/*

 * Copyright 2000-2008 Sun Microsystems, Inc.  All Rights Reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Sun designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Sun in the LICENSE file that accompanied this code.

 *

 * This code 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 General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 */

package sun.nio.ch;

import java.lang.ref.SoftReference;

import java.lang.reflect.*;

import java.io.IOException;

import java.nio.ByteBuffer;

import java.nio.MappedByteBuffer;

import java.nio.channels.*;

import java.nio.channels.spi.*;

import java.security.AccessController;

import java.security.PrivilegedAction;

import java.util.*;

import sun.misc.Unsafe;

import sun.misc.Cleaner;

import sun.security.action.GetPropertyAction;

class Util {

    // -- Caches --

    // The number of temp buffers in our pool

    private static final int TEMP_BUF_POOL_SIZE = 3;

    // Per-thread soft cache of the last temporary direct buffer

    private static ThreadLocal<SoftReference<ByteBuffer>>[] bufferPool;

    static {

        for (int i=0; i<TEMP_BUF_POOL_SIZE; i++)

            bufferPool[i] = new ThreadLocal<SoftReference<ByteBuffer>>();

    }

    static ByteBuffer getTemporaryDirectBuffer(int size) {

        ByteBuffer buf = null;

        // Grab a buffer if available

        for (int i=0; i<TEMP_BUF_POOL_SIZE; i++) {

            SoftReference<ByteBuffer> ref = bufferPool[i].get();

            if ((ref != null) && ((buf = ref.get()) != null) &&

                (buf.capacity() >= size)) {

                buf.rewind();

                buf.limit(size);

                bufferPool[i].set(null);

                return buf;

            }

        }

        // Make a new one

        return ByteBuffer.allocateDirect(size);

    }

    static void releaseTemporaryDirectBuffer(ByteBuffer buf) {

        if (buf == null)

            return;

        // Put it in an empty slot if such exists

        for (int i=0; i<TEMP_BUF_POOL_SIZE; i++) {

            SoftReference<ByteBuffer> ref = bufferPool[i].get();

            if ((ref == null) || (ref.get() == null)) {

                bufferPool[i].set(new SoftReference<ByteBuffer>(buf));

                return;

            }

        }

        // Otherwise replace a smaller one in the cache if such exists

        for (int i=0; i<TEMP_BUF_POOL_SIZE; i++) {

            SoftReference<ByteBuffer> ref = bufferPool[i].get();

            ByteBuffer inCacheBuf = ref.get();

            if ((inCacheBuf == null) || (buf.capacity() > inCacheBuf.capacity())) {

                bufferPool[i].set(new SoftReference<ByteBuffer>(buf));

                return;

            }

        }

    }

    private static class SelectorWrapper {

        private Selector sel;

        private SelectorWrapper (Selector sel) {

            this.sel = sel;

            Cleaner.create(this, new Closer(sel));

        }

        private static class Closer implements Runnable {

            private Selector sel;

            private Closer (Selector sel) {

                this.sel = sel;

            }

            public void run () {

                try {

                    sel.close();

                } catch (Throwable th) {

                    throw new Error(th);

                }

            }

        }

        public Selector get() { return sel;}

    }

    // Per-thread cached selector

    private static ThreadLocal<SoftReference<SelectorWrapper>> localSelector

        = new ThreadLocal<SoftReference<SelectorWrapper>>();

    // Hold a reference to the selWrapper object to prevent it from

    // being cleaned when the temporary selector wrapped is on lease.

    private static ThreadLocal<SelectorWrapper> localSelectorWrapper

        = new ThreadLocal<SelectorWrapper>();

    // When finished, invoker must ensure that selector is empty

    // by cancelling any related keys and explicitly releasing

    // the selector by invoking releaseTemporarySelector()

    static Selector getTemporarySelector(SelectableChannel sc)

        throws IOException

    {

        SoftReference<SelectorWrapper> ref = localSelector.get();

        SelectorWrapper selWrapper = null;

        Selector sel = null;

        if (ref == null

            || ((selWrapper = ref.get()) == null)

            || ((sel = selWrapper.get()) == null)

            || (sel.provider() != sc.provider())) {

            sel = sc.provider().openSelector();

            selWrapper = new SelectorWrapper(sel);

            localSelector.set(new SoftReference<SelectorWrapper>(selWrapper));

        }

        localSelectorWrapper.set(selWrapper);

        return sel;

    }

    static void releaseTemporarySelector(Selector sel)

        throws IOException

    {

        // Selector should be empty

        sel.selectNow();                // Flush cancelled keys

        assert sel.keys().isEmpty() : "Temporary selector not empty";

        localSelectorWrapper.set(null);

    }

    // -- Random stuff --

    static ByteBuffer[] subsequence(ByteBuffer[] bs, int offset, int length) {

        if ((offset == 0) && (length == bs.length))

            return bs;

        int n = length;

        ByteBuffer[] bs2 = new ByteBuffer[n];

        for (int i = 0; i < n; i++)

            bs2[i] = bs[offset + i];

        return bs2;

    }

    static <E> Set<E> ungrowableSet(final Set<E> s) {

        return new Set<E>() {

                public int size()                 { return s.size(); }

                public boolean isEmpty()          { return s.isEmpty(); }

                public boolean contains(Object o) { return s.contains(o); }

                public Object[] toArray()         { return s.toArray(); }

                public <T> T[] toArray(T[] a)     { return s.toArray(a); }

                public String toString()          { return s.toString(); }

                public Iterator<E> iterator()     { return s.iterator(); }

                public boolean equals(Object o)   { return s.equals(o); }

                public int hashCode()             { return s.hashCode(); }

                public void clear()               { s.clear(); }

                public boolean remove(Object o)   { return s.remove(o); }

                public boolean containsAll(Collection<?> coll) {

                    return s.containsAll(coll);

                }

                public boolean removeAll(Collection<?> coll) {

                    return s.removeAll(coll);

                }

                public boolean retainAll(Collection<?> coll) {

                    return s.retainAll(coll);

                }

                public boolean add(E o){

                    throw new UnsupportedOperationException();

                }

                public boolean addAll(Collection<? extends E> coll) {

                    throw new UnsupportedOperationException();

                }

        };

    }

    // -- Unsafe access --

    private static Unsafe unsafe = Unsafe.getUnsafe();

    private static byte _get(long a) {

        return unsafe.getByte(a);

    }

    private static void _put(long a, byte b) {

        unsafe.putByte(a, b);

    }

    static void erase(ByteBuffer bb) {

        unsafe.setMemory(((DirectBuffer)bb).address(), bb.capacity(), (byte)0);

    }

    static Unsafe unsafe() {

        return unsafe;

    }

    private static int pageSize = -1;

    static int pageSize() {

        if (pageSize == -1)

            pageSize = unsafe().pageSize();

        return pageSize;

    }

    private static volatile Constructor directByteBufferConstructor = null;

    private static void initDBBConstructor() {

        AccessController.doPrivileged(new PrivilegedAction<Void>() {

                public Void run() {

                    try {

                        Class<?> cl = Class.forName("java.nio.DirectByteBuffer");

                        Constructor ctor = cl.getDeclaredConstructor(

                            new Class[] { int.class,

                                          long.class,

                                          Runnable.class });

                        ctor.setAccessible(true);

                        directByteBufferConstructor = ctor;

                    } catch (ClassNotFoundException x) {

                        throw new InternalError();

                    } catch (NoSuchMethodException x) {

                        throw new InternalError();

                    } catch (IllegalArgumentException x) {

                        throw new InternalError();

                    } catch (ClassCastException x) {

                        throw new InternalError();

                    }

                    return null;

                }});

    }

    static MappedByteBuffer newMappedByteBuffer(int size, long addr,

                                                Runnable unmapper)

    {

        MappedByteBuffer dbb;

        if (directByteBufferConstructor == null)

            initDBBConstructor();

        try {

            dbb = (MappedByteBuffer)directByteBufferConstructor.newInstance(

              new Object[] { new Integer(size),

                             new Long(addr),

                             unmapper });

        } catch (InstantiationException e) {

            throw new InternalError();

        } catch (IllegalAccessException e) {

            throw new InternalError();

        } catch (InvocationTargetException e) {

            throw new InternalError();

        }

        return dbb;

    }

    private static volatile Constructor directByteBufferRConstructor = null;

    private static void initDBBRConstructor() {

        AccessController.doPrivileged(new PrivilegedAction<Void>() {

                public Void run() {

                    try {

                        Class<?> cl = Class.forName("java.nio.DirectByteBufferR");

                        Constructor ctor = cl.getDeclaredConstructor(

                            new Class[] { int.class,

                                          long.class,

                                          Runnable.class });

                        ctor.setAccessible(true);

                        directByteBufferRConstructor = ctor;

                    } catch (ClassNotFoundException x) {

                        throw new InternalError();

                    } catch (NoSuchMethodException x) {

                        throw new InternalError();

                    } catch (IllegalArgumentException x) {

                        throw new InternalError();

                    } catch (ClassCastException x) {

                        throw new InternalError();

                    }

                    return null;

                }});

    }

    static MappedByteBuffer newMappedByteBufferR(int size, long addr,

                                                 Runnable unmapper)

    {

        MappedByteBuffer dbb;

        if (directByteBufferRConstructor == null)

            initDBBRConstructor();

        try {

            dbb = (MappedByteBuffer)directByteBufferRConstructor.newInstance(

              new Object[] { new Integer(size),

                             new Long(addr),

                             unmapper });

        } catch (InstantiationException e) {

            throw new InternalError();

        } catch (IllegalAccessException e) {

            throw new InternalError();

        } catch (InvocationTargetException e) {

            throw new InternalError();

        }

        return dbb;

    }

    // -- Bug compatibility --

    private static volatile String bugLevel = null;

    static boolean atBugLevel(String bl) {              // package-private

        if (bugLevel == null) {

            if (!sun.misc.VM.isBooted())

                return false;

            String value = AccessController.doPrivileged(

                new GetPropertyAction("sun.nio.ch.bugLevel"));

            bugLevel = (value != null) ? value : "";

        }

        return bugLevel.equals(bl);

    }

    // -- Initialization --

    private static boolean loaded = false;

    static void load() {

        synchronized (Util.class) {

            if (loaded)

                return;

            loaded = true;

            java.security.AccessController

                .doPrivileged(new sun.security.action.LoadLibraryAction("net"));

            java.security.AccessController

                .doPrivileged(new sun.security.action.LoadLibraryAction("nio"));

            // IOUtil must be initialized; Its native methods are called from

            // other places in native nio code so they must be set up.

            IOUtil.initIDs();

        }

    }

}