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authorLaurent Pinchart <laurent.pinchart@ideasonboard.com>2019-01-04 21:09:16 +0200
committerLaurent Pinchart <laurent.pinchart@ideasonboard.com>2019-01-08 16:23:16 +0200
commitd0fd42a4fde6cf29bae760d553d4a4f9b857810f (patch)
tree4c62ca91c483cd274663d6fb5f31d35bda5cbc8a /include
parent8b0de29c416c81be2d98b73effe6c7315b1fc1e1 (diff)
libcamera: Add signal/slot communication mechanism
Introduce a Signal class that allows connecting event sources (signals) to event listeners (slots) without adding any boilerplate code usually associated with the observer or listener design patterns. Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se> Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Diffstat (limited to 'include')
-rw-r--r--include/libcamera/meson.build1
-rw-r--r--include/libcamera/signal.h154
2 files changed, 155 insertions, 0 deletions
diff --git a/include/libcamera/meson.build b/include/libcamera/meson.build
index 3e04557d..6f87689e 100644
--- a/include/libcamera/meson.build
+++ b/include/libcamera/meson.build
@@ -2,6 +2,7 @@ libcamera_api = files([
'camera.h',
'camera_manager.h',
'libcamera.h',
+ 'signal.h',
])
install_headers(libcamera_api,
diff --git a/include/libcamera/signal.h b/include/libcamera/signal.h
new file mode 100644
index 00000000..0b437a48
--- /dev/null
+++ b/include/libcamera/signal.h
@@ -0,0 +1,154 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2019, Google Inc.
+ *
+ * signal.h - Signal & slot implementation
+ */
+#ifndef __LIBCAMERA_SIGNAL_H__
+#define __LIBCAMERA_SIGNAL_H__
+
+#include <list>
+#include <vector>
+
+namespace libcamera {
+
+template<typename... Args>
+class Signal;
+
+template<typename... Args>
+class SlotBase
+{
+public:
+ SlotBase(void *obj)
+ : obj_(obj) { }
+ virtual ~SlotBase() { }
+
+ virtual void invoke(Args... args) = 0;
+
+protected:
+ friend class Signal<Args...>;
+ void *obj_;
+};
+
+template<typename T, typename... Args>
+class SlotMember : public SlotBase<Args...>
+{
+public:
+ SlotMember(T *obj, void(T::*func)(Args...))
+ : SlotBase<Args...>(obj), func_(func) { }
+
+ void invoke(Args... args) { (reinterpret_cast<T *>(this->obj_)->*func_)(args...); }
+
+private:
+ friend class Signal<Args...>;
+ void(T::*func_)(Args...);
+};
+
+template<typename... Args>
+class SlotStatic : public SlotBase<Args...>
+{
+public:
+ SlotStatic(void(*func)(Args...))
+ : SlotBase<Args...>(nullptr), func_(func) { }
+
+ void invoke(Args... args) { (*func_)(args...); }
+
+private:
+ friend class Signal<Args...>;
+ void(*func_)(Args...);
+};
+
+template<typename... Args>
+class Signal
+{
+public:
+ Signal() { }
+ ~Signal()
+ {
+ for (SlotBase<Args...> *slot : slots_)
+ delete slot;
+ }
+
+ template<typename T>
+ void connect(T *object, void(T::*func)(Args...))
+ {
+ slots_.push_back(new SlotMember<T, Args...>(object, func));
+ }
+
+ void connect(void(*func)(Args...))
+ {
+ slots_.push_back(new SlotStatic<Args...>(func));
+ }
+
+ void disconnect()
+ {
+ for (SlotBase<Args...> *slot : slots_)
+ delete slot;
+ slots_.clear();
+ }
+
+ template<typename T>
+ void disconnect(T *object)
+ {
+ for (auto iter = slots_.begin(); iter != slots_.end(); ) {
+ SlotBase<Args...> *slot = *iter;
+ if (slot->obj_ == object) {
+ iter = slots_.erase(iter);
+ delete slot;
+ } else {
+ ++iter;
+ }
+ }
+ }
+
+ template<typename T>
+ void disconnect(T *object, void(T::*func)(Args...))
+ {
+ for (auto iter = slots_.begin(); iter != slots_.end(); ) {
+ SlotBase<Args...> *slot = *iter;
+ /*
+ * If the obj_ pointer matches the object types must
+ * match, so we can safely cast to SlotMember<T, Args>.
+ */
+ if (slot->obj_ == object &&
+ reinterpret_cast<SlotMember<T, Args...> *>(slot)->func_ == func) {
+ iter = slots_.erase(iter);
+ delete slot;
+ } else {
+ ++iter;
+ }
+ }
+ }
+
+ void disconnect(void(*func)(Args...))
+ {
+ for (auto iter = slots_.begin(); iter != slots_.end(); ) {
+ SlotBase<Args...> *slot = *iter;
+ if (slot->obj_ == nullptr &&
+ reinterpret_cast<SlotStatic<Args...> *>(slot)->func_ == func) {
+ iter = slots_.erase(iter);
+ delete slot;
+ } else {
+ ++iter;
+ }
+ }
+ }
+
+ void emit(Args... args)
+ {
+ /*
+ * Make a copy of the slots list as the slot could call the
+ * disconnect operation, invalidating the iterator.
+ */
+ std::vector<SlotBase<Args...> *> slots{ slots_.begin(), slots_.end() };
+ for (SlotBase<Args...> *slot : slots)
+ slot->invoke(args...);
+ }
+
+private:
+ std::list<SlotBase<Args...> *> slots_;
+};
+
+} /* namespace libcamera */
+
+#endif /* __LIBCAMERA_SIGNAL_H__ */