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The open source OpenXR runtime
u/limited_unique_id: Add process unique id generator
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src/xrt/auxiliary/util/CMakeLists.txt
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src/xrt/auxiliary/util/CMakeLists.txt
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src/xrt/auxiliary/util/u_limited_unique_id.cpp
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src/xrt/auxiliary/util/u_limited_unique_id.cpp
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// Copyright 2023, Collabora, Ltd.
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// SPDX-License-Identifier: BSL-1.0
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/*!
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* @file
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* @brief A very simple generator to create process unique ids.
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* @author Jakob Bornecrantz <jakob@collabora.com>
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* @ingroup aux_util
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*/
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#include "u_limited_unique_id.h"
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#include <atomic>
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/*
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* This code is in C++ and not C because MSVC doesn't implement C atomics yet,
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* but to make things even more fun the C++11 standard defines atomic_uint64_t
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* as optional, but atomic_uint_fast64_t is listed as required, so here we are.
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*/
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static std::atomic_uint_fast64_t generator;
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extern "C" xrt_limited_unique_id_t
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u_limited_unique_id_get(void)
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{
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return xrt_limited_unique_id_t{static_cast<uint64_t>(++generator)};
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}
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src/xrt/auxiliary/util/u_limited_unique_id.h
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src/xrt/auxiliary/util/u_limited_unique_id.h
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// Copyright 2023, Collabora, Ltd.
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// SPDX-License-Identifier: BSL-1.0
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/*!
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* @file
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* @brief A very simple generator to create process unique ids.
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* @author Jakob Bornecrantz <jakob@collabora.com>
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* @ingroup aux_util
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*/
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#pragma once
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#include "xrt/xrt_defines.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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/*!
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* This function returns a unsigned 64 bit value that is guaranteed to be unique
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* within the current running process, and not zero. There is of course the
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* limit of running out of those ID once all values has been returned, but the
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* value is 64 bit so that should not be a practical limit. The value is useful
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* when needing to implement caching of a complex object, this lets us not use
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* memory addresses as keys which may be reused by underlying alloc
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* implementation and could lead to false hits.
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*
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* The current implementation is naive and is a simple monotonic counter.
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*
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* @ingroup aux_util
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*/
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xrt_limited_unique_id_t
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u_limited_unique_id_get(void);
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#ifdef __cplusplus
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}
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#endif