/* Copyright (c) 2008-2020, Nathan Sweet
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following
 * conditions are met:
 * 
 * - Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
 * - 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.
 * - Neither the name of Esoteric Software nor the names of its contributors may be used to endorse or promote products derived
 * from this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "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 THE COPYRIGHT HOLDER 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. */

package com.esotericsoftware.kryo.unsafe;

import static com.esotericsoftware.kryo.unsafe.UnsafeUtil.*;

import com.esotericsoftware.kryo.KryoException;
import com.esotericsoftware.kryo.io.ByteBufferInput;
import com.esotericsoftware.kryo.util.Util;

import java.io.InputStream;
import java.nio.Buffer;
import java.nio.ByteBuffer;

import sun.nio.ch.DirectBuffer;

/** A {@link ByteBufferInput} that reads data from direct ByteBuffer (off-heap memory) using sun.misc.Unsafe. Multi-byte primitive
 * types use native byte order, so the native byte order on different computers which read and write the data must be the same.
 * <p>
 * Not available on all JVMs. {@link Util#unsafe} can be checked before using this class.
 * <p>
 * This class may be much faster when {@link #setVariableLengthEncoding(boolean)} is false.
 * @author Roman Levenstein <romixlev@gmail.com>
 * @author Nathan Sweet */
@SuppressWarnings("restriction")
public class UnsafeByteBufferInput extends ByteBufferInput {
	/** Start address of the memory buffer. It must be non-movable, which normally means that is is allocated off-heap. */
	private long bufferAddress;

	/** Creates an uninitialized Input, {@link #setBuffer(ByteBuffer)} must be called before the Input is used. */
	public UnsafeByteBufferInput () {
	}

	/** Creates a new Input for reading from a direct {@link ByteBuffer}.
	 * @param bufferSize The size of the buffer. An exception is thrown if more bytes than this are read and
	 *           {@link #fill(ByteBuffer, int, int)} does not supply more bytes. */
	public UnsafeByteBufferInput (int bufferSize) {
		super(bufferSize);
		updateBufferAddress();
	}

	/** Creates a new Input for reading from a {@link ByteBuffer} which is filled with the specified bytes. */
	public UnsafeByteBufferInput (byte[] bytes) {
		super(bytes);
		updateBufferAddress();
	}

	/** Creates a new Input for reading from a {@link ByteBuffer} which is filled with the specified bytes. */
	public UnsafeByteBufferInput (byte[] bytes, int offset, int count) {
		super(bytes, offset, count);
		updateBufferAddress();
	}

	/** Creates a new Input for reading from a ByteBuffer. */
	public UnsafeByteBufferInput (ByteBuffer buffer) {
		super(buffer);
		updateBufferAddress();
	}

	/** Creates a new Input for reading from a ByteBuffer representing the memory region at the specified address and size. @throws
	 * UnsupportedOperationException if creating a ByteBuffer this way is not available. */
	public UnsafeByteBufferInput (long address, int size) {
		super(newDirectBuffer(address, size));
		updateBufferAddress();
	}

	/** Creates a new Input for reading from an InputStream with a buffer size of 4096. */
	public UnsafeByteBufferInput (InputStream inputStream) {
		super(inputStream);
		updateBufferAddress();
	}

	/** Creates a new Input for reading from an InputStream with the specified buffer size. */
	public UnsafeByteBufferInput (InputStream inputStream, int bufferSize) {
		super(inputStream, bufferSize);
		updateBufferAddress();
	}

	public void setBuffer (ByteBuffer buffer) {
		if (!(buffer instanceof DirectBuffer)) throw new IllegalArgumentException("buffer must be direct.");
		if (buffer != byteBuffer) UnsafeUtil.dispose(byteBuffer);
		super.setBuffer(buffer);
		updateBufferAddress();
	}

	private void updateBufferAddress () {
		bufferAddress = ((DirectBuffer)byteBuffer).address();
	}

	private void setBufferPosition (Buffer buffer, int position) {
		buffer.position(position);
	}

	public int read () throws KryoException {
		if (optional(1) <= 0) return -1;
		int result = unsafe.getByte(bufferAddress + position++) & 0xFF;
		setBufferPosition(byteBuffer, position);
		return result;
	}

	public byte readByte () throws KryoException {
		if (position == limit) require(1);
		byte result = unsafe.getByte(bufferAddress + position++);
		setBufferPosition(byteBuffer, position);
		return result;
	}

	public int readByteUnsigned () throws KryoException {
		if (position == limit) require(1);
		int result = unsafe.getByte(bufferAddress + position++) & 0xFF;
		setBufferPosition(byteBuffer, position);
		return result;
	}

	public int readInt () throws KryoException {
		require(4);
		int result = unsafe.getInt(bufferAddress + position);
		position += 4;
		setBufferPosition(byteBuffer, position);
		return result;
	}

	public long readLong () throws KryoException {
		require(8);
		long result = unsafe.getLong(bufferAddress + position);
		position += 8;
		setBufferPosition(byteBuffer, position);
		return result;
	}

	public float readFloat () throws KryoException {
		require(4);
		float result = unsafe.getFloat(bufferAddress + position);
		position += 4;
		setBufferPosition(byteBuffer, position);
		return result;
	}

	public double readDouble () throws KryoException {
		require(8);
		double result = unsafe.getDouble(bufferAddress + position);
		position += 8;
		setBufferPosition(byteBuffer, position);
		return result;
	}

	public short readShort () throws KryoException {
		require(2);
		short result = unsafe.getShort(bufferAddress + position);
		position += 2;
		setBufferPosition(byteBuffer, position);
		return result;
	}

	public char readChar () throws KryoException {
		require(2);
		char result = unsafe.getChar(bufferAddress + position);
		position += 2;
		setBufferPosition(byteBuffer, position);
		return result;
	}

	public boolean readBoolean () throws KryoException {
		if (position == limit) require(1);
		boolean result = unsafe.getByte(bufferAddress + position++) != 0;
		setBufferPosition(byteBuffer, position);
		return result;
	}

	public int[] readInts (int length) throws KryoException {
		int[] array = new int[length];
		readBytes(array, intArrayBaseOffset, length << 2);
		return array;
	}

	public long[] readLongs (int length) throws KryoException {
		long[] array = new long[length];
		readBytes(array, longArrayBaseOffset, length << 3);
		return array;
	}

	public float[] readFloats (int length) throws KryoException {
		float[] array = new float[length];
		readBytes(array, floatArrayBaseOffset, length << 2);
		return array;
	}

	public double[] readDoubles (int length) throws KryoException {
		double[] array = new double[length];
		readBytes(array, doubleArrayBaseOffset, length << 3);
		return array;
	}

	public short[] readShorts (int length) throws KryoException {
		short[] array = new short[length];
		readBytes(array, shortArrayBaseOffset, length << 1);
		return array;
	}

	public char[] readChars (int length) throws KryoException {
		char[] array = new char[length];
		readBytes(array, charArrayBaseOffset, length << 1);
		return array;
	}

	public boolean[] readBooleans (int length) throws KryoException {
		boolean[] array = new boolean[length];
		readBytes(array, booleanArrayBaseOffset, length);
		return array;
	}

	public void readBytes (byte[] bytes, int offset, int count) throws KryoException {
		readBytes(bytes, byteArrayBaseOffset + offset, count);
	}

	/** Read count bytes and write them to the object at the given offset inside the in-memory representation of the object. */
	public void readBytes (Object to, long offset, int count) throws KryoException {
		int copyCount = Math.min(limit - position, count);
		while (true) {
			unsafe.copyMemory(null, bufferAddress + position, to, offset, copyCount);
			position += copyCount;
			count -= copyCount;
			if (count == 0) break;
			offset += copyCount;
			copyCount = Math.min(count, capacity);
			require(copyCount);
		}
		setBufferPosition(byteBuffer, position);
	}

}
