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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
- /**
- \rst
- A dynamic version of `fmt::format_arg_store`.
- It's equipped with a storage to potentially temporary objects which lifetimes
- could be shorter than the format arguments object.
- It can be implicitly converted into `~fmt::basic_format_args` for passing
- into type-erased formatting functions such as `~fmt::vformat`.
- \endrst
- */
- 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;
- /**
- \rst
- Adds an argument into the dynamic store for later passing to a formatting
- function.
- Note that custom types and string types (but not string views) are copied
- into the store dynamically allocating memory if necessary.
- **Example**::
- fmt::dynamic_format_arg_store<fmt::format_context> store;
- store.push_back(42);
- store.push_back("abc");
- store.push_back(1.5f);
- std::string result = fmt::vformat("{} and {} and {}", store);
- \endrst
- */
- 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));
- }
- /**
- \rst
- Adds a reference to the argument into the dynamic store for later passing to
- a formatting function.
- **Example**::
- fmt::dynamic_format_arg_store<fmt::format_context> store;
- char band[] = "Rolling Stones";
- store.push_back(std::cref(band));
- band[9] = 'c'; // Changing str affects the output.
- std::string result = fmt::vformat("{}", store);
- // result == "Rolling Scones"
- \endrst
- */
- 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());
- }
- /**
- Adds named argument into the dynamic store for later passing to a formatting
- function. ``std::reference_wrapper`` is supported to avoid copying of the
- argument. The name is always copied into the store.
- */
- 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));
- }
- }
- /** Erase all elements from the store */
- void clear() {
- data_.clear();
- named_info_.clear();
- dynamic_args_ = detail::dynamic_arg_list();
- }
- /**
- \rst
- Reserves space to store at least *new_cap* arguments including
- *new_cap_named* named arguments.
- \endrst
- */
- 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_
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