Make user provide standalone Asio library to use

Instead of fetching a specific version of Asio to use when building
without boost, expect the user to provide a version to use similar to
how boost is used.

This is more flexible and probably what most users would expect.

.github/workflows/unittest.yml

@@ -141,14 +141,15 @@ jobs:
  uses: mxschmitt/action-tmate@v3
 
  unittest-standalone-asio:
- name: "Asio ${{matrix.build_type}} C++${{matrix.standard}}"
+ name: "${{matrix.asio_version}} ${{matrix.build_type}} C++${{matrix.standard}}"
  runs-on: ${{matrix.os}}
  defaults:
  run:
  shell: bash
  strategy:
  fail-fast: false
  matrix:
+ asio_version: ["asio-1-28-0", "asio-1-29-0"]
  os: [windows-2022]
  build_type: [Debug, Release]
  standard: [14, 17, 20]
@@ -162,6 +163,14 @@ jobs:
  - name: Create build directory
  run: mkdir build
 
+ - name: Checkout Asio
+ working-directory: build
+ uses: actions/checkout@v4
+ with:
+ repository: https://github.com/chriskohlhoff/asio.git
+ ref: ${{matrix.asio_version}}
+ fetch-depth: 0
+
  - name: Configure
  working-directory: build
  run: |

CMakeLists.txt

@@ -2,7 +2,6 @@ cmake_minimum_required(VERSION 3.15)
 
 set(CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake" ${CMAKE_MODULE_PATH})
 
-include(FetchContent)
 include(VersionFromGit)
 
 version_from_git()
@@ -35,36 +34,12 @@ option(WARNINGS_AS_ERRORS "Treat compiler warnings as errors" ON)
 
 add_library(${PROJECT_NAME} INTERFACE)
 
-if(ENABLE_WINTLS_STANDALONE_ASIO)
- FetchContent_Declare(
- asio
- GIT_REPOSITORY https://github.com/chriskohlhoff/asio.git
- GIT_TAG asio-1-28-0
- )
-
- FetchContent_GetProperties(asio)
- if(NOT asio_POPULATED)
- FetchContent_Populate(asio)
- endif()
-endif()
-
 target_include_directories(${PROJECT_NAME}
  INTERFACE
  $<BUILD_INTERFACE:${${PROJECT_NAME}_SOURCE_DIR}/include>
  $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>
 )
 
-if(ENABLE_WINTLS_STANDALONE_ASIO)
- target_include_directories(${PROJECT_NAME}
- INTERFACE
- ${asio_SOURCE_DIR}/asio/include
- )
- target_compile_definitions(${PROJECT_NAME}
- INTERFACE
- WINTLS_USE_STANDALONE_ASIO
- )
-endif()
-
 if(WIN32)
  set(Boost_USE_STATIC_LIBS ON)
  set(Boost_USE_MULTITHREADED ON)
@@ -149,7 +124,16 @@ if(WIN32)
  set(CMAKE_EXE_LINKER_FLAGS_RELEASE "${CMAKE_EXE_LINKER_FLAGS_RELEASE} /DEBUG /OPT:REF /OPT:ICF")
 endif()
 
-if(NOT ENABLE_WINTLS_STANDALONE_ASIO)
+if(ENABLE_WINTLS_STANDALONE_ASIO)
+ find_package(Asio REQUIRED)
+
+ target_link_libraries(${PROJECT_NAME} INTERFACE
+ Asio::Asio
+ )
+ target_compile_definitions(${PROJECT_NAME} INTERFACE
+ WINTLS_USE_STANDALONE_ASIO
+ )
+else()
  find_package(Boost REQUIRED)
 
  target_link_libraries(${PROJECT_NAME} INTERFACE

cmake/FindAsio.cmake

@@ -0,0 +1,44 @@
+include(FindPackageHandleStandardArgs)
+
+find_package(Threads QUIET)
+
+if (NOT Threads_FOUND)
+ message(FATAL_ERROR "Asio requires Threads")
+endif()
+
+if(DEFINED ENV{ASIO_ROOT})
+ set(ASIO_DIR "$ENV{ASIO_ROOT}/asio/include/")
+else()
+ set(ASIO_DIR "${CMAKE_CURRENT_BINARY_DIR}/asio/asio/include/")
+endif()
+
+find_path(ASIO_INCLUDE_DIR asio.hpp
+ HINTS
+ ${ASIO_DIR}
+)
+
+if(ASIO_INCLUDE_DIR AND EXISTS "${ASIO_INCLUDE_DIR}/asio/version.hpp")
+ file(STRINGS "${ASIO_INCLUDE_DIR}/asio/version.hpp" asio_version_str REGEX "^#define[ \t]+ASIO_VERSION[ \t]+.*")
+ string(REGEX REPLACE "^#define[ \t]+ASIO_VERSION[ \t]+([0-9]+).*$" "\\1" asio_version_number "${asio_version_str}")
+ math(EXPR asio_sub_minor_version "${asio_version_number} % 100")
+ math(EXPR asio_minor_version "${asio_version_number} / 100 % 1000")
+ math(EXPR asio_major_version "${asio_version_number} / 100000")
+ set(ASIO_VERSION_STRING "${asio_major_version}.${asio_minor_version}.${asio_sub_minor_version}")
+endif()
+
+find_package_handle_standard_args(
+ Asio
+ REQUIRED_VARS ASIO_INCLUDE_DIR
+ VERSION_VAR ASIO_VERSION_STRING
+)
+
+mark_as_advanced(ASIO_INCLUDE_DIR)
+
+if(ASIO_FOUND AND NOT TARGET Asio::Asio)
+ add_library(Asio::Asio INTERFACE IMPORTED)
+ target_include_directories(Asio::Asio
+ INTERFACE
+ ${ASIO_INCLUDE_DIR}
+ Threads::Threads
+ )
+endif()