src/core/common/frame_data.hpp

/*
 *  Copyright (c) 2022, The OpenThread Authors.
 *  All rights reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  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
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 *  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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 */

/**
 * @file
 *   This file includes definitions for `FrameData`.
 */

#ifndef FRAME_DATA_HPP_
#define FRAME_DATA_HPP_

#include "openthread-core-config.h"

#include "common/data.hpp"
#include "common/type_traits.hpp"

namespace ot {

/**
 * Represents a frame `Data` which is simply a wrapper over a pointer to a buffer with a given frame length.
 *
 * It provide helper method to parse the content. As data is parsed and read, the `FrameData` is updated to skip over
 * the read content.
 *
 */
class FrameData : public Data<kWithUint16Length>
{
public:
    /**
     * Indicates whether or not there are enough bytes remaining in the `FrameData` to read a given number
     * of bytes.
     *
     * @param[in] aLength   The read length to check.
     *
     * @retval TRUE   There are enough remaining bytes to read @p aLength bytes.
     * @retval FALSE  There are not enough remaining bytes to read @p aLength bytes.
     *
     */
    bool CanRead(uint16_t aLength) const { return GetLength() >= aLength; }

    /**
     * Reads an `uint8_t` value from the `FrameData`.
     *
     * If read successfully, the `FrameData` is updated to skip over the read content.
     *
     * @param[out] aUint8   A reference to an `uint8_t` to return the read value.
     *
     * @retval kErrorNone   Successfully read `uint8_t` value and skipped over it.
     * @retval kErrorParse  Not enough bytes remaining to read.
     *
     */
    Error ReadUint8(uint8_t &aUint8);

    /**
     * Reads an `uint16_t` value assuming big endian encoding from the `FrameData`.
     *
     * If read successfully, the `FrameData` is updated to skip over the read content.
     *
     * @param[out] aUint16   A reference to an `uint16_t` to return the read value.
     *
     * @retval kErrorNone   Successfully read `uint16_t` value and skipped over it.
     * @retval kErrorParse  Not enough bytes remaining to read.
     *
     */
    Error ReadBigEndianUint16(uint16_t &aUint16);

    /**
     * Reads an `uint32_t` value assuming big endian encoding from the `FrameData`.
     *
     * If read successfully, the `FrameData` is updated to skip over the read content.
     *
     * @param[out] aUint32   A reference to an `uint32_t` to return the read value.
     *
     * @retval kErrorNone   Successfully read `uint32_t` value and skipped over it.
     * @retval kErrorParse  Not enough bytes remaining to read.
     *
     */
    Error ReadBigEndianUint32(uint32_t &aUint32);

    /**
     * Reads an `uint16_t` value assuming little endian encoding from the `FrameData`.
     *
     * If read successfully, the `FrameData` is updated to skip over the read content.
     *
     * @param[out] aUint16   A reference to an `uint16_t` to return the read value.
     *
     * @retval kErrorNone   Successfully read `uint16_t` value and skipped over it.
     * @retval kErrorParse  Not enough bytes remaining to read.
     *
     */
    Error ReadLittleEndianUint16(uint16_t &aUint16);

    /**
     * Reads an `uint32_t` value assuming little endian encoding from the `FrameData`.
     *
     * If read successfully, the `FrameData` is updated to skip over the read content.
     *
     * @param[out] aUint32   A reference to an `uint32_t` to return the read value.
     *
     * @retval kErrorNone   Successfully read `uint32_t` value and skipped over it.
     * @retval kErrorParse  Not enough bytes remaining to read.
     *
     */
    Error ReadLittleEndianUint32(uint32_t &aUint32);

    /**
     * Reads a given number of bytes from the `FrameData`.
     *
     * If read successfully, the `FrameData` is updated to skip over the read content.
     *
     * @param[out] aBuffer   The buffer to copy the read bytes into.
     * @param[in]  aLength   Number of bytes to read.
     *
     * @retval kErrorNone   Successfully read @p aLength bytes into @p aBuffer and skipped over them.
     * @retval kErrorParse  Not enough bytes remaining to read @p aLength.
     *
     */
    Error ReadBytes(void *aBuffer, uint16_t aLength);

    /**
     * Reads an object from the `FrameData`.
     *
     * @tparam     ObjectType   The object type to read from the message.
     *
     * @param[out] aObject      A reference to the object to read into.
     *
     * @retval kErrorNone     Successfully read @p aObject and skipped over the read content.
     * @retval kErrorParse    Not enough bytes remaining to read the entire object.
     *
     */
    template <typename ObjectType> Error Read(ObjectType &aObject)
    {
        static_assert(!TypeTraits::IsPointer<ObjectType>::kValue, "ObjectType must not be a pointer");

        return ReadBytes(&aObject, sizeof(ObjectType));
    }

    /**
     * Skips over a given number of bytes from `FrameData`.
     *
     * The caller MUST make sure that the @p aLength is smaller than current data length. Otherwise the behavior of
     * this method is undefined.
     *
     * @param[in] aLength   The length (number of bytes) to skip over.
     *
     */
    void SkipOver(uint16_t aLength);
};

} // namespace ot

#endif // FRAME_DATA_HPP_