/* This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * <p/>
 * This library 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
 * Lesser General Public License for more details.  
 */
package com.sun.jna;

import java.io.UnsupportedEncodingException;
import java.lang.reflect.Array;
import java.nio.Buffer;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.util.ArrayList;
import java.util.List;

/**
 * An abstraction for a native pointer data type.  A Pointer instance 
 * represents, on the Java side, a native pointer.  The native pointer could 
 * be any <em>type</em> of native pointer.  Methods such as <code>write</code>, 
 * <code>read</code>, <code>getXXX</code>, and <code>setXXX</code>, provide 
 * means to access memory underlying the native pointer.<p>
 * The constructors are intentionally package-private, since it's not generally
 * a good idea to be creating C pointers de novo. 
 *
 * @author Sheng Liang, originator
 * @author Todd Fast, suitability modifications
 * @author Timothy Wall, robust library loading
 * @see    Function
 */
public class Pointer {

    /** Size of a native pointer, in bytes. */
    public static final int SIZE;
    
    static {
        // Force load of native library
        if ((SIZE = Native.POINTER_SIZE) == 0) {
            throw new Error("Native library not initialized");
        }
    }
    
    /** Convenience constant, same as <code>null</code>. */
    public static final Pointer NULL = null;
    
    /** Convenience constant, equivalent to <code>(void*)CONSTANT</code>. */
    public static final Pointer createConstant(long peer) {
        return new Opaque(peer);
    }
    
    /** Convenience constant, equivalent to <code>(void*)CONSTANT</code>.
        This version will avoid setting any of the high bits on 64-bit
        systems.
     */
    public static final Pointer createConstant(int peer) {
        return new Opaque((long)peer & 0xFFFFFFFF);
    }
    
    /** Pointer value of the real native pointer. Use long to be 64-bit safe. 
     */
    protected long peer;

    /** Derived class must assign peer pointer value. */
    Pointer() { }
    
    /** Create from native pointer.  Don't use this unless you know what
     * you're doing.
     */
    public Pointer(long peer) {
        this.peer = peer;
    }

    /** Provide a view of this memory using the given offset to calculate a new base address. */
    public Pointer share(long offset) {
        return share(offset, 0);
    }
    
    /** Provide a view of this memory using the given offset to calculate a
     * new base address, bounds-limiting the memory with the given size.
     */
    public Pointer share(long offset, long sz) {
        if (offset == 0) return this;
        return new Pointer(peer + offset);
    }

    /** Zero memory for the given number of bytes. */
    public void clear(long size) {
        setMemory(0, size, (byte)0);
    }

    /**
     * Compares this <code>Pointer</code> to the specified object.
     *
     * @param	o 
     *			A <code>Pointer</code> instance
     * @return	True if the other object is a <code>Pointer</code>, 
     *          and the C pointers being pointed to by these objects are also
     *			equal. Returns false otherwise.
     */
    public boolean equals(Object o) {
        if (o == this) return true;
        if (o == null) return false;
        return o instanceof Pointer && ((Pointer)o).peer == peer;
    }

    /**
     * Returns a hashcode for the native pointer represented by this
     * <code>Pointer</code> object
     *
     * @return	A hash code value for the represented native pointer
     */
    public int hashCode() {
        return (int)((peer >>> 32) + (peer & 0xFFFFFFFF));
    }


    //////////////////////////////////////////////////////////////////////////
    // Raw read methods
    //////////////////////////////////////////////////////////////////////////

    /** Returns the offset of the given value in memory from the given offset,
     * or -1 if the value is not found.
     */
    public long indexOf(long offset, byte value) {
        return Native.indexOf(peer + offset, value);
    }
    
    /**
     * Indirect the native pointer, copying <em>from</em> memory pointed to by
     * native pointer, into the specified array.
     *
     * @param offset byte offset from pointer into which data is copied
     * @param buf    <code>byte</code> array into which data is copied
     * @param index  array index from which to start copying
     * @param length number of elements from native pointer that must be copied
     */
    public void read(long offset, byte[] buf, int index, int length) {
        Native.read(peer + offset, buf, index, length);
    }

    /**
     * Indirect the native pointer, copying <em>from</em> memory pointed to by
     * native pointer, into the specified array.
     *
     * @param offset byte offset from pointer from which data is copied
     * @param buf    <code>short</code> array into which data is copied
     * @param index  array index to which data is copied
     * @param length number of elements from native pointer that must be copied
     */
    public void read(long offset, short[] buf, int index, int length) {
        Native.read(peer + offset, buf, index, length);
    }

    /**
     * Indirect the native pointer, copying <em>from</em> memory pointed to by
     * native pointer, into the specified array.
     *
     * @param offset byte offset from pointer from which data is copied
     * @param buf    <code>char</code> array into which data is copied
     * @param index  array index to which data is copied
     * @param length number of elements from native pointer that must be copied
     */
    public void read(long offset, char[] buf, int index, int length) {
        Native.read(peer + offset, buf, index, length);
    }
    
    /**
     * Indirect the native pointer, copying <em>from</em> memory pointed to by
     * native pointer, into the specified array.
     *
     * @param offset byte offset from pointer from which data is copied
     * @param buf    <code>int</code> array into which data is copied
     * @param index  array index to which data is copied
     * @param length number of elements from native pointer that must be copied
     */
    public void read(long offset, int[] buf, int index, int length) {
        Native.read(peer + offset, buf, index, length);
    }

    /**
     * Indirect the native pointer, copying <em>from</em> memory pointed to by
     * native pointer, into the specified array.
     *
     * @param offset byte offset from pointer from which data is copied
     * @param buf    <code>long</code> array into which data is copied
     * @param index  array index to which data is copied
     * @param length number of elements from native pointer that must be copied
     */
    public void read(long offset, long[] buf, int index, int length) {
        Native.read(peer + offset, buf, index, length);
    }

    /**
     * Indirect the native pointer, copying <em>from</em> memory pointed to by
     * native pointer, into the specified array.
     *
     * @param offset byte offset from pointer from which data is copied
     * @param buf    <code>float</code> array into which data is copied
     * @param index  array index to which data is copied
     * @param length number of elements from native pointer that must be copied
     */
    public void read(long offset, float[] buf, int index, int length) {
        Native.read(peer + offset, buf, index, length);
    }

    /**
     * Indirect the native pointer, copying <em>from</em> memory pointed to by
     * native pointer, into the specified array.
     *
     * @param offset byte offset from pointer from which data is copied
     * @param buf    <code>double</code> array into which data is copied
     * @param index  array index to which data is copied
     * @param length number of elements from native pointer that must be copied
     */
    public void read(long offset, double[] buf, int index, int length) {
        Native.read(peer + offset, buf, index, length);
    }

    /**
     * Indirect the native pointer, copying <em>from</em> memory pointed to by
     * native pointer, into the specified array.
     *
     * @param offset byte offset from pointer from which data is copied
     * @param buf    {@link Pointer} array into which data is copied
     * @param index  array index to which data is copied
     * @param length number of elements from native pointer that must be copied
     */
    public void read(long offset, Pointer[] buf, int index, int length) {
        for (int i=0;i < length;i++) {
            Pointer p = getPointer(offset + i*Pointer.SIZE);
            Pointer oldp = buf[i+index];
            // Avoid replacing the original pointer if it hasn't changed
            if (oldp == null || p == null || p.peer != oldp.peer) {
                buf[i+index] = p;
            }
        }
    }


    //////////////////////////////////////////////////////////////////////////
    // Raw write methods
    //////////////////////////////////////////////////////////////////////////

    /**
     * Indirect the native pointer, copying <em>into</em> memory pointed to by
     * native pointer, from the specified array.
     *
     * @param offset byte offset from pointer into which data is copied
     * @param buf    <code>byte</code> array from which to copy
     * @param index  array index from which to start copying
     * @param length number of elements from <code>buf</code> that must be
     *               copied
     */
    public void write(long offset, byte[] buf, int index, int length) {
        Native.write(peer + offset, buf, index, length);
    }

    /**
     * Indirect the native pointer, copying <em>into</em> memory pointed to by
     * native pointer, from the specified array.
     *
     * @param offset byte offset from pointer into which data is copied
     * @param buf    <code>short</code> array from which to copy
     * @param index  array index from which to start copying
     * @param length number of elements from <code>buf</code> that must be
     *               copied
     */
    public void write(long offset, short[] buf, int index, int length) {
        Native.write(peer + offset, buf, index, length);
    }

    /**
     * Indirect the native pointer, copying <em>into</em> memory pointed to by
     * native pointer, from the specified array.
     *
     * @param offset byte offset from pointer into which data is copied
     * @param buf    <code>char</code> array from which to copy
     * @param index  array index from which to start copying
     * @param length number of elements from <code>buf</code> that must be
     *               copied
     */
    public void write(long offset, char[] buf, int index, int length) {
        Native.write(peer + offset, buf, index, length);
    }

    /**
     * Indirect the native pointer, copying <em>into</em> memory pointed to by
     * native pointer, from the specified array.
     *
     * @param offset byte offset from pointer into which data is copied
     * @param buf    <code>int</code> array from which to copy
     * @param index  array index from which to start copying
     * @param length number of elements from <code>buf</code> that must be
     *               copied
     */
    public void write(long offset, int[] buf, int index, int length) {
        Native.write(peer + offset, buf, index, length);
    }

    /**
     * Indirect the native pointer, copying <em>into</em> memory pointed to by 
     * native pointer, from the specified array.
     *
     * @param offset byte offset from pointer into which data is copied
     * @param buf    <code>long</code> array from which to copy
     * @param index  array index from which to start copying
     * @param length number of elements from <code>buf</code> that must be
     *               copied
     */
    public void write(long offset, long[] buf, int index, int length) {
        Native.write(peer + offset, buf, index, length);
    }

    /**
     * Indirect the native pointer, copying <em>into</em> memory pointed to by
     * native pointer, from the specified array.
     *
     * @param offset byte offset from pointer into which data is copied
     * @param buf    <code>float</code> array from which to copy
     * @param index  array index from which to start copying
     * @param length number of elements from <code>buf</code> that must be
     *               copied
     */
    public void write(long offset, float[] buf, int index, int length) {
        Native.write(peer + offset, buf, index, length);
    }

    /**
     * Indirect the native pointer, copying <em>into</em> memory pointed to by
     * native pointer, from the specified array.
     *
     * @param offset byte offset from pointer into which data is copied
     * @param buf    <code>double</code> array from which to copy
     * @param index  array index from which to start copying
     * @param length number of elements from <code>buf</code> that must be
     *               copied
     */
    public void write(long offset, double[] buf, int index, int length) {
        Native.write(peer + offset, buf, index, length);
    }

    /** Write the given array of Pointer to native memory.
     * @param bOff   byte offset from pointer into which data is copied
     * @param buf    <code>Pointer</code> array from which to copy
     * @param index  array index from which to start copying
     * @param length number of elements from <code>buf</code> that must be
     *               copied
    */
    public void write(long bOff, Pointer[] buf, int index, int length) {
        for (int i=0;i < length;i++) {
            setPointer(bOff + i * Pointer.SIZE, buf[index + i]);
        }
    }

    //////////////////////////////////////////////////////////////////////////
    // Java type read methods
    //////////////////////////////////////////////////////////////////////////

    Object getValue(long offset, Class type, Object currentValue) {

        Object result = null;
        if (Structure.class.isAssignableFrom(type)) {
            Structure s = (Structure)currentValue;
            if (Structure.ByReference.class.isAssignableFrom(type)) {
                s = Structure.updateStructureByReference(type, s, getPointer(offset));
            }
            else {
                s.useMemory(this, (int)offset);
                s.read();
            }
            result = s;
        }
        else if (type == boolean.class || type == Boolean.class) {
            result = Function.valueOf(getInt(offset) != 0);
        }
        else if (type == byte.class || type == Byte.class) {
            result = new Byte(getByte(offset));
        }
        else if (type == short.class || type == Short.class) {
            result = new Short(getShort(offset));
        }
        else if (type == char.class || type == Character.class) {
            result = new Character(getChar(offset));
        }
        else if (type == int.class || type == Integer.class) {
            result = new Integer(getInt(offset));
        }
        else if (type == long.class || type == Long.class) {
            result = new Long(getLong(offset));
        }
        else if (type == float.class || type == Float.class) {
            result=new Float(getFloat(offset));
        }
        else if (type == double.class || type == Double.class) {
            result = new Double(getDouble(offset));
        }
        else if (Pointer.class.isAssignableFrom(type)) {
            Pointer p = getPointer(offset);
            if (p != null) {
                Pointer oldp = currentValue instanceof Pointer
                    ? (Pointer)currentValue : null;
                if (oldp == null || p.peer != oldp.peer)
                    result = p;
                else
                    result = oldp;
            }
        }
        else if (type == String.class) {
            Pointer p = getPointer(offset);
            result = p != null ? p.getString(0) : null;
        }
        else if (type == WString.class) {
            Pointer p = getPointer(offset);
            result = p != null ? new WString(p.getString(0, true)) : null;
        }
        else if (Callback.class.isAssignableFrom(type)) {
            // Overwrite the Java memory if the native pointer is a different
            // function pointer.
            Pointer fp = getPointer(offset);
            if (fp == null) {
                result = null;
            }
            else {
                Callback cb = (Callback)currentValue;
                Pointer oldfp = CallbackReference.getFunctionPointer(cb);
                if (!fp.equals(oldfp)) {
                    cb = CallbackReference.getCallback(type, fp);
                }
                result = cb;
            }
        }
        else if (Platform.HAS_BUFFERS && Buffer.class.isAssignableFrom(type)) {
            Pointer bp = getPointer(offset);
            if (bp == null) {
                result = null;
            }
            else {
                Pointer oldbp = currentValue == null ? null
                    : Native.getDirectBufferPointer((Buffer)currentValue);
                if (oldbp == null || !oldbp.equals(bp)) {
                    throw new IllegalStateException("Can't autogenerate a direct buffer on memory read");
                }
                result = currentValue;
            }
        }
        else if (NativeMapped.class.isAssignableFrom(type)) {
            NativeMapped nm = (NativeMapped)currentValue;
            if (nm != null) {
                Object value = getValue(offset, nm.nativeType(), null);
                result = nm.fromNative(value, new FromNativeContext(type));
                if (nm.equals(result)) {
                    result = nm;
                }
            }
            else {
                NativeMappedConverter tc = NativeMappedConverter.getInstance(type);
                Object value = getValue(offset, tc.nativeType(), null);
                result = tc.fromNative(value, new FromNativeContext(type));
            }
        }
        else if (type.isArray()) {
            result = currentValue;
            if (result == null) {
                throw new IllegalStateException("Need an initialized array");
            }
            getArrayValue(offset, result, type.getComponentType());
        }
        else {
            throw new IllegalArgumentException("Reading \""
                                               + type + "\" from memory is not supported");
        }
        return result;
    }

    /** Copy memory starting at offset into the array with element type cls. */
    private void getArrayValue(long offset, Object o, Class cls) {
        int length = 0;
        length = Array.getLength(o);
        Object result = o;
        
        if (cls == byte.class) {
            read(offset, (byte[])result, 0, length);
        }
        else if (cls == short.class) {
            read(offset, (short[])result, 0, length);
        }
        else if (cls == char.class) {
            read(offset, (char[])result, 0, length);
        }
        else if (cls == int.class) {
            read(offset, (int[])result, 0, length);
        }
        else if (cls == long.class) {
            read(offset, (long[])result, 0, length);
        }
        else if (cls == float.class) {
            read(offset, (float[])result, 0, length);
        }
        else if (cls == double.class) {
            read(offset, (double[])result, 0, length);
        }
        else if (Pointer.class.isAssignableFrom(cls)) {
            read(offset, (Pointer[])result, 0, length);
        }
        else if (Structure.class.isAssignableFrom(cls)) {
            Structure[] sarray = (Structure[])result;
            if (Structure.ByReference.class.isAssignableFrom(cls)) {
                Pointer[] parray = getPointerArray(offset, sarray.length);
                for (int i=0;i < sarray.length;i++) {
                    sarray[i] = Structure.updateStructureByReference(cls, sarray[i], parray[i]);
                }
            }
            else {
                for (int i=0;i < sarray.length;i++) {
                    if (sarray[i] == null) {
                        sarray[i] = Structure.newInstance(cls);
                    }
                    sarray[i].useMemory(this, (int)(offset + i * sarray[i].size()));
                    sarray[i].read();
                }
            }
        }
        else if (NativeMapped.class.isAssignableFrom(cls)) {
            NativeMapped[] array = (NativeMapped[])result;
            NativeMappedConverter tc = NativeMappedConverter.getInstance(cls);
            int size = Native.getNativeSize(result.getClass(), result) / array.length;
            for (int i=0;i < array.length;i++) {
                Object value = getValue(offset + size*i, tc.nativeType(), array[i]);
                array[i] = (NativeMapped)tc.fromNative(value, new FromNativeContext(cls));
            }
        }
        else {
            throw new IllegalArgumentException("Reading array of "
                                               + cls
                                               + " from memory not supported");
        }
    }

    /**
     * Indirect the native pointer as a pointer to <code>byte</code>.  This is
     * equivalent to the expression
     * <code>*((jbyte *)((char *)Pointer + offset))</code>.
     *
     * @param offset offset from pointer to perform the indirection
     * @return the <code>byte</code> value being pointed to
     */
    public byte getByte(long offset) {
        return Native.getByte(peer + offset);
    }

    /**
     * Indirect the native pointer as a pointer to <code>wchar_t</code>.  This
     * is equivalent to the expression
     * <code>*((wchar_t*)((char *)Pointer + offset))</code>.
     *
     * @param offset offset from pointer to perform the indirection
     * @return the <code>wchar_t</code> value being pointed to
     */
    public char getChar(long offset) {
        return Native.getChar(peer + offset);
    }

    /**
     * Indirect the native pointer as a pointer to <code>short</code>.  This is
     * equivalent to the expression
     * <code>*((jshort *)((char *)Pointer + offset))</code>.
     *
     * @param offset byte offset from pointer to perform the indirection
     * @return the <code>short</code> value being pointed to
     */
    public short getShort(long offset) {
        return Native.getShort(peer + offset);
    }

    /**
     * Indirect the native pointer as a pointer to <code>int</code>.  This is
     * equivalent to the expression
     * <code>*((jint *)((char *)Pointer + offset))</code>.
     *
     * @param offset byte offset from pointer to perform the indirection
     * @return the <code>int</code> value being pointed to
     */
    public int getInt(long offset) {
        return Native.getInt(peer + offset);
    }

    /**
     * Indirect the native pointer as a pointer to <code>long</code>.  This is
     * equivalent to the expression
     * <code>*((jlong *)((char *)Pointer + offset))</code>.
     *
     * @param offset byte offset from pointer to perform the indirection
     * @return the <code>long</code> value being pointed to
     */
    public long getLong(long offset) {
        return Native.getLong(peer + offset);
    }

    /**
     * Indirect the native pointer as a pointer to <code>long</code>.  This is
     * equivalent to the expression
     * <code>*((long *)((char *)Pointer + offset))</code>.
     *
     * @param offset byte offset from pointer to perform the indirection
     * @return the <code>long</code> value being pointed to
     */
    public NativeLong getNativeLong(long offset) {
        return new NativeLong(NativeLong.SIZE == 8 ? getLong(offset) : getInt(offset));
    }

    /**
     * Indirect the native pointer as a pointer to <code>float</code>.  This is
     * equivalent to the expression
     * <code>*((jfloat *)((char *)Pointer + offset))</code>.
     *
     * @param offset byte offset from pointer to perform the indirection
     * @return the <code>float</code> value being pointed to
     */
    public float getFloat(long offset) {
        return Native.getFloat(peer + offset);
    }

    /**
     * Indirect the native pointer as a pointer to <code>double</code>.  This
     * is equivalent to the expression
     * <code>*((jdouble *)((char *)Pointer + offset))</code>.
     *
     * @param offset byte offset from pointer to perform the indirection
     * @return the <code>double</code> value being pointed to
     */
    public double getDouble(long offset) {
        return Native.getDouble(peer + offset);
    }

    /**
     * Indirect the native pointer as a pointer to pointer.  This is equivalent
     * to the expression
     * <code>*((void **)((char *)Pointer + offset))</code>.
     *
     * @param offset byte offset from pointer to perform the indirection
     * @return a {@link Pointer} equivalent of the pointer value
     * being pointed to, or <code>null</code> if the pointer value is
     * <code>NULL</code>;
     */
    public Pointer getPointer(long offset) {
        return Native.getPointer(peer + offset);
    }

    /**
     * Get a ByteBuffer mapped to the memory pointed to by the pointer,
     * ensuring the buffer uses native byte order.
     *
     * @param offset byte offset from pointer to start the buffer
     * @param length Length of ByteBuffer
     * @return a direct ByteBuffer that accesses the memory being pointed to,
     */
    public ByteBuffer getByteBuffer(long offset, long length) {
        return Native.getDirectByteBuffer(peer + offset, length).order(ByteOrder.nativeOrder());
    }

    /**
     * Copy native memory to a Java String.  If <code>wide</code> is true,
     * access the memory as an array of <code>wchar_t</code>, otherwise 
     * as an array of <code>char</code>, using the default platform encoding.
     *
     * @param offset byte offset from pointer to obtain the native string
v     * @param wide whether to convert from a wide or standard C string
     * @return the <code>String</code> value being pointed to 
     */
    public String getString(long offset, boolean wide) {
        return Native.getString(peer + offset, wide);
    }
    
    /**
     * Copy native memory to a Java String.  If the system property 
     * <code>jna.encoding</code> is set, uses it as the native charset
     * when decoding the value, otherwise falls back to the default platform
     * encoding.
     *
     * @param offset byte offset from pointer to obtain the native string
     * @return the <code>String</code> value being pointed to 
     */
    public String getString(long offset) {
        String encoding = System.getProperty("jna.encoding");
        if (encoding != null) {
            long len = indexOf(offset, (byte)0);
            if (len != -1) {
                if (len > Integer.MAX_VALUE) {
                    throw new OutOfMemoryError("String exceeds maximum length: " + len);
                }
                byte[] data = getByteArray(offset, (int)len);
                try {
                    return new String(data, encoding);
                }
                catch(UnsupportedEncodingException e) { 
                }
            }
        }
        return getString(offset, false);
    }

    /** Read a native array of bytes of size <code>arraySize</code> from the
        given <code>offset</code> from this {@link Pointer}.
    */
    public byte[] getByteArray(long offset, int arraySize) {
        byte[] buf = new byte[arraySize];
        read(offset, buf, 0, arraySize);
        return buf;
    }
    
    /** Read a native array of wchar_t of size <code>arraySize</code> from the
        given <code>offset</code> from this {@link Pointer}.
    */
    public char[] getCharArray(long offset, int arraySize) {
        char[] buf = new char[arraySize];
        read(offset, buf, 0, arraySize);
        return buf;
    }

    /** Read a native array of int16 of size <code>arraySize</code> from the
        given <code>offset</code> from this {@link Pointer}.
    */
    public short[] getShortArray(long offset, int arraySize) {
        short[] buf = new short[arraySize];
        read(offset, buf, 0, arraySize);
        return buf;
    }

    /** Read a native array of int32 of size <code>arraySize</code> from the
        given <code>offset</code> from this {@link Pointer}.
    */
    public int[] getIntArray(long offset, int arraySize) {
        int[] buf = new int[arraySize];
        read(offset, buf, 0, arraySize);
        return buf;
    }

    /** Read a native array of int64 of size <code>arraySize</code> from the
        given <code>offset</code> from this {@link Pointer}.
    */
    public long[] getLongArray(long offset, int arraySize) {
        long[] buf = new long[arraySize];
        read(offset, buf, 0, arraySize);
        return buf;
    }

    /** Read a native array of float of size <code>arraySize</code> from the
        given <code>offset</code> from this {@link Pointer}.
    */
    public float[] getFloatArray(long offset, int arraySize) {
        float[] buf = new float[arraySize];
        read(offset, buf, 0, arraySize);
        return buf;
    }

    /** Read a native array of double of size <code>arraySize</code> from the
        given <code>offset</code> from this {@link Pointer}.
    */
    public double[] getDoubleArray(long offset, int arraySize) {
        double[] buf = new double[arraySize];
        read(offset, buf, 0, arraySize);
        return buf;
    }

    /** Returns an array of {@link Pointer}.  The array length is
     * determined by a NULL-valued terminating element.
     */
    public Pointer[] getPointerArray(long offset) {
        List array = new ArrayList();
        int addOffset = 0;
        Pointer p = getPointer(offset);
        while (p != null) {
            array.add(p);
            addOffset += Pointer.SIZE;
            p = getPointer(offset + addOffset);
        }
        return (Pointer[])array.toArray(new Pointer[array.size()]);
    }

    /** Returns an array of {@link Pointer} of the requested size. */
    public Pointer[] getPointerArray(long offset, int arraySize) {
        Pointer[] buf = new Pointer[arraySize];
        read(offset, buf, 0, arraySize);
        return buf;
    }

    /** Returns an array of <code>String</code> based on a native array
     * of <code>char *</code>.  The array length is determined by a
     * NULL-valued terminating element. 
     */
    public String[] getStringArray(long offset) {
        return getStringArray(offset, -1, false);
    }

    /** Returns an array of <code>String</code> based on a native array
     * of <code>char *</code>, using the given array length. 
     */
    public String[] getStringArray(long offset, int length) {
        return getStringArray(offset, length, false);
    }

    /** Returns an array of <code>String</code> based on a native array
     * of <code>char*</code> or <code>wchar_t*</code> based on the
     * <code>wide</code> parameter.  The array length is determined by a
     * NULL-valued terminating element. 
     */
    public String[] getStringArray(long offset, boolean wide) {
        return getStringArray(offset, -1, wide);
    }

    /** Returns an array of <code>String</code> based on a native array
     * of <code>char*</code> or <code>wchar_t*</code> based on the
     * <code>wide</code> parameter, using the given array length.
     */
    public String[] getStringArray(long offset, int length, boolean wide) {
    
        List strings = new ArrayList();
        Pointer p;
        int addOffset = 0;
        if (length != -1) {
            p = getPointer(offset + addOffset);
            int count = 0;
            while (count++ < length) {
                String s = p == null ? null : p.getString(0, wide);
                strings.add(s);
                if (count < length) {
                    addOffset += SIZE;
                    p = getPointer(offset + addOffset);
                }
            }
        }
        else {
            while ((p = getPointer(offset + addOffset)) != null) {
                String s = p == null ? null : p.getString(0, wide);
                strings.add(s);
                addOffset += SIZE;
            }
        }
        return (String[])strings.toArray(new String[strings.size()]);
    }

    //////////////////////////////////////////////////////////////////////////
    // Java type write methods
    //////////////////////////////////////////////////////////////////////////

    void setValue(long offset, Object value, Class type) {

        // Set the value at the offset according to its type
        if (type == boolean.class || type == Boolean.class) {
            setInt(offset, Boolean.TRUE.equals(value) ? -1 : 0);
        }
        else if (type == byte.class || type == Byte.class) {
            setByte(offset, value == null ? 0 : ((Byte)value).byteValue());
        }
        else if (type == short.class || type == Short.class) {
            setShort(offset, value == null ? 0 : ((Short)value).shortValue());
        }
        else if (type == char.class || type == Character.class) {
            setChar(offset, value == null ? 0 : ((Character)value).charValue());
        }
        else if (type == int.class || type == Integer.class) {
            setInt(offset, value == null ? 0 : ((Integer)value).intValue());
        }
        else if (type == long.class || type == Long.class) {
            setLong(offset, value == null ? 0 : ((Long)value).longValue());
        }
        else if (type == float.class || type == Float.class) {
            setFloat(offset, value == null ? 0f : ((Float)value).floatValue());
        }
        else if (type == double.class || type == Double.class) {
            setDouble(offset, value == null ? 0.0 : ((Double)value).doubleValue());
        }
        else if (type == Pointer.class) {
            setPointer(offset, (Pointer)value);
        }
        else if (type == String.class) {
            setPointer(offset, (Pointer)value);
        }
        else if (type == WString.class) {
            setPointer(offset, (Pointer)value);
        }
        else if (Structure.class.isAssignableFrom(type)) {
            Structure s = (Structure)value;
            if (Structure.ByReference.class.isAssignableFrom(type)) {
                setPointer(offset, s == null ? null : s.getPointer());
                if (s != null) {
                    s.autoWrite();
                }
            }
            else {
                s.useMemory(this, (int)offset);
                s.write();
            }
        }
        else if (Callback.class.isAssignableFrom(type)) {
            setPointer(offset, CallbackReference.getFunctionPointer((Callback)value));
        }
        else if (Platform.HAS_BUFFERS && Buffer.class.isAssignableFrom(type)) {
            Pointer p = value == null ? null
                : Native.getDirectBufferPointer((Buffer)value);
            setPointer(offset, p);
        }
        else if (NativeMapped.class.isAssignableFrom(type)) {
            NativeMappedConverter tc = NativeMappedConverter.getInstance(type);
            Class nativeType = tc.nativeType();
            setValue(offset, tc.toNative(value, new ToNativeContext()), nativeType);
        }
        else if (type.isArray()) {
            setArrayValue(offset, value, type.getComponentType());
        }
        else {
            throw new IllegalArgumentException("Writing " + type + " to memory is not supported");
        }
    }

    private void setArrayValue(long offset, Object value, Class cls) {
        if (cls == byte.class) {
            byte[] buf = (byte[])value;
            write(offset, buf, 0, buf.length);
        }
        else if (cls == short.class) {
            short[] buf = (short[])value;
            write(offset, buf, 0, buf.length);
        }
        else if (cls == char.class) {
            char[] buf = (char[])value;
            write(offset, buf, 0, buf.length);
        }
        else if (cls == int.class) {
            int[] buf = (int[])value;
            write(offset, buf, 0, buf.length);
        }
        else if (cls == long.class) {
            long[] buf = (long[])value;
            write(offset, buf, 0, buf.length);
        }
        else if (cls == float.class) {
            float[] buf = (float[])value;
            write(offset, buf, 0, buf.length);
        }
        else if (cls == double.class) {
            double[] buf = (double[])value;
            write(offset, buf, 0, buf.length);
        }
        else if (Pointer.class.isAssignableFrom(cls)) {
            Pointer[] buf = (Pointer[])value;
            write(offset, buf, 0, buf.length);
        }
        else if (Structure.class.isAssignableFrom(cls)) {
            Structure[] sbuf = (Structure[])value;
            if (Structure.ByReference.class.isAssignableFrom(cls)) {
                Pointer[] buf = new Pointer[sbuf.length];
                for (int i=0;i < sbuf.length;i++) {
                    if (sbuf[i] == null) {
                        buf[i] = null;
                    }
                    else {
                        buf[i] = sbuf[i].getPointer();
                        sbuf[i].write();
                    }
                }
                write(offset, buf, 0, buf.length);
            }
            else {
                for (int i=0;i < sbuf.length;i++) {
                    if (sbuf[i] == null) {
                        sbuf[i] = Structure.newInstance(cls);
                    }
                    sbuf[i].useMemory(this, (int)(offset + i * sbuf[i].size()));
                    sbuf[i].write();
                }
            }
        }
        else if (NativeMapped.class.isAssignableFrom(cls)) {
            NativeMapped[] buf = (NativeMapped[])value;
            NativeMappedConverter tc = NativeMappedConverter.getInstance(cls);
            Class nativeType = tc.nativeType();
            int size = Native.getNativeSize(value.getClass(), value) / buf.length;
            for (int i=0;i < buf.length;i++) {
                Object element = tc.toNative(buf[i], new ToNativeContext());
                setValue(offset + i*size, element, nativeType);
            }
        }
        else {
            throw new IllegalArgumentException("Writing array of "
                                               + cls + " to memory not supported");
        }
    }

    /** Write <code>value</code> to the requested bank of memory. 
     * @param offset byte offset from pointer to start
     * @param length number of bytes to write
     * @param value value to be written
     */
    public void setMemory(long offset, long length, byte value) {
        Native.setMemory(peer + offset, length, value);
    }
    
    /**
     * Set <code>value</code> at location being pointed to. This is equivalent
     * to the expression
     * <code>*((jbyte *)((char *)Pointer + offset)) = value</code>.
     *
     * @param offset byte offset from pointer at which <code>value</code>
     *		     must be set
     * @param value <code>byte</code> value to set
     */
    public void setByte(long offset, byte value) {
        Native.setByte(peer + offset, value);
    }

    /**
     * Set <code>value</code> at location being pointed to. This is equivalent
     * to the expression
     * <code>*((jshort *)((char *)Pointer + offset)) = value</code>.
     *
     * @param offset byte offset from pointer at which <code>value</code>
     *		     must be set
     * @param value <code>short</code> value to set
     */
    public void setShort(long offset, short value) {
        Native.setShort(peer + offset, value);
    }
    
    /**
     * Set <code>value</code> at location being pointed to. This is equivalent
     * to the expression
     * <code>*((wchar_t *)((char *)Pointer + offset)) = value</code>.
     *
     * @param offset byte offset from pointer at which <code>value</code>
     *               must be set
     * @param value <code>char</code> value to set
     */
    public void setChar(long offset, char value) {
        Native.setChar(peer + offset, value);
    }
    
    /**
     * Set <code>value</code> at location being pointed to. This is equivalent
     * to the expression
     * <code>*((jint *)((char *)Pointer + offset)) = value</code>.
     *
     * @param offset byte offset from pointer at which <code>value</code>
     *		     must be set
     * @param value <code>int</code> value to set
     */
    public void setInt(long offset, int value) {
        Native.setInt(peer + offset, value);
    }

    /**
     * Set <code>value</code> at location being pointed to. This is equivalent
     * to the expression
     * <code>*((jlong *)((char *)Pointer + offset)) = value</code>.
     *
     * @param offset byte offset from pointer at which <code>value</code>
     *               must be set
     * @param value <code>long</code> value to set
     */
    public void setLong(long offset, long value) {
        Native.setLong(peer + offset, value);
    }
    
    /**
     * Set <code>value</code> at location being pointed to. This is equivalent
     * to the expression
     * <code>*((long *)((char *)Pointer + offset)) = value</code>.
     *
     * @param offset byte offset from pointer at which <code>value</code>
     *               must be set
     * @param value <code>long</code> value to set
     */
    public void setNativeLong(long offset, NativeLong value) {
        if (NativeLong.SIZE == 8) {
            setLong(offset, value.longValue());
        } else {
            setInt(offset, value.intValue());
        }
    }

    /**
     * Set <code>value</code> at location being pointed to. This is equivalent
     * to the expression
     * <code>*((jfloat *)((char *)Pointer + offset)) = value</code>.
     *
     * @param offset byte offset from pointer at which <code>value</code>
     *               must be set
     * @param value <code>float</code> value to set
     */
    public void setFloat(long offset, float value) {
        Native.setFloat(peer + offset, value);
    }
    
    /**
     * Set <code>value</code> at location being pointed to. This is equivalent
     * to the expression
     * <code>*((jdouble *)((char *)Pointer + offset)) = value</code>.
     *
     * @param offset byte offset from pointer at which <code>value</code>
     *               must be set
     * @param value <code>double</code> value to set
     */
    public void setDouble(long offset, double value) {
        Native.setDouble(peer + offset, value);
    }

    /**
     * Set <code>value</code> at location being pointed to. This is equivalent
     * to the expression 
     * <code>*((void **)((char *)Pointer + offset)) = value</code>.
     *
     * @param offset byte offset from pointer at which <code>value</code> 
     *               must be set
     * @param value <code>Pointer</code> holding the actual pointer value to 
     * set, which may be <code>null</code> to indicate a <code>NULL</code>
     * pointer.
     */
    public void setPointer(long offset, Pointer value) {
        Native.setPointer(peer + offset, value != null ? value.peer : 0);
    }

    /**
     * Copy string <code>value</code> to the location being pointed to.  Copy
     * each element in <code>value</code>, converted to native encoding, at an
     * <code>offset</code>from the location pointed to by this pointer.
     *
     * @param offset byte offset from pointer at which characters in
     * 		     <code>value</code> must be set
     * @param value  <code>java.lang.String</code> value to set
     * @param wide whether to write the native string as an array of 
     * <code>wchar_t</code>.  If false, writes as a NUL-terminated array of 
     * <code>char</code> using the default platform encoding. 
     */
    public void setString(long offset, String value, boolean wide) {
        Native.setString(peer + offset, value, wide);
    }
    
    /**
     * Copy string <code>value</code> to the location being pointed to.  Copy
     * each element in <code>value</code>, converted to native encoding, at an
     * <code>offset</code>from the location pointed to by this pointer.
     * Uses the value of the system property <code>jna.encoding</code>, if set, 
     * to determine the appropriate native charset in which to encode the value.  
     * If the property is not set, uses the default platform encoding.
     *
     * @param offset byte offset from pointer at which characters in
     *               <code>value</code> must be set
     * @param value  <code>java.lang.String</code> value to set
     */
    public void setString(long offset, String value) {
        byte[] data = Native.getBytes(value);
        write(offset, data, 0, data.length);
        setByte(offset + data.length, (byte)0);
    }
    
    public String toString() {
        return "native@0x" + Long.toHexString(peer);
    }
    
    /** Read the native peer value.  Use with caution. */
    public static long nativeValue(Pointer p) {
        return p.peer;
    }

    /** Set the native peer value.  Use with caution. */
    public static void nativeValue(Pointer p, long value) {
        p.peer = value;
    }

    /** Pointer which disallows all read/write access. */
    private static class Opaque extends Pointer {
        private Opaque(long peer) { super(peer); }
        private final String MSG = "This pointer is opaque: " + this;
        public long indexOf(long offset, byte value) {
            throw new UnsupportedOperationException(MSG);
        }
        public void read(long bOff, byte[] buf, int index, int length) { 
            throw new UnsupportedOperationException(MSG); 
        }
        public void read(long bOff, char[] buf, int index, int length) { 
            throw new UnsupportedOperationException(MSG); 
        }
        public void read(long bOff, short[] buf, int index, int length) { 
            throw new UnsupportedOperationException(MSG); 
        }
        public void read(long bOff, int[] buf, int index, int length) { 
            throw new UnsupportedOperationException(MSG); 
        }
        public void read(long bOff, long[] buf, int index, int length) { 
            throw new UnsupportedOperationException(MSG); 
        }
        public void read(long bOff, float[] buf, int index, int length) { 
            throw new UnsupportedOperationException(MSG); 
        }
        public void read(long bOff, double[] buf, int index, int length) { 
            throw new UnsupportedOperationException(MSG); 
        }
        public void write(long bOff, byte[] buf, int index, int length) { 
            throw new UnsupportedOperationException(MSG); 
        }
        public void write(long bOff, char[] buf, int index, int length) { 
            throw new UnsupportedOperationException(MSG); 
        }
        public void write(long bOff, short[] buf, int index, int length) { 
            throw new UnsupportedOperationException(MSG); 
        }
        public void write(long bOff, int[] buf, int index, int length) { 
            throw new UnsupportedOperationException(MSG); 
        }
        public void write(long bOff, long[] buf, int index, int length) { 
            throw new UnsupportedOperationException(MSG); 
        }
        public void write(long bOff, float[] buf, int index, int length) { 
            throw new UnsupportedOperationException(MSG); 
        }
        public void write(long bOff, double[] buf, int index, int length) { 
            throw new UnsupportedOperationException(MSG); 
        }
        public byte getByte(long bOff) {
            throw new UnsupportedOperationException(MSG); 
        }
        public char getChar(long bOff) {
            throw new UnsupportedOperationException(MSG); 
        }
        public short getShort(long bOff) {
            throw new UnsupportedOperationException(MSG); 
        }
        public int getInt(long bOff) {
            throw new UnsupportedOperationException(MSG); 
        }
        public long getLong(long bOff) {
            throw new UnsupportedOperationException(MSG); 
        }
        public float getFloat(long bOff) {
            throw new UnsupportedOperationException(MSG); 
        }
        public double getDouble(long bOff) {
            throw new UnsupportedOperationException(MSG); 
        }
        public Pointer getPointer(long bOff) {
            throw new UnsupportedOperationException(MSG); 
        }
        public String getString(long bOff, boolean wide) {
            throw new UnsupportedOperationException(MSG); 
        }
        public void setByte(long bOff, byte value) {
            throw new UnsupportedOperationException(MSG); 
        }
        public void setChar(long bOff, char value) {
            throw new UnsupportedOperationException(MSG); 
        }
        public void setShort(long bOff, short value) {
            throw new UnsupportedOperationException(MSG); 
        }
        public void setInt(long bOff, int value) {
            throw new UnsupportedOperationException(MSG); 
        }
        public void setLong(long bOff, long value) {
            throw new UnsupportedOperationException(MSG); 
        }
        public void setFloat(long bOff, float value) {
            throw new UnsupportedOperationException(MSG); 
        }
        public void setDouble(long bOff, double value) {
            throw new UnsupportedOperationException(MSG); 
        }
        public void setPointer(long offset, Pointer value) {
            throw new UnsupportedOperationException(MSG); 
        }
        public void setString(long offset, String value, boolean wide) {
            throw new UnsupportedOperationException(MSG); 
        }
        public String toString() {
            return "opaque@0x" + Long.toHexString(peer);
        }
    }
}
