add Chapter03

Chapter03/google_test_example.cpp

@@ -0,0 +1,91 @@
+#include <array>
+
+#include <cstdio>
+
+#include "gtest/gtest.h"
+
+template <class T, std::size_t N> struct ring_buffer {
+
+  std::array<T, N> arr;
+
+  std::size_t write_idx = 0;
+
+  std::size_t read_idx = 0;
+
+  std::size_t count = 0;
+
+  void push(T t) {
+
+    arr.at(write_idx) = t;
+
+    write_idx = (write_idx + 1) % N;
+
+    if (count < N) {
+
+      count++;
+
+    } else {
+
+      read_idx = (read_idx + 1) % N;
+    }
+  }
+
+  T pop() {
+
+    if (count == 0) {
+
+      return T{};
+    }
+
+    T value = arr.at(read_idx);
+
+    read_idx = (read_idx + 1) % N;
+
+    --count;
+
+    return value;
+  }
+
+  bool is_empty() const { return count == 0; }
+
+  std::size_t get_count() const { return count; }
+};
+
+TEST(RingBufferInt, PushPop) {
+
+  ring_buffer<int, 2> rb;
+
+  rb.push(1);
+
+  rb.push(2);
+
+  EXPECT_EQ(rb.pop(), 1);
+
+  EXPECT_EQ(rb.pop(), 2);
+}
+
+TEST(RingBufferInt, GetCount) {
+
+  ring_buffer<int, 20> rb;
+
+  for (int i = 0; i < 50; i++) {
+
+    rb.push(i);
+  }
+
+  EXPECT_EQ(rb.get_count(), 20);
+
+  for (int i = 0; i < 10; i++) {
+
+    rb.pop();
+  }
+
+  EXPECT_EQ(rb.get_count(), 10);
+}
+
+int main() {
+
+  testing::InitGoogleTest();
+
+  return RUN_ALL_TESTS();
+}

Chapter03/out_of_bound.cpp

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+#include <array> 
+
+int main() {
+    std::array<int, 4> arr{1, 2, 3, 4};
+
+    return arr[4];
+}

Chapter03/uninitialized_value.cpp

@@ -0,0 +1,13 @@
+#include <array> 
+
+int sum(const std::array<int, 4> &arr) { 
+
+    int ret; 
+
+    for(int elem: arr) { 
+        ret += elem; 
+    } 
+
+    return ret; 
+
+}