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	/*
	* Copyright (c) 2016, 2018, Oracle and/or its affiliates. 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. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package jdk.jfr.internal.consumer;

	import java.io.DataInput;
	import java.io.EOFException;
	import java.io.File;
	import java.io.IOException;
	import java.io.RandomAccessFile;
	import java.nio.charset.Charset;

	public final class RecordingInput implements DataInput, AutoCloseable {

	public static final byte STRING_ENCODING_NULL = 0;
	public static final byte STRING_ENCODING_EMPTY_STRING = 1;
	public static final byte STRING_ENCODING_CONSTANT_POOL = 2;
	public static final byte STRING_ENCODING_UTF8_BYTE_ARRAY = 3;
	public static final byte STRING_ENCODING_CHAR_ARRAY = 4;
	public static final byte STRING_ENCODING_LATIN1_BYTE_ARRAY = 5;

	private final static int DEFAULT_BLOCK_SIZE = 16 * 1024 * 1024;
	private final static Charset UTF8 = Charset.forName("UTF-8");
	private final static Charset LATIN1 = Charset.forName("ISO-8859-1");

	private static final class Block {
	private byte[] bytes = new byte[0];
	private long blockPosition;

	boolean contains(long position) {
	return position >= blockPosition && position < blockPosition + bytes.length;
	}

	public void read(RandomAccessFile file, int amount) throws IOException {
	blockPosition = file.getFilePointer();
	// reuse byte array, if possible
	if (amount != bytes.length) {
	bytes = new byte[amount];
	}
	file.readFully(bytes);
	}

	public byte get(long position) {
	return bytes[(int) (position - blockPosition)];
	}
	}

	private final RandomAccessFile file;
	private final long size;
	private Block currentBlock = new Block();
	private Block previousBlock = new Block();
	private long position;
	private final int blockSize;

	private RecordingInput(File f, int blockSize) throws IOException {
	this.size = f.length();
	this.blockSize = blockSize;
	this.file = new RandomAccessFile(f, "r");
	if (size < 8) {
	throw new IOException("Not a valid Flight Recorder file. File length is only " + size + " bytes.");
	}
	}

	public RecordingInput(File f) throws IOException {
	this(f, DEFAULT_BLOCK_SIZE);
	}

	@Override
	public final byte readByte() throws IOException {
	if (!currentBlock.contains(position)) {
	position(position);
	}
	return currentBlock.get(position++);
	}

	@Override
	public final void readFully(byte[] dest, int offset, int length) throws IOException {
	// TODO: Optimize, use Arrays.copy if all bytes are in current block
	// array
	for (int i = 0; i < length; i++) {
	dest[i + offset] = readByte();
	}
	}

	@Override
	public final void readFully(byte[] dst) throws IOException {
	readFully(dst, 0, dst.length);
	}

	public final short readRawShort() throws IOException {
	// copied from java.io.Bits
	byte b0 = readByte();
	byte b1 = readByte();
	return (short) ((b1 & 0xFF) + (b0 << 8));
	}

	@Override
	public final double readDouble() throws IOException {
	// copied from java.io.Bits
	return Double.longBitsToDouble(readRawLong());
	}

	@Override
	public final float readFloat() throws IOException {
	// copied from java.io.Bits
	return Float.intBitsToFloat(readRawInt());
	}

	public final int readRawInt() throws IOException {
	// copied from java.io.Bits
	byte b0 = readByte();
	byte b1 = readByte();
	byte b2 = readByte();
	byte b3 = readByte();
	return ((b3 & 0xFF)) + ((b2 & 0xFF) << 8) + ((b1 & 0xFF) << 16) + ((b0) << 24);
	}

	public final long readRawLong() throws IOException {
	// copied from java.io.Bits
	byte b0 = readByte();
	byte b1 = readByte();
	byte b2 = readByte();
	byte b3 = readByte();
	byte b4 = readByte();
	byte b5 = readByte();
	byte b6 = readByte();
	byte b7 = readByte();
	return ((b7 & 0xFFL)) + ((b6 & 0xFFL) << 8) + ((b5 & 0xFFL) << 16) + ((b4 & 0xFFL) << 24) + ((b3 & 0xFFL) << 32) + ((b2 & 0xFFL) << 40) + ((b1 & 0xFFL) << 48) + (((long) b0) << 56);
	}

	public final long position() throws IOException {
	return position;
	}

	public final void position(long newPosition) throws IOException {
	if (!currentBlock.contains(newPosition)) {
	if (!previousBlock.contains(newPosition)) {
	if (newPosition > size()) {
	throw new EOFException("Trying to read at " + newPosition + ", but file is only " + size() + " bytes.");
	}
	long blockStart = trimToFileSize(calculateBlockStart(newPosition));
	file.seek(blockStart);
	// trim amount to file size
	long amount = Math.min(size() - blockStart, blockSize);
	previousBlock.read(file, (int) amount);
	}
	// swap previous and current
	Block tmp = currentBlock;
	currentBlock = previousBlock;
	previousBlock = tmp;
	}
	position = newPosition;
	}

	private final long trimToFileSize(long position) throws IOException {
	return Math.min(size(), Math.max(0, position));
	}

	private final long calculateBlockStart(long newPosition) {
	// align to end of current block
	if (currentBlock.contains(newPosition - blockSize)) {
	return currentBlock.blockPosition + currentBlock.bytes.length;
	}
	// align before current block
	if (currentBlock.contains(newPosition + blockSize)) {
	return currentBlock.blockPosition - blockSize;
	}
	// not near current block, pick middle
	return newPosition - blockSize / 2;
	}

	public final long size() throws IOException {
	return size;
	}

	public final void close() throws IOException {
	file.close();
	}

	@Override
	public final int skipBytes(int n) throws IOException {
	long position = position();
	position(position + n);
	return (int) (position() - position);
	}

	@Override
	public final boolean readBoolean() throws IOException {
	return readByte() != 0;
	}

	@Override
	public int readUnsignedByte() throws IOException {
	return readByte() & 0x00FF;
	}

	@Override
	public int readUnsignedShort() throws IOException {
	return readShort() & 0xFFFF;
	}

	@Override
	public final String readLine() throws IOException {
	throw new UnsupportedOperationException();
	}

	// NOTE, this method should really be called readString
	// but can't be renamed without making RecordingInput a
	// public class.
	//
	// This method DOES Not read as expected (s2 + utf8 encoded character)
	// instead it read:
	// byte encoding
	// int size
	// data (byte or char)
	//
	// where encoding
	//
	// 0, means null
	// 1, means UTF8 encoded byte array
	// 2, means char array
	// 3, means latin-1 (ISO-8859-1) encoded byte array
	// 4, means ""
	@Override
	public String readUTF() throws IOException {
	return readEncodedString(readByte());
	}

	public String readEncodedString(byte encoding) throws IOException {
	if (encoding == STRING_ENCODING_NULL) {
	return null;
	}
	if (encoding == STRING_ENCODING_EMPTY_STRING) {
	return "";
	}
	int size = readInt();
	if (encoding == STRING_ENCODING_CHAR_ARRAY) {
	char[] c = new char[size];
	for (int i = 0; i < size; i++) {
	c[i] = readChar();
	}
	return new String(c);
	}
	byte[] bytes = new byte[size];
	readFully(bytes); // TODO: optimize, check size, and copy only if needed
	if (encoding == STRING_ENCODING_UTF8_BYTE_ARRAY) {
	return new String(bytes, UTF8);
	}

	if (encoding == STRING_ENCODING_LATIN1_BYTE_ARRAY) {
	return new String(bytes, LATIN1);
	}
	throw new IOException("Unknown string encoding " + encoding);
	}

	@Override
	public char readChar() throws IOException {
	return (char) readLong();
	}

	@Override
	public short readShort() throws IOException {
	return (short) readLong();
	}

	@Override
	public int readInt() throws IOException {
	return (int) readLong();
	}

	@Override
	public long readLong() throws IOException {
	// can be optimized by branching checks, but will do for now
	byte b0 = readByte();
	long ret = (b0 & 0x7FL);
	if (b0 >= 0) {
	return ret;
	}
	int b1 = readByte();
	ret += (b1 & 0x7FL) << 7;
	if (b1 >= 0) {
	return ret;
	}
	int b2 = readByte();
	ret += (b2 & 0x7FL) << 14;
	if (b2 >= 0) {
	return ret;
	}
	int b3 = readByte();
	ret += (b3 & 0x7FL) << 21;
	if (b3 >= 0) {
	return ret;
	}
	int b4 = readByte();
	ret += (b4 & 0x7FL) << 28;
	if (b4 >= 0) {
	return ret;
	}
	int b5 = readByte();
	ret += (b5 & 0x7FL) << 35;
	if (b5 >= 0) {
	return ret;
	}
	int b6 = readByte();
	ret += (b6 & 0x7FL) << 42;
	if (b6 >= 0) {
	return ret;
	}
	int b7 = readByte();
	ret += (b7 & 0x7FL) << 49;
	if (b7 >= 0) {
	return ret;
	}
	int b8 = readByte(); // read last byte raw
	return ret + (((long) (b8 & 0XFF)) << 56);
	}
	}

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