src/cam/event_loop.h

/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
 * Copyright (C) 2020, Google Inc.
 *
 * span.h - C++20 std::span<> implementation for C++11
 */

#pragma once

#include <array>
#include <iterator>
#include <limits>
#include <stddef.h>
#include <type_traits>

namespace libcamera {

static constexpr std::size_t dynamic_extent = std::numeric_limits<std::size_t>::max();

template<typename T, std::size_t Extent = dynamic_extent>
class Span;

namespace details {

template<typename U>
struct is_array : public std::false_type {
};

template<typename U, std::size_t N>
struct is_array<std::array<U, N>> : public std::true_type {
};

template<typename U>
struct is_span : public std::false_type {
};

template<typename U, std::size_t Extent>
struct is_span<Span<U, Extent>> : public std::true_type {
};

} /* namespace details */

namespace utils {

template<typename C>
constexpr auto size(const C &c) -> decltype(c.size())
{
	return c.size();
}

template<typename C>
constexpr auto data(const C &c) -> decltype(c.data())
{
	return c.data();
}

template<typename C>
constexpr auto data(C &c) -> decltype(c.data())
{
	return c.data();
}

template<class T, std::size_t N>
constexpr T *data(T (&array)[N]) noexcept
{
	return array;
}

template<std::size_t I, typename T>
struct tuple_element;

template<std::size_t I, typename T, std::size_t N>
struct tuple_element<I, Span<T, N>> {
	using type = T;
};

template<typename T>
struct tuple_size;

template<typename T, std::size_t N>
struct tuple_size<Span<T, N>> : public std::integral_constant<std::size_t, N> {
};

template<typename T>
struct tuple_size<Span<T, dynamic_extent>>;

} /* namespace utils */

template<typename T, std::size_t Extent>
class Span
{
public:
	using element_type = T;
	using value_type = typename std::remove_cv_t<T>;
	using size_type = std::size_t;
	using difference_type = std::ptrdiff_t;
	using pointer = T *;
	using const_pointer = const T *;
	using reference = T &;
	using const_reference = const T &;
	using iterator = pointer;
	using const_iterator = const_pointer;
	using reverse_iterator = std::reverse_iterator<iterator>;
	using const_reverse_iterator = std::reverse_iterator<const_iterator>;

	static constexpr std::size_t extent = Extent;

	template<bool Dependent = false,
		 typename = std::enable_if_t<Dependent || Extent == 0>>
	constexpr Span() noexcept
		: data_(nullptr)
	{
	}

	explicit constexpr Span(pointer ptr, [[maybe_unused]] size_type count)
		: data_(ptr)
	{
	}

	explicit constexpr Span(pointer first, [[maybe_unused]] pointer last)
		: data_(first)
	{
	}

	template<std::size_t N>
	constexpr Span(element_type (&arr)[N],
		       std::enable_if_t<std::is_convertible<std::remove_pointer_t<decltype(utils::data(arr))> (*)[],
							    element_type (*)[]>::value &&
					N == Extent,
					std::nullptr_t> = nullptr) noexcept
		: data_(arr)
	{
	}

	template<std::size_t N>
	constexpr Span(std::array<value_type, N> &arr,
		       std::enable_if_t<std::is_convertible<std::remove_pointer_t<decltype(utils::data(arr))> (*)[],
							    element_type (*)[]>::value &&
					N == Extent,
					std::nullptr_t> = nullptr) noexcept
		: data_(arr.data())
	{
	}

	template<std::size_t N>
	constexpr Span(const std::array<value_type, N> &arr,
		       std::enable_if_t<std::is_convertible<std::remove_pointer_t<decltype(utils::data(arr))> (*)[],
							    element_type (*)[]>::value &&
					N == Extent,
					std::nullptr_t> = nullptr) noexcept
		: data_(arr.data())
	{
	}

	template<class Container>
	explicit constexpr Span(Container &cont,
				std::enable_if_t<!details::is_span<Container>::value &&
						 !details::is_array<Container>::value &&
						 !std::is_array<Container>::value &&
						 std::is_convertible<std::remove_pointer_t<decltype(utils::data(cont))> (*)[],
								     element_type (*)[]>::value,
						 std::nullptr_t> = nullptr)
		: data_(utils::data(cont))
	{
	}

	template<class Container>
	explicit constexpr Span(const Container &cont,
				std::enable_if_t<!details::is_span<Container>::value &&
						 !details::is_array<Container>::value &&
						 !std::is_array<Container>::value &&
						 std::is_convertible<std::remove_pointer_t<decltype(utils::data(cont))> (*)[],
								     element_type (*)[]>::value,
						 std::nullptr_t> = nullptr)
		: data_(utils::data(cont))
	{
		static_assert(utils::size(cont) == Extent, "Size mismatch");
	}

	template<class U, std::size_t N>
	explicit constexpr Span(const Span<U, N> &s,
				std::enable_if_t<std::is_convertible<U (*)[], element_type (*)[]>::value &&
						 N == Extent,
						 std::nullptr_t> = nullptr) noexcept
		: data_(s.data())
	{
	}

	constexpr Span(const Span &other) noexcept = default;
	constexpr Span &operator=(const Span &other) noexcept = default;

	constexpr iterator begin() const { return data(); }
	constexpr const_iterator cbegin() const { return begin(); }
	constexpr iterator end() const { return data() + size(); }
	constexpr const_iterator cend() const { return end(); }
	constexpr reverse_iterator rbegin() const { return reverse_iterator(end()); }
	constexpr const_reverse_iterator crbegin() const { return rbegin(); }
	constexpr reverse_iterator rend() const { return reverse_iterator(begin()); }
	constexpr const_reverse_iterator crend() const { return rend(); }

	constexpr reference front() const { return *data(); }
	constexpr reference back() const { return *(data() + size() - 1); }
	constexpr reference operator[](size_type idx) const { return data()[idx]; }
	constexpr pointer data() const noexcept { return data_; }

	constexpr size_type size() const noexcept { return Extent; }
	constexpr size_type size_bytes() const noexcept { return size() * sizeof(element_type); }
	constexpr bool empty() const noexcept { return size() == 0; }

	template<std::size_t Count>
	constexpr Span<element_type, Count> first() const
	{
		static_assert(Count <= Extent, "Count larger than size");
		return Span<element_type, Count>{ data(), Count };
	}

	constexpr Span<element_type, dynamic_extent> first(std::size_t Count) const
	{
		return Span<element_type, dynamic_extent>{ data(), Count };
	}

	template<std::size_t Count>
	constexpr Span<element_type, Count> last() const
	{
		static_assert(Count <= Extent, "Count larger than size");
		return Span<element_type, Count>{ data() + size() - Count, Count };
	}

	constexpr Span<element_type, dynamic_extent> last(std::size_t Count) const
	{
		return Span<element_type, dynamic_extent>{ data() + size() - Count, Count };
	}

	template<std::size_t Offset, std::size_t Count = dynamic_extent>
	constexpr Span<element_type, Count != dynamic_extent ? Count : Extent - Offset> subspan() const
	{
		static_assert(Offset <= Extent, "Offset larger than size");
		static_assert(Count == dynamic_extent || Count + Offset <= Extent,
			      "Offset + Count larger than size");
		return Span<element_type, Count != dynamic_extent ? Count : Extent - Offset>{
			data() + Offset,
			Count == dynamic_extent ? size() - Offset : Count
		};
	}

	constexpr Span<element_type, dynamic_extent>
	subspan(std::size_t Offset, std::size_t Count = dynamic_extent) const
	{
		return Span<element_type, dynamic_extent>{
			data() + Offset,
			Count == dynamic_extent ? size() - Offset : Count
		};
	}

private:
	pointer data_;
};

template<typename T>
class Span<T, dynamic_extent>
{
public:
	using element_type = T;
	using value_type = typename std::remove_cv_t<T>;
	using size_type = std::size_t;
	using difference_type = std::ptrdiff_t;
	using pointer = T *;
	using const_pointer = const T *;
	using reference = T &;
	using const_reference = const T &;
	using iterator = T *;
	using const_iterator = const T *;
	using reverse_iterator = std::reverse_iterator<iterator>;
	using const_reverse_iterator = std::reverse_iterator<const_iterator>;

	static constexpr std::size_t extent = dynamic_extent;

	constexpr Span() noexcept
		: data_(nullptr), size_(0)
	{
	}

	constexpr Span(pointer ptr, size_type count)
		: data_(ptr), size_(count)
	{
	}

	constexpr Span(pointer first, pointer last)
		: data_(first), size_(last - first)
	{
	}

	template<std::size_t N>
	constexpr Span(element_type (&arr)[N],
		       std::enable_if_t<std::is_convertible<std::remove_pointer_t<decltype(utils::data(arr))> (*)[],
							    element_type (*)[]>::value,
					std::nullptr_t> = nullptr) noexcept
		: data_(arr), size_(N)
	{
	}

	template<std::size_t N>
	constexpr Span(std::array<value_type, N> &arr,
		       std::enable_if_t<std::is_convertible<std::remove_pointer_t<decltype(utils::data(arr))> (*)[],
							    element_type (*)[]>::value,
					std::nullptr_t> = nullptr) noexcept
		: data_(utils::data(arr)), size_(N)
	{
	}

	template<std::size_t N>
	constexpr Span(const std::array<value_type, N> &arr) noexcept
		: data_(utils::data(arr)), size_(N)
	{
	}

	template<class Container>
	constexpr Span(Container &cont,
		       std::enable_if_t<!details::is_span<Container>::value &&
					!details::is_array<Container>::value &&
					!std::is_array<Container>::value &&
					std::is_convertible<std::remove_pointer_t<decltype(utils::data(cont))> (*)[],
							    element_type (*)[]>::value,
					std::nullptr_t> = nullptr)
		: data_(utils::data(cont)), size_(utils::size(cont))
	{
	}

	template<class Container>
	constexpr Span(const Container &cont,
		       std::enable_if_t<!details::is_span<Container>::value &&
					!details::is_array<Container>::value &&
					!std::is_array<Container>::value &&
					std::is_convertible<std::remove_pointer_t<decltype(utils::data(cont))> (*)[],
							    element_type (*)[]>::value,
					std::nullptr_t> = nullptr)
		: data_(utils::data(cont)), size_(utils::size(cont))
	{
	}

	template<class U, std::size_t N>
	constexpr Span(const Span<U, N> &s,
		       std::enable_if_t<std::is_convertible<U (*)[], element_type (*)[]>::value,
					std::nullptr_t> = nullptr) noexcept
		: data_(s.data()), size_(s.size())
	{
	}

	constexpr Span(const Span &other) noexcept = default;

	constexpr Span &operator=(const Span &other) noexcept
	{
		data_ = other.data_;
		size_ = other.size_;
		return *this;
	}

	constexpr iterator begin() const { return data(); }
	constexpr const_iterator cbegin() const { return begin(); }
	constexpr iterator end() const { return data() + size(); }
	constexpr const_iterator cend() const { return end(); }
	constexpr reverse_iterator rbegin() const { return reverse_iterator(end()); }
	constexpr const_reverse_iterator crbegin() const { return rbegin(); }
	constexpr reverse_iterator rend() const { return reverse_iterator(begin()); }
	constexpr const_reverse_iterator crend() const { return rend(); }

	constexpr reference front() const { return *data(); }
	constexpr reference back() const { return *(data() + size() - 1); }
	constexpr reference operator[](size_type idx) const { return data()[idx]; }
	constexpr pointer data() const noexcept { return data_; }

	constexpr size_type size() const noexcept { return size_; }
	constexpr size_type size_bytes() const noexcept { return size() * sizeof(element_type); }
	constexpr bool empty() const noexcept { return size() == 0; }

	template<std::size_t Count>
	constexpr Span<element_type, Count> first() const
	{
		return Span<element_type, Count>{ data(), Count };
	}

	constexpr Span<element_type, dynamic_extent> first(std::size_t Count) const
	{
		return { data(), Count };
	}

	template<std::size_t Count>
	constexpr Span<element_type, Count> last() const
	{
		return Span<element_type, Count>{ data() + size() - Count, Count };
	}

	constexpr Span<element_type, dynamic_extent> last(std::size_t Count) const
	{
		return Span<element_type, dynamic_extent>{ data() + size() - Count, Count };
	}

	template<std::size_t Offset, std::size_t Count = dynamic_extent>
	constexpr Span<element_type, Count> subspan() const
	{
		return Span<element_type, Count>{
			data() + Offset,
			Count == dynamic_extent ? size() - Offset : Count
		};
	}

	constexpr Span<element_type, dynamic_extent>
	subspan(std::size_t Offset, std::size_t Count = dynamic_extent) const
	{
		return Span<element_type, dynamic_extent>{
			data() + Offset,
			Count == dynamic_extent ? size() - Offset : Count
		};
	}

private:
	pointer data_;
	size_type size_;
};

} /* namespace libcamera */
Age	Commit message (Collapse)	Author
2022-05-23	cam: event_loop: Add timer events to event loop	Eric Curtin
	Extend the EventLoop class to support periodic timer events. This can be used to run tasks periodically, such as handling the event loop of SDL. Signed-off-by: Eric Curtin <ecurtin@redhat.com> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com> Tested-by: Jacopo Mondi <jacopo@jmondi.org> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
2022-05-23	cam: event_loop: Rename addEvent to addFdEvent	Eric Curtin
	With the addition of addTimerEvent, the naming of addEvent is specific to the management of an fd, while the naming is generic. Update the name to make the naming scheme consistent in specifying the type of event to be added. Signed-off-by: Eric Curtin <ecurtin@redhat.com> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com> Tested-by: Jacopo Mondi <jacopo@jmondi.org> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
2021-11-24	cam: Convert to pragma once	Kieran Bingham
	Remove the verbose #ifndef/#define/#endif pattern for maintaining header idempotency, and replace it with a simple #pragma once. This simplifies the headers, and prevents redundant changes when header files get moved. Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Reviewed-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
2021-08-05	cam: event_loop: Add support for file descriptor events	Laurent Pinchart
	Extend the EventLoop class to support watching file descriptors for read and write events. Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se> Reviewed-by: Paul Elder <paul.elder@ideasonboard.com> Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com> Reviewed-by: Umang Jain <umang.jain@ideasonboard.com>
2021-02-05	cam: event_loop: Execute events in the libevent loop	Niklas Söderlund
	Cam uses libevent to deal with threads and idle loop while still implementing its own event queue. This creates issues when the event loop is terminated as it might get stuck in the idle loop if exit() is called while the thread is busy with dispatchCalls(). Solve this by removing the custom event execution and instead injecting the calls as events to the base event loop. Reported-by: Sebastian Fricke <sebastian.fricke@posteo.net> Signed-off-by: Niklas Söderlund <niklas.soderlund@ragnatech.se> Reviewed-by: Jacopo Mondi <jacopo@jmondi.org> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
2021-02-05	cam: event_loop: Rename event_ to base_	Niklas Söderlund
	The 'event' variable name is usually used for events added to the base event loop, not the loop itself. Rename the struct event_base member to base_ as a preparation for future work adding events to the loop. There is no functional change. Signed-off-by: Niklas Söderlund <niklas.soderlund@ragnatech.se> Reviewed-by: Jacopo Mondi <jacopo@jmondi.org> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
2020-11-15	cam: event_loop: Add deferred calls support	Laurent Pinchart
	Add a deferred cals queue to the EventLoop class to support queuing calls from a different thread and processing them in the event loop's thread. Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com> Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
2020-11-15	cam: Use libevent to implement event loop	Laurent Pinchart
	To prepare for removal of the EventDispatcher from the libcamera public API, switch to libevent to handle the event loop. Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com> Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
2019-11-08	libcamera: Remove unneeded semicolons	Laurent Pinchart
	Comply with the coding style by removing lots of unneeded semicolons. Fix a few other coding style violations on the lines touched by those fixes. Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
2019-01-25	cam: Add event loop	Laurent Pinchart
	Add a simple event loop to the cam application and use it in the main() function, with an example of how to handle SIGINT to gracefully stop the loop. Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>