feat: add version header (#40)

### Briefly, what does this PR introduce?
This adds a version header to the installation of EDM4eic. This allows
us to make downstream code behave differently based on the version.

Note: with `.gitattributes` (in particular `export-subst`) we could
automate the filling of this version information with the most recent
tag and such. Maybe something to look into.

---------

Co-authored-by: Dmitry Kalinkin <[email protected]>

CMakeLists.txt

@@ -2,10 +2,15 @@
 # Copyright (C) 2022 Whitney Armstrong, Sylvester Joosten, Wouter Deconinck
 
 cmake_minimum_required(VERSION 3.12)
+
 project(EDM4EIC
-  VERSION 1.1.0
   LANGUAGES CXX)
 
+SET( ${PROJECT_NAME}_VERSION_MAJOR 2 )
+SET( ${PROJECT_NAME}_VERSION_MINOR 1 )
+SET( ${PROJECT_NAME}_VERSION_PATCH 0 )
+SET( ${PROJECT_NAME}_VERSION  "${${PROJECT_NAME}_VERSION_MAJOR}.${${PROJECT_NAME}_VERSION_MINOR}.${${PROJECT_NAME}_VERSION_PATCH}" )
+
 # C++ standard
 set(CMAKE_CXX_STANDARD 17 CACHE STRING "Set the C++ standard to be used")
 if(NOT CMAKE_CXX_STANDARD MATCHES "17|20")
@@ -97,6 +102,14 @@ else()
   message(STATUS "Doxygen not found; no documentation will be built.")
 endif()
 
+# -------------------------
+# add version files
+
+configure_file(${CMAKE_CURRENT_SOURCE_DIR}/EDM4eicVersion.h.in
+               ${CMAKE_CURRENT_BINARY_DIR}/EDM4eicVersion.h )
+install(FILES ${CMAKE_CURRENT_BINARY_DIR}/EDM4eicVersion.h
+  DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}/edm4eic )
+
 # -------------------------
 # install library config
 include(CMakePackageConfigHelpers)
@@ -119,7 +132,7 @@ configure_package_config_file(
 
 write_basic_package_version_file(
   ${PROJECT_NAME}ConfigVersion.cmake
-  VERSION ${VERSION}
+  VERSION ${${PROJECT_NAME}_VERSION}
   COMPATIBILITY SameMajorVersion
   )
 

EDM4eicVersion.h.in

@@ -0,0 +1,91 @@
+// SPDX-License-Identifier: Apache-2.0
+// Ref: https://github.com/key4hep/EDM4hep/blob/e0762272e0f718df2811fc1bf4590af976bac70d/EDM4hepVersion.h.in
+
+#ifndef EDM4EIC_VERSION_H
+#define EDM4EIC_VERSION_H
+
+#include <cstdint>
+#include <tuple>
+#include <ostream>
+#if __cplusplus >= 202002L
+#include <compare>
+#endif
+
+// Some preprocessor constants and macros for the use cases where they might be
+// necessary
+
+/// Define a version to be used in edm4eic.
+#define EDM4EIC_VERSION(major, minor, patch) ((UINT64_C(major) << 32) | (UINT64_C(minor) << 16) | (UINT64_C(patch)))
+/// Get the major version from a preprocessor defined version
+#define EDM4EIC_MAJOR_VERSION(v) (((v) & (-1UL >> 16)) >> 32)
+/// Get the minor version from a preprocessor defined version
+#define EDM4EIC_MINOR_VERSION(v) (((v) & (-1UL >> 32)) >> 16)
+/// Get the patch version from a preprocessor defined version
+#define EDM4EIC_PATCH_VERSION(v) ((v) & (-1UL >> 48))
+
+// Some helper constants that are populated by the cmake configure step
+#define EDM4EIC_VERSION_MAJOR @EDM4EIC_VERSION_MAJOR@
+#define EDM4EIC_VERSION_MINOR @EDM4EIC_VERSION_MINOR@
+#define EDM4EIC_VERSION_PATCH @EDM4EIC_VERSION_PATCH@
+#define edm4hep_VERSION EDM4EIC_VERSION(EDM4EIC_VERSION_MAJOR, EDM4EIC_VERSION_MINOR, EDM4EIC_VERSION_PATCH)
+
+/// The encoded version with which EDM4EIC has been built
+#define EDM4EIC_BUILD_VERSION EDM4EIC_VERSION(EDM4EIC_VERSION_MAJOR, EDM4EIC_VERSION_MINOR, EDM4EIC_VERSION_PATCH)
+
+namespace edm4eic::version {
+
+  /**
+   * Version class consisting of 3 16 bit unsigned integers to hold the major,
+   * minor and patch version. Provides constexpr comparison operators that allow
+   * to use this class in constexpr-if clauses.
+   */
+  struct Version {
+    uint16_t major{0};
+    uint16_t minor{0};
+    uint16_t patch{0};
+
+#if __cplusplus >= 202002L
+    auto operator<=>(const Version&) const = default;
+#else
+// No spaceship yet in c++17
+#define DEFINE_COMP_OPERATOR(OP)                                                   \
+    constexpr bool operator OP(const Version& o) const noexcept {                  \
+      return std::tie(major, minor, patch) OP std::tie(o.major, o.minor, o.patch); \
+    }
+
+    DEFINE_COMP_OPERATOR(<)
+    DEFINE_COMP_OPERATOR(<=)
+    DEFINE_COMP_OPERATOR(>)
+    DEFINE_COMP_OPERATOR(>=)
+    DEFINE_COMP_OPERATOR(==)
+    DEFINE_COMP_OPERATOR(!=)
+
+#undef DEFINE_COMP_OPERATOR
+#endif
+
+    friend std::ostream& operator<<(std::ostream&, const Version& v);
+  };
+
+  inline std::ostream& operator<<(std::ostream& os, const Version& v) {
+    return os << v.major << "." << v.minor << "." << v.patch;
+  }
+
+  /**
+   * The current build version
+   */
+  static constexpr Version build_version{EDM4EIC_VERSION_MAJOR, EDM4EIC_VERSION_MINOR, EDM4EIC_VERSION_PATCH};
+
+  /**
+   * Decode a version from a 64 bit unsigned
+   */
+  static constexpr Version decode_version(uint64_t version) noexcept {
+    return Version{
+      (uint16_t) EDM4EIC_MAJOR_VERSION(version),
+      (uint16_t) EDM4EIC_MINOR_VERSION(version),
+      (uint16_t) EDM4EIC_PATCH_VERSION(version)
+    };
+  }
+}
+
+
+#endif