Adds pop_back() method to FixedSizeVector

Test: ./run_tests.sh and verify all pass
Change-Id: I0756ce103cfa37d7c5642406d504b1dc3058c094

3 files changed, 35 insertions, 0 deletions

diff --git a/util/include/chre/util/fixed_size_vector.h b/util/include/chre/util/fixed_size_vector.h
index 3a4236d2..85384e59 100644
--- a/util/include/chre/util/fixed_size_vector.h
+++ b/util/include/chre/util/fixed_size_vector.h
@@ -110,6 +110,13 @@ class FixedSizeVector : public NonCopyable {
   void emplace_back(Args&&... args);
 
   /**
+   * Erases the last element in the vector. Invalid to call on an empty vector.
+   *
+   * Invalidates any references to back() and end()/cend().
+   */
+  void pop_back();
+
+  /**
    * Obtains an element of the vector given an index. It is illegal to index
    * this vector out of bounds and the user of the API must check the size()
    * function prior to indexing this vector to ensure that they will not read
diff --git a/util/include/chre/util/fixed_size_vector_impl.h b/util/include/chre/util/fixed_size_vector_impl.h
index 4c8cbee7..79ef6a5f 100644
--- a/util/include/chre/util/fixed_size_vector_impl.h
+++ b/util/include/chre/util/fixed_size_vector_impl.h
@@ -104,6 +104,12 @@ void FixedSizeVector<ElementType, kCapacity>::emplace_back(Args&&... args) {
 }
 
 template<typename ElementType, size_t kCapacity>
+void FixedSizeVector<ElementType, kCapacity>::pop_back() {
+  CHRE_ASSERT(!empty());
+  erase(mSize - 1);
+}
+
+template<typename ElementType, size_t kCapacity>
 ElementType& FixedSizeVector<ElementType, kCapacity>::operator[](
     size_t index) {
   CHRE_ASSERT(index < mSize);
diff --git a/util/tests/fixed_size_vector_test.cc b/util/tests/fixed_size_vector_test.cc
index 577b957f..89e3365c 100644
--- a/util/tests/fixed_size_vector_test.cc
+++ b/util/tests/fixed_size_vector_test.cc
@@ -99,6 +99,28 @@ TEST(FixedSizeVector, PushBackAndErase) {
   ASSERT_EQ(vector.size(), 3);
 }
 
+TEST(FixedSizeVector, PushBackAndPopBack) {
+  FixedSizeVector<int, 8> vector;
+  vector.push_back(0x1337);
+  vector.push_back(0xcafe);
+  vector.push_back(0xbeef);
+  vector.push_back(0xface);
+
+  ASSERT_EQ(vector.size(), 4);
+  ASSERT_EQ(vector.back(), 0xface);
+  vector.pop_back();
+  ASSERT_EQ(vector.size(), 3);
+  ASSERT_EQ(vector.back(), 0xbeef);
+  vector.pop_back();
+  ASSERT_EQ(vector.size(), 2);
+  ASSERT_EQ(vector.back(), 0xcafe);
+  vector.pop_back();
+  ASSERT_EQ(vector.size(), 1);
+  ASSERT_EQ(vector.back(), 0x1337);
+  vector.pop_back();
+  ASSERT_EQ(vector.size(), 0);
+}
+
 TEST(FixedSizeVector, EraseDestructorCalled) {
   FixedSizeVector<Foo, 4> vector;
   for (size_t i = 0; i < 4; ++i) {