/**
 * Copyright 2007-2016, Kaazing Corporation. All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.mina.core.buffer;

/**
 * Provides utility methods to dump an {@link IoBuffer} into a hex formatted string.
 *
 * @author <a href="http://mina.apache.org">Apache MINA Project</a>
 */
class IoBufferHexDumper {

    /**
     * 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 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(IoBuffer 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();
    }
}