Add checked index for circular buffer

docs/containers/queues & stacks/circular-buffer.md

@@ -123,6 +123,7 @@ const_reference operator[](size_t i) const
 ```
 **Description**  
 Returns a reference or const reference to the indexed element.
+Emits an `etl::circular_buffer_out_of_bounds` if ETL_CHECK_INDEX_OPERATOR is defined and the index is out of range of the deque. Undefined behaviour if asserts or exceptions are not enabled.
 
 ---
 

include/etl/circular_buffer.h

@@ -83,6 +83,19 @@ namespace etl
     }
   };
 
+  //***************************************************************************
+  /// circular_buffer out of bounds exception.
+  //***************************************************************************
+  class circular_buffer_out_of_bounds : public etl::circular_buffer_exception
+  {
+  public:
+
+    circular_buffer_out_of_bounds(string_type file_name_, numeric_type line_number_)
+      : etl::circular_buffer_exception(ETL_ERROR_TEXT("circular_buffer:bounds", ETL_CIRCULAR_BUFFER_FILE_ID"C"), file_name_, line_number_)
+    {
+    }
+  };
+
   //***************************************************************************
   ///
   //***************************************************************************
@@ -888,6 +901,8 @@ namespace etl
     //*************************************************************************
     reference operator[](size_t index)
     {
+      ETL_ASSERT_CHECK_INDEX_OPERATOR(index < size(), ETL_ERROR(circular_buffer_out_of_bounds));
+
       return pbuffer[(out + index) % buffer_size];
     }
 
@@ -897,6 +912,8 @@ namespace etl
     //*************************************************************************
     const_reference operator[](size_t index) const
     {
+      ETL_ASSERT_CHECK_INDEX_OPERATOR(index < size(), ETL_ERROR(circular_buffer_out_of_bounds));
+
       return pbuffer[(out + index) % buffer_size];
     }
 

test/test_circular_buffer.cpp

@@ -647,6 +647,8 @@ namespace
       {
         CHECK_EQUAL(input2[i], data[i]);
       }
+
+      CHECK_THROW(data[data.size()], etl::circular_buffer_out_of_bounds);
     }
 
     //*************************************************************************
@@ -662,6 +664,8 @@ namespace
       {
         CHECK_EQUAL(input[i + 3], data[i]);
       }
+
+      CHECK_THROW(data[data.size()], etl::circular_buffer_out_of_bounds);
     }
 
     //*************************************************************************