Use more CMake functionality

Use CTest and create tests/ subdir
Use CMake to optionally build examples
Add .gitignore

.gitignore

@@ -0,0 +1,12 @@
+# CMake
+CMakeLists.txt.user
+CMakeCache.txt
+CMakeFiles
+CMakeScripts
+Testing
+Makefile
+cmake_install.cmake
+install_manifest.txt
+compile_commands.json
+CTestTestfile.cmake
+_deps

CMakeLists.txt

@@ -1,8 +1,36 @@
 cmake_minimum_required(VERSION 3.14)
 
-project(hmac-sha256)
+set(CMAKE_C_STANDARD 99)
 
-add_library(hmac-sha256 STATIC hmac_sha256.c sha256.c )
+# For "CMAKE_INSTALL_<dir>" standard installation directories
+include(GNUInstallDirs)
 
-install(TARGETS hmac-sha256 DESTINATION lib)
-install(FILES hmac-sha256.h DESTINATION include)
+project(hmac_sha256 LANGUAGES C CXX)
+
+option(HMAC_SHA256_TESTS "Build unit tests" FALSE)
+option(HMAC_SHA256_EXAMPLES "Build the examples" FALSE)
+
+add_library(hmac_sha256 STATIC
+  ${CMAKE_CURRENT_SOURCE_DIR}/sha256.c
+  ${CMAKE_CURRENT_SOURCE_DIR}/hmac_sha256.c
+)
+target_include_directories(hmac_sha256 INTERFACE ${CMAKE_CURRENT_SOURCE_DIR})
+
+install(TARGETS hmac_sha256
+  LIBRARY DESTINATION "${CMAKE_INSTALL_LIBDIR}"
+  ARCHIVE DESTINATION "${CMAKE_INSTALL_LIBDIR}"
+)
+
+install(FILES
+  ${CMAKE_CURRENT_SOURCE_DIR}/hmac_sha256.h
+  DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}"
+)
+
+if (HMAC_SHA256_TESTS)
+  enable_testing()
+  add_subdirectory(tests)
+endif()
+
+if(HMAC_SHA256_EXAMPLES)
+  add_subdirectory(examples)
+endif()

examples/.gitignore

@@ -0,0 +1,12 @@
+# CMake
+CMakeLists.txt.user
+CMakeCache.txt
+CMakeFiles
+CMakeScripts
+Testing
+Makefile
+cmake_install.cmake
+install_manifest.txt
+compile_commands.json
+CTestTestfile.cmake
+_deps

examples/CMakeLists.txt

@@ -0,0 +1,13 @@
+set(CMAKE_CXX_STANDARD 11)
+set(CMAKE_CXX_STANDARD_REQUIRED TRUE)
+
+add_executable(hmac_cxx_example
+  hmac_cxx_example.cpp
+)
+
+add_executable(hmac_c_example
+  hmac_c_example.c
+)
+
+target_link_libraries(hmac_cxx_example hmac_sha256)
+target_link_libraries(hmac_c_example hmac_sha256)

tests/CMakeLists.txt

@@ -0,0 +1,7 @@
+set(CMAKE_CXX_STANDARD 11)
+set(CMAKE_CXX_STANDARD_REQUIRED TRUE)
+
+add_executable(tests tests.cpp)
+target_link_libraries(tests hmac_sha256)
+
+add_test(hmac_sha256-tests tests)