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
115 lines
3.5 KiB
C++
115 lines
3.5 KiB
C++
/*
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* Copyright (C) 2015-present ScyllaDB
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*/
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/*
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* SPDX-License-Identifier: AGPL-3.0-or-later
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*/
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#pragma once
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#include <map>
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#include <set>
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#include <seastar/core/future.hh>
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#include <seastar/core/shared_ptr.hh>
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#include <seastar/core/sstring.hh>
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#include "exceptions/exceptions.hh"
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class compressor {
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sstring _name;
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public:
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compressor(sstring);
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virtual ~compressor() {}
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/**
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* Unpacks data in "input" to output. If output_len is of insufficient size,
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* exception is thrown. I.e. you should keep track of the uncompressed size.
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*/
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virtual size_t uncompress(const char* input, size_t input_len, char* output,
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size_t output_len) const = 0;
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/**
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* Packs data in "input" to output. If output_len is of insufficient size,
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* exception is thrown. Maximum required size is obtained via "compress_max_size"
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*/
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virtual size_t compress(const char* input, size_t input_len, char* output,
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size_t output_len) const = 0;
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/**
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* Returns the maximum output size for compressing data on "input_len" size.
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*/
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virtual size_t compress_max_size(size_t input_len) const = 0;
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/**
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* Returns accepted option names for this compressor
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*/
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virtual std::set<sstring> option_names() const;
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/**
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* Returns original options used in instantiating this compressor
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*/
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virtual std::map<sstring, sstring> options() const;
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/**
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* Compressor class name.
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*/
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const sstring& name() const {
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return _name;
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}
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// to cheaply bridge sstable compression options / maps
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using opt_string = std::optional<sstring>;
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using opt_getter = std::function<opt_string(const sstring&)>;
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using ptr_type = shared_ptr<compressor>;
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static ptr_type create(const sstring& name, const opt_getter&);
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static ptr_type create(const std::map<sstring, sstring>&);
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static thread_local const ptr_type lz4;
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static thread_local const ptr_type snappy;
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static thread_local const ptr_type deflate;
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static const sstring namespace_prefix;
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};
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template<typename BaseType, typename... Args>
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class class_registry;
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using compressor_ptr = compressor::ptr_type;
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using compressor_registry = class_registry<compressor, const typename compressor::opt_getter&>;
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class compression_parameters {
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public:
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static constexpr int32_t DEFAULT_CHUNK_LENGTH = 4 * 1024;
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static constexpr double DEFAULT_CRC_CHECK_CHANCE = 1.0;
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static const sstring SSTABLE_COMPRESSION;
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static const sstring CHUNK_LENGTH_KB;
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static const sstring CHUNK_LENGTH_KB_ERR;
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static const sstring CRC_CHECK_CHANCE;
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private:
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compressor_ptr _compressor;
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std::optional<int> _chunk_length;
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std::optional<double> _crc_check_chance;
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public:
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compression_parameters();
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compression_parameters(compressor_ptr);
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compression_parameters(const std::map<sstring, sstring>& options);
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~compression_parameters();
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compressor_ptr get_compressor() const { return _compressor; }
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int32_t chunk_length() const { return _chunk_length.value_or(int(DEFAULT_CHUNK_LENGTH)); }
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double crc_check_chance() const { return _crc_check_chance.value_or(double(DEFAULT_CRC_CHECK_CHANCE)); }
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void validate();
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std::map<sstring, sstring> get_options() const;
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bool operator==(const compression_parameters& other) const;
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static compression_parameters no_compression() {
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return compression_parameters(nullptr);
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}
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private:
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void validate_options(const std::map<sstring, sstring>&);
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};
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