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)));
    }
  };
};
}
 
#endif  // OR_TOOLS_BASE_DYNAMIC_LIBRARY_H_