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174 changes: 80 additions & 94 deletions include/fmt/args.h
Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
// Formatting library for C++ - dynamic format arguments
// Formatting library for C++ - dynamic argument lists
//
// Copyright (c) 2012 - present, Victor Zverovich
// All rights reserved.
Expand All @@ -8,34 +8,39 @@
#ifndef FMT_ARGS_H_
#define FMT_ARGS_H_

#include <functional> // std::reference_wrapper
#include <memory> // std::unique_ptr
#include <vector>
#ifndef FMT_MODULE
# include <functional> // std::reference_wrapper
# include <memory> // std::unique_ptr
# include <vector>
#endif

#include "core.h"
#include "format.h" // std_string_view

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) {
template <typename T> auto unwrap(const T& v) -> const T& { return v; }
template <typename T>
auto unwrap(const std::reference_wrapper<T>& v) -> const T& {
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;
};
// node is defined outside dynamic_arg_list to workaround a C2504 bug in MSVC
// 2022 (v17.10.0).
//
// 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 node is made a fake template.
template <typename = void> struct node {
virtual ~node() = default;
std::unique_ptr<node<>> next;
};

class dynamic_arg_list {
template <typename T> struct typed_node : node<> {
T value;

Expand All @@ -50,7 +55,7 @@ class dynamic_arg_list {
std::unique_ptr<node<>> head_;

public:
template <typename T, typename Arg> const T& push(const Arg& arg) {
template <typename T, typename Arg> auto push(const Arg& arg) -> const T& {
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_);
Expand All @@ -61,28 +66,18 @@ class dynamic_arg_list {
} // 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
* A dynamic list of formatting arguments with storage.
*
* It can be implicitly converted into `fmt::basic_format_args` for passing
* into type-erased formatting functions such as `fmt::vformat`.
*/
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
{
template <typename Context> class dynamic_format_arg_store {
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;
detail::mapped_type_constant<T, char_type>::value;

enum {
value = !(detail::is_reference_wrapper<T>::value ||
Expand All @@ -95,7 +90,7 @@ class dynamic_format_arg_store
};

template <typename T>
using stored_type = conditional_t<
using stored_t = conditional_t<
std::is_convertible<T, std::basic_string<char_type>>::value &&
!detail::is_reference_wrapper<T>::value,
std::basic_string<char_type>, T>;
Expand All @@ -110,80 +105,72 @@ class dynamic_format_arg_store

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 {
auto data() const -> const basic_format_arg<Context>* {
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));
data_.emplace_back(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)));
if (named_info_.empty())
data_.insert(data_.begin(), basic_format_arg<Context>(nullptr, 0));
data_.emplace_back(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()};
data_[0] = {named_info_.data(), named_info_.size()};
guard.release();
}

public:
constexpr dynamic_format_arg_store() = default;

operator basic_format_args<Context>() const {
return basic_format_args<Context>(data(), static_cast<int>(data_.size()),
!named_info_.empty());
}

/**
\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
*/
* 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);
*/
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));
emplace_arg(dynamic_args_.push<stored_t<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
*/
* 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"
*/
template <typename T> void push_back(std::reference_wrapper<T> arg) {
static_assert(
need_copy<T>::value,
Expand All @@ -192,41 +179,40 @@ class dynamic_format_arg_store
}

/**
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.
*/
* 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)));
fmt::arg(arg_name, dynamic_args_.push<stored_t<T>>(arg.value)));
} else {
emplace_arg(fmt::arg(arg_name, arg.value));
}
}

/** Erase all elements from the store */
/// Erase all elements from the store.
void clear() {
data_.clear();
named_info_.clear();
dynamic_args_ = detail::dynamic_arg_list();
dynamic_args_ = {};
}

/**
\rst
Reserves space to store at least *new_cap* arguments including
*new_cap_named* named arguments.
\endrst
*/
/// Reserves space to store at least `new_cap` arguments including
/// `new_cap_named` named arguments.
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");
"set of arguments includes set of named arguments");
data_.reserve(new_cap);
named_info_.reserve(new_cap_named);
}

/// Returns the number of elements in the store.
size_t size() const noexcept { return data_.size(); }
};

FMT_END_NAMESPACE
Expand Down
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