#include <benchmark/benchmark.h>
#include <cstddef>
#include <cstring>
#include <numeric>
#include <random>

const size_t N = 1 << 20;

char string[N] = {};

struct init
{
    init()
    {
        std::random_device device;
        std::mt19937_64 generator(device());
        std::uniform_int_distribution<char> distribution('a', 'z');
        auto rng = [&]() { return distribution(generator); };
        std::ranges::generate(string, rng);
        string[N - 1] = 0;
    }
} _;

size_t f1(char *str)
{
    size_t len = 0;
    while (*str++)
        ++len;
    return len;
}

size_t f2(const char *str)
{
    const char *tmp = str;
    while (*str)
        ++str;
    return str - tmp;
}

size_t f3(const char *str)
{
    const char *tmp = str;
    while (*tmp++)
        ;
    return tmp - str - 1;
}

size_t f4(const char *str)
{
    if (*str == 0)
        return 0;
    else
        return f4(++str) + 1;
}

size_t f5(const char *s)
{
    size_t len = 0;
    for (;;)
    {
        unsigned x = *(unsigned *)s;
        if ((x & 0x000000FF) == 0)
            return len + 0;
        if ((x & 0x0000FF00) == 0)
            return len + 1;
        if ((x & 0x00FF0000) == 0)
            return len + 2;
        if ((x & 0xFF000000) == 0)
            return len + 3;
        len += 4, s += 4;
    }
}

size_t f6(const char *s)
{
    unsigned x = *(unsigned *)s;
    if ((x & 0x000000FF) == 0)
        return 0;
    if ((x & 0x0000FF00) == 0)
        return 1;
    if ((x & 0x00FF0000) == 0)
        return 2;
    if ((x & 0xFF000000) == 0)
        return 3;
    return f6(s + 4) + 4;
}

size_t f7(const char *s)
{
    if (*s == 0) [[unlikely]]
        return 0;
    else
        return f7(s + 1) + 1;
}

size_t f8(const char *s)
{
    if (*s == 0) [[likely]]
        return 0;
    else
        return f8(s + 1) + 1;
}

size_t fc(char *str) { return strlen(str); }

template<auto f> static void test(benchmark::State &state)
{
    unsigned r = 0;
    for (auto _: state)
        benchmark::DoNotOptimize(r = f(string));
    state.SetLabel(std::to_string(r));
}

BENCHMARK(test<f1>);
BENCHMARK(test<f2>);
BENCHMARK(test<f3>);
BENCHMARK(test<f4>);
BENCHMARK(test<f5>);
BENCHMARK(test<f6>);
BENCHMARK(test<f7>);
BENCHMARK(test<f8>);
BENCHMARK(test<fc>);

BENCHMARK_MAIN();