SnugLog/Tests/disruptor.cpp

#include <thread>
#include "catch2/catch_all.hpp"
#include "../LibSnugLog/include/disruptor.h"

struct strategy {
	static constexpr overflow_response_t on_overflow = overflow_response_t::must_wait;
	void wait() {}
};

TEST_CASE("Disruptor works sequentially") {
	std::array<char, 8192> buffer{};
	disruptor<strategy> v{buffer.data(), buffer.size()};

	SECTION("117") {
		auto W = v.reserve_write(100);
		v[W.start] = 117;
		v.conclude_write(W);
		auto R = v.reserve_read();
		REQUIRE(v[R.start]== 117);
		v.conclude_read(R);
	}

	SECTION("12") {
		{
			auto W = v.reserve_write(6);
			v[W.start] = 12;
			v.conclude_write(W);
			auto R = v.reserve_read();
			REQUIRE(v[R.start]== 12);
			v.conclude_read(R);
		}

		{
			auto W = v.reserve_write(6);
			v[W.start] = 8;
			v.conclude_write(W);
			auto R = v.reserve_read();
			REQUIRE(v[R.start]== 8);
			v.conclude_read(R);
		}
	}

	SECTION("Disruptor loop around") {
		std::multiset<char> mset;
		for(int i = 0; i != 255; i++) {
			auto W = v.reserve_write(100);
			v[W.start] = (char)i;
			for(size_t idx = W.start; idx != W.end; idx = (idx+1)%v.size()) {
				v[idx] = (char)i;
			}
			v.conclude_write(W);
			auto R = v.reserve_read();
			for(size_t idx = R.start; idx != R.end; idx = (idx+1)%v.size()) {
				mset.insert(v[idx]);
			}
			v.conclude_read(R);
		}
		for(int i = 0; i != 255; i++) {
			REQUIRE(mset.count((char)i) == 100);
		}
	}

	SECTION("Disruptor concurrent odd vs even") {
		std::atomic<bool> trigger = false;
		std::multiset<char> mset;
		std::stringstream continuity;
		
		int acc = 0;
		for(int i = 0; i<= 255; i++) {
			acc+=i;
		}
		
		std::thread reader([&](){
			int cnt = 0;
			while (cnt != acc) {
				auto R = v.reserve_read();
				for (size_t idx = R.start; idx != R.end; idx = (idx + 1) % v.size()) {
					mset.insert(v[idx]);
					continuity << (char)v[idx];
				}
				v.conclude_read(R);
				cnt += (R.end > R.start) * (R.end - R.start)
					+  (R.end < R.start) * (v.size() - R.start + R.end);
			}
		});

		std::thread even([&]() {
			while(!trigger.load());
			for (int i = 2; i <= 255; i += 2) {
				auto W = v.reserve_write(i);
				v[W.start] = (char) i;
				for (size_t idx = W.start; idx != W.end; idx = (idx + 1) % v.size()) {
					v[idx] = (char) i;
				}
				v.conclude_write(W);
			}
		});
		
		std::thread odd([&]() {
			while(!trigger.load());
			for (int i = 1; i <= 255; i += 2) {
				auto W = v.reserve_write(i);
				v[W.start] = (char) i;
				for (size_t idx = W.start; idx != W.end; idx = (idx + 1) % v.size()) {
					v[idx] = (char) i;
				}
				v.conclude_write(W);
			}
		});
		
		// byte received count test
		trigger.store(true);
		reader.join(); even.join(); odd.join();
		for(int i = 1; i <= 255; i++) {
			REQUIRE(mset.count((char)i) == i);
		}
		
		
		// Continuity tests
		int changes = 0;
		auto str = continuity.str();
		char current = *str.begin();
		auto it = str.begin();
		for(;it != str.end();) {
			while(it != str.end() && *it == current) {++it;}
			changes += 1;
			current = *it;
		}
		REQUIRE(changes == 255);
	}
}

TEST_CASE("Fails if buffer too small") {
	REQUIRE_THROWS_AS(disruptor<OverflowWait>(nullptr, page_size), disruptor_exception);
}

TEST_CASE("Fails if buffer size is 0") {
	REQUIRE_THROWS_AS(disruptor<OverflowWait>(nullptr, 0), disruptor_exception);
}