mozaic/lib/av/av_base.hpp

#pragma once

extern "C" {
#include <libavutil/mem.h>
}

#include <stdexcept>
#include <memory>

namespace av {
	// Generic error class
	struct error : public std::runtime_error {
		using runtime_error::runtime_error;
	};

	// Type of a freeing function (for wrapper)
	template <typename T>
	using deleter = void(*)(T*);

	// Kind of unique_ptr, but with const-semantics
	template <typename T, typename D = deleter<T>>
	struct wrapper {
		wrapper(T * data_ = nullptr, D deleter_ = D())
		: data(data_)
		, deleter(deleter_)
		{}

		wrapper(wrapper && o)
		: data(o.data)
		, deleter(o.deleter)
		{ o.release(); }

		wrapper & operator=(wrapper && o) {
			data = o.data;
			deleter = o.deleter;
			o.release();
			return *this;
		}

		wrapper(wrapper const & o) = delete;
		wrapper & operator=(wrapper const & o) = delete;

		~wrapper(){ reset(); }

		T *       get()       { return data; }
		T const * get() const { return data; }
		T &       operator*()       { return *get(); }
		T const & operator*() const { return *get(); }
		T *       operator->()       { return get(); }
		T const * operator->() const { return get(); }

		T * release() { auto t = data; data = nullptr; return t; }
		void reset() { if(data && deleter) deleter(data); data = nullptr; }
		operator bool() const { return get(); }
	private:
		T * data;
		D deleter;
	};

	// Allocator
	template <typename T>
	struct allocator {
		using value_type = T;
		using size_type = size_t;

		T* allocate(size_type n) const {
			auto ptr = av_malloc(n * sizeof(T));
			if(!ptr) throw std::bad_alloc();
			return static_cast<T*>(ptr);
		}

		void deallocate(T* ptr, size_type /*n*/) const noexcept {
			av_free(ptr);
		}
	};

	template <typename T, typename S>
	bool operator==(allocator<T> const &, allocator<S> const &) noexcept { return true; }
	template <typename T, typename S>
	bool operator!=(allocator<T> const &, allocator<S> const &) noexcept { return false; }
}