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f5b05cf981
in C++20, compiler generate operator!=() if the corresponding operator==() is already defined, the language now understands that the comparison is symmetric in the new standard. fortunately, our operator!=() is always equivalent to `! operator==()`, this matches the behavior of the default generated operator!=(). so, in this change, all `operator!=` are removed. in addition to the defaulted operator!=, C++20 also brings to us the defaulted operator==() -- it is able to generated the operator==() if the member-wise lexicographical comparison. under some circumstances, this is exactly what we need. so, in this change, if the operator==() is also implemented as a lexicographical comparison of all memeber variables of the class/struct in question, it is implemented using the default generated one by removing its body and mark the function as `default`. moreover, if the class happen to have other comparison operators which are implemented using lexicographical comparison, the default generated `operator<=>` is used in place of the defaulted `operator==`. sometimes, we fail to mark the operator== with the `const` specifier, in this change, to fulfil the need of C++ standard, and to be more correct, the `const` specifier is added. also, to generate the defaulted operator==, the operand should be `const class_name&`, but it is not always the case, in the class of `version`, we use `version` as the parameter type, to fulfill the need of the C++ standard, the parameter type is changed to `const version&` instead. this does not change the semantic of the comparison operator. and is a more idiomatic way to pass non-trivial struct as function parameters. please note, because in C++20, both operator= and operator<=> are symmetric, some of the operators in `multiprecision` are removed. they are the symmetric form of the another variant. if they were not removed, compiler would, for instance, find ambiguous overloaded operator '=='. this change is a cleanup to modernize the code base with C++20 features. Signed-off-by: Kefu Chai <kefu.chai@scylladb.com> Closes #13687
127 lines
3.1 KiB
C++
127 lines
3.1 KiB
C++
/*
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* Copyright (C) 2015-present ScyllaDB
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*
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* Modified by ScyllaDB
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*/
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/*
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* SPDX-License-Identifier: (AGPL-3.0-or-later and Apache-2.0)
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*/
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#pragma once
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#include "schema/schema.hh"
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#include <algorithm>
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#include <functional>
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#include <iosfwd>
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namespace cql3 {
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class column_identifier_raw;
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/**
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* Represents an identifer for a CQL column definition.
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* TODO : should support light-weight mode without text representation for when not interned
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*/
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class column_identifier final {
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public:
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bytes bytes_;
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private:
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sstring _text;
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public:
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// less comparator sorting by text
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struct text_comparator {
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bool operator()(const column_identifier& c1, const column_identifier& c2) const;
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};
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column_identifier(sstring raw_text, bool keep_case);
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column_identifier(bytes bytes_, data_type type);
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column_identifier(bytes bytes_, sstring text);
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bool operator==(const column_identifier& other) const;
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const sstring& text() const;
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const bytes& name() const;
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sstring to_string() const;
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sstring to_cql_string() const;
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friend std::ostream& operator<<(std::ostream& out, const column_identifier& i) {
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return out << i._text;
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}
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#if 0
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public ColumnIdentifier clone(AbstractAllocator allocator)
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{
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return new ColumnIdentifier(allocator.clone(bytes), text);
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}
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#endif
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using raw = column_identifier_raw;
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};
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/**
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* Because Thrift-created tables may have a non-text comparator, we cannot determine the proper 'key' until
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* we know the comparator. ColumnIdentifier.Raw is a placeholder that can be converted to a real ColumnIdentifier
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* once the comparator is known with prepare(). This should only be used with identifiers that are actual
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* column names. See CASSANDRA-8178 for more background.
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*/
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class column_identifier_raw final {
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private:
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const sstring _raw_text;
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sstring _text;
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public:
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column_identifier_raw(sstring raw_text, bool keep_case);
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// for selectable::with_expression::raw:
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::shared_ptr<column_identifier> prepare(const schema& s) const;
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::shared_ptr<column_identifier> prepare_column_identifier(const schema& s) const;
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// for selectable::with_expression::raw:
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bool processes_selection() const;
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bool operator==(const column_identifier_raw& other) const;
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virtual sstring to_string() const;
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sstring to_cql_string() const;
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friend std::hash<column_identifier_raw>;
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friend std::ostream& operator<<(std::ostream& out, const column_identifier_raw& id);
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};
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static inline
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const column_definition* get_column_definition(const schema& schema, const column_identifier& id) {
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return schema.get_column_definition(id.bytes_);
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}
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static inline
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::shared_ptr<column_identifier> to_identifier(const column_definition& def) {
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return def.column_specification->name;
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}
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}
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namespace std {
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template<>
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struct hash<cql3::column_identifier> {
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size_t operator()(const cql3::column_identifier& i) const {
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return std::hash<bytes>()(i.bytes_);
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}
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};
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template<>
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struct hash<cql3::column_identifier_raw> {
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size_t operator()(const cql3::column_identifier::raw& r) const {
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return std::hash<sstring>()(r._text);
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}
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};
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}
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