39 lines
1.2 KiB
C++
39 lines
1.2 KiB
C++
/*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/.
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*
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* Copyright 2017-2019 Danny Robson <danny@nerdcruft.net>
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*/
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#pragma once
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#include <cstdint>
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namespace cruft {
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namespace detail { int typeidx_next (void); }
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/// Return a globally unique runtime ID for a given type.
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///
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/// This is intended to be used as a lightweight type check for variants
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/// and such without requiring RTTI.
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///
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/// The identifier is constructed at runtime and is not guaranteed to be
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/// stable across executions (particularly in the case of threads and
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/// other non-determinism). However it _is_ threadsafe to call this.
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///
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/// The value 0 will never be returned from this function and can be used
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/// to indicate an 'unknown' state.
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///
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/// The range of identifiers is _probably_ contiguous. This should not
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/// be relied upon for correctness, but may be used for performance
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/// concerns.
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template <typename T>
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int
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typeidx (void)
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{
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static auto id = detail::typeidx_next ();
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return id;
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}
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}
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