src/core/common/tlvs.hpp

/*
 *  Copyright (c) 2016, The OpenThread Authors.
 *  All rights reserved.
 *
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 *  modification, are permitted provided that the following conditions are met:
 *  1. Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *  2. 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.
 *  3. Neither the name of the copyright holder 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
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 *  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 *  POSSIBILITY OF SUCH DAMAGE.
 */

/**
 * @file
 *   This file includes definitions for generating and processing MLE TLVs.
 */

#ifndef TLVS_HPP_
#define TLVS_HPP_

#include "utils/wrap_string.h"

#include <openthread/types.h>

#include "common/encoding.hpp"
#include "common/message.hpp"

using ot::Encoding::BigEndian::HostSwap16;
using ot::Encoding::BigEndian::HostSwap32;

namespace ot {

/**
 * This class implements TLV generation and parsing.
 *
 */
OT_TOOL_PACKED_BEGIN
class Tlv
{
public:
    /**
     * Default constructor.
     *
     */
    Tlv(void):
        mType(0),
        mLength(0) {}

    /**
     * This method returns the Type value.
     *
     * @returns The Type value.
     *
     */
    uint8_t GetType(void) const { return mType; }

    /**
     * This method sets the Type value.
     *
     * @param[in]  aType  The Type value.
     *
     */
    void SetType(uint8_t aType) { mType = aType; }

    /**
     * This method returns the Length value.
     *
     * @returns The Length value.
     *
     */
    uint8_t GetLength(void) const { return mLength; }

    /**
     * This method sets the Length value.
     *
     * @param[in]  aLength  The Length value.
     *
     */
    void SetLength(uint8_t aLength) { mLength = aLength; }

    /**
     * This method returns the total size including Type, Length, and Value fields.
     *
     * @returns The total size include Type, Length, and Value fields.
     *
     */
    uint8_t GetSize(void) const { return sizeof(Tlv) + mLength; }

    /**
     * This method returns a pointer to the Value.
     *
     * @returns A pointer to the value.
     *
     */
    uint8_t *GetValue(void) { return reinterpret_cast<uint8_t *>(this) + sizeof(Tlv); }

    /**
     * This method returns a pointer to the Value.
     *
     * @returns A pointer to the value.
     *
     */
    const uint8_t *GetValue(void) const { return reinterpret_cast<const uint8_t *>(this) + sizeof(Tlv); }

    /**
     * This method returns a pointer to the next TLV.
     *
     * @returns A pointer to the next TLV.
     *
     */
    Tlv *GetNext(void) {
        return reinterpret_cast<Tlv *>(reinterpret_cast<uint8_t *>(this) + sizeof(*this) + mLength);
    }

    /**
     * This method returns a pointer to the next TLV.
     *
     * @returns A pointer to the next TLV.
     *
     */
    const Tlv *GetNext(void) const {
        return reinterpret_cast<const Tlv *>(reinterpret_cast<const uint8_t *>(this) + sizeof(*this) + mLength);
    }

    /**
     * This static method reads the requested TLV out of @p aMessage.
     *
     * @param[in]   aMessage    A reference to the message.
     * @param[in]   aType       The Type value to search for.
     * @param[in]   aMaxLength  Maximum number of bytes to read.
     * @param[out]  aTlv        A reference to the TLV that will be copied to.
     *
     * @retval OT_ERROR_NONE       Successfully copied the TLV.
     * @retval OT_ERROR_NOT_FOUND  Could not find the TLV with Type @p aType.
     *
     */
    static otError Get(const Message &aMessage, uint8_t aType, uint16_t aMaxLength, Tlv &aTlv);

    /**
     * This static method obtains the offset of a TLV within @p aMessage.
     *
     * @param[in]   aMessage    A reference to the message.
     * @param[in]   aType       The Type value to search for.
     * @param[out]  aOffset     A reference to the offset of the TLV.
     *
     * @retval OT_ERROR_NONE       Successfully copied the TLV.
     * @retval OT_ERROR_NOT_FOUND  Could not find the TLV with Type @p aType.
     *
     */
    static otError GetOffset(const Message &aMessage, uint8_t aType, uint16_t &aOffset);

    /**
     * This static method finds the offset and length of a given TLV type.
     *
     * @param[in]   aMessage    A reference to the message.
     * @param[in]   aType       The Type value to search for.
     * @param[out]  aOffset     The offset where the value starts.
     * @param[out]  aLength     The length of the value.
     *
     * @retval OT_ERROR_NONE       Successfully found the TLV.
     * @retval OT_ERROR_NOT_FOUND  Could not find the TLV with Type @p aType.
     *
     */
    static otError GetValueOffset(const Message &aMesasge, uint8_t aType, uint16_t &aOffset, uint16_t &aLength);

protected:
    /**
     * Length values.
     *
     */
    enum
    {
        kExtendedLength = 255, ///< Extended Length value
    };

private:
    uint8_t mType;
    uint8_t mLength;
} OT_TOOL_PACKED_END;

OT_TOOL_PACKED_BEGIN
class ExtendedTlv: public Tlv
{
public:
    /**
     * This method returns the Length value.
     *
     */
    uint16_t GetLength(void) const { return HostSwap16(mLength); }

    /**
     * This method sets the Length value.
     *
     * @param[in]  aLength  The Length value.
     *
     */
    void SetLength(uint16_t aLength) { Tlv::SetLength(kExtendedLength); mLength = HostSwap16(aLength); }

private:
    uint16_t mLength;
} OT_TOOL_PACKED_END;

}  // namespace ot

#endif  // TLVS_HPP_