dynamiclibrary.hpp

Go to the documentation of this file.

// 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 __STOUT_POSIX_DYNAMICLIBRARY_HPP__
#define __STOUT_POSIX_DYNAMICLIBRARY_HPP__

#include <dlfcn.h>

#include <memory>
#include <string>

#include <stout/nothing.hpp>
#include <stout/option.hpp>
#include <stout/try.hpp>

class DynamicLibrary
{
public:
  DynamicLibrary()
    : handle_(nullptr, [](void* handle) {
        if (handle == nullptr) {
          return 0;
        }

        return dlclose(handle);
      })
  {}

  virtual ~DynamicLibrary() = default;

  Try<Nothing> open(const std::string& path)
  {
    // Check if we've already opened a library.
    if (handle_ != nullptr) {
      return Error("Library already opened");
    }

    handle_.reset(dlopen(path.c_str(), RTLD_NOW));

    if (handle_ == nullptr) {
      return Error("Could not load library '" + path + "': " + dlerror());
    }

    path_ = path;

    return Nothing();
  }

  Try<Nothing> close()
  {
    if (handle_ == nullptr) {
      return Error("Could not close library; handle was already `nullptr`");
    }

    if (dlclose(handle_.get()) != 0) {
      return Error(
          "Could not close library '" +
          (path_.isSome() ? path_.get() : "") + "': " + dlerror());
    }

    // Release the handle so the default `dlclose` operation is not
    // invoked anymore as after successful explicit `dlclose` it does
    // not point to an open shared object anymore.
    handle_.release();

    handle_ = nullptr;
    path_ = None();

    return Nothing();
  }

  Try<void*> loadSymbol(const std::string& name)
  {
    if (handle_ == nullptr) {
      return Error(
          "Could not get symbol '" + name + "'; library handle was `nullptr`");
    }

    void* symbol = dlsym(handle_.get(), name.c_str());

    if (symbol == nullptr) {
      return Error(
          "Error looking up symbol '" + name + "' in '" +
          (path_.isSome() ? path_.get() : "") + "' : " + dlerror());
    }

    return symbol;
  }

private:
  std::unique_ptr<void, int (*)(void*)> handle_;
  Option<std::string> path_;
};

#endif // __STOUT_POSIX_DYNAMICLIBRARY_HPP__