mirror of
https://github.com/matrix-construct/construct
synced 2024-11-09 11:31:11 +01:00
106 lines
3 KiB
C++
106 lines
3 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) 2016-2019 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_M_QUERY_H
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namespace ircd::m
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{
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template<class R> R query(std::nothrow_t, const event::idx &, const string_view &key, R&& def, const std::function<R (const string_view &)> &);
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template<class F> auto query(std::nothrow_t, const event::idx &, const string_view &key, F&&);
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template<class R, class F> R query(const event::idx &, const string_view &key, R&& def, F&&);
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template<class F> auto query(const event::idx &, const string_view &key, F&&);
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}
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/// Like m::get(), but the closure returns a value which will then be returned
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/// by these functions. This elides the pattern of returning a result through
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/// the lambda capture when one simply wants to condition on the fetched value
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/// rather than make further use of it.
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///
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template<class F>
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auto
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ircd::m::query(const event::idx &event_idx,
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const string_view &key,
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F&& closure)
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{
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using R = typename std::invoke_result<F, const string_view &>::type;
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R ret;
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m::get(event_idx, key, [&ret, &closure]
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(const string_view &value)
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{
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ret = closure(value);
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});
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return ret;
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}
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template<class R,
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class F>
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R
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ircd::m::query(const event::idx &event_idx,
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const string_view &key,
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R&& r,
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F&& f)
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{
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return query(std::nothrow, event_idx, key, std::forward<R>(r), std::forward<F>(f));
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}
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/// See other overload documentation first. This overload implements
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/// non-throwing behavior when the event_idx/key(column) is not found by
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/// calling the closure with a default-constructed string so the closure can
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/// return a default value.
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///
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template<class F>
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auto
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ircd::m::query(std::nothrow_t,
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const event::idx &event_idx,
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const string_view &key,
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F&& closure)
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{
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using R = typename std::invoke_result<F, const string_view &>::type;
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R ret;
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const auto assign
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{
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[&ret, &closure](const string_view &value)
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{
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ret = closure(value);
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}
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};
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if(unlikely(!m::get(std::nothrow, event_idx, key, assign)))
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assign(string_view{});
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return ret;
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}
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/// See other overload documentation first. This overload implements
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/// non-throwing behavior when the event_idx/key(column) is not found by
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/// returning a default value supplied by the caller.
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///
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template<class R>
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R
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ircd::m::query(std::nothrow_t,
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const event::idx &event_idx,
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const string_view &key,
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R&& default_,
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const std::function<R (const string_view &)> &closure)
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{
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R ret{std::forward<R>(default_)};
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m::get(std::nothrow, event_idx, key, [&ret, &closure]
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(const string_view &value)
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{
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ret = closure(value);
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});
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return ret;
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}
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