From 19fcec84d8d7d21e796c7624e521b60d28ee21ed Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 20:45:59 +0200 Subject: Adding upstream version 16.2.11+ds. Signed-off-by: Daniel Baumann --- src/common/item_history.h | 47 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 47 insertions(+) create mode 100644 src/common/item_history.h (limited to 'src/common/item_history.h') diff --git a/src/common/item_history.h b/src/common/item_history.h new file mode 100644 index 000000000..87512a28c --- /dev/null +++ b/src/common/item_history.h @@ -0,0 +1,47 @@ +// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*- +// vim: ts=8 sw=2 smarttab + +#pragma once + +#include +#include + +/* + +Keep a history of item values so that readers can dereference the pointer to +the latest value and continue using it as long as they want. This container +is only appropriate for values that are updated a handful of times over their +total lifetime. + +*/ + +template +class safe_item_history { +private: + std::mutex lock; + std::list history; + T *current = nullptr; + +public: + safe_item_history() { + history.emplace_back(T()); + current = &history.back(); + } + + // readers are lock-free + const T& operator*() const { + return *current; + } + const T *operator->() const { + return current; + } + + // writes are serialized + const T& operator=(const T& other) { + std::lock_guard l(lock); + history.push_back(other); + current = &history.back(); + return *current; + } + +}; -- cgit v1.2.3