/*
 * coreMQTT <DEVELOPMENT BRANCH>
 * Copyright (C) 2022 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
 *
 * SPDX-License-Identifier: MIT
 *
 * 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.
 */

/**
 * @file core_mqtt_utils.c
 * @brief Implements the utility functions in core_mqtt_utils.h.
 */
#include <string.h>
#include <assert.h>
#include <stdint.h>

/* Include config defaults header to get default values of configs. */
#include "core_mqtt_config_defaults.h"
#include "core_mqtt_utils.h"

uint8_t * encodeVariableLength( uint8_t * pDestination,
                                size_t length )
{
    uint8_t lengthByte;
    uint8_t * pLengthEnd = NULL;
    size_t remainingLength = length;

    assert( pDestination != NULL );

    pLengthEnd = pDestination;

    /* This algorithm is copied from the MQTT 5.0 spec. */
    do
    {
        lengthByte = ( uint8_t ) ( remainingLength % 128U );
        remainingLength = remainingLength / 128U;

        /* Set the high bit of this byte, indicating that there's more data. */
        if( remainingLength > 0U )
        {
            UINT8_SET_BIT( lengthByte, 7 );
        }

        /* Output a single encoded byte. */
        *pLengthEnd = lengthByte;
        pLengthEnd++;
    } while( remainingLength > 0U );

    return pLengthEnd;
}