| 1 | // Formatting library for C++ - dynamic format arguments |
| 2 | // |
| 3 | // Copyright (c) 2012 - present, Victor Zverovich |
| 4 | // All rights reserved. |
| 5 | // |
| 6 | // For the license information refer to format.h. |
| 7 | |
| 8 | #ifndef FMT_ARGS_H_ |
| 9 | #define FMT_ARGS_H_ |
| 10 | |
| 11 | #include <functional> // std::reference_wrapper |
| 12 | #include <memory> // std::unique_ptr |
| 13 | #include <vector> |
| 14 | |
| 15 | #include "core.h" |
| 16 | |
| 17 | FMT_BEGIN_NAMESPACE |
| 18 | |
| 19 | namespace detail { |
| 20 | |
| 21 | template <typename T> struct is_reference_wrapper : std::false_type {}; |
| 22 | template <typename T> |
| 23 | struct is_reference_wrapper<std::reference_wrapper<T>> : std::true_type {}; |
| 24 | |
| 25 | template <typename T> const T& unwrap(const T& v) { return v; } |
| 26 | template <typename T> const T& unwrap(const std::reference_wrapper<T>& v) { |
| 27 | return static_cast<const T&>(v); |
| 28 | } |
| 29 | |
| 30 | class dynamic_arg_list { |
| 31 | // Workaround for clang's -Wweak-vtables. Unlike for regular classes, for |
| 32 | // templates it doesn't complain about inability to deduce single translation |
| 33 | // unit for placing vtable. So storage_node_base is made a fake template. |
| 34 | template <typename = void> struct node { |
| 35 | virtual ~node() = default; |
| 36 | std::unique_ptr<node<>> next; |
| 37 | }; |
| 38 | |
| 39 | template <typename T> struct typed_node : node<> { |
| 40 | T value; |
| 41 | |
| 42 | template <typename Arg> |
| 43 | FMT_CONSTEXPR typed_node(const Arg& arg) : value(arg) {} |
| 44 | |
| 45 | template <typename Char> |
| 46 | FMT_CONSTEXPR typed_node(const basic_string_view<Char>& arg) |
| 47 | : value(arg.data(), arg.size()) {} |
| 48 | }; |
| 49 | |
| 50 | std::unique_ptr<node<>> head_; |
| 51 | |
| 52 | public: |
| 53 | template <typename T, typename Arg> const T& push(const Arg& arg) { |
| 54 | auto new_node = std::unique_ptr<typed_node<T>>(new typed_node<T>(arg)); |
| 55 | auto& value = new_node->value; |
| 56 | new_node->next = std::move(head_); |
| 57 | head_ = std::move(new_node); |
| 58 | return value; |
| 59 | } |
| 60 | }; |
| 61 | } // namespace detail |
| 62 | |
| 63 | /** |
| 64 | \rst |
| 65 | A dynamic version of `fmt::format_arg_store`. |
| 66 | It's equipped with a storage to potentially temporary objects which lifetimes |
| 67 | could be shorter than the format arguments object. |
| 68 | |
| 69 | It can be implicitly converted into `~fmt::basic_format_args` for passing |
| 70 | into type-erased formatting functions such as `~fmt::vformat`. |
| 71 | \endrst |
| 72 | */ |
| 73 | template <typename Context> |
| 74 | class dynamic_format_arg_store |
| 75 | #if FMT_GCC_VERSION && FMT_GCC_VERSION < 409 |
| 76 | // Workaround a GCC template argument substitution bug. |
| 77 | : public basic_format_args<Context> |
| 78 | #endif |
| 79 | { |
| 80 | private: |
| 81 | using char_type = typename Context::char_type; |
| 82 | |
| 83 | template <typename T> struct need_copy { |
| 84 | static constexpr detail::type mapped_type = |
| 85 | detail::mapped_type_constant<T, Context>::value; |
| 86 | |
| 87 | enum { |
| 88 | value = !(detail::is_reference_wrapper<T>::value || |
| 89 | std::is_same<T, basic_string_view<char_type>>::value || |
| 90 | std::is_same<T, detail::std_string_view<char_type>>::value || |
| 91 | (mapped_type != detail::type::cstring_type && |
| 92 | mapped_type != detail::type::string_type && |
| 93 | mapped_type != detail::type::custom_type)) |
| 94 | }; |
| 95 | }; |
| 96 | |
| 97 | template <typename T> |
| 98 | using stored_type = conditional_t<detail::is_string<T>::value && |
| 99 | !has_formatter<T, Context>::value && |
| 100 | !detail::is_reference_wrapper<T>::value, |
| 101 | std::basic_string<char_type>, T>; |
| 102 | |
| 103 | // Storage of basic_format_arg must be contiguous. |
| 104 | std::vector<basic_format_arg<Context>> data_; |
| 105 | std::vector<detail::named_arg_info<char_type>> named_info_; |
| 106 | |
| 107 | // Storage of arguments not fitting into basic_format_arg must grow |
| 108 | // without relocation because items in data_ refer to it. |
| 109 | detail::dynamic_arg_list dynamic_args_; |
| 110 | |
| 111 | friend class basic_format_args<Context>; |
| 112 | |
| 113 | unsigned long long get_types() const { |
| 114 | return detail::is_unpacked_bit | data_.size() | |
| 115 | (named_info_.empty() |
| 116 | ? 0ULL |
| 117 | : static_cast<unsigned long long>(detail::has_named_args_bit)); |
| 118 | } |
| 119 | |
| 120 | const basic_format_arg<Context>* data() const { |
| 121 | return named_info_.empty() ? data_.data() : data_.data() + 1; |
| 122 | } |
| 123 | |
| 124 | template <typename T> void emplace_arg(const T& arg) { |
| 125 | data_.emplace_back(detail::make_arg<Context>(arg)); |
| 126 | } |
| 127 | |
| 128 | template <typename T> |
| 129 | void emplace_arg(const detail::named_arg<char_type, T>& arg) { |
| 130 | if (named_info_.empty()) { |
| 131 | constexpr const detail::named_arg_info<char_type>* zero_ptr{nullptr}; |
| 132 | data_.insert(data_.begin(), {zero_ptr, 0}); |
| 133 | } |
| 134 | data_.emplace_back(detail::make_arg<Context>(detail::unwrap(arg.value))); |
| 135 | auto pop_one = [](std::vector<basic_format_arg<Context>>* data) { |
| 136 | data->pop_back(); |
| 137 | }; |
| 138 | std::unique_ptr<std::vector<basic_format_arg<Context>>, decltype(pop_one)> |
| 139 | guard{&data_, pop_one}; |
| 140 | named_info_.push_back({arg.name, static_cast<int>(data_.size() - 2u)}); |
| 141 | data_[0].value_.named_args = {named_info_.data(), named_info_.size()}; |
| 142 | guard.release(); |
| 143 | } |
| 144 | |
| 145 | public: |
| 146 | constexpr dynamic_format_arg_store() = default; |
| 147 | |
| 148 | /** |
| 149 | \rst |
| 150 | Adds an argument into the dynamic store for later passing to a formatting |
| 151 | function. |
| 152 | |
| 153 | Note that custom types and string types (but not string views) are copied |
| 154 | into the store dynamically allocating memory if necessary. |
| 155 | |
| 156 | **Example**:: |
| 157 | |
| 158 | fmt::dynamic_format_arg_store<fmt::format_context> store; |
| 159 | store.push_back(42); |
| 160 | store.push_back("abc"); |
| 161 | store.push_back(1.5f); |
| 162 | std::string result = fmt::vformat("{} and {} and {}", store); |
| 163 | \endrst |
| 164 | */ |
| 165 | template <typename T> void push_back(const T& arg) { |
| 166 | if (detail::const_check(need_copy<T>::value)) |
| 167 | emplace_arg(dynamic_args_.push<stored_type<T>>(arg)); |
| 168 | else |
| 169 | emplace_arg(detail::unwrap(arg)); |
| 170 | } |
| 171 | |
| 172 | /** |
| 173 | \rst |
| 174 | Adds a reference to the argument into the dynamic store for later passing to |
| 175 | a formatting function. |
| 176 | |
| 177 | **Example**:: |
| 178 | |
| 179 | fmt::dynamic_format_arg_store<fmt::format_context> store; |
| 180 | char band[] = "Rolling Stones"; |
| 181 | store.push_back(std::cref(band)); |
| 182 | band[9] = 'c'; // Changing str affects the output. |
| 183 | std::string result = fmt::vformat("{}", store); |
| 184 | // result == "Rolling Scones" |
| 185 | \endrst |
| 186 | */ |
| 187 | template <typename T> void push_back(std::reference_wrapper<T> arg) { |
| 188 | static_assert( |
| 189 | need_copy<T>::value, |
| 190 | "objects of built-in types and string views are always copied"); |
| 191 | emplace_arg(arg.get()); |
| 192 | } |
| 193 | |
| 194 | /** |
| 195 | Adds named argument into the dynamic store for later passing to a formatting |
| 196 | function. ``std::reference_wrapper`` is supported to avoid copying of the |
| 197 | argument. The name is always copied into the store. |
| 198 | */ |
| 199 | template <typename T> |
| 200 | void push_back(const detail::named_arg<char_type, T>& arg) { |
| 201 | const char_type* arg_name = |
| 202 | dynamic_args_.push<std::basic_string<char_type>>(arg.name).c_str(); |
| 203 | if (detail::const_check(need_copy<T>::value)) { |
| 204 | emplace_arg( |
| 205 | fmt::arg(arg_name, dynamic_args_.push<stored_type<T>>(arg.value))); |
| 206 | } else { |
| 207 | emplace_arg(fmt::arg(arg_name, arg.value)); |
| 208 | } |
| 209 | } |
| 210 | |
| 211 | /** Erase all elements from the store */ |
| 212 | void clear() { |
| 213 | data_.clear(); |
| 214 | named_info_.clear(); |
| 215 | dynamic_args_ = detail::dynamic_arg_list(); |
| 216 | } |
| 217 | |
| 218 | /** |
| 219 | \rst |
| 220 | Reserves space to store at least *new_cap* arguments including |
| 221 | *new_cap_named* named arguments. |
| 222 | \endrst |
| 223 | */ |
| 224 | void reserve(size_t new_cap, size_t new_cap_named) { |
| 225 | FMT_ASSERT(new_cap >= new_cap_named, |
| 226 | "Set of arguments includes set of named arguments"); |
| 227 | data_.reserve(new_cap); |
| 228 | named_info_.reserve(new_cap_named); |
| 229 | } |
| 230 | }; |
| 231 | |
| 232 | FMT_END_NAMESPACE |
| 233 | |
| 234 | #endif // FMT_ARGS_H_ |