chromium/third_party/libc++/src/include/__format/buffer.h

// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP___FORMAT_BUFFER_H
#define _LIBCPP___FORMAT_BUFFER_H

#include <__algorithm/copy_n.h>
#include <__algorithm/fill_n.h>
#include <__algorithm/max.h>
#include <__algorithm/min.h>
#include <__algorithm/ranges_copy_n.h>
#include <__algorithm/transform.h>
#include <__algorithm/unwrap_iter.h>
#include <__concepts/same_as.h>
#include <__config>
#include <__format/concepts.h>
#include <__format/enable_insertable.h>
#include <__format/format_to_n_result.h>
#include <__iterator/back_insert_iterator.h>
#include <__iterator/concepts.h>
#include <__iterator/incrementable_traits.h>
#include <__iterator/iterator_traits.h>
#include <__iterator/wrap_iter.h>
#include <__memory/addressof.h>
#include <__memory/allocate_at_least.h>
#include <__memory/allocator_traits.h>
#include <__memory/construct_at.h>
#include <__memory/ranges_construct_at.h>
#include <__memory/uninitialized_algorithms.h>
#include <__type_traits/add_pointer.h>
#include <__type_traits/conditional.h>
#include <__utility/exception_guard.h>
#include <__utility/move.h>
#include <cstddef>
#include <string_view>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#  pragma GCC system_header
#endif

_LIBCPP_PUSH_MACROS
#include <__undef_macros>

_LIBCPP_BEGIN_NAMESPACE_STD

#if _LIBCPP_STD_VER >= 20

namespace __format {

/// A "buffer" that handles writing to the proper iterator.
///
/// This helper is used together with the @ref back_insert_iterator to offer
/// type-erasure for the formatting functions. This reduces the number to
/// template instantiations.
template <__fmt_char_type _CharT>
class _LIBCPP_TEMPLATE_VIS __output_buffer {};

/// A storage using an internal buffer.
///
/// This storage is used when writing a single element to the output iterator
/// is expensive.
template <__fmt_char_type _CharT>
class _LIBCPP_TEMPLATE_VIS __internal_storage {};

/// A storage writing directly to the storage.
///
/// This requires the storage to be a contiguous buffer of \a _CharT.
/// Since the output is directly written to the underlying storage this class
/// is just an empty class.
template <__fmt_char_type _CharT>
class _LIBCPP_TEMPLATE_VIS __direct_storage {};

__enable_direct_output;

/// Write policy for directly writing to the underlying output.
template <class _OutIt, __fmt_char_type _CharT>
class _LIBCPP_TEMPLATE_VIS __writer_direct {};

/// Write policy for copying the buffer to the output.
template <class _OutIt, __fmt_char_type _CharT>
class _LIBCPP_TEMPLATE_VIS __writer_iterator {};

/// Concept to see whether a \a _Container is insertable.
///
/// The concept is used to validate whether multiple calls to a
/// \ref back_insert_iterator can be replace by a call to \c _Container::insert.
///
/// \note a \a _Container needs to opt-in to the concept by specializing
/// \ref __enable_insertable.
__insertable;

/// Extract the container type of a \ref back_insert_iterator.
template <class _It>
struct _LIBCPP_TEMPLATE_VIS __back_insert_iterator_container {};

__back_insert_iterator_container<back_insert_iterator<_Container>>;

/// Write policy for inserting the buffer in a container.
template <class _Container>
class _LIBCPP_TEMPLATE_VIS __writer_container {};

/// Selects the type of the writer used for the output iterator.
template <class _OutIt, class _CharT>
class _LIBCPP_TEMPLATE_VIS __writer_selector {};

/// The generic formatting buffer.
template <class _OutIt, __fmt_char_type _CharT>
  requires(output_iterator<_OutIt, const _CharT&>)
class _LIBCPP_TEMPLATE_VIS __format_buffer {};

/// A buffer that counts the number of insertions.
///
/// Since \ref formatted_size only needs to know the size, the output itself is
/// discarded.
template <__fmt_char_type _CharT>
class _LIBCPP_TEMPLATE_VIS __formatted_size_buffer {};

/// The base of a buffer that counts and limits the number of insertions.
template <class _OutIt, __fmt_char_type _CharT, bool>
  requires(output_iterator<_OutIt, const _CharT&>)
struct _LIBCPP_TEMPLATE_VIS __format_to_n_buffer_base {};

/// The base of a buffer that counts and limits the number of insertions.
///
/// This version is used when \c __enable_direct_output<_OutIt, _CharT> == true.
///
/// This class limits the size available to the direct writer so it will not
/// exceed the maximum number of code units.
__format_to_n_buffer_base<_OutIt, _CharT, true>;

/// The buffer that counts and limits the number of insertions.
template <class _OutIt, __fmt_char_type _CharT>
  requires(output_iterator<_OutIt, const _CharT&>)
struct _LIBCPP_TEMPLATE_VIS __format_to_n_buffer final
    : public __format_to_n_buffer_base< _OutIt, _CharT, __enable_direct_output<_OutIt, _CharT>> {};

// A dynamically growing buffer intended to be used for retargeting a context.
//
// P2286 Formatting ranges adds range formatting support. It allows the user to
// specify the minimum width for the entire formatted range.  The width of the
// range is not known until the range is formatted. Formatting is done to an
// output_iterator so there's no guarantee it would be possible to add the fill
// to the front of the output. Instead the range is formatted to a temporary
// buffer and that buffer is formatted as a string.
//
// There is an issue with that approach, the format context used in
// std::formatter<T>::format contains the output iterator used as part of its
// type. So using this output iterator means there needs to be a new format
// context and the format arguments need to be retargeted to the new context.
// This retargeting is done by a basic_format_context specialized for the
// __iterator of this container.
//
// This class uses its own buffer management, since using vector
// would lead to a circular include with formatter for vector<bool>.
template <__fmt_char_type _CharT>
class _LIBCPP_TEMPLATE_VIS __retarget_buffer {};

} // namespace __format

#endif // _LIBCPP_STD_VER >= 20

_LIBCPP_END_NAMESPACE_STD

_LIBCPP_POP_MACROS

#endif // _LIBCPP___FORMAT_BUFFER_H