Introduce bn::base::function_ref, a non-owning function wrapper inspired by C++26's std::function_ref

This is to `std::function` as `std::string_view` is to `std::string`.

Author: bdash

CMakeLists.txt

@@ -29,11 +29,17 @@ if(NOT DEMO)
     endif()
 endif()
 
+if(NOT BN_INTERNAL_BUILD)
+    add_subdirectory(base)
+endif()
+
 add_library(binaryninjaapi STATIC ${BN_API_SOURCES})
 
 target_include_directories(binaryninjaapi
     PUBLIC ${PROJECT_SOURCE_DIR})
 
+target_link_libraries(binaryninjaapi PUBLIC binaryninjabase)
+
 # Store path to user plugin dir
 if(WIN32)
     set(BN_USER_PLUGINS_DIR "$ENV{APPDATA}\\Binary Ninja\\plugins")

base/CMakeLists.txt

@@ -0,0 +1,24 @@
+cmake_minimum_required(VERSION 3.15 FATAL_ERROR)
+
+file(GLOB BN_BASE_SOURCES CONFIGURE_DEPENDS *.cpp *.h)
+
+add_library(binaryninjabase OBJECT ${BN_BASE_SOURCES})
+set_target_properties(binaryninjabase PROPERTIES LINKER_LANGUAGE CXX)
+
+target_include_directories(binaryninjabase
+    PUBLIC ${PROJECT_SOURCE_DIR})
+
+set_target_properties(binaryninjabase PROPERTIES
+    CXX_STANDARD 20
+    CXX_VISIBILITY_PRESET hidden
+    CXX_STANDARD_REQUIRED ON
+    VISIBILITY_INLINES_HIDDEN ON
+    POSITION_INDEPENDENT_CODE ON)
+
+if(BN_REF_COUNT_DEBUG)
+    target_compile_definitions(binaryninjabase PUBLIC BN_REF_COUNT_DEBUG)
+endif()
+
+if(CMAKE_BUILD_TYPE MATCHES Debug OR CMAKE_BUILD_TYPE MATCHES RelWithDebInfo)
+    target_compile_definitions(binaryninjabase PRIVATE BN_ENABLE_LOG_TRACE)
+endif()

base/function_ref.h

@@ -0,0 +1,90 @@
+// Copyright (c) 2025 Vector 35 Inc
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to
+// deal in the Software without restriction, including without limitation the
+// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+// sell copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+// IN THE SOFTWARE.
+
+#pragma once
+
+#include <type_traits>
+#include <utility>
+#include <functional>
+
+namespace bn::base {
+
+template <typename Sig>
+class function_ref;
+
+// A non-owning reference to a callable object, inspired by C++26's std::function_ref.
+// If the callable needs to be stored or copied, use std::function instead.
+template <typename R, typename... Args>
+class function_ref<R(Args...)>
+{
+private:
+    union Storage
+    {
+        const void* object = nullptr;
+        R (*func)(Args...);
+    };
+
+    Storage m_storage;
+    R (*m_invoker)(const Storage&, Args...) = nullptr;
+    
+    static R invoke_function(const Storage& storage, Args... args)
+    {
+        auto fn = storage.func;
+        return fn(std::forward<Args>(args)...);
+    }
+    
+    template <typename T>
+    static R invoke_callable(const Storage& storage, Args... args)
+    {
+        return std::invoke(*static_cast<const T*>(storage.object), std::forward<Args>(args)...);
+    }
+    
+public:
+    function_ref() = delete;
+
+    // Constructor that accepts a function pointer
+    function_ref(R (*f)(Args...)) noexcept
+        : m_storage{.func = f}
+        , m_invoker(&invoke_function)
+    {
+    }
+
+    // Constructor that accepts any callable object that is not function_ref
+    template<typename F>
+        requires (!std::is_same_v<std::remove_cvref_t<F>, function_ref>) &&
+                 std::is_invocable_r_v<R, F&, Args...>
+    function_ref(const F& f) noexcept
+        : m_storage{.object = &f}
+        , m_invoker(&invoke_callable<std::remove_cvref_t<F>>)
+    {
+    }
+    
+    R operator()(Args... args) const
+    {
+        return m_invoker(m_storage, std::forward<Args>(args)...);
+    }
+
+    function_ref(const function_ref&) noexcept = default;
+    function_ref(function_ref&&) noexcept = default;
+    function_ref& operator=(const function_ref&) noexcept = default;
+    function_ref& operator=(function_ref&&) noexcept = default;
+};
+
+} // namespace bn::base