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This is the api to interact with Concourse, a schemaless and distributed version control database with optimistic availability, serializable transactions and full-text search. Concourse provides a more intuitive approach to data management that is easy to deploy, access and scale with minimal tuning while also maintaining the referential integrity and ACID characteristics of traditional database systems.
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/*
 * The MIT License (MIT)
 * 
 * Copyright (c) 2013 Jeff Nelson, Cinchapi Software Collective
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
package org.cinchapi.concourse.util;

import java.nio.ByteBuffer;
import java.nio.charset.CharacterCodingException;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import java.nio.charset.CodingErrorAction;
import java.nio.charset.StandardCharsets;

import com.google.common.base.Preconditions;
import com.google.common.base.Throwables;

/**
 * Additional utility methods for ByteBuffers that are not found in the
 * {@link ByteBuffer} class.
 * 
 * @author jnelson
 */
public abstract class ByteBuffers {

	/**
	 * Return a ByteBuffer that is a new read-only buffer that shares the
	 * content of {@code source} and has the same byte order, but maintains a
	 * distinct position, mark and limit.
	 * 
	 * @param source
	 * @return the new, read-only byte buffer
	 */
	public static ByteBuffer asReadOnlyBuffer(ByteBuffer source) {
		int position = source.position();
		source.rewind();
		ByteBuffer duplicate = source.asReadOnlyBuffer();
		duplicate.order(source.order()); // byte order is not natively preserved
											// when making duplicates:
											// http://blog.mustardgrain.com/2008/04/04/bytebufferduplicate-does-not-preserve-byte-order/
		source.position(position);
		duplicate.rewind();
		return duplicate;
	}

	/**
	 * Return a clone of {@code buffer} that has a copy of all its
	 * content and the same position and limit. Unlike the
	 * {@link ByteBuffer#slice()} method, the returned clone
	 * does not share its content with {@code buffer}, so
	 * subsequent operations to {@code buffer} or its clone will be
	 * completely independent and won't affect the other.
	 * 
	 * @param buffer
	 * @return a clone of {@code buffer}
	 */
	public static ByteBuffer clone(ByteBuffer buffer) {
		ByteBuffer clone = ByteBuffer.allocate(buffer.capacity());
		int position = buffer.position();
		int limit = buffer.limit();
		buffer.rewind();
		clone.put(buffer);
		buffer.position(position);
		clone.position(position);
		buffer.limit(limit);
		clone.limit(limit);
		return clone;
	}

	/**
	 * Encode the remaining bytes in as {@link ByteBuffer} as a hex string and
	 * maintain the current position.
	 * 
	 * @param buffer
	 * @return the hex string
	 */
	public static String encodeAsHexString(ByteBuffer buffer) {
		StringBuilder sb = new StringBuilder();
		buffer.mark();
		while (buffer.hasRemaining()) {
			sb.append(String.format("%02x", buffer.get()));
		}
		buffer.reset();
		return sb.toString();
	}

	/**
	 * Relative get method. Reads the byte at the current position in
	 * {@code buffer} as a boolean, and then increments the position.
	 * 
	 * @param buffer
	 * @return the boolean value at the current position
	 * @see {@link ByteBufferOutputStream#write(boolean)}
	 */
	public static boolean getBoolean(ByteBuffer buffer) {
		return buffer.get() > 0 ? true : false;
	}

	/**
	 * Return a ByteBuffer that has a copy of {@code length} bytes from
	 * {@code buffer} starting from the current position. This method will
	 * advance the position of the source buffer.
	 * 
	 * @param buffer
	 * @param bytes
	 * @return a ByteBuffer that has {@code length} bytes from {@code buffer}
	 */
	public static ByteBuffer get(ByteBuffer buffer, int length) {
		Preconditions
				.checkArgument(buffer.remaining() >= length,
						"The number of bytes remaining in the buffer cannot be less than length");
		byte[] backingArray = new byte[length];
		buffer.get(backingArray);
		return ByteBuffer.wrap(backingArray);
	}

	/**
	 * Relative get method. Reads the enum at the current position in
	 * {@code buffer} and then increments the position by four.
	 * 
	 * @param buffer
	 * @param clazz
	 * @return the enum value at the current position
	 * @see {@link ByteBufferOutputStream#write(Enum)}
	 */
	public static > T getEnum(ByteBuffer buffer,
			Class clazz) {
		return clazz.getEnumConstants()[buffer.getInt()];
	}

	/**
	 * Relative get method. Reads the UTF-8 encoded string at
	 * the current position in {@code buffer}.
	 * 
	 * @param buffer
	 * @param charset
	 * @return the string value at the current position
	 * @see {@link ByteBufferOutputStream#write(String)}
	 */
	public static String getString(ByteBuffer buffer) {
		return getString(buffer, StandardCharsets.UTF_8);
	}

	/**
	 * Relative get method. Reads the {@code charset} encoded string at
	 * the current position in {@code buffer}.
	 * 
	 * @param buffer
	 * @param charset
	 * @return the string value at the current position
	 * @see {@link ByteBufferOutputStream#write(String, Charset)}
	 */
	public static String getString(ByteBuffer buffer, Charset charset) {
		try {
			CharsetDecoder decoder = charset.newDecoder();
			decoder.onMalformedInput(CodingErrorAction.IGNORE);
			return decoder.decode(buffer).toString().trim(); // it
																// is
																// necessary
																// to
																// trim
																// here
																// because
																// the
																// decoding
																// picks
																// up
																// trailing
																// whitespace
																// sometimes
		}
		catch (CharacterCodingException e) {
			throw Throwables.propagate(e);
		}
	}

	/**
	 * Return a new ByteBuffer whose content is a shared subsequence of the
	 * content in {@code buffer} starting at the current position to
	 * current position + {@code length} (non-inclusive). Invoking this method
	 * has the same affect as doing the following:
	 * 
	 * 	 * buffer.mark();
	 * int oldLimit = buffer.limit();
	 * buffer.limit(buffer.position() + length);
	 * 
	 * ByteBuffer slice = buffer.slice();
	 * 
	 * buffer.reset();
	 * buffer.limit(oldLimit);
	 * 
	 * 
	 * @param buffer
	 * @param length
	 * @return the new ByteBuffer slice
	 * @see {@link ByteBuffer#slice()}
	 */
	public static ByteBuffer slice(ByteBuffer buffer, int length) {
		return slice(buffer, buffer.position(), length);
	}

	/**
	 * Return a new ByteBuffer whose content is a shared subsequence of the
	 * content in {@code buffer} starting at {@code position} to
	 * {@code position} + {@code length} (non-inclusive). Invoking this method
	 * has the same affect as doing the following:
	 * 
	 * 	 * buffer.mark();
	 * int oldLimit = buffer.limit();
	 * buffer.position(position);
	 * buffer.limit(position + length);
	 * 
	 * ByteBuffer slice = buffer.slice();
	 * 
	 * buffer.reset();
	 * buffer.limit(oldLimit);
	 * 
	 * 
	 * @param buffer
	 * @param position
	 * @param length
	 * @return the new ByteBuffer slice
	 * @see {@link ByteBuffer#slice()}
	 */
	public static ByteBuffer slice(ByteBuffer buffer, int position, int length) {
		int oldPosition = buffer.position();
		int oldLimit = buffer.limit();
		buffer.position(position);
		buffer.limit(position + length);
		ByteBuffer slice = buffer.slice();
		buffer.limit(oldLimit);
		buffer.position(oldPosition);
		return slice;
	}

	/**
	 * Return a byte array with the content of {@code buffer}. This method
	 * returns the byte array that backs {@code buffer} if one exists, otherwise
	 * it creates a new byte array with the content between the current position
	 * of {@code buffer} and its limit.
	 * 
	 * @param buffer
	 * @return the byte array with the content of {@code buffer}
	 */
	public static byte[] toByteArray(ByteBuffer buffer) {
		if(buffer.hasArray()) {
			return buffer.array();
		}
		else {
			buffer.mark();
			byte[] array = new byte[buffer.remaining()];
			buffer.get(array);
			buffer.reset();
			return array;
		}
	}

}