NioBufferHexDumper.java

package com.jds.jn_module.utils.buffer;


/**
 * Provides utility methods to dump an {@link jds.mina.core.buffer.IoBuffer} into a hex formatted string.
 *
 * @author The Apache MINA Project (dev@mina.apache.org)
 */
class NioBufferHexDumper
{

	/**
	 * The high digits lookup table.
	 */
	private static final byte[] highDigits;

	/**
	 * The low digits lookup table.
	 */
	private static final byte[] lowDigits;

	/**
	 * Initialize lookup tables.
	 */
	static
	{
		final byte[] digits = {
				'0',
				'1',
				'2',
				'3',
				'4',
				'5',
				'6',
				'7',
				'8',
				'9',
				'A',
				'B',
				'C',
				'D',
				'E',
				'F'
		};

		int i;
		byte[] high = new byte[256];
		byte[] low = new byte[256];

		for (i = 0; i < 256; i++)
		{
			high[i] = digits[i >>> 4];
			low[i] = digits[i & 0x0F];
		}

		highDigits = high;
		lowDigits = low;
	}

	/**
	 * Dumps an {@link jds.mina.core.buffer.IoBuffer} to a hex formatted string.
	 *
	 * @param in		  the buffer to dump
	 * @param lengthLimit the limit at which hex dumping will stop
	 * @return a hex formatted string representation of the <i>in</i> {@link Iobuffer}.
	 */
	public static String getHexdump(NioBuffer in, int lengthLimit)
	{
		if (lengthLimit == 0)
		{
			throw new IllegalArgumentException("lengthLimit: " + lengthLimit + " (expected: 1+)");
		}

		boolean truncate = in.remaining() > lengthLimit;
		int size;
		if (truncate)
		{
			size = lengthLimit;
		}
		else
		{
			size = in.remaining();
		}

		if (size == 0)
		{
			return "empty";
		}

		StringBuilder out = new StringBuilder(size * 3 + 3);

		int mark = in.position();

		// fill the first
		int byteValue = in.get() & 0xFF;
		out.append((char) highDigits[byteValue]);
		out.append((char) lowDigits[byteValue]);
		size--;

		// and the others, too
		for (; size > 0; size--)
		{
			out.append(' ');
			byteValue = in.get() & 0xFF;
			out.append((char) highDigits[byteValue]);
			out.append((char) lowDigits[byteValue]);
		}

		in.position(mark);

		if (truncate)
		{
			out.append("...");
		}

		return out.toString();
	}
}