Introduce SerialQueue to track in flight resources

src/tests/unittests/SerialQueueTests.cpp

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+// Copyright 2017 The NXT Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <gtest/gtest.h>
+
+#include "backend/common/SerialQueue.h"
+
+using SerialQueue = backend::SerialQueue<int>;
+
+// A number of basic tests for SerialQueue that are difficult to split from one another
+TEST(SerialQueue, BasicTest) {
+    SerialQueue queue;
+
+    // Queue starts empty
+    ASSERT_TRUE(queue.Empty());
+
+    // Iterating on empty queue 1) works 2) doesn't produce any values
+    for (int value : queue.IterateAll()) {
+        ASSERT_TRUE(false);
+    }
+
+    // Enqueuing values as const ref or rvalue ref
+    queue.Enqueue(1, 0);
+    queue.Enqueue(2, 0);
+    queue.Enqueue(std::move(3), 1);
+
+    // Iterating over a non-empty queue produces the expected result
+    std::vector<int> expectedValues = {1, 2, 3};
+    for (int value : queue.IterateAll()) {
+        EXPECT_EQ(expectedValues.front(), value);
+        ASSERT_FALSE(expectedValues.empty());
+        expectedValues.erase(expectedValues.begin());
+    }
+    ASSERT_TRUE(expectedValues.empty());
+
+    // Clear works and makes the queue empty and iteration does nothing.
+    queue.Clear();
+    ASSERT_TRUE(queue.Empty());
+
+    for (int value : queue.IterateAll()) {
+        ASSERT_TRUE(false);
+    }
+}
+
+// Test enqueuing vectors works
+TEST(SerialQueue, EnqueueVectors) {
+    SerialQueue queue;
+
+    std::vector<int> vector1 = {1, 2, 3, 4};
+    std::vector<int> vector2 = {5, 6, 7, 8};
+    std::vector<int> vector3 = {9, 0};
+
+    queue.Enqueue(vector1, 0);
+    queue.Enqueue(std::move(vector2), 0);
+    queue.Enqueue(vector3, 1);
+
+    std::vector<int> expectedValues = {1, 2, 3, 4, 5, 6, 7, 8, 9, 0};
+    for (int value : queue.IterateAll()) {
+        EXPECT_EQ(expectedValues.front(), value);
+        ASSERT_FALSE(expectedValues.empty());
+        expectedValues.erase(expectedValues.begin());
+    }
+    ASSERT_TRUE(expectedValues.empty());
+}
+
+// Test IterateUpTo
+TEST(SerialQueue, IterateUpTo) {
+    SerialQueue queue;
+
+    std::vector<int> vector1 = {1, 2, 3, 4};
+    std::vector<int> vector2 = {5, 6, 7, 8};
+    std::vector<int> vector3 = {9, 0};
+
+    queue.Enqueue(vector1, 0);
+    queue.Enqueue(std::move(vector2), 1);
+    queue.Enqueue(vector3, 2);
+
+    std::vector<int> expectedValues = {1, 2, 3, 4, 5, 6, 7, 8};
+    for (int value : queue.IterateUpTo(1)) {
+        EXPECT_EQ(expectedValues.front(), value);
+        ASSERT_FALSE(expectedValues.empty());
+        expectedValues.erase(expectedValues.begin());
+    }
+    ASSERT_TRUE(expectedValues.empty());
+}
+
+// Test ClearUpTo
+TEST(SerialQueue, ClearUpTo) {
+    SerialQueue queue;
+
+    std::vector<int> vector1 = {1, 2, 3, 4};
+    std::vector<int> vector2 = {5, 6, 7, 8};
+    std::vector<int> vector3 = {9, 0};
+
+    queue.Enqueue(vector1, 0);
+    queue.Enqueue(std::move(vector2), 0);
+    queue.Enqueue(vector3, 1);
+
+    queue.ClearUpTo(0);
+
+    std::vector<int> expectedValues = {9, 0};
+    for (int value : queue.IterateAll()) {
+        EXPECT_EQ(expectedValues.front(), value);
+        ASSERT_FALSE(expectedValues.empty());
+        expectedValues.erase(expectedValues.begin());
+    }
+    ASSERT_TRUE(expectedValues.empty());
+}