args.h

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// Formatting library for C++ - dynamic format arguments
//
// Copyright (c) 2012 - present, Victor Zverovich
// All rights reserved.
//
// For the license information refer to format.h.
 
#ifndef FMT_ARGS_H_
#define FMT_ARGS_H_
 
#include <functional> // std::reference_wrapper
#include <memory>     // std::unique_ptr
#include <vector>
 
#include "core.h"
 
FMT_BEGIN_NAMESPACE
 
namespace detail
{
 
    template <typename T>
    struct is_reference_wrapper : std::false_type
    {
    };
    template <typename T>
    struct is_reference_wrapper<std::reference_wrapper<T>> : std::true_type
    {
    };
 
    template <typename T>
    const T& unwrap(const T& v)
    {
        return v;
    }
    template <typename T>
    const T& unwrap(const std::reference_wrapper<T>& v)
    {
        return static_cast<const T&>(v);
    }
 
    class dynamic_arg_list
    {
        // Workaround for clang's -Wweak-vtables. Unlike for regular classes, for
        // templates it doesn't complain about inability to deduce single translation
        // unit for placing vtable. So storage_node_base is made a fake template.
        template <typename = void>
        struct node
        {
            virtual ~node() = default;
            std::unique_ptr<node<>> next;
        };
 
        template <typename T>
        struct typed_node : node<>
        {
            T value;
 
            template <typename Arg>
            FMT_CONSTEXPR typed_node(const Arg& arg)
                : value(arg)
            {
            }
 
            template <typename Char>
            FMT_CONSTEXPR typed_node(const basic_string_view<Char>& arg)
                : value(arg.data(), arg.size())
            {
            }
        };
 
        std::unique_ptr<node<>> head_;
 
    public:
        template <typename T, typename Arg>
        const T& push(const Arg& arg)
        {
            auto  new_node = std::unique_ptr<typed_node<T>>(new typed_node<T>(arg));
            auto& value    = new_node->value;
            new_node->next = std::move(head_);
            head_          = std::move(new_node);
            return value;
        }
    };
} // namespace detail
 
template <typename Context>
class dynamic_format_arg_store
#if FMT_GCC_VERSION && FMT_GCC_VERSION < 409
    // Workaround a GCC template argument substitution bug.
    : public basic_format_args<Context>
#endif
{
private:
    using char_type = typename Context::char_type;
 
    template <typename T>
    struct need_copy
    {
        static constexpr detail::type mapped_type =
            detail::mapped_type_constant<T, Context>::value;
 
        enum
        {
            value = !(detail::is_reference_wrapper<T>::value ||
                      std::is_same<T, basic_string_view<char_type>>::value ||
                      std::is_same<T, detail::std_string_view<char_type>>::value ||
                      (mapped_type != detail::type::cstring_type &&
                       mapped_type != detail::type::string_type &&
                       mapped_type != detail::type::custom_type))
        };
    };
 
    template <typename T>
    using stored_type = conditional_t<
        std::is_convertible<T, std::basic_string<char_type>>::value &&
            !detail::is_reference_wrapper<T>::value,
        std::basic_string<char_type>,
        T>;
 
    // Storage of basic_format_arg must be contiguous.
    std::vector<basic_format_arg<Context>>         data_;
    std::vector<detail::named_arg_info<char_type>> named_info_;
 
    // Storage of arguments not fitting into basic_format_arg must grow
    // without relocation because items in data_ refer to it.
    detail::dynamic_arg_list dynamic_args_;
 
    friend class basic_format_args<Context>;
 
    unsigned long long get_types() const
    {
        return detail::is_unpacked_bit | data_.size() |
               (named_info_.empty()
                    ? 0ULL
                    : static_cast<unsigned long long>(detail::has_named_args_bit));
    }
 
    const basic_format_arg<Context>* data() const
    {
        return named_info_.empty() ? data_.data() : data_.data() + 1;
    }
 
    template <typename T>
    void emplace_arg(const T& arg)
    {
        data_.emplace_back(detail::make_arg<Context>(arg));
    }
 
    template <typename T>
    void emplace_arg(const detail::named_arg<char_type, T>& arg)
    {
        if (named_info_.empty())
        {
            constexpr const detail::named_arg_info<char_type>* zero_ptr{nullptr};
            data_.insert(data_.begin(), {zero_ptr, 0});
        }
        data_.emplace_back(detail::make_arg<Context>(detail::unwrap(arg.value)));
        auto pop_one = [](std::vector<basic_format_arg<Context>>* data) {
            data->pop_back();
        };
        std::unique_ptr<std::vector<basic_format_arg<Context>>, decltype(pop_one)>
            guard{&data_, pop_one};
        named_info_.push_back({arg.name, static_cast<int>(data_.size() - 2u)});
        data_[0].value_.named_args = {named_info_.data(), named_info_.size()};
        guard.release();
    }
 
public:
    constexpr dynamic_format_arg_store() = default;
 
    template <typename T>
    void push_back(const T& arg)
    {
        if (detail::const_check(need_copy<T>::value))
            emplace_arg(dynamic_args_.push<stored_type<T>>(arg));
        else
            emplace_arg(detail::unwrap(arg));
    }
 
    template <typename T>
    void push_back(std::reference_wrapper<T> arg)
    {
        static_assert(
            need_copy<T>::value,
            "objects of built-in types and string views are always copied");
        emplace_arg(arg.get());
    }
 
    template <typename T>
    void push_back(const detail::named_arg<char_type, T>& arg)
    {
        const char_type* arg_name =
            dynamic_args_.push<std::basic_string<char_type>>(arg.name).c_str();
        if (detail::const_check(need_copy<T>::value))
        {
            emplace_arg(
                fmt::arg(arg_name, dynamic_args_.push<stored_type<T>>(arg.value)));
        }
        else
        {
            emplace_arg(fmt::arg(arg_name, arg.value));
        }
    }
 
    void clear()
    {
        data_.clear();
        named_info_.clear();
        dynamic_args_ = detail::dynamic_arg_list();
    }
 
    void reserve(size_t new_cap, size_t new_cap_named)
    {
        FMT_ASSERT(new_cap >= new_cap_named,
                   "Set of arguments includes set of named arguments");
        data_.reserve(new_cap);
        named_info_.reserve(new_cap_named);
    }
};
 
FMT_END_NAMESPACE
 
#endif // FMT_ARGS_H_