mirror of
https://github.com/matrix-construct/construct
synced 2024-11-16 15:00:51 +01:00
78 lines
2 KiB
C++
78 lines
2 KiB
C++
// Matrix Construct
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//
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// Copyright (C) Matrix Construct Developers, Authors & Contributors
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// Copyright (C) 2016-2018 Jason Volk <jason@zemos.net>
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//
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// Permission to use, copy, modify, and/or distribute this software for any
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// purpose with or without fee is hereby granted, provided that the above
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// copyright notice and this permission notice is present in all copies. The
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// full license for this software is available in the LICENSE file.
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#pragma once
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#define HAVE_IRCD_UTIL_VA_RTTI_H
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namespace ircd {
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inline namespace util
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{
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struct va_rtti;
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const size_t VA_RTTI_MAX_SIZE
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{
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12
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};
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}}
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//
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// Similar to a va_list, but conveying std-c++ type data acquired from a variadic template
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// parameter pack acting as the ...) elipsis. This is used to implement fmt::snprintf(),
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// exceptions and logger et al in their respective translation units rather than the header
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// files.
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//
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// Limitations: The choice of a fixed array of N is because std::initializer_list doesn't
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// work here and other containers may be heavy in this context. Ideas to improve this are
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// welcome.
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//
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struct ircd::util::va_rtti
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:std::array<std::tuple<const void *, const std::type_info *>, ircd::util::VA_RTTI_MAX_SIZE>
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{
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using base_type = std::array<value_type, ircd::util::VA_RTTI_MAX_SIZE>;
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static constexpr size_t max_size()
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{
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return std::tuple_size<base_type>();
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}
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size_t argc;
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const size_t &size() const
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{
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return argc;
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}
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template<class... Args>
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va_rtti(Args&&... args)
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:base_type
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{{
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std::make_tuple(std::addressof(args), std::addressof(typeid(Args)))...
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}}
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,argc
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{
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sizeof...(args)
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}
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{
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assert(argc <= max_size());
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static_assert
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(
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sizeof...(args) <= max_size(),
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"Too many arguments to va_rtti"
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);
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}
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};
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static_assert
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(
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sizeof(ircd::util::va_rtti) == (ircd::util::va_rtti::max_size() * 16) + 8,
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"va_rtti should be (8 + 8) * N + 8;"
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" where 8 + 8 are the two pointers carrying the argument and its type data;"
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" where N is the max arguments;"
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" where the final + 8 bytes holds the actual number of arguments passed;"
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);
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