106 lines
3.3 KiB
C++
106 lines
3.3 KiB
C++
//
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// ZoneMinder Monitor Class Interfaces
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// Copyright (C) 2022 ZoneMinder Inc
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//
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// This program is free software; you can redistribute it and/or
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// modify it under the terms of the GNU General Public License
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// as published by the Free Software Foundation; either version 2
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// of the License, or (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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//
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#ifndef ZM_MONITORLINK_EVAL_H
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#define ZM_MONITORLINK_EVAL_H
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#include "zm_utils.h"
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#include "zm_monitorlink_token.h"
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#include <istream>
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#include <string>
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class MonitorLinkExpression {
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public:
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/**
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* struct node
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*
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* Represents the tree node containing references to left and right child nodes
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* as well as the token that the node represents in the actual expression tree.
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*/
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class Node {
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public:
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Token token{ Token::TokenType::unknown };
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std::unique_ptr< Node > left { nullptr };
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std::unique_ptr< Node > right{ nullptr };
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constexpr Node() noexcept = default;
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Node( Node && rhs ) noexcept = default;
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Node( Node const & rhs ) noexcept = delete;
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constexpr Node(Token::TokenType const type) noexcept : token(type) {}
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constexpr Node(Token const &token) noexcept : token(token) {}
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Node & operator=( Node && rhs ) noexcept = default;
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Node & operator=( Node const & rhs ) noexcept = delete;
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~Node() noexcept = default;
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};
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struct Result {
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/**
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* True if evaluation process is successful. Otherwise, false.
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*/
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bool success{ false };
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/**
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* Message in case of the fault.
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*/
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std::string_view message{};
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int score {-1};
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};
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public:
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using Tokens = std::vector< Token >;
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private:
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std::unique_ptr<Node> tree_;
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int score_;
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static std::unique_ptr< Node > parse_and_operation ( Tokens const & tokens, std::size_t & current );
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static std::unique_ptr< Node > parse_or_operation ( Tokens const & tokens, std::size_t & current );
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static std::unique_ptr< Node > parse_parentheses ( Tokens const & tokens, std::size_t & current );
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static std::unique_ptr< Node > parse_terminal ( Tokens const & tokens, std::size_t & current );
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static std::unique_ptr<Node> parse_expression( Tokens const & tokens, std::size_t & current );
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static inline bool has_unused( Tokens const & tokens, std::size_t const current ) noexcept {
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return current < std::size( tokens );
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}
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static Result visit(Node const &node);
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static Result visit_logical_and(Node const &node);
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static Result visit_logical_or(Node const &node);
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public:
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MonitorLinkExpression();
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MonitorLinkExpression(const std::string &expression) : expression_(expression) {
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};
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int score() { return score_; }
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bool evaluate();
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const Result result();
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bool parse();
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private:
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const std::string_view delimiters_ = "|&(),";
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std::string_view expression_;
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};
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#endif
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