src/core/common/bit_utils.cpp

/*
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/**
 * @file
 *   This file includes implementation of bit manipulation utility functions.
 */

#include "bit_utils.hpp"

#include "common/code_utils.hpp"
#include "common/num_utils.hpp"

namespace ot {

uint16_t CountMatchingBits(const uint8_t *aFirst, const uint8_t *aSecond, uint16_t aMaxBitLength)
{
    uint16_t remainingLen = aMaxBitLength;
    uint16_t matchedLen   = 0;
    uint8_t  diffMask     = 0;

    while (remainingLen > 0)
    {
        uint16_t len = Min<uint16_t>(remainingLen, kBitsPerByte);

        diffMask = (aFirst[0] ^ aSecond[0]);

        if (diffMask != 0)
        {
            break;
        }

        matchedLen += len;
        remainingLen -= len;
        aFirst++;
        aSecond++;
    }

    VerifyOrExit(diffMask != 0);

    while (remainingLen > 0)
    {
        if ((diffMask & 0x80) != 0)
        {
            break;
        }

        diffMask <<= 1;
        matchedLen++;
        remainingLen--;
    }

exit:
    return matchedLen;
}

} // namespace ot