mirror of
https://github.com/matrix-construct/construct
synced 2024-08-24 02:24:47 +02:00
136 lines
5.5 KiB
C++
136 lines
5.5 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_CELL_H
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namespace ircd::db
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{
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struct cell;
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const std::string &name(const cell &);
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uint64_t sequence(const cell &);
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template<class pos> bool seek(cell &c, const pos &p, gopts = {});
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std::ostream &operator<<(std::ostream &s, const cell &c);
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}
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/// A cell is a single key-value element existing within a column. This structure
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/// provides the necessary facilities for working with a single cell. Many simple
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/// operations can also be done through the column interface itself so check column.h
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/// for satisfaction. Cells from different columns sharing the same key are composed
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/// into a `row` (see: row.h).
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///
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/// When composed into a `row` or `object` remember that calls to cell::key() will
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/// all be the same index key -- not the name of the column the cell is representing
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/// in the row. You probably want cell::col() when iterating the row to build a
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/// JSON object's keys when iterating across a row.
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///
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/// NOTE that this cell struct is type-agnostic. The database is capable of storing
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/// binary data in the key or the value for a cell. The string_view will work with
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/// both a normal string and binary data, so this class is not a template and offers
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/// no conversions at this level. see: value.h/object.h
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///
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struct ircd::db::cell
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{
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struct delta;
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column c;
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database::snapshot ss;
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std::unique_ptr<rocksdb::Iterator> it;
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public:
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operator const rocksdb::Iterator &() const { return *it; }
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operator const database::snapshot &() const { return ss; }
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explicit operator const column &() const { return c; }
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operator rocksdb::Iterator &() { return *it; }
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operator database::snapshot &() { return ss; }
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explicit operator column &() { return c; }
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bool valid() const; // cell exists
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bool valid(const string_view &) const; // valid equal key
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bool valid_gt(const string_view &) const; // valid greater than key
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bool valid_lte(const string_view &) const; // valid less than or equal key
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operator bool() const { return valid(); }
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bool operator!() const { return !valid(); }
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// [GET] read from cell (zero-copy)
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string_view col() const { return name(c); /* always column name */ }
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string_view key() const; // key == index or empty on invalid
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string_view val() const; // empty on !valid()
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string_view key(); // reload then key == index or empty on invalid
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string_view val(); // reload then empty on !valid()
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// [GET] read from cell (zero-copy)
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explicit operator string_view() const; // empty on !valid()
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explicit operator string_view(); // reload then empty on !valid()
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// [SET] Perform operation on this cell only
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void operator()(const op &, const string_view &val = {}, const sopts & = {});
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// [SET] assign cell
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cell &operator=(const string_view &);
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// [GET] load cell only (returns valid)
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bool load(const string_view &index = {}, gopts = {});
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cell(column, std::unique_ptr<rocksdb::Iterator>, const gopts & = {});
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cell(column, const string_view &index, std::unique_ptr<rocksdb::Iterator>, const gopts & = {});
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cell(column, const string_view &index = {}, const gopts & = {});
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cell(database &, const string_view &column, const string_view &index, const gopts & = {});
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cell(database &, const string_view &column, const gopts & = {});
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cell();
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cell(cell &&) noexcept;
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cell(const cell &) = delete;
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cell &operator=(cell &&) noexcept;
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cell &operator=(const cell &) = delete;
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~cell() noexcept;
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};
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namespace ircd::db
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{
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// [SET] Perform operations in a sequence as a single transaction. No template
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// iterators supported yet, just a ptr range good for contiguous sequences like
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// vectors and initializer_lists. Alternatively, see: iov.h.
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void write(const cell::delta *const &begin, const cell::delta *const &end, const sopts & = {});
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void write(const std::initializer_list<cell::delta> &, const sopts & = {});
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void write(const sopts &, const std::initializer_list<cell::delta> &);
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void write(const cell::delta &, const sopts & = {});
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}
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///
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/// A delta is an element of a database transaction. You can use this to change
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/// the values of cells. Use cell deltas to make an all-succeed-or-all-fail
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/// transaction across many cells in various columns at once.
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///
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struct ircd::db::cell::delta
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:std::tuple<op, cell *, string_view>
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{
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enum
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{
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OP, CELL, VAL,
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};
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delta(cell &c, const string_view &val, const enum op &op = op::SET)
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:std::tuple<enum op, cell *, string_view>{op, &c, val}
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{}
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delta(const enum op &op, cell &c, const string_view &val = {})
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:std::tuple<enum op, cell *, string_view>{op, &c, val}
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{}
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};
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inline std::ostream &
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ircd::db::operator<<(std::ostream &s, const cell &c)
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{
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s << string_view{c};
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return s;
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}
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