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// -*- 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_PARSER_STD_FORMAT_SPEC_H
#define _LIBCPP___FORMAT_PARSER_STD_FORMAT_SPEC_H
#include <__algorithm/find_if.h>
#include <__algorithm/min.h>
#include <__config>
#include <__debug>
#include <__format/format_arg.h>
#include <__format/format_error.h>
#include <__format/format_string.h>
#include <__variant/monostate.h>
#include <bit>
#include <concepts>
#include <cstdint>
#include <type_traits>
#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 > 17
// TODO FMT Remove this once we require compilers with proper C++20 support.
// If the compiler has no concepts support, the format header will be disabled.
// Without concepts support enable_if needs to be used and that too much effort
// to support compilers with partial C++20 support.
# if !defined(_LIBCPP_HAS_NO_CONCEPTS)
namespace __format_spec {
/**
* Contains the flags for the std-format-spec.
*
* Some format-options can only be used for specific C++types and may depend on
* the selected format-type.
* * The C++type filtering can be done using the proper policies for
* @ref __parser_std.
* * The format-type filtering needs to be done post parsing in the parser
* derived from @ref __parser_std.
*/
class _LIBCPP_TYPE_VIS _Flags {
public:
enum class _LIBCPP_ENUM_VIS _Alignment : uint8_t {
/**
* No alignment is set in the format string.
*
* Zero-padding is ignored when an alignment is selected.
* The default alignment depends on the selected format-type.
*/
__default,
__left,
__center,
__right
};
enum class _LIBCPP_ENUM_VIS _Sign : uint8_t {
/**
* No sign is set in the format string.
*
* The sign isn't allowed for certain format-types. By using this value
* it's possible to detect whether or not the user explicitly set the sign
* flag. For formatting purposes it behaves the same as @ref __minus.
*/
__default,
__minus,
__plus,
__space
};
_Alignment __alignment : 2 {_Alignment::__default};
_Sign __sign : 2 {_Sign::__default};
uint8_t __alternate_form : 1 {false};
uint8_t __zero_padding : 1 {false};
uint8_t __locale_specific_form : 1 {false};
enum class _LIBCPP_ENUM_VIS _Type : uint8_t {
__default,
__string,
__binary_lower_case,
__binary_upper_case,
__octal,
__decimal,
__hexadecimal_lower_case,
__hexadecimal_upper_case,
__pointer,
__char,
__float_hexadecimal_lower_case,
__float_hexadecimal_upper_case,
__scientific_lower_case,
__scientific_upper_case,
__fixed_lower_case,
__fixed_upper_case,
__general_lower_case,
__general_upper_case
};
_Type __type{_Type::__default};
};
namespace __detail {
template <class _CharT>
_LIBCPP_HIDE_FROM_ABI constexpr bool
__parse_alignment(_CharT __c, _Flags& __flags) noexcept {
switch (__c) {
case _CharT('<'):
__flags.__alignment = _Flags::_Alignment::__left;
return true;
case _CharT('^'):
__flags.__alignment = _Flags::_Alignment::__center;
return true;
case _CharT('>'):
__flags.__alignment = _Flags::_Alignment::__right;
return true;
}
return false;
}
} // namespace __detail
template <class _CharT>
class _LIBCPP_TEMPLATE_VIS __parser_fill_align {
public:
// TODO FMT The standard doesn't specify this character is a Unicode
// character. Validate what fmt and MSVC have implemented.
_CharT __fill{_CharT(' ')};
protected:
_LIBCPP_HIDE_FROM_ABI constexpr const _CharT*
__parse(const _CharT* __begin, const _CharT* __end, _Flags& __flags) {
_LIBCPP_ASSERT(__begin != __end,
"When called with an empty input the function will cause "
"undefined behavior by evaluating data not in the input");
if (__begin + 1 != __end) {
if (__detail::__parse_alignment(*(__begin + 1), __flags)) {
if (*__begin == _CharT('{') || *__begin == _CharT('}'))
__throw_format_error(
"The format-spec fill field contains an invalid character");
__fill = *__begin;
return __begin + 2;
}
}
if (__detail::__parse_alignment(*__begin, __flags))
return __begin + 1;
return __begin;
}
};
template <class _CharT>
_LIBCPP_HIDE_FROM_ABI constexpr const _CharT*
__parse_sign(const _CharT* __begin, _Flags& __flags) noexcept {
switch (*__begin) {
case _CharT('-'):
__flags.__sign = _Flags::_Sign::__minus;
break;
case _CharT('+'):
__flags.__sign = _Flags::_Sign::__plus;
break;
case _CharT(' '):
__flags.__sign = _Flags::_Sign::__space;
break;
default:
return __begin;
}
return __begin + 1;
}
template <class _CharT>
_LIBCPP_HIDE_FROM_ABI constexpr const _CharT*
__parse_alternate_form(const _CharT* __begin, _Flags& __flags) noexcept {
if (*__begin == _CharT('#')) {
__flags.__alternate_form = true;
++__begin;
}
return __begin;
}
template <class _CharT>
_LIBCPP_HIDE_FROM_ABI constexpr const _CharT*
__parse_zero_padding(const _CharT* __begin, _Flags& __flags) noexcept {
if (*__begin == _CharT('0')) {
__flags.__zero_padding = true;
++__begin;
}
return __begin;
}
template <class _CharT>
_LIBCPP_HIDE_FROM_ABI constexpr __format::__parse_number_result< _CharT>
__parse_arg_id(const _CharT* __begin, const _CharT* __end, auto& __parse_ctx) {
// This function is a wrapper to call the real parser. But it does the
// validation for the pre-conditions and post-conditions.
if (__begin == __end)
__throw_format_error("End of input while parsing format-spec arg-id");
__format::__parse_number_result __r =
__format::__parse_arg_id(__begin, __end, __parse_ctx);
if (__r.__ptr == __end || *__r.__ptr != _CharT('}'))
__throw_format_error("A format-spec arg-id should terminate at a '}'");
++__r.__ptr;
return __r;
}
template <class _Context>
_LIBCPP_HIDE_FROM_ABI constexpr uint32_t
__substitute_arg_id(basic_format_arg<_Context> __arg) {
return visit_format_arg(
[](auto __arg) -> uint32_t {
using _Type = decltype(__arg);
if constexpr (integral<_Type>) {
if constexpr (signed_integral<_Type>) {
if (__arg < 0)
__throw_format_error("A format-spec arg-id replacement shouldn't "
"have a negative value");
}
using _CT = common_type_t<_Type, decltype(__format::__number_max)>;
if (static_cast<_CT>(__arg) >
static_cast<_CT>(__format::__number_max))
__throw_format_error("A format-spec arg-id replacement exceeds "
"the maximum supported value");
return __arg;
} else if constexpr (same_as<_Type, monostate>)
__throw_format_error("Argument index out of bounds");
else
__throw_format_error("A format-spec arg-id replacement argument "
"isn't an integral type");
},
__arg);
}
class _LIBCPP_TYPE_VIS __parser_width {
public:
/** Contains a width or an arg-id. */
uint32_t __width : 31 {0};
/** Determines whether the value stored is a width or an arg-id. */
uint32_t __width_as_arg : 1 {0};
protected:
/**
* Does the supplied std-format-spec contain a width field?
*
* When the field isn't present there's no padding required. This can be used
* to optimize the formatting.
*/
constexpr bool __has_width_field() const noexcept {
return __width_as_arg || __width;
}
/**
* Does the supplied width field contain an arg-id?
*
* If @c true the formatter needs to call @ref __substitute_width_arg_id.
*/
constexpr bool __width_needs_substitution() const noexcept {
return __width_as_arg;
}
template <class _CharT>
_LIBCPP_HIDE_FROM_ABI constexpr const _CharT*
__parse(const _CharT* __begin, const _CharT* __end, auto& __parse_ctx) {
if (*__begin == _CharT('0'))
__throw_format_error(
"A format-spec width field shouldn't have a leading zero");
if (*__begin == _CharT('{')) {
__format::__parse_number_result __r =
__parse_arg_id(++__begin, __end, __parse_ctx);
__width = __r.__value;
__width_as_arg = 1;
return __r.__ptr;
}
if (*__begin < _CharT('0') || *__begin > _CharT('9'))
return __begin;
__format::__parse_number_result __r =
__format::__parse_number(__begin, __end);
__width = __r.__value;
_LIBCPP_ASSERT(__width != 0,
"A zero value isn't allowed and should be impossible, "
"due to validations in this function");
return __r.__ptr;
}
_LIBCPP_HIDE_FROM_ABI constexpr void __substitute_width_arg_id(auto __arg) {
_LIBCPP_ASSERT(__width_as_arg == 1,
"Substitute width called when no substitution is required");
// The clearing of the flag isn't required but looks better when debugging
// the code.
__width_as_arg = 0;
__width = __substitute_arg_id(__arg);
if (__width == 0)
__throw_format_error(
"A format-spec width field replacement should have a positive value");
}
};
class _LIBCPP_TYPE_VIS __parser_precision {
public:
/** Contains a precision or an arg-id. */
uint32_t __precision : 31 {__format::__number_max};
/**
* Determines whether the value stored is a precision or an arg-id.
*
* @note Since @ref __precision == @ref __format::__number_max is a valid
* value, the default value contains an arg-id of INT32_MAX. (This number of
* arguments isn't supported by compilers.) This is used to detect whether
* the std-format-spec contains a precision field.
*/
uint32_t __precision_as_arg : 1 {1};
protected:
/**
* Does the supplied std-format-spec contain a precision field?
*
* When the field isn't present there's no truncating required. This can be
* used to optimize the formatting.
*/
constexpr bool __has_precision_field() const noexcept {
return __precision_as_arg == 0 || // Contains a value?
__precision != __format::__number_max; // The arg-id is valid?
}
/**
* Does the supplied precision field contain an arg-id?
*
* If @c true the formatter needs to call @ref __substitute_precision_arg_id.
*/
constexpr bool __precision_needs_substitution() const noexcept {
return __precision_as_arg && __precision != __format::__number_max;
}
template <class _CharT>
_LIBCPP_HIDE_FROM_ABI constexpr const _CharT*
__parse(const _CharT* __begin, const _CharT* __end, auto& __parse_ctx) {
if (*__begin != _CharT('.'))
return __begin;
++__begin;
if (__begin == __end)
__throw_format_error("End of input while parsing format-spec precision");
if (*__begin == _CharT('0')) {
++__begin;
if (__begin != __end && *__begin >= '0' && *__begin <= '9')
__throw_format_error(
"A format-spec precision field shouldn't have a leading zero");
__precision = 0;
__precision_as_arg = 0;
return __begin;
}
if (*__begin == _CharT('{')) {
__format::__parse_number_result __arg_id =
__parse_arg_id(++__begin, __end, __parse_ctx);
_LIBCPP_ASSERT(__arg_id.__value != __format::__number_max,
"Unsupported number of arguments, since this number of "
"arguments is used a special value");
__precision = __arg_id.__value;
return __arg_id.__ptr;
}
if (*__begin < _CharT('0') || *__begin > _CharT('9'))
__throw_format_error(
"The format-spec precision field doesn't contain a value or arg-id");
__format::__parse_number_result __r =
__format::__parse_number(__begin, __end);
__precision = __r.__value;
__precision_as_arg = 0;
return __r.__ptr;
}
_LIBCPP_HIDE_FROM_ABI constexpr void __substitute_precision_arg_id(
auto __arg) {
_LIBCPP_ASSERT(
__precision_as_arg == 1 && __precision != __format::__number_max,
"Substitute precision called when no substitution is required");
// The clearing of the flag isn't required but looks better when debugging
// the code.
__precision_as_arg = 0;
__precision = __substitute_arg_id(__arg);
}
};
template <class _CharT>
_LIBCPP_HIDE_FROM_ABI constexpr const _CharT*
__parse_locale_specific_form(const _CharT* __begin, _Flags& __flags) noexcept {
if (*__begin == _CharT('L')) {
__flags.__locale_specific_form = true;
++__begin;
}
return __begin;
}
template <class _CharT>
_LIBCPP_HIDE_FROM_ABI constexpr const _CharT*
__parse_type(const _CharT* __begin, _Flags& __flags) {
// Determines the type. It does not validate whether the selected type is
// valid. Most formatters have optional fields that are only allowed for
// certain types. These parsers need to do validation after the type has
// been parsed. So its easier to implement the validation for all types in
// the specific parse function.
switch (*__begin) {
case 'A':
__flags.__type = _Flags::_Type::__float_hexadecimal_upper_case;
break;
case 'B':
__flags.__type = _Flags::_Type::__binary_upper_case;
break;
case 'E':
__flags.__type = _Flags::_Type::__scientific_upper_case;
break;
case 'F':
__flags.__type = _Flags::_Type::__fixed_upper_case;
break;
case 'G':
__flags.__type = _Flags::_Type::__general_upper_case;
break;
case 'X':
__flags.__type = _Flags::_Type::__hexadecimal_upper_case;
break;
case 'a':
__flags.__type = _Flags::_Type::__float_hexadecimal_lower_case;
break;
case 'b':
__flags.__type = _Flags::_Type::__binary_lower_case;
break;
case 'c':
__flags.__type = _Flags::_Type::__char;
break;
case 'd':
__flags.__type = _Flags::_Type::__decimal;
break;
case 'e':
__flags.__type = _Flags::_Type::__scientific_lower_case;
break;
case 'f':
__flags.__type = _Flags::_Type::__fixed_lower_case;
break;
case 'g':
__flags.__type = _Flags::_Type::__general_lower_case;
break;
case 'o':
__flags.__type = _Flags::_Type::__octal;
break;
case 'p':
__flags.__type = _Flags::_Type::__pointer;
break;
case 's':
__flags.__type = _Flags::_Type::__string;
break;
case 'x':
__flags.__type = _Flags::_Type::__hexadecimal_lower_case;
break;
default:
return __begin;
}
return ++__begin;
}
/**
* The parser for the std-format-spec.
*
* [format.string.std]/1 specifies the std-format-spec:
* fill-and-align sign # 0 width precision L type
*
* All these fields are optional. Whether these fields can be used depend on:
* - The type supplied to the format string.
* E.g. A string never uses the sign field so the field may not be set.
* This constrain is validated by the parsers in this file.
* - The supplied value for the optional type field.
* E.g. A int formatted as decimal uses the sign field.
* When formatted as a char the sign field may no longer be set.
* This constrain isn't validated by the parsers in this file.
*
* The base classes are ordered to minimize the amount of padding.
*
* This implements the parser for the string types.
*/
template <class _CharT>
class _LIBCPP_TEMPLATE_VIS __parser_string
: public __parser_width, // provides __width(|as_arg)
public __parser_precision, // provides __precision(|as_arg)
public __parser_fill_align<_CharT>, // provides __fill and uses __flags
public _Flags // provides __flags
{
public:
using char_type = _CharT;
_LIBCPP_HIDE_FROM_ABI constexpr __parser_string() {
this->__alignment = _Flags::_Alignment::__left;
}
/**
* The low-level std-format-spec parse function.
*
* @pre __begin points at the beginning of the std-format-spec. This means
* directly after the ':'.
* @pre The std-format-spec parses the entire input, or the first unmatched
* character is a '}'.
*
* @returns The iterator pointing at the last parsed character.
*/
_LIBCPP_HIDE_FROM_ABI constexpr auto parse(auto& __parse_ctx)
-> decltype(__parse_ctx.begin()) {
auto __it = __parse(__parse_ctx);
__process_display_type();
return __it;
}
private:
/**
* Parses the std-format-spec.
*
* @throws __throw_format_error When @a __parse_ctx contains an ill-formed
* std-format-spec.
*
* @returns An iterator to the end of input or point at the closing '}'.
*/
_LIBCPP_HIDE_FROM_ABI constexpr auto __parse(auto& __parse_ctx)
-> decltype(__parse_ctx.begin()) {
auto __begin = __parse_ctx.begin();
auto __end = __parse_ctx.end();
if (__begin == __end)
return __begin;
__begin = __parser_fill_align<_CharT>::__parse(__begin, __end,
static_cast<_Flags&>(*this));
if (__begin == __end)
return __begin;
__begin = __parser_width::__parse(__begin, __end, __parse_ctx);
if (__begin == __end)
return __begin;
__begin = __parser_precision::__parse(__begin, __end, __parse_ctx);
if (__begin == __end)
return __begin;
__begin = __parse_type(__begin, static_cast<_Flags&>(*this));
if (__begin != __end && *__begin != _CharT('}'))
__throw_format_error(
"The format-spec should consume the input or end with a '}'");
return __begin;
}
/** Processes the parsed std-format-spec based on the parsed display type. */
_LIBCPP_HIDE_FROM_ABI constexpr void __process_display_type() {
switch (this->__type) {
case _Flags::_Type::__default:
case _Flags::_Type::__string:
break;
default:
__throw_format_error("The format-spec type has a type not supported for "
"a string argument");
}
}
};
/**
* The parser for the std-format-spec.
*
* This implements the parser for the integral types. This includes the
* character type and boolean type.
*
* See @ref __parser_string.
*/
template <class _CharT>
class _LIBCPP_TEMPLATE_VIS __parser_integral
: public __parser_width, // provides __width(|as_arg)
public __parser_fill_align<_CharT>, // provides __fill and uses __flags
public _Flags // provides __flags
{
public:
using char_type = _CharT;
protected:
/**
* The low-level std-format-spec parse function.
*
* @pre __begin points at the beginning of the std-format-spec. This means
* directly after the ':'.
* @pre The std-format-spec parses the entire input, or the first unmatched
* character is a '}'.
*
* @returns The iterator pointing at the last parsed character.
*/
_LIBCPP_HIDE_FROM_ABI constexpr auto __parse(auto& __parse_ctx)
-> decltype(__parse_ctx.begin()) {
auto __begin = __parse_ctx.begin();
auto __end = __parse_ctx.end();
if (__begin == __end)
return __begin;
__begin = __parser_fill_align<_CharT>::__parse(__begin, __end,
static_cast<_Flags&>(*this));
if (__begin == __end)
return __begin;
__begin = __parse_sign(__begin, static_cast<_Flags&>(*this));
if (__begin == __end)
return __begin;
__begin = __parse_alternate_form(__begin, static_cast<_Flags&>(*this));
if (__begin == __end)
return __begin;
__begin = __parse_zero_padding(__begin, static_cast<_Flags&>(*this));
if (__begin == __end)
return __begin;
__begin = __parser_width::__parse(__begin, __end, __parse_ctx);
if (__begin == __end)
return __begin;
__begin =
__parse_locale_specific_form(__begin, static_cast<_Flags&>(*this));
if (__begin == __end)
return __begin;
__begin = __parse_type(__begin, static_cast<_Flags&>(*this));
if (__begin != __end && *__begin != _CharT('}'))
__throw_format_error(
"The format-spec should consume the input or end with a '}'");
return __begin;
}
/**
* Handles the post-parsing updates for the integer types.
*
* Updates the zero-padding and alignment for integer types.
*
* [format.string.std]/13
* If the 0 character and an align option both appear, the 0 character is
* ignored.
*
* For the formatter a @ref __default alignment means zero-padding. Update
* the alignment based on parsed format string.
*/
_LIBCPP_HIDE_FROM_ABI constexpr void __handle_integer() noexcept {
this->__zero_padding &= this->__alignment == _Flags::_Alignment::__default;
if (!this->__zero_padding &&
this->__alignment == _Flags::_Alignment::__default)
this->__alignment = _Flags::_Alignment::__right;
}
/**
* Handles the post-parsing updates for the character types.
*
* Sets the alignment and validates the format flags set for a character type.
*
* At the moment the validation for a character and a Boolean behave the
* same, but this may change in the future.
* Specifically at the moment the locale-specific form is allowed for the
* char output type, but it has no effect on the output.
*/
_LIBCPP_HIDE_FROM_ABI constexpr void __handle_char() { __handle_bool(); }
/**
* Handles the post-parsing updates for the Boolean types.
*
* Sets the alignment and validates the format flags set for a Boolean type.
*/
_LIBCPP_HIDE_FROM_ABI constexpr void __handle_bool() {
if (this->__sign != _Flags::_Sign::__default)
__throw_format_error("A sign field isn't allowed in this format-spec");
if (this->__alternate_form)
__throw_format_error(
"An alternate form field isn't allowed in this format-spec");
if (this->__zero_padding)
__throw_format_error(
"A zero-padding field isn't allowed in this format-spec");
if (this->__alignment == _Flags::_Alignment::__default)
this->__alignment = _Flags::_Alignment::__left;
}
};
// TODO FMT Add a parser for floating-point values.
// TODO FMT Add a parser for pointer values.
/** Helper struct returned from @ref __get_string_alignment. */
template <class _CharT>
struct _LIBCPP_TEMPLATE_VIS __string_alignment {
/** Points beyond the last character to write to the output. */
const _CharT* __last;
/**
* The estimated number of columns in the output or 0.
*
* Only when the output needs to be aligned it's required to know the exact
* number of columns in the output. So if the formatted output has only a
* minimum width the exact size isn't important. It's only important to know
* the minimum has been reached. The minimum width is the width specified in
* the format-spec.
*
* For example in this code @code std::format("{:10}", MyString); @endcode
* the width estimation can stop once the algorithm has determined the output
* width is 10 columns.
*
* So if:
* * @ref __align == @c true the @ref __size is the estimated number of
* columns required.
* * @ref __align == @c false the @ref __size is the estimated number of
* columns required or 0 when the estimation algorithm stopped prematurely.
*/
ptrdiff_t __size;
/**
* Does the output need to be aligned.
*
* When alignment is needed the output algorithm needs to add the proper
* padding. Else the output algorithm just needs to copy the input up to
* @ref __last.
*/
bool __align;
};
#ifndef _LIBCPP_HAS_NO_UNICODE
namespace __detail {
/**
* Unicode column width estimates.
*
* Unicode can be stored in several formats: UTF-8, UTF-16, and UTF-32.
* Depending on format the relation between the number of code units stored and
* the number of output columns differs. The first relation is the number of
* code units forming a code point. (The text assumes the code units are
* unsigned.)
* - UTF-8 The number of code units is between one and four. The first 127
* Unicode code points match the ASCII character set. When the highest bit is
* set it means the code point has more than one code unit.
* - UTF-16: The number of code units is between 1 and 2. When the first
* code unit is in the range [0xd800,0xdfff) it means the code point uses two
* code units.
* - UTF-32: The number of code units is always one.
*
* The code point to the number of columns isn't well defined. The code uses the
* estimations defined in [format.string.std]/11. This list might change in the
* future.
*
* The algorithm of @ref __get_string_alignment uses two different scanners:
* - The simple scanner @ref __estimate_column_width_fast. This scanner assumes
* 1 code unit is 1 column. This scanner stops when it can't be sure the
* assumption is valid:
* - UTF-8 when the code point is encoded in more than 1 code unit.
* - UTF-16 and UTF-32 when the first multi-column code point is encountered.
* (The code unit's value is lower than 0xd800 so the 2 code unit encoding
* is irrelevant for this scanner.)
* Due to these assumptions the scanner is faster than the full scanner. It
* can process all text only containing ASCII. For UTF-16/32 it can process
* most (all?) European languages. (Note the set it can process might be
* reduced in the future, due to updates in the scanning rules.)
* - The full scanner @ref __estimate_column_width. This scanner, if needed,
* converts multiple code units into one code point then converts the code
* point to a column width.
*
* See also:
* - [format.string.general]/11
* - https://en.wikipedia.org/wiki/UTF-8#Encoding
* - https://en.wikipedia.org/wiki/UTF-16#U+D800_to_U+DFFF
*/
/**
* The first 2 column code point.
*
* This is the point where the fast UTF-16/32 scanner needs to stop processing.
*/
inline constexpr uint32_t __two_column_code_point = 0x1100;
/** Helper concept for an UTF-8 character type. */
template <class _CharT>
concept __utf8_character = same_as<_CharT, char> || same_as<_CharT, char8_t>;
/** Helper concept for an UTF-16 character type. */
template <class _CharT>
concept __utf16_character = (same_as<_CharT, wchar_t> && sizeof(wchar_t) == 2) || same_as<_CharT, char16_t>;
/** Helper concept for an UTF-32 character type. */
template <class _CharT>
concept __utf32_character = (same_as<_CharT, wchar_t> && sizeof(wchar_t) == 4) || same_as<_CharT, char32_t>;
/** Helper concept for an UTF-16 or UTF-32 character type. */
template <class _CharT>
concept __utf16_or_32_character = __utf16_character<_CharT> || __utf32_character<_CharT>;
/**
* Converts a code point to the column width.
*
* The estimations are conforming to [format.string.general]/11
*
* This version expects a value less than 0x1'0000, which is a 3-byte UTF-8
* character.
*/
_LIBCPP_HIDE_FROM_ABI inline constexpr int __column_width_3(uint32_t __c) noexcept {
_LIBCPP_ASSERT(__c < 0x1'0000,
"Use __column_width_4 or __column_width for larger values");
// clang-format off
return 1 + (__c >= 0x1100 && (__c <= 0x115f ||
(__c >= 0x2329 && (__c <= 0x232a ||
(__c >= 0x2e80 && (__c <= 0x303e ||
(__c >= 0x3040 && (__c <= 0xa4cf ||
(__c >= 0xac00 && (__c <= 0xd7a3 ||
(__c >= 0xf900 && (__c <= 0xfaff ||
(__c >= 0xfe10 && (__c <= 0xfe19 ||
(__c >= 0xfe30 && (__c <= 0xfe6f ||
(__c >= 0xff00 && (__c <= 0xff60 ||
(__c >= 0xffe0 && (__c <= 0xffe6
))))))))))))))))))));
// clang-format on
}
/**
* @overload
*
* This version expects a value greater than or equal to 0x1'0000, which is a
* 4-byte UTF-8 character.
*/
_LIBCPP_HIDE_FROM_ABI inline constexpr int __column_width_4(uint32_t __c) noexcept {
_LIBCPP_ASSERT(__c >= 0x1'0000,
"Use __column_width_3 or __column_width for smaller values");
// clang-format off
return 1 + (__c >= 0x1'f300 && (__c <= 0x1'f64f ||
(__c >= 0x1'f900 && (__c <= 0x1'f9ff ||
(__c >= 0x2'0000 && (__c <= 0x2'fffd ||
(__c >= 0x3'0000 && (__c <= 0x3'fffd
))))))));
// clang-format on
}
/**
* @overload
*
* The general case, accepting all values.
*/
_LIBCPP_HIDE_FROM_ABI inline constexpr int __column_width(uint32_t __c) noexcept {
if (__c < 0x1'0000)
return __column_width_3(__c);
return __column_width_4(__c);
}
/**
* Estimate the column width for the UTF-8 sequence using the fast algorithm.
*/
template <__utf8_character _CharT>
_LIBCPP_HIDE_FROM_ABI constexpr const _CharT*
__estimate_column_width_fast(const _CharT* __first,
const _CharT* __last) noexcept {
return _VSTD::find_if(__first, __last,
[](unsigned char __c) { return __c & 0x80; });
}
/**
* @overload
*
* The implementation for UTF-16/32.
*/
template <__utf16_or_32_character _CharT>
_LIBCPP_HIDE_FROM_ABI constexpr const _CharT*
__estimate_column_width_fast(const _CharT* __first,
const _CharT* __last) noexcept {
return _VSTD::find_if(__first, __last,
[](uint32_t __c) { return __c >= 0x1100; });
}
template <class _CharT>
struct _LIBCPP_TEMPLATE_VIS __column_width_result {
/** The number of output columns. */
size_t __width;
/**
* The last parsed element.
*
* This limits the original output to fit in the wanted number of columns.
*/
const _CharT* __ptr;
};
/**
* Small helper to determine the width of malformed Unicode.
*
* @note This function's only needed for UTF-8. During scanning UTF-8 there
* are multiple place where it can be detected that the Unicode is malformed.
* UTF-16 only requires 1 test and UTF-32 requires no testing.
*/
template <__utf8_character _CharT>
_LIBCPP_HIDE_FROM_ABI constexpr __column_width_result<_CharT>
__estimate_column_width_malformed(const _CharT* __first, const _CharT* __last,
size_t __maximum, size_t __result) noexcept {
size_t __size = __last - __first;
size_t __n = _VSTD::min(__size, __maximum);
return {__result + __n, __first + __n};
}
/**
* Determines the number of output columns needed to render the input.
*
* @note When the scanner encounters malformed Unicode it acts as-if every code
* unit at the end of the input is one output column. It's expected the output
* terminal will replace these malformed code units with a one column
* replacement characters.
*
* @param __first Points to the first element of the input range.
* @param __last Points beyond the last element of the input range.
* @param __maximum The maximum number of output columns. The returned number
* of estimated output columns will not exceed this value.
*/
template <__utf8_character _CharT>
_LIBCPP_HIDE_FROM_ABI constexpr __column_width_result<_CharT>
__estimate_column_width(const _CharT* __first, const _CharT* __last,
size_t __maximum) noexcept {
size_t __result = 0;
while (__first != __last) {
// Based on the number of leading 1 bits the number of code units in the
// code point can be determined. See
// https://en.wikipedia.org/wiki/UTF-8#Encoding
switch (_VSTD::countl_one(static_cast<unsigned char>(*__first))) {
case 0: // 1-code unit encoding: all 1 column
++__result;
++__first;
break;
case 2: // 2-code unit encoding: all 1 column
// Malformed Unicode.
if (__last - __first < 2) [[unlikely]]
return __estimate_column_width_malformed(__first, __last, __maximum,
__result);
__first += 2;
++__result;
break;
case 3: // 3-code unit encoding: either 1 or 2 columns
// Malformed Unicode.
if (__last - __first < 3) [[unlikely]]
return __estimate_column_width_malformed(__first, __last, __maximum,
__result);
{
uint32_t __c = static_cast<unsigned char>(*__first++) & 0x0f;
__c <<= 6;
__c |= static_cast<unsigned char>(*__first++) & 0x3f;
__c <<= 6;
__c |= static_cast<unsigned char>(*__first++) & 0x3f;
__result += __column_width_3(__c);
if (__result > __maximum)
return {__result - 2, __first - 3};
}
break;
case 4: // 4-code unit encoding: either 1 or 2 columns
// Malformed Unicode.
if (__last - __first < 4) [[unlikely]]
return __estimate_column_width_malformed(__first, __last, __maximum,
__result);
{
uint32_t __c = static_cast<unsigned char>(*__first++) & 0x07;
__c <<= 6;
__c |= static_cast<unsigned char>(*__first++) & 0x3f;
__c <<= 6;
__c |= static_cast<unsigned char>(*__first++) & 0x3f;
__c <<= 6;
__c |= static_cast<unsigned char>(*__first++) & 0x3f;
__result += __column_width_4(__c);
if (__result > __maximum)
return {__result - 2, __first - 4};
}
break;
default:
// Malformed Unicode.
return __estimate_column_width_malformed(__first, __last, __maximum,
__result);
}
if (__result >= __maximum)
return {__result, __first};
}
return {__result, __first};
}
template <__utf16_character _CharT>
_LIBCPP_HIDE_FROM_ABI constexpr __column_width_result<_CharT>
__estimate_column_width(const _CharT* __first, const _CharT* __last,
size_t __maximum) noexcept {
size_t __result = 0;
while (__first != __last) {
uint32_t __c = *__first;
// Is the code unit part of a surrogate pair? See
// https://en.wikipedia.org/wiki/UTF-16#U+D800_to_U+DFFF
if (__c >= 0xd800 && __c <= 0xDfff) {
// Malformed Unicode.
if (__last - __first < 2) [[unlikely]]
return {__result + 1, __first + 1};
__c -= 0xd800;
__c <<= 10;
__c += (*(__first + 1) - 0xdc00);
__c += 0x10'000;
__result += __column_width_4(__c);
if (__result > __maximum)
return {__result - 2, __first};
__first += 2;
} else {
__result += __column_width_3(__c);
if (__result > __maximum)
return {__result - 2, __first};
++__first;
}
if (__result >= __maximum)
return {__result, __first};
}
return {__result, __first};
}
template <__utf32_character _CharT>
_LIBCPP_HIDE_FROM_ABI constexpr __column_width_result<_CharT>
__estimate_column_width(const _CharT* __first, const _CharT* __last,
size_t __maximum) noexcept {
size_t __result = 0;
while (__first != __last) {
wchar_t __c = *__first;
__result += __column_width(__c);
if (__result > __maximum)
return {__result - 2, __first};
++__first;
if (__result >= __maximum)
return {__result, __first};
}
return {__result, __first};
}
} // namespace __detail
template <class _CharT>
_LIBCPP_HIDE_FROM_ABI constexpr __string_alignment<_CharT>
__get_string_alignment(const _CharT* __first, const _CharT* __last,
ptrdiff_t __width, ptrdiff_t __precision) noexcept {
_LIBCPP_ASSERT(__width != 0 || __precision != -1,
"The function has no effect and shouldn't be used");
// TODO FMT There might be more optimizations possible:
// If __precision == __format::__number_max and the encoding is:
// * UTF-8 : 4 * (__last - __first) >= __width
// * UTF-16 : 2 * (__last - __first) >= __width
// * UTF-32 : (__last - __first) >= __width
// In these cases it's certain the output is at least the requested width.
// It's unknown how often this happens in practice. For now the improvement
// isn't implemented.
/*
* First assume there are no special Unicode code units in the input.
* - Apply the precision (this may reduce the size of the input). When
* __precison == -1 this step is omitted.
* - Scan for special code units in the input.
* If our assumption was correct the __pos will be at the end of the input.
*/
const ptrdiff_t __length = __last - __first;
const _CharT* __limit =
__first +
(__precision == -1 ? __length : _VSTD::min(__length, __precision));
ptrdiff_t __size = __limit - __first;
const _CharT* __pos =
__detail::__estimate_column_width_fast(__first, __limit);
if (__pos == __limit)
return {__limit, __size, __size < __width};
/*
* Our assumption was wrong, there are special Unicode code units.
* The range [__first, __pos) contains a set of code units with the
* following property:
* Every _CharT in the range will be rendered in 1 column.
*
* If there's no maximum width and the parsed size already exceeds the
* minimum required width. The real size isn't important. So bail out.
*/
if (__precision == -1 && (__pos - __first) >= __width)
return {__last, 0, false};
/* If there's a __precision, truncate the output to that width. */
ptrdiff_t __prefix = __pos - __first;
if (__precision != -1) {
_LIBCPP_ASSERT(__precision > __prefix, "Logic error.");
auto __lengh_info = __detail::__estimate_column_width(
__pos, __last, __precision - __prefix);
__size = __lengh_info.__width + __prefix;
return {__lengh_info.__ptr, __size, __size < __width};
}
/* Else use __width to determine the number of required padding characters. */
_LIBCPP_ASSERT(__width > __prefix, "Logic error.");
/*
* The column width is always one or two columns. For the precision the wanted
* column width is the maximum, for the width it's the minimum. Using the
* width estimation with its truncating behavior will result in the wrong
* result in the following case:
* - The last code unit processed requires two columns and exceeds the
* maximum column width.
* By increasing the __maximum by one avoids this issue. (It means it may
* pass one code point more than required to determine the proper result;
* that however isn't a problem for the algorithm.)
*/
size_t __maximum = 1 + __width - __prefix;
auto __lengh_info =
__detail::__estimate_column_width(__pos, __last, __maximum);
if (__lengh_info.__ptr != __last) {
// Consumed the width number of code units. The exact size of the string
// is unknown. We only know we don't need to align the output.
_LIBCPP_ASSERT(static_cast<ptrdiff_t>(__lengh_info.__width + __prefix) >=
__width,
"Logic error");
return {__last, 0, false};
}
__size = __lengh_info.__width + __prefix;
return {__last, __size, __size < __width};
}
#else // _LIBCPP_HAS_NO_UNICODE
template <class _CharT>
_LIBCPP_HIDE_FROM_ABI constexpr __string_alignment<_CharT>
__get_string_alignment(const _CharT* __first, const _CharT* __last,
ptrdiff_t __width, ptrdiff_t __precision) noexcept {
const ptrdiff_t __length = __last - __first;
const _CharT* __limit =
__first +
(__precision == -1 ? __length : _VSTD::min(__length, __precision));
ptrdiff_t __size = __limit - __first;
return {__limit, __size, __size < __width};
}
#endif // _LIBCPP_HAS_NO_UNICODE
} // namespace __format_spec
# endif // !defined(_LIBCPP_HAS_NO_CONCEPTS)
#endif //_LIBCPP_STD_VER > 17
_LIBCPP_END_NAMESPACE_STD
_LIBCPP_POP_MACROS
#endif // _LIBCPP___FORMAT_PARSER_STD_FORMAT_SPEC_H