callback_container.hpp

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#pragma once
#include <ossia/detail/config.hpp>
 
#include <ossia/detail/mutex.hpp>
 
#if defined(__cpp_exceptions)
#include <exception>
#endif
#include <list>
#include <mutex>
 
namespace ossia
{
 
#if defined(__cpp_exceptions)
struct OSSIA_EXPORT invalid_callback_error final : public std::exception
{
  ~invalid_callback_error() override;
  invalid_callback_error();
  const char* what() const noexcept override;
};
#endif
 
template <typename T>
class callback_container
{
  using mutex = OSSIA_CALLBACK_CONTAINER_MUTEX;
  using lock_guard = std::lock_guard<mutex>;
 
public:
  callback_container() = default;
  callback_container(const callback_container& other)
  {
    lock_guard lck{other.m_mutx};
    m_callbacks = other.m_callbacks;
  }
  callback_container(callback_container&& other) noexcept
  {
    lock_guard lck{other.m_mutx};
    m_callbacks = std::move(other.m_callbacks);
  }
  callback_container& operator=(const callback_container& other)
  {
    lock_guard lck{other.m_mutx};
    m_callbacks = other.m_callbacks;
    return *this;
  }
  callback_container& operator=(callback_container&& other) noexcept
  {
    lock_guard lck{other.m_mutx};
    m_callbacks = std::move(other.m_callbacks);
    return *this;
  }
 
  virtual ~callback_container() = default;
 
  using impl = std::list<T>;
  using iterator = typename impl::iterator;
 
  iterator add_callback(T&& callback)
  {
    if(callback)
    {
      lock_guard lck{m_mutx};
      auto it = m_callbacks.insert(m_callbacks.begin(), std::move(callback));
      if(m_callbacks.size() == 1)
        on_first_callback_added();
      return it;
    }
    else
    {
#if defined(__cpp_exceptions)
      throw invalid_callback_error{};
#else
      return {};
#endif
    }
  }
 
  void remove_callback(iterator it)
  {
    lock_guard lck{m_mutx};
    if(m_callbacks.size() == 1)
      on_removing_last_callback();
 
    m_callbacks.erase(it);
  }
 
  void replace_callback(iterator it, T&& cb)
  {
    lock_guard lck{m_mutx};
    *m_callbacks.erase(it, it) = std::move(cb);
  }
 
  void replace_callbacks(impl&& cbs)
  {
    lock_guard lck{m_mutx};
    m_callbacks = std::move(cbs);
  }
 
  class disabled_callback
  {
  public:
    explicit disabled_callback(callback_container& self)
        : self{self}
        , old_callbacks{self.m_callbacks}
    {
    }
 
    ~disabled_callback() { self.replace_callbacks(std::move(old_callbacks)); }
 
  private:
    callback_container& self;
    callback_container::impl old_callbacks;
  };
 
  disabled_callback disable_callback(iterator it)
  {
    lock_guard lck{m_mutx};
    disabled_callback dis{*this};
 
    // TODO should we also call on_removing_last_blah ?
    // I don't think so : it's supposed to be a short operation
    m_callbacks.erase(it);
    return dis;
  }
 
  std::size_t callback_count() const
  {
    lock_guard lck{m_mutx};
    return m_callbacks.size();
  }
 
  bool callbacks_empty() const
  {
    lock_guard lck{m_mutx};
    return m_callbacks.empty();
  }
 
  template <typename... Args>
  void send(Args&&... args)
  {
    lock_guard lck{m_mutx};
    for(auto& callback : m_callbacks)
    {
      if(callback)
        callback(std::forward<Args>(args)...);
    }
  }
 
  void callbacks_clear()
  {
    lock_guard lck{m_mutx};
    if(!m_callbacks.empty())
      on_removing_last_callback();
    m_callbacks.clear();
  }
 
protected:
  virtual void on_first_callback_added() { }
 
  virtual void on_removing_last_callback() { }
 
  //private:
public:
  impl m_callbacks TS_GUARDED_BY(m_mutx);
  mutable mutex m_mutx;
};
 
}