openthread/tests/unit/test_bit_utils.cpp

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#include <openthread/config.h>

#include "test_platform.h"
#include "test_util.hpp"

#include "common/bit_utils.hpp"

namespace ot {

void TestCountBitsInMask(void)
{
    VerifyOrQuit(CountBitsInMask(0) == 0);
    VerifyOrQuit(CountBitsInMask(1) == 1);
    VerifyOrQuit(CountBitsInMask(2) == 1);
    VerifyOrQuit(CountBitsInMask(3) == 2);
    VerifyOrQuit(CountBitsInMask(4) == 1);
    VerifyOrQuit(CountBitsInMask(7) == 3);
    VerifyOrQuit(CountBitsInMask(11) == 3);
    VerifyOrQuit(CountBitsInMask(15) == 4);
    VerifyOrQuit(CountBitsInMask(0x11) == 2);
    VerifyOrQuit(CountBitsInMask(0xef) == 7);
    VerifyOrQuit(CountBitsInMask(0xff) == 8);

    VerifyOrQuit(CountBitsInMask(0xff00) == 8);
    VerifyOrQuit(CountBitsInMask(0xaa55) == 8);
    VerifyOrQuit(CountBitsInMask(0xffff) == 16);

    VerifyOrQuit(CountBitsInMask(0x10000) == 1);
    VerifyOrQuit(CountBitsInMask(0xff0055) == 12);
    VerifyOrQuit(CountBitsInMask(0xaa0055) == 8);
    VerifyOrQuit(CountBitsInMask(0xaa007700) == 10);
    VerifyOrQuit(CountBitsInMask(0xffff0000) == 16);
    VerifyOrQuit(CountBitsInMask(0xffffffff) == 32);

    printf("TestCountBitsInMask() passed\n");
}

void TestCountMatchingBitsAllCombinations(void)
{
    // This test iterates through all possible byte combinations and
    // bit-lengths (0-8). It calculates the expected matched length
    // by exhaustively checking bits one-by-one and then verifies
    // that `CountMatchingBits()` returns the correct length.

    uint8_t firstByte = 0;

    do
    {
        uint8_t secondByte = 0;

        do
        {
            for (uint8_t blen = 0; blen <= 8; blen++)
            {
                uint16_t matchedLen = 0;

                for (uint8_t i = 0; i < blen; i++)
                {
                    uint8_t bit = (0x80 >> i);

                    if ((firstByte & bit) != (secondByte & bit))
                    {
                        break;
                    }

                    matchedLen++;
                }

                VerifyOrQuit(CountMatchingBits(&firstByte, &secondByte, blen) == matchedLen);
            }

            secondByte++;
        } while (secondByte != 0);

        firstByte++;

    } while (firstByte != 0);

    printf("TestCountMatchingBitsAllCombinations() passed\n");
}

void TestCountMatchingBitsExamples(void)
{
    struct TestCase
    {
        uint8_t mFirst[3];
        uint8_t mSecond[3];
        uint8_t mBitLength;
        uint8_t mExpectedMatchedLength;
    };

    static const TestCase kTestCases[] = {
        {{0x00, 0x00, 0x00}, {0x00, 0x11, 0x22}, 0, 0},   {{0x6d, 0x13, 0xb0}, {0x6d, 0x13, 0xb0}, 20, 20},
        {{0x6d, 0x13, 0xb0}, {0x6d, 0x13, 0xbf}, 20, 20}, {{0x6d, 0x13, 0xb0}, {0x6d, 0x13, 0xa0}, 20, 19},
        {{0x6d, 0xa3, 0xb0}, {0x6d, 0xa3, 0xa0}, 20, 19}, {{0x77, 0xa3, 0x25}, {0x77, 0xa3, 0xa5}, 20, 16},
        {{0x77, 0xa3, 0x25}, {0x77, 0xa3, 0x65}, 20, 17}, {{0x77, 0xa3, 0x25}, {0x77, 0xa3, 0x05}, 20, 18},
        {{0x77, 0xa3, 0x25}, {0x77, 0xa3, 0x05}, 18, 18}, {{0x77, 0xa3, 0x25}, {0x77, 0xa3, 0x05}, 17, 17},
    };

    for (const TestCase &testCase : kTestCases)
    {
        uint16_t matchedLen = CountMatchingBits(testCase.mFirst, testCase.mSecond, testCase.mBitLength);

        VerifyOrQuit(matchedLen == testCase.mExpectedMatchedLength);
    }

    printf("TestCountMatchingBitsExamples() passed\n");
}

void TestDetermineMinBitSize(void)
{
    VerifyOrQuit(DetermineMinBitSizeFor(0) == 1);
    VerifyOrQuit(DetermineMinBitSizeFor(1) == 1);

    VerifyOrQuit(DetermineMinBitSizeFor(2) == 2);
    VerifyOrQuit(DetermineMinBitSizeFor(3) == 2);

    VerifyOrQuit(DetermineMinBitSizeFor(4) == 3);
    VerifyOrQuit(DetermineMinBitSizeFor(6) == 3);
    VerifyOrQuit(DetermineMinBitSizeFor(7) == 3);

    VerifyOrQuit(DetermineMinBitSizeFor(8) == 4);
    VerifyOrQuit(DetermineMinBitSizeFor(11) == 4);
    VerifyOrQuit(DetermineMinBitSizeFor(15) == 4);

    VerifyOrQuit(DetermineMinBitSizeFor(16) == 5);
    VerifyOrQuit(DetermineMinBitSizeFor(30) == 5);
    VerifyOrQuit(DetermineMinBitSizeFor(32) == 6);

    VerifyOrQuit(DetermineMinBitSizeFor(127) == 7);
    VerifyOrQuit(DetermineMinBitSizeFor(128) == 8);
    VerifyOrQuit(DetermineMinBitSizeFor(255) == 8);
    VerifyOrQuit(DetermineMinBitSizeFor(256) == 9);
    VerifyOrQuit(DetermineMinBitSizeFor(500) == 9);

    VerifyOrQuit(DetermineMinBitSizeFor(1000) == 10);
    VerifyOrQuit(DetermineMinBitSizeFor(1023) == 10);
    VerifyOrQuit(DetermineMinBitSizeFor(1024) == 11);
    VerifyOrQuit(DetermineMinBitSizeFor(2000) == 11);

    VerifyOrQuit(DetermineMinBitSizeFor(0xffff) == 16);
    VerifyOrQuit(DetermineMinBitSizeFor(0x10000) == 17);

    VerifyOrQuit(DetermineMinBitSizeFor(0x7fffffff) == 31);
    VerifyOrQuit(DetermineMinBitSizeFor(0x80000000) == 32);
    VerifyOrQuit(DetermineMinBitSizeFor(0xffffffff) == 32);

    printf("TestDetermineMinBitSize() passed\n");
}

} // namespace ot

int main(void)
{
    ot::TestCountBitsInMask();
    ot::TestCountMatchingBitsAllCombinations();
    ot::TestCountMatchingBitsExamples();
    ot::TestDetermineMinBitSize();

    printf("All tests passed\n");
    return 0;
}