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Diffstat (limited to 'src/mongo/logv2/attribute_storage.h')
| -rw-r--r-- | src/mongo/logv2/attribute_storage.h | 177 |
1 files changed, 177 insertions, 0 deletions
diff --git a/src/mongo/logv2/attribute_storage.h b/src/mongo/logv2/attribute_storage.h new file mode 100644 index 00000000000..cd6c37b785e --- /dev/null +++ b/src/mongo/logv2/attribute_storage.h @@ -0,0 +1,177 @@ +/** + * Copyright (C) 2019-present MongoDB, Inc. + * + * This program is free software: you can redistribute it and/or modify + * it under the terms of the Server Side Public License, version 1, + * as published by MongoDB, Inc. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * Server Side Public License for more details. + * + * You should have received a copy of the Server Side Public License + * along with this program. If not, see + * <http://www.mongodb.com/licensing/server-side-public-license>. + * + * As a special exception, the copyright holders give permission to link the + * code of portions of this program with the OpenSSL library under certain + * conditions as described in each individual source file and distribute + * linked combinations including the program with the OpenSSL library. You + * must comply with the Server Side Public License in all respects for + * all of the code used other than as permitted herein. If you modify file(s) + * with this exception, you may extend this exception to your version of the + * file(s), but you are not obligated to do so. If you do not wish to do so, + * delete this exception statement from your version. If you delete this + * exception statement from all source files in the program, then also delete + * it in the license file. + */ + +#pragma once + +#include "mongo/base/string_data.h" +#include "mongo/stdx/variant.h" + +#include <functional> + +namespace mongo { +namespace logv2 { + +class TypeErasedAttributeStorage; + +// Custom type, storage for how to call its formatters +struct CustomAttributeValue { + std::function<BSONObj()> toBSON; + std::function<std::string()> toString; +}; + +namespace detail { +namespace { + +// Helper traits to figure out capabilities on custom types +template <class T, class = void> +struct HasToBSON : std::false_type {}; + +template <class T> +struct HasToBSON<T, std::void_t<decltype(std::declval<T>().toBSON())>> : std::true_type {}; + +template <class T, class = void> +struct HasToString : std::false_type {}; + +template <class T> +struct HasToString<T, std::void_t<decltype(std::declval<T>().toString())>> : std::true_type {}; + +} // namespace + +// Named attribute, storage for a name-value attribute. +class NamedAttribute { +public: + NamedAttribute() = default; + NamedAttribute(StringData n, int val) : name(n), value(val) {} + NamedAttribute(StringData n, unsigned int val) : name(n), value(val) {} + // long is 32bit on Windows and 64bit on posix. To avoid ambiguity where different platforms we + // treat long as 64bit always + NamedAttribute(StringData n, long val) : name(n), value(static_cast<long long>(val)) {} + NamedAttribute(StringData n, unsigned long val) + : name(n), value(static_cast<unsigned long long>(val)) {} + NamedAttribute(StringData n, long long val) : name(n), value(val) {} + NamedAttribute(StringData n, unsigned long long val) : name(n), value(val) {} + NamedAttribute(StringData n, double val) : name(n), value(val) {} + NamedAttribute(StringData n, bool val) : name(n), value(val) {} + NamedAttribute(StringData n, StringData val) : name(n), value(val) {} + NamedAttribute(StringData n, BSONObj const& val) : name(n), value(&val) {} + NamedAttribute(StringData n, const char* val) : NamedAttribute(n, StringData(val)) {} + NamedAttribute(StringData n, float val) : NamedAttribute(n, static_cast<double>(val)) {} + NamedAttribute(StringData n, std::string const& val) : NamedAttribute(n, StringData(val)) {} + NamedAttribute(StringData n, long double val) = delete; + + template <typename T, + typename = std::enable_if_t<!std::is_integral_v<T> && !std::is_floating_point_v<T>>> + NamedAttribute(StringData n, const T& val) : name(n) { + static_assert(HasToString<T>::value, "custom type needs toString() implementation"); + + CustomAttributeValue custom; + if constexpr (HasToBSON<T>::value) { + custom.toBSON = std::bind(&T::toBSON, val); + } + if constexpr (HasToString<T>::value) { + custom.toString = std::bind(&T::toString, val); + } + + value = std::move(custom); + } + + StringData name; + stdx::variant<int, + unsigned int, + long long, + unsigned long long, + bool, + double, + StringData, + const BSONObj*, + CustomAttributeValue> + value; +}; + +// Attribute Storage stores an array of Named Attributes. +template <typename... Args> +class AttributeStorage { +public: + AttributeStorage(const Args&... args) + : _data{detail::NamedAttribute(StringData(args.name.data(), args.name.size()), + args.value)...} {} + +private: + static const size_t kNumArgs = sizeof...(Args); + + // Arrays need a size of at least 1, add dummy element if needed (kNumArgs above is still 0) + NamedAttribute _data[kNumArgs ? kNumArgs : 1]; + + // This class is meant to be wrapped by TypeErasedAttributeStorage below that provides public + // accessors. Let it access all our internals. + friend class mongo::logv2::TypeErasedAttributeStorage; +}; + +template <typename... Args> +AttributeStorage<Args...> makeAttributeStorage(const Args&... args) { + return {args...}; +} + +} // namespace detail + +// Wrapper around internal pointer of AttributeStorage so it does not need any template parameters +class TypeErasedAttributeStorage { +public: + TypeErasedAttributeStorage() : _size(0) {} + + template <typename... Args> + TypeErasedAttributeStorage(const detail::AttributeStorage<Args...>& store) { + _data = store._data; + _size = store.kNumArgs; + } + + bool empty() const { + return _size == 0; + } + + std::size_t size() const { + return _size; + } + + // Applies a function to every stored named attribute in order they are captured + template <typename Func> + void apply(Func&& f) const { + std::for_each(_data, _data + _size, [&f](const detail::NamedAttribute& attr) { + StringData name = attr.name; + stdx::visit([name, &f](auto&& val) { f(name, val); }, attr.value); + }); + } + +private: + const detail::NamedAttribute* _data; + size_t _size; +}; + +} // namespace logv2 +} // namespace mongo |