    MappedByteBufferInputStream(final FileChannel fc, final FileChannel.MapMode mmode, final CacheMode cmode,
+                                final int sliceShift, final MappedByteBuffer[] bufs, final long totalSize,
+                                final int currSlice) throws IOException {
+        this.sliceShift = sliceShift;
+        this.fc = fc;
+        this.mmode = mmode;
+        this.slices = bufs;
+        this.sliceCount = bufs.length;
+        this.slices2GC = new WeakReference[sliceCount];
+        this.totalSize = totalSize;
+        if( 0 >= totalSize || 0 >= sliceCount ) {
+            throw new IllegalArgumentException("Zero sized: total "+totalSize+", slices "+sliceCount);
+        }
+
+        this.cleanerInit = false;
+        this.hasCleaner = false;
+        this.cmode = cmode;
+
+        this.currSlice = currSlice;
+        this.mark = -1;
+
+        slice(currSlice).position(0);
+    }
+
+    /**
+     * Creates a new instance using the given {@link FileChannel},
+     * {@link FileChannel.MapMode#READ_ONLY read-only} mapping mode, {@link CacheMode#FLUSH_PRE_SOFT}
+     * and the {@link #DEFAULT_SLICE_SHIFT}.
+     * <p>
+     * The {@link MappedByteBuffer} slices will be mapped {@link FileChannel.MapMode#READ_ONLY} lazily at first usage.
+     * </p>
+     * @param fileChannel the file channel to be used.
+     * @throws IOException
+     */
+    public static MappedByteBufferInputStream create(final FileChannel fileChannel) throws IOException {
+        return create(fileChannel, FileChannel.MapMode.READ_ONLY, CacheMode.FLUSH_PRE_SOFT, DEFAULT_SLICE_SHIFT);
+    }
+
+    /**
+     * Creates a new instance using the given {@link FileChannel},
+     * {@link FileChannel.MapMode#READ_ONLY read-only} mapping mode and the {@link #DEFAULT_SLICE_SHIFT}.
+     * <p>
+     * The {@link MappedByteBuffer} slices will be mapped {@link FileChannel.MapMode#READ_ONLY} lazily at first usage.
+     * </p>
+     * @param fileChannel the file channel to be used.
+     * @param cmode the caching mode, default is {@link CacheMode#FLUSH_PRE_SOFT}.
+     * @throws IOException
+     */
+    public static MappedByteBufferInputStream create(final FileChannel fileChannel, final CacheMode cmode) throws IOException {
+        return create(fileChannel, FileChannel.MapMode.READ_ONLY, cmode, DEFAULT_SLICE_SHIFT);
+    }
+
+    /**
+     * Creates a new instance using the given {@link FileChannel}.
+     * <p>
+     * The {@link MappedByteBuffer} slices will be mapped lazily at first usage.
+     * </p>
+     * @param fileChannel the file channel to be mapped lazily.
+     * @param mmode the map mode, default is {@link FileChannel.MapMode#READ_ONLY}.
+     * @param cmode the caching mode, default is {@link CacheMode#FLUSH_PRE_SOFT}.
+     * @param sliceShift the pow2 slice size, default is {@link #DEFAULT_SLICE_SHIFT}.
+     * @throws IOException
+     */
+    public static MappedByteBufferInputStream create(final FileChannel fileChannel,
+                                                     final FileChannel.MapMode mmode,
+                                                     final CacheMode cmode,
+                                                     final int sliceShift) throws IOException {
+        final long sliceSize = 1L << sliceShift;
+        final long totalSize = fileChannel.size();
+        final int sliceCount = (int)( ( totalSize + ( sliceSize - 1 ) ) / sliceSize );
+        final MappedByteBuffer[] bufs = new MappedByteBuffer[ sliceCount ];
+        return new MappedByteBufferInputStream(fileChannel, mmode, cmode, sliceShift, bufs, totalSize, 0);
+    }
+
+    @Override
+    public final synchronized void close() throws IOException {
+        for(int i=0; i<sliceCount; i++) {
+            final MappedByteBuffer s = slices[i];
+            if( null != s ) {
+                slices[i] = null;
+                cleanBuffer(s);
+            }
+            slices2GC[i] = null;
+        }
+        if( mmode != FileChannel.MapMode.READ_ONLY ) {
+            fc.force(true);
+        }
+        fc.close();
+        mark = -1;
+        currSlice = -1;
+        super.close();
+    }
+
+    private synchronized MappedByteBuffer slice(final int i) throws IOException {
+        if ( null != slices[i] ) {
+            return slices[i];
+        } else {
+            if( CacheMode.FLUSH_PRE_SOFT == cmode ) {
+                final WeakReference<MappedByteBuffer> ref = slices2GC[i];
+                if( null != ref ) {
+                    final MappedByteBuffer mbb = ref.get();
+                    slices2GC[i] = null;
+                    if( null != mbb ) {
+                        slices[i] = mbb;
+                        return mbb;
+                    }
+                }
+            }
+            final long pos = (long)i << sliceShift;
+            slices[i] = fc.map(mmode, pos, Math.min(1L << sliceShift, totalSize - pos));
+            return slices[i];
+        }
+    }
+
+    private synchronized void flushSlice(final int i) throws IOException {
+        final MappedByteBuffer s = slices[i];
+        if ( null != s ) {
+            slices[i] = null; // GC a slice is enough
+            if( CacheMode.FLUSH_PRE_HARD == cmode ) {
+                if( !cleanBuffer(s) ) {
+                    cmode = CacheMode.FLUSH_PRE_SOFT;
+                    slices2GC[i] = new WeakReference<MappedByteBuffer>(s);
+                }
+            } else {
+                slices2GC[i] = new WeakReference<MappedByteBuffer>(s);
+            }
+        }
+    }
+    private synchronized boolean cleanBuffer(final MappedByteBuffer mbb) {
+        if( !cleanerInit ) {
+            initCleaner(mbb);
+        }
+        if ( !hasCleaner || !mbb.isDirect() ) {
+            return false;
+        }
+        try {
+            cClean.invoke(mbbCleaner.invoke(mbb));
+            return true;
+        } catch(final Throwable t) {
+            hasCleaner = false;
+            if( DEBUG ) {
+                System.err.println("Caught "+t.getMessage());
+                t.printStackTrace();
+            }
+            return false;
+        }
+    }
+    private synchronized void initCleaner(final ByteBuffer bb) {
+        final Method[] _mbbCleaner = { null };
+        final Method[] _cClean = { null };
+        AccessController.doPrivileged(new PrivilegedAction<Object>() {
+            @Override
+            public Object run() {
+                try {
+                    _mbbCleaner[0] = bb.getClass().getMethod("cleaner");
+                    _mbbCleaner[0].setAccessible(true);
+                    _cClean[0] = Class.forName("sun.misc.Cleaner").getMethod("clean");
+                    _cClean[0].setAccessible(true);
+                } catch(final Throwable t) {
+                    if( DEBUG ) {
+                        System.err.println("Caught "+t.getMessage());
+                        t.printStackTrace();
+                    }
+                }
+                return null;
+            } } );
+        mbbCleaner = _mbbCleaner[0];
+        cClean = _cClean[0];
+        final boolean res = null != mbbCleaner && null != cClean;
+        if( DEBUG ) {
+            System.err.println("initCleaner: Has cleaner: "+res+", mbbCleaner "+mbbCleaner+", cClean "+cClean);
+        }
+        hasCleaner = res;
+        cleanerInit = true;
+    }
+
+    /**
+     * Return the used {@link CacheMode}.
+     * <p>
+     * If a desired {@link CacheMode} is not available, it may fall back to an available one at runtime,
+     * see {@link CacheMode#FLUSH_PRE_HARD}.<br>
+     * This evaluation only happens if the {@link CacheMode} != {@link CacheMode#FLUSH_NONE}
+     * and while attempting to flush an unused buffer slice.
+     * </p>
+     */
+    public final synchronized CacheMode getCacheMode() { return cmode; }
+
+    /**
+     * Returns the total size in bytes of the {@link InputStream}
+     * <pre>
+     *   <code>0 <= {@link #position()} <= {@link #length()}</code>
+     * </pre>
+     */
+    // @Override
+    public final long length() {
+        return totalSize;
+    }
+
+    /**
+     * Returns the number of remaining available bytes of the {@link InputStream},
+     * i.e. <code>{@link #length()} - {@link #position()}</code>.
+     * <pre>
+     *   <code>0 <= {@link #position()} <= {@link #length()}</code>
+     * </pre>
+     * <p>
+     * In contrast to {@link InputStream}'s {@link #available()} method,
+     * this method returns the proper return type {@code long}.
+     * </p>
+     * @throws IOException
+     */
+    public final synchronized long remaining() throws IOException {
+        return totalSize - position();
+    }
+
+    /**
+     * <i>See {@link #remaining()} for an accurate variant.</i>
+     * <p>
+     * {@inheritDoc}
+     * </p>
+     */
+    @Override
+    public final synchronized int available() throws IOException {
+        final long available = remaining();
+        return available <= Integer.MAX_VALUE ? (int)available : Integer.MAX_VALUE;
+    }
+
+    /**
+     * Returns the absolute position of the {@link InputStream}.
+     * <pre>
+     *   <code>0 <= {@link #position()} <= {@link #length()}</code>
+     * </pre>
+     * @throws IOException
+     */
+    // @Override
+    public final synchronized long position() throws IOException {
+        return ( (long)currSlice << sliceShift ) + slice( currSlice ).position();
+    }
+
+    /**
+     * Sets the absolute position of the {@link InputStream} to {@code newPosition}.
+     * <pre>
+     *   <code>0 <= {@link #position()} <= {@link #length()}</code>
+     * </pre>
+     * @param newPosition The new position, which must be non-negative and &le; {@link #length()}.
+     * @return this instance
+     * @throws IOException
+     */
+    // @Override
+    public final synchronized MappedByteBufferInputStream position( final long newPosition ) throws IOException {
+        if ( totalSize < newPosition || 0 > newPosition ) {
+            throw new IllegalArgumentException("new position "+newPosition+" not within [0.."+totalSize+"]");
+        }
+        final int preSlice = currSlice;
+        if ( totalSize == newPosition ) {
+            currSlice = sliceCount - 1;
+            final MappedByteBuffer s = slice( currSlice );
+            s.position( s.capacity() );
+        } else {
+            currSlice = (int)( newPosition >>> sliceShift );
+            slice( currSlice ).position( (int)( newPosition - ( (long)currSlice << sliceShift ) ) );
+        }
+        if( CacheMode.FLUSH_NONE != cmode && preSlice != currSlice) {
+            flushSlice(preSlice);
+        }
+        return this;
+    }
+
+    @Override
+    public final boolean markSupported() {
+        return true;
+    }
+
+    @Override
+    public final synchronized void mark( final int unused ) {
+        try {
+            mark = position();
+        } catch (final IOException e) {
+            throw new RuntimeException(e); // FIXME: oops
+        }
+    }
+
+    @Override
+    public final synchronized void reset() throws IOException {
+        if ( mark == -1 ) {
+            throw new IOException("mark not set");
+        }
+        position( mark );
+    }
+
+    @Override
+    public final synchronized long skip( final long n ) throws IOException {
+        if( 0 > n ) {
+            return 0;
+        }
+        final long pos = position();
+        final long rem = totalSize - pos; // remaining
+        final long s = Math.min( rem, n );
+        position( pos + s );
+        return s;
+    }
+
+    @Override
+    public final synchronized int read() throws IOException {
+        if ( ! slice( currSlice ).hasRemaining() ) {
+            if ( currSlice < sliceCount - 1 ) {
+                final int preSlice = currSlice;
+                currSlice++;
+                slice( currSlice ).position( 0 );
+                if( CacheMode.FLUSH_NONE != cmode ) {
+                    flushSlice(preSlice);
+                }
+            } else {
+                return -1;
+            }
+        }
+        return slices[ currSlice ].get() & 0xFF;
+    }
+
+    @Override
+    public final synchronized int read( final byte[] b, final int off, final int len ) throws IOException {
+        if (b == null) {
+            throw new NullPointerException();
+        } else if (off < 0 || len < 0 || len > b.length - off) {
+            throw new IndexOutOfBoundsException("offset "+off+", length "+len+", b.length "+b.length);
+        }
+        if ( 0 == len ) {
+            return 0;
+        }
+        final long totalRem = remaining();
+        if ( 0 == totalRem ) {
+            return -1;
+        }
+        final int maxLen = (int)Math.min( totalRem, len );
+        int read = 0;
+        while( read < maxLen ) {
+            int currRem = slice( currSlice ).remaining();
+            if ( 0 == currRem ) {
+                final int preSlice = currSlice;
+                currSlice++;
+                slice( currSlice ).position( 0 );
+                currRem = slice( currSlice ).remaining();
+                if( CacheMode.FLUSH_NONE != cmode ) {
+                    flushSlice(preSlice);
+                }
+            }
+            slices[ currSlice ].get( b, off + read, Math.min( maxLen - read, currRem ) );
+            read += Math.min( maxLen - read, currRem );
+        }
+        return maxLen;
+    }
+}