From a175314c3e5827eb193872241446f2f8f5c9d33c Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sat, 4 May 2024 20:07:14 +0200 Subject: Adding upstream version 1:10.5.12. Signed-off-by: Daniel Baumann --- storage/rocksdb/atomic_stat.h | 94 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 94 insertions(+) create mode 100644 storage/rocksdb/atomic_stat.h (limited to 'storage/rocksdb/atomic_stat.h') diff --git a/storage/rocksdb/atomic_stat.h b/storage/rocksdb/atomic_stat.h new file mode 100644 index 00000000..04e59bd9 --- /dev/null +++ b/storage/rocksdb/atomic_stat.h @@ -0,0 +1,94 @@ +/* This is an atomic integer abstract data type, for high-performance + tracking of a single stat. It intentionally permits inconsistent + atomic operations and reads, for better performance. This means + that, though no data should ever be lost by this stat, reads of it + at any time may not include all changes up to any particular point. + + So, values read from these may only be approximately correct. + + If your use-case will fail under these conditions, do not use this. + + Copyright (C) 2012 - 2014 Steaphan Greene + + This program is free software; you can redistribute it and/or + modify it under the terms of the GNU General Public License + as published by the Free Software Foundation; either version 2 + of the License, or (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program; if not, write to the + Free Software Foundation, Inc. + 51 Franklin Street, Fifth Floor + Boston, MA 02110-1301, USA. +*/ + +#ifndef _atomic_stat_h_ +#define _atomic_stat_h_ + +#include + +template < typename TYPE > +class atomic_stat { +public: + // Initialize value to the default for the type + atomic_stat() : value_(TYPE()) {}; + + // This enforces a strict order, as all absolute sets should + void clear() { + value_.store(TYPE(), std::memory_order_seq_cst); + }; + + // Reads can get any valid value, it doesn't matter which, exactly + TYPE load() const { + return value_.load(std::memory_order_relaxed); + }; + + // This only supplies relative arithmetic operations + // These are all done atomically, and so can show up in any order + void inc(const TYPE &other) { + value_.fetch_add(other, std::memory_order_relaxed); + }; + + void dec(const TYPE &other) { + value_.fetch_sub(other, std::memory_order_relaxed); + }; + + void inc() { + value_.fetch_add(1, std::memory_order_relaxed); + }; + + void dec() { + value_.fetch_sub(1, std::memory_order_relaxed); + }; + + // This will make one attempt to set the value to the max of + // the current value, and the passed-in value. It can fail + // for any reason, and we only try it once. + void set_max_maybe(const TYPE &new_val) { + TYPE old_val = value_; + if (new_val > old_val) { + value_.compare_exchange_weak(old_val, new_val, + std::memory_order_relaxed, + std::memory_order_relaxed); + } + }; + + // This will make one attempt to assign the value to the passed-in + // value. It can fail for any reason, and we only try it once. + void set_maybe(const TYPE &new_val) { + TYPE old_val = value_; + value_.compare_exchange_weak(old_val, new_val, + std::memory_order_relaxed, + std::memory_order_relaxed); + }; + +private: + std::atomic value_; +}; + +#endif // _atomic_stat_h_ -- cgit v1.2.3