dynamic_library.h

// Copyright 2010-2022 Google LLC
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
 
#ifndef OR_TOOLS_BASE_DYNAMIC_LIBRARY_H_
#define OR_TOOLS_BASE_DYNAMIC_LIBRARY_H_
 
#include <functional>
#include <stdexcept>
#include <string>
#include <vector>
 
#if defined(_MSC_VER)
#define WIN32_LEAN_AND_MEAN // disables several conflicting macros
#include <windows.h>
#elif defined(__GNUC__)
#include <dlfcn.h>
#endif
 
namespace Solver
{
class DynamicLibrary
{
    static constexpr size_t kMaxFunctionsNotFound = 10;
 
public:
    DynamicLibrary():
        library_handle_(nullptr)
    {
    }
 
    ~DynamicLibrary()
    {
        if (library_handle_ == nullptr)
        {
            return;
        }
 
#if defined(_MSC_VER)
        FreeLibrary(static_cast<HINSTANCE>(library_handle_));
#elif defined(__GNUC__)
        dlclose(library_handle_);
#endif
    }
 
    bool TryToLoad(const std::string& library_name)
    {
        library_name_ = std::string(library_name);
#if defined(_MSC_VER)
        library_handle_ = static_cast<void*>(LoadLibraryA(library_name.c_str()));
#elif defined(__GNUC__)
        library_handle_ = dlopen(library_name.c_str(), RTLD_NOW);
#endif
        return library_handle_ != nullptr;
    }
 
    bool LibraryIsLoaded() const
    {
        return library_handle_ != nullptr;
    }
 
    const std::vector<std::string>& FunctionsNotFound() const
    {
        return functions_not_found_;
    }
 
    template<typename T>
    std::function<T> GetFunction(const char* function_name)
    {
        const void* function_address =
#if defined(_MSC_VER)
          static_cast<void*>(
            GetProcAddress(static_cast<HINSTANCE>(library_handle_), function_name));
#else
          dlsym(library_handle_, function_name);
#endif
        // We don't really need the full list of missing functions,
        // just a few are enough.
        if (!function_address && functions_not_found_.size() < kMaxFunctionsNotFound)
        {
            functions_not_found_.push_back(function_name);
        }
 
        return TypeParser<T>::CreateFunction(function_address);
    }
 
    template<typename T>
    std::function<T> GetFunction(const std::string& function_name)
    {
        return GetFunction<T>(function_name.c_str());
    }
 
    template<typename T>
    void GetFunction(std::function<T>* function, const char* function_name)
    {
        *function = GetFunction<T>(function_name);
    }
 
    template<typename T>
    void GetFunction(std::function<T>* function, const std::string function_name)
    {
        GetFunction<T>(function, function_name.c_str());
    }
 
private:
    void* library_handle_ = nullptr;
    std::string library_name_;
    std::vector<std::string> functions_not_found_;
 
    template<typename T>
    struct TypeParser
    {
    };
 
    template<typename Ret, typename... Args>
    struct TypeParser<Ret(Args...)>
    {
        static std::function<Ret(Args...)> CreateFunction(const void* function_address)
        {
            return std::function<Ret(Args...)>(
              reinterpret_cast<Ret (*)(Args...)>(const_cast<void*>(function_address)));
        }
    };
};
} // namespace Solver
 
#endif // OR_TOOLS_BASE_DYNAMIC_LIBRARY_H_