add README

README.md

@@ -0,0 +1,46 @@
+# cxx-ring-buffer
+
+a small implementation of a C++ ring-buffer container wrapper and STL-style
+iterators.
+
+## Overview
+
+This projects provides the following types:
+
+- the template `basic_ring_buffer<ContainerType>`, defined in `<ring-buffer.h>`  
+  augments an existing container to be used as a ring buffer
+- the alias template `ring_buffer<ValueType, Size>`, defined in `<ring-buffer.h>`  
+  an alias for `basic_ring_buffer<std::array<ValueType, Size>>`
+- the template `ring_buffer_iterator<ContainerType>`, defined in `<ring-buffer-iterator.h>`  
+  a random access iterator over a `basic_ring_buffer` with the same container type
+- the template `ring_buffer_const_iterator<ContainerType>`, defined in `<ring-buffer-iterator.h>`  
+  a random access iterator over a `basic_ring_buffer` with the same container type,
+  giving `const` access to the elements
+
+This project can be configured via CMake options or preprocessor defines
+
+## CMake options
+
+- `RING_BUFFER_DEFAULT_CXXFLAGS` (default OFF)  
+  set the C++ compiler flags to `-Wall -Wextra`, and try to detect the newest supported C++ standard.
+- `RING_BUFFER_BUILD_TESTS` (default OFF)  
+  build the test programs from the `test/` subdirectory
+- `RING_BUFFER_FEATURE_DETECT` (default ON)  
+  try to detect the values for the following feature options automatically
+- `RING_BUFFER_NOEXCEPT` (default OFF)  
+  enable use of the `noexcept(bool-expr)` conditional noexcept operator (needs C++11)
+- `RING_BUFFER_CONSTEXPR` (default OFF)  
+  make all member functions of `basic_ring_buffer` and its iterators `constexpr` (needs C++14)
+- `RING_BUFFER_CONSTEXPR_DESTRUCTORS` (default OFF)  
+  make the destructors of `basic_ring_buffer` and its iterators explicitly `constexpr` (needs C++20)
+
+The last 3 options set preprocessor defines with the same name when enabled.
+
+## Preprocessor defines
+
+- `RING_BUFFER_NOEXCEPT` (default OFF)  
+  enable use of the `noexcept(bool-expr)` conditional noexcept operator (needs C++11)
+- `RING_BUFFER_CONSTEXPR` (default OFF)  
+  make all member functions of `basic_ring_buffer` and its iterators `constexpr` (needs C++14)
+- `RING_BUFFER_CONSTEXPR_DESTRUCTORS` (default OFF)  
+  make the destructors of `basic_ring_buffer` and its iterators explicitly `constexpr` (needs C++20)