etl

Fix numeric overflow in bip buffer's get_write_reserve

#1088

Merged

#include <format>
#include <iostream>

#include <etl/bip_buffer_spsc_atomic.h>

int main()
{
    etl::bip_buffer_spsc_atomic<uint8_t, 256> buf;

    auto b1 = buf.write_reserve_optimal();
    assert(b1.size() == 256);
    buf.write_commit(b1.first(256));

    auto b2 = buf.read_reserve();
    assert(b2.size() == 256);

    auto b3 = buf.write_reserve_optimal();
    assert(b3.size() == 0);

    buf.read_commit(b2.first(17));

    auto b4 = buf.read_reserve();
    assert(b4.size() == 239);

    auto b5 = buf.write_reserve_optimal();
    assert(b5.size() == 16);
    buf.write_commit(b5.first(16));

    buf.read_commit(b4.first(10));

    auto b6 = buf.read_reserve();
    assert(b6.size() == 229);

    auto b7 = buf.write_reserve_optimal(); // will cause numeric overflow and return huge span
    std::cout << std::format("b7.size() = {}\n", b7.size());
    assert(b7.size() <= 256);

    return 0;
}