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llvm-project/libcxx/include/__format/formatter_integral.h

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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_FORMATTER_INTEGRAL_H
#define _LIBCPP___FORMAT_FORMATTER_INTEGRAL_H
#include <__algorithm/copy.h>
#include <__algorithm/copy_n.h>
#include <__algorithm/fill_n.h>
#include <__algorithm/transform.h>
#include <__assert>
#include <__config>
#include <__format/format_error.h>
#include <__format/format_fwd.h>
#include <__format/formatter.h>
#include <__format/parser_std_format_spec.h>
#include <__utility/unreachable.h>
#include <array>
#include <charconv>
#include <concepts>
#include <limits>
#include <string>
#ifndef _LIBCPP_HAS_NO_LOCALIZATION
#include <locale>
#endif
#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
/**
* Integral formatting classes.
*
* There are two types used here:
* * C++-type, the type as used in C++.
* * format-type, the output type specified in the std-format-spec.
*
* Design of the integral formatters consists of several layers.
* * @ref __parser_integral The basic std-format-spec parser for all integral
* classes. This parser does the basic sanity checks. It also contains some
* helper functions that are nice to have available for all parsers.
* * A C++-type specific parser. These parsers must derive from
* @ref __parser_integral. Their task is to validate whether the parsed
* std-format-spec is valid for the C++-type and selected format-type. After
* validation they need to make sure all members are properly set. For
* example, when the alignment hasn't changed it needs to set the proper
* default alignment for the format-type. The following parsers are available:
* - @ref __parser_integer
* - @ref __parser_char
* - @ref __parser_bool
* * A general formatter for all integral types @ref __formatter_integral. This
* formatter can handle all formatting of integers and characters. The class
* derives from the proper formatter.
* Note the boolean string format-type isn't supported in this class.
* * A typedef C++-type group combining the @ref __formatter_integral with a
* parser:
* * @ref __formatter_integer
* * @ref __formatter_char
* * @ref __formatter_bool
* * Then every C++-type has its own formatter specializations. They inherit
* from the C++-type group typedef. Most specializations need nothing else.
* Others need some additional specializations in this class.
*/
namespace __format_spec {
/** Wrapper around @ref to_chars, returning the output pointer. */
template <integral _Tp>
_LIBCPP_HIDE_FROM_ABI char* __to_buffer(char* __first, char* __last,
_Tp __value, int __base) {
// TODO FMT Evaluate code overhead due to not calling the internal function
// directly. (Should be zero overhead.)
to_chars_result __r = _VSTD::to_chars(__first, __last, __value, __base);
_LIBCPP_ASSERT(__r.ec == errc(0), "Internal buffer too small");
return __r.ptr;
}
/**
* Helper to determine the buffer size to output a integer in Base @em x.
*
* There are several overloads for the supported bases. The function uses the
* base as template argument so it can be used in a constant expression.
*/
template <unsigned_integral _Tp, size_t _Base>
_LIBCPP_HIDE_FROM_ABI constexpr size_t __buffer_size() noexcept
requires(_Base == 2) {
return numeric_limits<_Tp>::digits // The number of binary digits.
+ 2 // Reserve space for the '0[Bb]' prefix.
+ 1; // Reserve space for the sign.
}
template <unsigned_integral _Tp, size_t _Base>
_LIBCPP_HIDE_FROM_ABI constexpr size_t __buffer_size() noexcept
requires(_Base == 8) {
return numeric_limits<_Tp>::digits // The number of binary digits.
/ 3 // Adjust to octal.
+ 1 // Turn floor to ceil.
+ 1 // Reserve space for the '0' prefix.
+ 1; // Reserve space for the sign.
}
template <unsigned_integral _Tp, size_t _Base>
_LIBCPP_HIDE_FROM_ABI constexpr size_t __buffer_size() noexcept
requires(_Base == 10) {
return numeric_limits<_Tp>::digits10 // The floored value.
+ 1 // Turn floor to ceil.
+ 1; // Reserve space for the sign.
}
template <unsigned_integral _Tp, size_t _Base>
_LIBCPP_HIDE_FROM_ABI constexpr size_t __buffer_size() noexcept
requires(_Base == 16) {
return numeric_limits<_Tp>::digits // The number of binary digits.
/ 4 // Adjust to hexadecimal.
+ 2 // Reserve space for the '0[Xx]' prefix.
+ 1; // Reserve space for the sign.
}
/**
* Determines the required grouping based on the size of the input.
*
* The grouping's last element will be repeated. For simplicity this repeating
* is unwrapped based on the length of the input. (When the input is short some
* groups are not processed.)
*
* @returns The size of the groups to write. This means the number of
* separator characters written is size() - 1.
*
* @note Since zero-sized groups cause issues they are silently ignored.
*
* @note The grouping field of the locale is always a @c std::string,
* regardless whether the @c std::numpunct's type is @c char or @c wchar_t.
*/
_LIBCPP_HIDE_FROM_ABI inline string
__determine_grouping(ptrdiff_t __size, const string& __grouping) {
_LIBCPP_ASSERT(!__grouping.empty() && __size > __grouping[0],
"The slow grouping formatting is used while there will be no "
"separators written");
string __r;
auto __end = __grouping.end() - 1;
auto __ptr = __grouping.begin();
while (true) {
__size -= *__ptr;
if (__size > 0)
__r.push_back(*__ptr);
else {
// __size <= 0 so the value pushed will be <= *__ptr.
__r.push_back(*__ptr + __size);
return __r;
}
// Proceed to the next group.
if (__ptr != __end) {
do {
++__ptr;
// Skip grouping with a width of 0.
} while (*__ptr == 0 && __ptr != __end);
}
}
__libcpp_unreachable();
}
template <class _Parser>
requires __formatter::__char_type<typename _Parser::char_type>
class _LIBCPP_TEMPLATE_VIS __formatter_integral : public _Parser {
public:
using _CharT = typename _Parser::char_type;
template <integral _Tp>
_LIBCPP_HIDE_FROM_ABI auto format(_Tp __value, auto& __ctx)
-> decltype(__ctx.out()) {
if (this->__width_needs_substitution())
this->__substitute_width_arg_id(__ctx.arg(this->__width));
if (this->__type == _Flags::_Type::__char)
return __format_as_char(__value, __ctx);
if constexpr (unsigned_integral<_Tp>)
return __format_unsigned_integral(__value, false, __ctx);
else {
// Depending on the std-format-spec string the sign and the value
// might not be outputted together:
// - alternate form may insert a prefix string.
// - zero-padding may insert additional '0' characters.
// Therefore the value is processed as a positive unsigned value.
// The function @ref __insert_sign will a '-' when the value was negative.
auto __r = __to_unsigned_like(__value);
bool __negative = __value < 0;
if (__negative)
__r = __complement(__r);
return __format_unsigned_integral(__r, __negative, __ctx);
}
}
private:
/** Generic formatting for format-type c. */
_LIBCPP_HIDE_FROM_ABI auto __format_as_char(integral auto __value,
auto& __ctx)
-> decltype(__ctx.out()) {
if (this->__alignment == _Flags::_Alignment::__default)
this->__alignment = _Flags::_Alignment::__right;
using _Tp = decltype(__value);
if constexpr (!same_as<_CharT, _Tp>) {
// cmp_less and cmp_greater can't be used for character types.
if constexpr (signed_integral<_CharT> == signed_integral<_Tp>) {
if (__value < numeric_limits<_CharT>::min() ||
__value > numeric_limits<_CharT>::max())
__throw_format_error(
"Integral value outside the range of the char type");
} else if constexpr (signed_integral<_CharT>) {
// _CharT is signed _Tp is unsigned
if (__value >
static_cast<make_unsigned_t<_CharT>>(numeric_limits<_CharT>::max()))
__throw_format_error(
"Integral value outside the range of the char type");
} else {
// _CharT is unsigned _Tp is signed
if (__value < 0 || static_cast<make_unsigned_t<_Tp>>(__value) >
numeric_limits<_CharT>::max())
__throw_format_error(
"Integral value outside the range of the char type");
}
}
const auto __c = static_cast<_CharT>(__value);
return __write(_VSTD::addressof(__c), _VSTD::addressof(__c) + 1,
__ctx.out());
}
/**
* Generic formatting for format-type bBdoxX.
*
* This small wrapper allocates a buffer with the required size. Then calls
* the real formatter with the buffer and the prefix for the base.
*/
_LIBCPP_HIDE_FROM_ABI auto
__format_unsigned_integral(unsigned_integral auto __value, bool __negative,
auto& __ctx) -> decltype(__ctx.out()) {
switch (this->__type) {
case _Flags::_Type::__binary_lower_case: {
array<char, __buffer_size<decltype(__value), 2>()> __array;
return __format_unsigned_integral(__array.begin(), __array.end(), __value,
__negative, 2, __ctx, "0b");
}
case _Flags::_Type::__binary_upper_case: {
array<char, __buffer_size<decltype(__value), 2>()> __array;
return __format_unsigned_integral(__array.begin(), __array.end(), __value,
__negative, 2, __ctx, "0B");
}
case _Flags::_Type::__octal: {
// Octal is special; if __value == 0 there's no prefix.
array<char, __buffer_size<decltype(__value), 8>()> __array;
return __format_unsigned_integral(__array.begin(), __array.end(), __value,
__negative, 8, __ctx,
__value != 0 ? "0" : nullptr);
}
case _Flags::_Type::__decimal: {
array<char, __buffer_size<decltype(__value), 10>()> __array;
return __format_unsigned_integral(__array.begin(), __array.end(), __value,
__negative, 10, __ctx, nullptr);
}
case _Flags::_Type::__hexadecimal_lower_case: {
array<char, __buffer_size<decltype(__value), 16>()> __array;
return __format_unsigned_integral(__array.begin(), __array.end(), __value,
__negative, 16, __ctx, "0x");
}
case _Flags::_Type::__hexadecimal_upper_case: {
array<char, __buffer_size<decltype(__value), 16>()> __array;
return __format_unsigned_integral(__array.begin(), __array.end(), __value,
__negative, 16, __ctx, "0X");
}
default:
_LIBCPP_ASSERT(false, "The parser should have validated the type");
__libcpp_unreachable();
}
}
template <class _Tp>
requires(same_as<char, _Tp> || same_as<wchar_t, _Tp>) _LIBCPP_HIDE_FROM_ABI
auto __write(const _Tp* __first, const _Tp* __last, auto __out_it)
-> decltype(__out_it) {
unsigned __size = __last - __first;
if (this->__type != _Flags::_Type::__hexadecimal_upper_case) [[likely]] {
if (__size >= this->__width)
return _VSTD::copy(__first, __last, _VSTD::move(__out_it));
return __formatter::__write(_VSTD::move(__out_it), __first, __last,
__size, this->__width, this->__fill,
this->__alignment);
}
// this->__type == _Flags::_Type::__hexadecimal_upper_case
// This means all characters in the range [a-f] need to be changed to their
// uppercase representation. The transformation is done as transformation
// in the output routine instead of before. This avoids another pass over
// the data.
// TODO FMT See whether it's possible to do this transformation during the
// conversion. (This probably requires changing std::to_chars' alphabet.)
if (__size >= this->__width)
return _VSTD::transform(__first, __last, _VSTD::move(__out_it),
__hex_to_upper);
return __formatter::__write(_VSTD::move(__out_it), __first, __last, __size,
__hex_to_upper, this->__width, this->__fill,
this->__alignment);
}
_LIBCPP_HIDE_FROM_ABI auto
__format_unsigned_integral(char* __begin, char* __end,
unsigned_integral auto __value, bool __negative,
int __base, auto& __ctx, const char* __prefix)
-> decltype(__ctx.out()) {
char* __first = __insert_sign(__begin, __negative, this->__sign);
if (this->__alternate_form && __prefix)
while (*__prefix)
*__first++ = *__prefix++;
char* __last = __to_buffer(__first, __end, __value, __base);
#ifndef _LIBCPP_HAS_NO_LOCALIZATION
if (this->__locale_specific_form) {
const auto& __np = use_facet<numpunct<_CharT>>(__ctx.locale());
string __grouping = __np.grouping();
ptrdiff_t __size = __last - __first;
// Writing the grouped form has more overhead than the normal output
// routines. If there will be no separators written the locale-specific
// form is identical to the normal routine. Test whether to grouped form
// is required.
if (!__grouping.empty() && __size > __grouping[0])
return __format_grouping(__ctx.out(), __begin, __first, __last,
__determine_grouping(__size, __grouping),
__np.thousands_sep());
}
#endif
auto __out_it = __ctx.out();
if (this->__alignment != _Flags::_Alignment::__default)
__first = __begin;
else {
// __buf contains [sign][prefix]data
// ^ location of __first
// The zero padding is done like:
// - Write [sign][prefix]
// - Write data right aligned with '0' as fill character.
__out_it = _VSTD::copy(__begin, __first, _VSTD::move(__out_it));
this->__alignment = _Flags::_Alignment::__right;
this->__fill = _CharT('0');
uint32_t __size = __first - __begin;
this->__width -= _VSTD::min(__size, this->__width);
}
return __write(__first, __last, _VSTD::move(__out_it));
}
#ifndef _LIBCPP_HAS_NO_LOCALIZATION
/** Format's the locale-specific form's groupings. */
template <class _OutIt, class _CharT>
_LIBCPP_HIDE_FROM_ABI _OutIt
__format_grouping(_OutIt __out_it, const char* __begin, const char* __first,
const char* __last, string&& __grouping, _CharT __sep) {
// TODO FMT This function duplicates some functionality of the normal
// output routines. Evaluate whether these parts can be efficiently
// combined with the existing routines.
unsigned __size = (__first - __begin) + // [sign][prefix]
(__last - __first) + // data
(__grouping.size() - 1); // number of separator characters
__formatter::__padding_size_result __padding = {0, 0};
if (this->__alignment == _Flags::_Alignment::__default) {
// Write [sign][prefix].
__out_it = _VSTD::copy(__begin, __first, _VSTD::move(__out_it));
if (this->__width > __size) {
// Write zero padding.
__padding.__before = this->__width - __size;
__out_it = _VSTD::fill_n(_VSTD::move(__out_it), this->__width - __size,
_CharT('0'));
}
} else {
if (this->__width > __size) {
// Determine padding and write padding.
__padding = __formatter::__padding_size(__size, this->__width,
this->__alignment);
__out_it = _VSTD::fill_n(_VSTD::move(__out_it), __padding.__before,
this->__fill);
}
// Write [sign][prefix].
__out_it = _VSTD::copy(__begin, __first, _VSTD::move(__out_it));
}
auto __r = __grouping.rbegin();
auto __e = __grouping.rend() - 1;
_LIBCPP_ASSERT(__r != __e, "The slow grouping formatting is used while "
"there will be no separators written.");
// The output is divided in small groups of numbers to write:
// - A group before the first separator.
// - A separator and a group, repeated for the number of separators.
// - A group after the last separator.
// This loop achieves that process by testing the termination condition
// midway in the loop.
//
// TODO FMT This loop evaluates the loop invariant `this->__type !=
// _Flags::_Type::__hexadecimal_upper_case` for every iteration. (This test
// happens in the __write call.) Benchmark whether making two loops and
// hoisting the invariant is worth the effort.
while (true) {
if (this->__type == _Flags::_Type::__hexadecimal_upper_case) {
__last = __first + *__r;
__out_it = _VSTD::transform(__first, __last, _VSTD::move(__out_it),
__hex_to_upper);
__first = __last;
} else {
__out_it = _VSTD::copy_n(__first, *__r, _VSTD::move(__out_it));
__first += *__r;
}
if (__r == __e)
break;
++__r;
*__out_it++ = __sep;
}
return _VSTD::fill_n(_VSTD::move(__out_it), __padding.__after,
this->__fill);
}
#endif // _LIBCPP_HAS_NO_LOCALIZATION
};
} // namespace __format_spec
#endif //_LIBCPP_STD_VER > 17
_LIBCPP_END_NAMESPACE_STD
_LIBCPP_POP_MACROS
#endif // _LIBCPP___FORMAT_FORMATTER_INTEGRAL_H
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