std::basic_string<CharT,Traits,Allocator>::resize_and_overwrite

#include <algorithm>
#include <cassert>
#include <cstddef>
#include <cstring>
#include <iomanip>
#include <iostream>
#include <string>
#include <string_view>
static_assert(__cpp_lib_string_resize_and_overwrite);

constexpr std::string_view fruits[]{"apple", "banana", "coconut", "date", "elderberry"};

int main()
{
    //  :   fruits[0].    .
    std::string s{"Food: "};
    s.resize_and_overwrite(16, [sz = s.size()](char* buf, std::size_t buf_size)
    {
        const auto to_copy = std::min(buf_size - sz, fruits[0].size());
        std::memcpy(buf + sz, fruits[0].data(), to_copy);
        return sz + to_copy;
    });
    std::cout << "1. " << std::quoted(s) << '\n';

    //    .  ,  -
    //   .

    s.resize_and_overwrite(10, [](char* buf, int n)
    {
        return std::find(buf, buf + n, ':') - buf;
    });
    std::cout << "2. " << std::quoted(s) << '\n';

    std::cout << "3.     ,    . "
                 "   .\n";
    std::string food{"Food:"};
    const auto resize_to{27};
    std::cout << ", food.size: " << food.size()
              << ", food.capacity: " << food.capacity()
              << ", resize_to: " << resize_to
              << ", food: " << std::quoted(food) << '\n';

    food.resize_and_overwrite(
        resize_to,
        [food_size = food.size()](char* p, std::size_t n) noexcept -> std::size_t
        {
            // p[0]..p[n]  
            // p[0]..p[min(n, food_size) - 1]   
            // (    )

            //  :
            std::cout << " Operation(); n: " << n << '\n';

            //  fruits   p,   .
            char* first = p + food_size;

            for (char* const end = p + n; const std::string_view fruit : fruits)
            {
                char* last = first + fruit.size() + 1;
                if (last > end)
                    break;
                *first++ = ' ';
                std::ranges::copy(fruit, first);
                first = last;
            }

            const auto final_size{static_cast<std::size_t>(first - p)};

            //  :
            std::cout << " Operation(); final_size: " << final_size << '\n';

            assert(final_size <= n);
            return final_size; //      
                               // .      0..n.
        });

    std::cout << ", food.size: " << food.size()
              << ", food.capacity: " << food.capacity()
              << ", food: " << std::quoted(food) << '\n';
}