AK: Implement AK::Stack

Author: https://github.com/Quaker762
Commit: https://github.com/SerenityOS/serenity/commit/2b123cc5925
Pull-request: https://github.com/SerenityOS/serenity/pull/7024
Reviewed-by: https://github.com/alimpfard
Reviewed-by: https://github.com/ccapitalK
Reviewed-by: https://github.com/predmond
Reviewed-by: https://github.com/sunverwerth

AK/Stack.h

@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) 2021, Jesse Buhagiar <jooster669@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Vector.h>
+
+namespace AK {
+
+template<typename T, size_t stack_size>
+class Stack {
+public:
+    Stack() = default;
+    ~Stack() = default;
+
+    bool push(const T& item)
+    {
+        if (m_stack.size() >= stack_size)
+            return false;
+
+        m_stack.append(item);
+        return true;
+    }
+
+    bool push(T&& item)
+    {
+        if (m_stack.size() >= stack_size)
+            return false;
+
+        m_stack.append(move(item));
+        return true;
+    }
+
+    bool is_empty() const
+    {
+        return m_stack.is_empty();
+    }
+
+    size_t size() const
+    {
+        return m_stack.size();
+    }
+
+    bool pop()
+    {
+        if (is_empty())
+            return false;
+
+        m_stack.resize_and_keep_capacity(m_stack.size() - 1);
+        return true;
+    }
+
+    T& top()
+    {
+        return m_stack.last();
+    }
+
+    const T& top() const
+    {
+        return m_stack.last();
+    }
+
+private:
+    Vector<T, stack_size> m_stack;
+};
+
+}
+
+using AK::Stack;

Tests/AK/CMakeLists.txt

@@ -47,6 +47,7 @@ set(AK_TEST_SOURCES
     TestSourceGenerator.cpp
     TestSourceLocation.cpp
     TestSpan.cpp
+    TestStack.cpp
     TestString.cpp
     TestStringUtils.cpp
     TestStringView.cpp

Tests/AK/TestStack.cpp

@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2021, Jesse Buhagiar <jooster669@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibTest/TestCase.h>
+
+#include <AK/Stack.h>
+
+TEST_CASE(basic)
+{
+    AK::Stack<int, 3> stack;
+
+    EXPECT(stack.is_empty() == true);
+    stack.push(2);
+    stack.push(4);
+    stack.push(17);
+    EXPECT(stack.size() == 3);
+    EXPECT(stack.top() == 17);
+    EXPECT_EQ(stack.pop(), true);
+    EXPECT_EQ(stack.pop(), true);
+    EXPECT_EQ(stack.pop(), true);
+    EXPECT(stack.is_empty());
+}
+
+TEST_CASE(complex_type)
+{
+    AK::Stack<String, 4> stack;
+
+    EXPECT_EQ(stack.is_empty(), true);
+    EXPECT(stack.push("Well"));
+    EXPECT(stack.push("Hello"));
+    EXPECT(stack.push("Friends"));
+    EXPECT(stack.push(":^)"));
+    EXPECT_EQ(stack.top(), ":^)");
+    EXPECT_EQ(stack.pop(), true);
+    EXPECT_EQ(stack.top(), "Friends");
+    EXPECT_EQ(stack.pop(), true);
+    EXPECT_EQ(stack.top(), "Hello");
+    EXPECT_EQ(stack.pop(), true);
+    EXPECT_EQ(stack.top(), "Well");
+    EXPECT_EQ(stack.pop(), true);
+    EXPECT(stack.is_empty());
+}