mirror of
https://github.com/matrix-construct/construct
synced 2024-08-28 20:35:16 +02:00
115 lines
2.7 KiB
C++
115 lines
2.7 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_DB_COMPARATOR_H
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namespace ircd::db
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{
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struct comparator;
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struct cmp_int64_t;
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struct reverse_cmp_int64_t;
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struct cmp_string_view;
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struct reverse_cmp_string_view;
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}
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struct ircd::db::comparator
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{
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string_view name;
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std::function<bool (const string_view &, const string_view &)> less;
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std::function<bool (const string_view &, const string_view &)> equal;
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};
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struct ircd::db::cmp_string_view
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:db::comparator
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{
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static bool less(const string_view &a, const string_view &b)
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{
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return a < b;
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}
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static bool equal(const string_view &a, const string_view &b)
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{
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return a == b;
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}
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cmp_string_view()
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:db::comparator{"string_view", &less, &equal}
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{}
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};
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struct ircd::db::reverse_cmp_string_view
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:db::comparator
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{
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static bool less(const string_view &a, const string_view &b)
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{
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/// RocksDB sez things will not work correctly unless a shorter string
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/// result returns less than a longer string even if one intends some
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/// reverse ordering
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if(a.size() < b.size())
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return true;
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/// Furthermore, b.size() < a.size() returning false from this function
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/// appears to not be correct. The reversal also has to also come in
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/// the form of a bytewise forward iteration.
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return std::memcmp(a.data(), b.data(), std::min(a.size(), b.size())) > 0;
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}
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static bool equal(const string_view &a, const string_view &b)
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{
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return a == b;
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}
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reverse_cmp_string_view()
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:db::comparator{"reverse_string_view", &less, &equal}
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{}
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};
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struct ircd::db::cmp_int64_t
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:db::comparator
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{
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static bool less(const string_view &sa, const string_view &sb)
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{
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assert(sa.size() == sizeof(int64_t) && sb.size() == sizeof(int64_t));
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const byte_view<int64_t> a{sa}, b{sb};
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return a < b;
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}
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static bool equal(const string_view &sa, const string_view &sb)
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{
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assert(sa.size() == sizeof(int64_t) && sb.size() == sizeof(int64_t));
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const byte_view<int64_t> a{sa}, b{sb};
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return a == b;
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}
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cmp_int64_t()
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:db::comparator{"int64_t", &less, &equal}
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{}
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};
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struct ircd::db::reverse_cmp_int64_t
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:db::comparator
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{
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static bool less(const string_view &a, const string_view &b)
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{
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return !cmp_int64_t::less(a, b);
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}
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static bool equal(const string_view &a, const string_view &b)
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{
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return cmp_int64_t::equal(a, b);
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}
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reverse_cmp_int64_t()
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:db::comparator{"reverse_int64_t", &less, &equal}
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{}
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};
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