using std::span from c++20

- Added the ability to use span from std when standard 20 is enabled.
- Previous catch version didn't work with 20 standard.

CMakeLists.txt

@@ -4,6 +4,7 @@ set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${CMAKE_SOURCE_DIR}/cmake")
 
 option(UUID_BUILD_TESTS "Build the unit tests" ON)
 option(UUID_SYSTEM_GENERATOR "Enable operating system uuid generator" ON)
+option(UUID_USING_CXX20_SPAN "Using span from std instead of gsl" OFF)
 
 # Library target
 add_library(${PROJECT_NAME} INTERFACE)
@@ -26,6 +27,11 @@ if (UUID_SYSTEM_GENERATOR)
     endif ()
 endif ()
 
+# Using span from std
+if (NOT UUID_USING_CXX20_SPAN)
+    target_include_directories(${PROJECT_NAME} INTERFACE ${CMAKE_SOURCE_DIR}/gsl)
+endif ()
+
 # Tests
 if (UUID_BUILD_TESTS)
     add_subdirectory(test)

gsl/gsl

@@ -17,13 +17,13 @@
 #ifndef GSL_GSL_H
 #define GSL_GSL_H
 
-#include <gsl/gsl_algorithm> // copy
-#include <gsl/gsl_assert>    // Ensures/Expects
-#include <gsl/gsl_byte>      // byte
-#include <gsl/gsl_util>      // finally()/narrow()/narrow_cast()...
-#include <gsl/multi_span>    // multi_span, strided_span...
-#include <gsl/pointers>      // owner, not_null
-#include <gsl/span>          // span
-#include <gsl/string_span>   // zstring, string_span, zstring_builder...
+#include "gsl_algorithm" // copy
+#include "gsl_assert"    // Ensures/Expects
+#include "gsl_byte"      // byte
+#include "gsl_util"      // finally()/narrow()/narrow_cast()...
+#include "multi_span"    // multi_span, strided_span...
+#include "pointers"      // owner, not_null
+#include "span"          // span
+#include "string_span"   // zstring, string_span, zstring_builder...
 
 #endif // GSL_GSL_H

gsl/gsl_algorithm

@@ -17,8 +17,8 @@
 #ifndef GSL_ALGORITHM_H
 #define GSL_ALGORITHM_H
 
-#include <gsl/gsl_assert> // for Expects
-#include <gsl/span>       // for dynamic_extent, span
+#include "gsl_assert" // for Expects
+#include "span"       // for dynamic_extent, span
 
 #include <algorithm>   // for copy_n
 #include <cstddef>     // for ptrdiff_t

gsl/gsl_util

@@ -17,7 +17,7 @@
 #ifndef GSL_UTIL_H
 #define GSL_UTIL_H
 
-#include <gsl/gsl_assert> // for Expects
+#include "gsl_assert" // for Expects
 
 #include <array>
 #include <cstddef>          // for ptrdiff_t, size_t

gsl/multi_span

@@ -17,9 +17,9 @@
 #ifndef GSL_MULTI_SPAN_H
 #define GSL_MULTI_SPAN_H
 
-#include <gsl/gsl_assert> // for Expects
-#include <gsl/gsl_byte>   // for byte
-#include <gsl/gsl_util>   // for narrow_cast
+#include "gsl_assert" // for Expects
+#include "gsl_byte"   // for byte
+#include "gsl_util"   // for narrow_cast
 
 #include <algorithm> // for transform, lexicographical_compare
 #include <array>     // for array

gsl/pointers

@@ -17,7 +17,7 @@
 #ifndef GSL_POINTERS_H
 #define GSL_POINTERS_H
 
-#include <gsl/gsl_assert>  // for Ensures, Expects
+#include "gsl_assert" // for Ensures, Expects
 
 #include <algorithm>    // for forward
 #include <iosfwd>       // for ptrdiff_t, nullptr_t, ostream, size_t

gsl/span

@@ -17,9 +17,9 @@
 #ifndef GSL_SPAN_H
 #define GSL_SPAN_H
 
-#include <gsl/gsl_assert> // for Expects
-#include <gsl/gsl_byte>   // for byte
-#include <gsl/gsl_util>   // for narrow_cast, narrow
+#include "gsl_assert" // for Expects
+#include "gsl_byte"   // for byte
+#include "gsl_util"   // for narrow_cast, narrow
 
 #include <algorithm> // for lexicographical_compare
 #include <array>     // for array

gsl/string_span

@@ -17,9 +17,9 @@
 #ifndef GSL_STRING_SPAN_H
 #define GSL_STRING_SPAN_H
 
-#include <gsl/gsl_assert> // for Ensures, Expects
-#include <gsl/gsl_util>   // for narrow_cast
-#include <gsl/span>       // for operator!=, operator==, dynamic_extent
+#include "gsl_assert" // for Ensures, Expects
+#include "gsl_util"   // for narrow_cast
+#include "span"       // for operator!=, operator==, dynamic_extent
 
 #include <algorithm> // for equal, lexicographical_compare
 #include <array>     // for array

include/uuid.h

@@ -15,7 +15,7 @@
 #include <chrono>
 #include <numeric>
 #include <atomic>
-#include <gsl/span>
+#include <span>
 
 #ifdef _WIN32
 #ifndef WIN32_LEAN_AND_MEAN
@@ -50,6 +50,14 @@
 
 namespace uuids
 {
+#ifdef __cpp_lib_span
+   template <class ElementType, std::size_t Extent>
+   using span = std::span<ElementType, Extent>;
+#else
+   template <class ElementType, std::ptrdiff_t Extent>
+   using span = gsl::span<ElementType, Extent>;
+#endif
+
    namespace detail
    {
       template <typename TChar>
@@ -352,7 +360,7 @@ namespace uuids
          std::copy(std::cbegin(arr), std::cend(arr), std::begin(data));
       }
 
-      explicit uuid(gsl::span<value_type, 16> bytes)
+      explicit uuid(span<value_type, 16> bytes)
       {
          std::copy(std::cbegin(bytes), std::cend(bytes), std::begin(data));
       }
@@ -403,9 +411,9 @@ namespace uuids
          data.swap(other.data);
       }
 
-      inline gsl::span<std::byte const, 16> as_bytes() const
+      inline span<std::byte const, 16> as_bytes() const
       {
-         return gsl::span<std::byte const, 16>(reinterpret_cast<std::byte const*>(data.data()), 16);
+         return span<std::byte const, 16>(reinterpret_cast<std::byte const*>(data.data()), 16);
       }
 
       template<class CharT = char>

test/CMakeLists.txt

@@ -4,15 +4,19 @@ enable_testing()
 add_executable(test_${PROJECT_NAME} main.cpp test_generators.cpp test_uuid.cpp)
 target_include_directories(test_${PROJECT_NAME} PRIVATE ${PROJECT_SOURCE_DIR}/catch)
 target_link_libraries(test_${PROJECT_NAME} PRIVATE ${PROJECT_NAME})
-set_target_properties(test_${PROJECT_NAME} PROPERTIES CXX_STANDARD 17)
-if(WIN32)
+if (UUID_USING_CXX20_SPAN)
+    set_target_properties(test_${PROJECT_NAME} PROPERTIES CXX_STANDARD 20)
+else ()
+    set_target_properties(test_${PROJECT_NAME} PROPERTIES CXX_STANDARD 17)
+endif ()
+if (WIN32)
     target_compile_options(test_${PROJECT_NAME} PRIVATE /EHc)
     target_compile_definitions(test_${PROJECT_NAME} PRIVATE _SCL_SECURE_NO_WARNINGS)
-elseif(APPLE)
+elseif (APPLE)
     target_compile_options(test_${PROJECT_NAME} PRIVATE -fexceptions -g -Wall)
-else()
+else ()
     target_compile_options(test_${PROJECT_NAME} PRIVATE -fexceptions -g -Wall)
-endif()
+endif ()
 get_target_property(CURRENT_COMPILE_OPTIONS test_${PROJECT_NAME} COMPILE_OPTIONS)
 message(STATUS "** ${CMAKE_CXX_COMPILER_ID} flags: ${CURRENT_COMPILE_OPTIONS}")