mirror of
https://github.com/matrix-construct/construct
synced 2024-11-30 02:32:43 +01:00
104 lines
3.5 KiB
C++
104 lines
3.5 KiB
C++
/*
|
|
* Copyright (C) 2016 Charybdis Development Team
|
|
* Copyright (C) 2016 Jason Volk <jason@zemos.net>
|
|
*
|
|
* Permission to use, copy, modify, and/or distribute this software for any
|
|
* purpose with or without fee is hereby granted, provided that the above
|
|
* copyright notice and this permission notice is present in all copies.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
|
|
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
|
|
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
|
|
* DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
|
|
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
|
|
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
|
|
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
|
|
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
|
|
* IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
|
|
* POSSIBILITY OF SUCH DAMAGE.
|
|
*
|
|
*/
|
|
|
|
#pragma once
|
|
#define HAVE_IRCD_DB_INDEX_H
|
|
|
|
namespace ircd::db
|
|
{
|
|
struct index;
|
|
}
|
|
|
|
/// An index is a glorified column; the database descriptor for this column
|
|
/// must specify a prefix-extractor otherwise this index just behaves like
|
|
/// a regular key/value column. Index is used to create iterable domains of
|
|
/// a column which all share the same key-prefix.
|
|
///
|
|
/// The index allows a concatenation of two strings to form a key. This con-
|
|
/// catenated key is still unique for the column as a whole and is stored as
|
|
/// the full concatenation -- however, as stated above the prefix function must
|
|
/// be aware of how such a concatenation can be separated back into two
|
|
/// strings.
|
|
///
|
|
/// db::index allows the user to query for either just the first string, or
|
|
/// the whole concatenation. In either case, the resulting iterator can move
|
|
/// only around the keys and values within the domain of that first string.
|
|
/// The iterator presents the user with it.first = second string only, thereby
|
|
/// hiding the prefix allowing for easier iteration of the domain.
|
|
///
|
|
/// Index is not good at reverse iteration due to limitations in RocksDB. Thus
|
|
/// it's better to just flip the comparator function for the column.
|
|
///
|
|
struct ircd::db::index
|
|
:column
|
|
{
|
|
struct const_iterator_base;
|
|
struct const_iterator;
|
|
struct const_reverse_iterator;
|
|
|
|
using iterator_type = const_iterator;
|
|
using const_iterator_type = const_iterator;
|
|
|
|
static const gopts applied_opts;
|
|
|
|
const_iterator end(const string_view &key, gopts = {});
|
|
const_iterator begin(const string_view &key, gopts = {});
|
|
const_reverse_iterator rend(const string_view &key, gopts = {});
|
|
const_reverse_iterator rbegin(const string_view &key, gopts = {});
|
|
|
|
using column::column;
|
|
};
|
|
|
|
struct ircd::db::index::const_iterator_base
|
|
:ircd::db::column::const_iterator_base
|
|
{
|
|
friend class index;
|
|
|
|
const value_type &operator*() const;
|
|
const value_type *operator->() const;
|
|
|
|
using column::const_iterator_base::const_iterator_base;
|
|
|
|
template<class pos> friend bool seek(index::const_iterator_base &, const pos &, gopts = {});
|
|
};
|
|
|
|
struct ircd::db::index::const_iterator
|
|
:ircd::db::index::const_iterator_base
|
|
{
|
|
friend class index;
|
|
|
|
const_iterator &operator++();
|
|
const_iterator &operator--();
|
|
|
|
using index::const_iterator_base::const_iterator_base;
|
|
};
|
|
|
|
struct ircd::db::index::const_reverse_iterator
|
|
:ircd::db::index::const_iterator_base
|
|
{
|
|
friend class index;
|
|
|
|
const_reverse_iterator &operator++();
|
|
const_reverse_iterator &operator--();
|
|
|
|
using index::const_iterator_base::const_iterator_base;
|
|
};
|