chromium/base/strings/to_string.h

// Copyright 2023 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef BASE_STRINGS_TO_STRING_H_
#define BASE_STRINGS_TO_STRING_H_

#include <concepts>
#include <ios>
#include <memory>
#include <sstream>
#include <string>
#include <tuple>
#include <type_traits>
#include <utility>

#include "base/types/supports_ostream_operator.h"

namespace base {

template <typename... Ts>
std::string ToString(const Ts&... values);

namespace internal {

SupportsToString;

// I/O manipulators are function pointers, but should be sent directly to the
// `ostream` instead of being cast to `const void*` like other function
// pointers.
IsIomanip;
IsIomanip;

// Function pointers implicitly convert to `bool`, so use this to avoid printing
// function pointers as 1 or 0.
WillBeIncorrectlyStreamedAsBool;

// Fallback case when there is no better representation.
template <typename T>
struct ToStringHelper { … };

// Most streamables.
ToStringHelper<T>;

// Functions and function pointers.
ToStringHelper<T>;

// Non-streamables that have a `ToString` member.
ToStringHelper<T>;

// Non-streamable enums (i.e. scoped enums where no `operator<<` overload was
// declared).
ToStringHelper<T>;

// Tuples. Will recursively apply `ToString()` to each value in the tuple.
ToStringHelper<std::tuple<T...>>;

}  // namespace internal

// Converts any type to a string, preferring defined operator<<() or ToString()
// methods if they exist. If multiple `values` are given, returns the
// concatenation of the result of applying `ToString` to each value.
template <typename... Ts>
std::string ToString(const Ts&... values) { … }

}  // namespace base

#endif  // BASE_STRINGS_TO_STRING_H_