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Diffstat (limited to '')
-rw-r--r-- | src/common/item_history.h | 47 |
1 files changed, 47 insertions, 0 deletions
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 <list> +#include <mutex> + +/* + +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 T> +class safe_item_history { +private: + std::mutex lock; + std::list<T> 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; + } + +}; |