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Diffstat (limited to 'src/libutil/lazy.hh')
-rw-r--r-- | src/libutil/lazy.hh | 48 |
1 files changed, 0 insertions, 48 deletions
diff --git a/src/libutil/lazy.hh b/src/libutil/lazy.hh deleted file mode 100644 index d073e486c..000000000 --- a/src/libutil/lazy.hh +++ /dev/null @@ -1,48 +0,0 @@ -#include <exception> -#include <functional> -#include <mutex> - -namespace nix { - -/* A helper class for lazily-initialized variables. - - Lazy<T> var([]() { return value; }); - - declares a variable of type T that is initialized to 'value' (in a - thread-safe way) on first use, that is, when var() is first - called. If the initialiser code throws an exception, then all - subsequent calls to var() will rethrow that exception. */ -template<typename T> -class Lazy -{ - - typedef std::function<T()> Init; - - Init init; - - std::once_flag done; - - T value; - - std::exception_ptr ex; - -public: - - Lazy(Init init) : init(init) - { } - - const T & operator () () - { - std::call_once(done, [&]() { - try { - value = init(); - } catch (...) { - ex = std::current_exception(); - } - }); - if (ex) std::rethrow_exception(ex); - return value; - } -}; - -} |