Add optional CMake config module export.

This is a CMakeLists.txt file that writes the proper config import
files and nothing else. Doesn't replace or "enhance" the actual build
system, just something that exists on the side. I've intentionally
written it to require pretty much no maintenance, but if it ever does
just ping me (github or e-mail) and I'll get it sorted as soon as I
have time.

Author: Xaymar

CMakeLists.txt

@@ -0,0 +1,112 @@
+# Copyright (c) 2026 Narta Xaymar Dirks (info at xaymar dot com)
+#
+# Distributed under the Boost Software License, Version 1.0. (See accompanying
+# file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+# Require the latest CMake version.
+cmake_minimum_required(VERSION 4.2.1)
+
+project(asio)
+
+# Is this the new or old layout?
+if(EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/include")
+	# New Layout
+	set(_src "${CMAKE_CURRENT_SOURCE_DIR}")
+else()
+	# Old Layout
+	set(_src "${CMAKE_CURRENT_SOURCE_DIR}/asio")
+endif()
+
+# Figure out the version from the provided version.hpp.
+if(EXISTS "${_src}/include/asio/version.hpp")
+	file(READ "${_src}/include/asio/version.hpp" ASIO_VERSION_HPP)
+	string(REGEX MATCH "#define ASIO_VERSION ([0-9]+) // ([0-9]+)\.([0-9]+)\.([0-9]+)" ASIO_VERSION "${ASIO_VERSION_HPP}")
+	set(ASIO_VERSION_INT ${CMAKE_MATCH_1})
+	set(ASIO_VERSION_MAJOR ${CMAKE_MATCH_2}) # Trust the comment for now.
+	set(ASIO_VERSION_MINOR ${CMAKE_MATCH_3})
+	set(ASIO_VERSION_PATCH ${CMAKE_MATCH_4})
+	project(${PROJECT_NAME} VERSION "${ASIO_VERSION_MAJOR}.${ASIO_VERSION_MINOR}.${ASIO_VERSION_PATCH}")
+endif()
+
+
+#--------------------------------------------------------------------------------#
+# Options
+#--------------------------------------------------------------------------------#
+
+# What options?
+
+#--------------------------------------------------------------------------------#
+# Library
+#--------------------------------------------------------------------------------#
+
+add_library(${PROJECT_NAME} INTERFACE)
+
+target_include_directories(${PROJECT_NAME}
+	INTERFACE
+		$<BUILD_INTERFACE:${_src}/include/>
+		$<INSTALL_INTERFACE:include/>
+)
+
+target_compile_definitions(${PROJECT_NAME}
+	INTERFACE
+		ASIO_STANDALONE
+)
+
+set_target_properties(${PROJECT_NAME} PROPERTIES
+	# Only necessary for source builds, which only work on MSVC anyway.
+	CXX_STANDARD 11
+	CXX_STANDARD_REQUIRED ON
+	CXX_EXTENSIONS OFF
+)
+
+#--------------------------------------------------------------------------------#
+# Install
+#--------------------------------------------------------------------------------#
+
+install(TARGETS ${PROJECT_NAME}
+	EXPORT ${PROJECT_NAME}-targets
+	LIBRARY RUNTIME FRAMEWORK
+	PERMISSIONS OWNER_WRITE GROUP_WRITE OWNER_READ GROUP_READ WORLD_READ OWNER_EXECUTE GROUP_EXECUTE WORLD_EXECUTE
+)
+install(
+	DIRECTORY "${_src}/include/"
+	TYPE INCLUDE
+	FILE_PERMISSIONS OWNER_READ OWNER_WRITE GROUP_READ GROUP_WRITE WORLD_READ
+	DIRECTORY_PERMISSIONS OWNER_WRITE GROUP_WRITE OWNER_READ GROUP_READ WORLD_READ OWNER_EXECUTE GROUP_EXECUTE WORLD_EXECUTE
+	FILES_MATCHING
+		REGEX ".*\.hpp$"
+		REGEX ".*\.ipp$"
+)
+install(
+	FILES
+		"${CMAKE_CURRENT_BINARY_DIR}/asio-config.cmake"
+		"${CMAKE_CURRENT_BINARY_DIR}/asio-config-version.cmake"
+	DESTINATION "share/cmake/asio/"
+)
+
+#--------------------------------------------------------------------------------#
+# CMake Config
+#--------------------------------------------------------------------------------#
+
+include(CMakePackageConfigHelpers)
+configure_package_config_file(
+	"cmake/config.cmake.in"
+	"${PROJECT_NAME}-config.cmake"
+	INSTALL_DESTINATION "share/cmake/asio/"
+)
+write_basic_package_version_file(
+	"${PROJECT_NAME}-config-version.cmake"
+	COMPATIBILITY SameMinorVersion
+	ARCH_INDEPENDENT
+)
+
+# Generate asio-targets.cmake and asio-targets${CMAKE_BUILD_TYPE}.cmake files.
+export(EXPORT ${PROJECT_NAME}-targets
+	FILE "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}-targets.cmake"
+	NAMESPACE ${PROJECT_NAME}::
+)
+install(EXPORT ${PROJECT_NAME}-targets
+	DESTINATION "share/cmake/asio/"
+	NAMESPACE ${PROJECT_NAME}::
+)
+

cmake/config.cmake.in

@@ -0,0 +1,8 @@
+# Copyright (c) 2026 Narta Xaymar Dirks (info at xaymar dot com)
+# 
+# Distributed under the Boost Software License, Version 1.0. (See accompanying
+# file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+@PACKAGE_INIT@
+
+include("${CMAKE_CURRENT_LIST_DIR}/asio-targets.cmake")