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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
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 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License. You can obtain
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 * or glassfish/bootstrap/legal/LICENSE.txt.  See the License for the specific
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package com.sun.grizzly.memory.slab;

import com.sun.grizzly.memory.*;


/**
 * The SlabByteBufferWrapper knows both the MemoryManager and the slab used 
 * to allocate it. Both are needed in the BufferWrapper.trim() and 
 * BufferWrapper.dispose() methods:
 * 
 * trim() is used to allocate a buffer as large as the free space in a slab 
 * for reading, so that very large reads can be made efficiently. 
 * After reading the data, trim() is called in order to reduce 
 * the space needed to the actual data read. 
 * This works best in the case where a slab is used by a single reader thread, 
 * which is the expected mode of use. 
 * 
 * dispose() is used to release a buffer once the stream is done with it 
 * (directly from the Reader, most likely as part 
 * of the BufferHandler in the Writer). 
 * Here both the allocator and the slab are needed: the slab tracks whether 
 * or not all of its allocated space has been freed, and the allocator 
 * (in the pool case by delegating to the SlabPoolImpl) tracks empty, 
 * partial and full slabs for recycling memory. 
 * 
 * @author Ken Cavanaugh
 * @author John Vieten 
 */
public class SlabByteBufferWrapper extends ByteBufferWrapper {

    private Slab slab;
    private final int slabPosition;    // starting position in the Slab before

    /** Allocate a buffer that contains dataSize data.
     */
    public SlabByteBufferWrapper(final ByteBufferManager allocator, final Slab slab,
            final int size) {
        super(allocator, slab.allocate(size));
        this.slab = slab;
        this.slabPosition = slab.currentPosition();
       
    }


    /** Trim the buffer by reducing capacity to position, if possible.
     * May return without changing capacity.  Also resets the position to 0,
     * like reset().
     */
    @Override
    public void trim() {
        checkDispose();
        final int sizeNeeded =  visible.position();
        visible = slab.trim(
                slabPosition,
                visible,
                sizeNeeded);
        visible.position(0);
    }

    /** Notify the allocator that the space for this BufferWrapper is no longer needed.
     * All calls to methods on a BufferWrapper will fail after a call to dispose().
     */
    @Override
    public void dispose() {
        checkDispose();
        ((SlabMemoryManagerBase) memoryManager).dispose(slab, visible);
        super.dispose();
        slab = null;
       

    }

    private void checkDispose() {
        if (visible == null) {
            throw new IllegalStateException("BufferWrapper has already been disposed");
        }
    }

   

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder("SlabByteBufferWrapper ");
        sb.append(", visible=[").append(visible).append(']');
        sb.append(']');
        return sb.toString();
    }
}