libcryfs/test/cpp-utils/thread/LeftRightTest.cpp

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#include <cpp-utils/thread/LeftRight.h>
#include <gtest/gtest.h>
#include <vector>
using cpputils::LeftRight;
using std::vector;
TEST(LeftRightTest, givenInt_whenWritingAndReading_thenChangesArePresent) {
LeftRight<int> obj;
obj.write([] (auto& obj) {obj = 5;});
int read = obj.read([] (auto& obj) {return obj;});
EXPECT_EQ(5, read);
// check changes are also present in background copy
obj.write([] (auto&) {}); // this switches to the background copy
read = obj.read([] (auto& obj) {return obj;});
EXPECT_EQ(5, read);
}
TEST(LeftRightTest, givenVector_whenWritingAndReading_thenChangesArePresent) {
LeftRight<vector<int>> obj;
obj.write([] (auto& obj) {obj.push_back(5);});
vector<int> read = obj.read([] (auto& obj) {return obj;});
EXPECT_EQ((vector<int>{5}), read);
obj.write([] (auto& obj) {obj.push_back(6);});
read = obj.read([] (auto& obj) {return obj;});
EXPECT_EQ((vector<int>{5, 6}), read);
}
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TEST(LeftRightTest, givenVector_whenWritingReturnsValue_thenValueIsReturned) {
LeftRight<vector<int>> obj;
auto a = obj.write([] (auto&) -> int {return 5;});
static_assert(std::is_same<int, decltype(a)>::value, "");
EXPECT_EQ(5, a);
}
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TEST(LeftRightTest, readsCanBeConcurrent) {
LeftRight<int> obj;
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std::atomic<int> num_running_readers{0};
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std::thread reader1([&] () {
obj.read([&] (auto&) {
++num_running_readers;
while(num_running_readers.load() < 2) {}
});
});
std::thread reader2([&] () {
obj.read([&] (auto&) {
++num_running_readers;
while(num_running_readers.load() < 2) {}
});
});
// the threads only finish after both entered the read function.
// if LeftRight didn't allow concurrency, this would cause a deadlock.
reader1.join();
reader2.join();
}
TEST(LeftRightTest, writesCanBeConcurrentWithReads_readThenWrite) {
LeftRight<int> obj;
std::atomic<bool> reader_running{false};
std::atomic<bool> writer_running{false};
std::thread reader([&] () {
obj.read([&] (auto&) {
reader_running = true;
while(!writer_running.load()) {}
});
});
std::thread writer([&] () {
// run read first, write second
while (!reader_running.load()) {}
obj.write([&] (auto&) {
writer_running = true;
});
});
// the threads only finish after both entered the read function.
// if LeftRight didn't allow concurrency, this would cause a deadlock.
reader.join();
writer.join();
}
TEST(LeftRightTest, writesCanBeConcurrentWithReads_writeThenRead) {
LeftRight<int> obj;
std::atomic<bool> writer_running{false};
std::atomic<bool> reader_running{false};
std::thread writer([&] () {
obj.read([&] (auto&) {
writer_running = true;
while(!reader_running.load()) {}
});
});
std::thread reader([&] () {
// run write first, read second
while (!writer_running.load()) {}
obj.read([&] (auto&) {
reader_running = true;
});
});
// the threads only finish after both entered the read function.
// if LeftRight didn't allow concurrency, this would cause a deadlock.
writer.join();
reader.join();
}
TEST(LeftRightTest, writesCannotBeConcurrentWithWrites) {
LeftRight<int> obj;
std::atomic<bool> first_writer_started{false};
std::atomic<bool> first_writer_finished{false};
std::thread writer1([&] () {
obj.write([&] (auto&) {
first_writer_started = true;
std::this_thread::sleep_for(std::chrono::milliseconds(50));
first_writer_finished = true;
});
});
std::thread writer2([&] () {
// make sure the other writer runs first
while (!first_writer_started.load()) {}
obj.write([&] (auto&) {
// expect the other writer finished before this one starts
EXPECT_TRUE(first_writer_finished.load());
});
});
writer1.join();
writer2.join();
}
namespace {
class MyException : std::exception {};
}
TEST(LeftRightTest, whenReadThrowsException_thenThrowsThrough) {
LeftRight<int> obj;
EXPECT_THROW(
obj.read([](auto&) {throw MyException();}),
MyException
);
}
TEST(LeftRightTest, whenWriteThrowsException_thenThrowsThrough) {
LeftRight<int> obj;
EXPECT_THROW(
obj.write([](auto&) {throw MyException();}),
MyException
);
}
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TEST(LeftRightTest, givenInt_whenWriteThrowsExceptionOnFirstCall_thenResetsToOldState) {
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LeftRight<int> obj;
obj.write([](auto& obj) {obj = 5;});
EXPECT_THROW(
obj.write([](auto& obj) {
obj = 6;
throw MyException();
}),
MyException
);
// check reading it returns old value
int read = obj.read([] (auto& obj) {return obj;});
EXPECT_EQ(5, read);
// check changes are also present in background copy
obj.write([] (auto&) {}); // this switches to the background copy
read = obj.read([] (auto& obj) {return obj;});
EXPECT_EQ(5, read);
}
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// note: each write is executed twice, on the foreground and background copy.
// We need to test a thrown exception in either call is handled correctly.
TEST(LeftRightTest, givenInt_whenWriteThrowsExceptionOnSecondCall_thenKeepsNewState) {
LeftRight<int> obj;
obj.write([](auto& obj) {obj = 5;});
bool write_called = false;
EXPECT_THROW(
obj.write([&](auto& obj) {
obj = 6;
if (write_called) {
// this is the second time the write callback is executed
throw MyException();
} else {
write_called = true;
}
}),
MyException
);
// check reading it returns new value
int read = obj.read([] (auto& obj) {return obj;});
EXPECT_EQ(6, read);
// check changes are also present in background copy
obj.write([] (auto&) {}); // this switches to the background copy
read = obj.read([] (auto& obj) {return obj;});
EXPECT_EQ(6, read);
}
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TEST(LeftRightTest, givenVector_whenWriteThrowsException_thenResetsToOldState) {
LeftRight<vector<int>> obj;
obj.write([](auto& obj) {obj.push_back(5);});
EXPECT_THROW(
obj.write([](auto& obj) {
obj.push_back(6);
throw MyException();
}),
MyException
);
// check reading it returns old value
vector<int> read = obj.read([] (auto& obj) {return obj;});
EXPECT_EQ((vector<int>{5}), read);
// check changes are also present in background copy
obj.write([] (auto&) {}); // this switches to the background copy
read = obj.read([] (auto& obj) {return obj;});
EXPECT_EQ((vector<int>{5}), read);
}