[libc][fixedvector] Add const_iterator begin/end (#96714)

2 files changed, 15 insertions, 0 deletions

diff --git a/libc/src/__support/fixedvector.h b/libc/src/__support/fixedvector.h
index 403b162..5161c0d 100644
--- a/libc/src/__support/fixedvector.h
+++ b/libc/src/__support/fixedvector.h
@@ -90,6 +90,11 @@ public:
 
   LIBC_INLINE constexpr iterator begin() { return store.begin(); }
   LIBC_INLINE constexpr iterator end() { return iterator{&store[item_count]}; }
+
+  LIBC_INLINE constexpr const_iterator begin() const { return store.begin(); }
+  LIBC_INLINE constexpr const_iterator end() const {
+    return const_iterator{&store[item_count]};
+  }
 };
 
 } // namespace LIBC_NAMESPACE
diff --git a/libc/test/src/__support/fixedvector_test.cpp b/libc/test/src/__support/fixedvector_test.cpp
index 212e1ae..b73df04 100644
--- a/libc/test/src/__support/fixedvector_test.cpp
+++ b/libc/test/src/__support/fixedvector_test.cpp
@@ -96,3 +96,13 @@ TEST(LlvmLibcFixedVectorTest, ForwardIteration) {
     ASSERT_EQ(*it, arr[idx]);
   }
 }
+
+TEST(LlvmLibcFixedVectorTest, ConstForwardIteration) {
+  const LIBC_NAMESPACE::cpp::array<int, 4> arr{1, 2, 3, 4};
+  const LIBC_NAMESPACE::FixedVector<int, 5> vec(arr.begin(), arr.end());
+  ASSERT_EQ(vec.size(), arr.size());
+  for (auto it = vec.begin(); it != vec.end(); ++it) {
+    auto idx = it - vec.begin();
+    ASSERT_EQ(*it, arr[idx]);
+  }
+}