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Differential D145590 Diff 505163 libcxx/include/__charconv/to_chars_integral.h

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libcxx/include/__charconv/to_chars_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___CHARCONV_TO_CHARS_INTEGRAL_H
#define _LIBCPP___CHARCONV_TO_CHARS_INTEGRAL_H
#include <__algorithm/copy_n.h>
#include <__bit/countl.h>
#include <__charconv/tables.h>
#include <__charconv/to_chars_base_10.h>
#include <__charconv/to_chars_result.h>
#include <__charconv/traits.h>
#include <__config>
#include <__errc>
#include <__type_traits/enable_if.h>
#include <__type_traits/integral_constant.h>
#include <__type_traits/is_same.h>
#include <__type_traits/make_32_64_or_128_bit.h>
#include <__type_traits/make_unsigned.h>
#include <__utility/unreachable.h>
#include <cstddef>
#include <cstdint>
#include <limits>
#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
to_chars_result to_chars(char*, char*, bool, int = 10) = delete;
template <typename _Tp>
inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
__to_chars_itoa(char* __first, char* __last, _Tp __value, false_type);
template <typename _Tp>
inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
__to_chars_itoa(char* __first, char* __last, _Tp __value, true_type)
{
auto __x = std::__to_unsigned_like(__value);
if (__value < 0 && __first != __last)
{
*__first++ = '-';
__x = std::__complement(__x);
}
return std::__to_chars_itoa(__first, __last, __x, false_type());
}
template <typename _Tp>
inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
__to_chars_itoa(char* __first, char* __last, _Tp __value, false_type)
{
using __tx = __itoa::__traits<_Tp>;
auto __diff = __last - __first;
if (__tx::digits <= __diff || __tx::__width(__value) <= __diff)
return {__tx::__convert(__first, __value), errc(0)};
else
return {__last, errc::value_too_large};
}
# ifndef _LIBCPP_HAS_NO_INT128
template <>
inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
__to_chars_itoa(char* __first, char* __last, __uint128_t __value, false_type)
{
// When the value fits in 64-bits use the 64-bit code path. This reduces
// the number of expensive calculations on 128-bit values.
//
// NOTE the 128-bit code path requires this optimization.
if(__value <= numeric_limits<uint64_t>::max())
return __to_chars_itoa(__first, __last, static_cast<uint64_t>(__value), false_type());
using __tx = __itoa::__traits<__uint128_t>;
auto __diff = __last - __first;
if (__tx::digits <= __diff || __tx::__width(__value) <= __diff)
return {__tx::__convert(__first, __value), errc(0)};
else
return {__last, errc::value_too_large};
}
#endif
template <class _Tp>
inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
__to_chars_integral(char* __first, char* __last, _Tp __value, int __base, false_type);
template <typename _Tp>
inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
__to_chars_integral(char* __first, char* __last, _Tp __value, int __base,
true_type)
{
auto __x = std::__to_unsigned_like(__value);
if (__value < 0 && __first != __last)
{
*__first++ = '-';
__x = std::__complement(__x);
}
return std::__to_chars_integral(__first, __last, __x, __base, false_type());
}
namespace __itoa {
template <unsigned _Base>
struct _LIBCPP_HIDDEN __integral;
template <>
struct _LIBCPP_HIDDEN __integral<2> {
template <typename _Tp>
_LIBCPP_HIDE_FROM_ABI static constexpr int __width(_Tp __value) noexcept {
// If value == 0 still need one digit. If the value != this has no
// effect since the code scans for the most significant bit set. (Note
// that __libcpp_clz doesn't work for 0.)
return numeric_limits<_Tp>::digits - std::__libcpp_clz(__value | 1);
}
template <typename _Tp>
_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI static to_chars_result __to_chars(char* __first, char* __last, _Tp __value) {
ptrdiff_t __cap = __last - __first;
int __n = __width(__value);
if (__n > __cap)
return {__last, errc::value_too_large};
__last = __first + __n;
char* __p = __last;
const unsigned __divisor = 16;
while (__value > __divisor) {
unsigned __c = __value % __divisor;
__value /= __divisor;
__p -= 4;
std::copy_n(&__base_2_lut[4 * __c], 4, __p);
}
do {
unsigned __c = __value % 2;
__value /= 2;
*--__p = "01"[__c];
} while (__value != 0);
return {__last, errc(0)};
}
};
template <>
struct _LIBCPP_HIDDEN __integral<8> {
template <typename _Tp>
_LIBCPP_HIDE_FROM_ABI static constexpr int __width(_Tp __value) noexcept {
// If value == 0 still need one digit. If the value != this has no
// effect since the code scans for the most significat bit set. (Note
// that __libcpp_clz doesn't work for 0.)
return ((numeric_limits<_Tp>::digits - std::__libcpp_clz(__value | 1)) + 2) / 3;
}
template <typename _Tp>
_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI static to_chars_result __to_chars(char* __first, char* __last, _Tp __value) {
ptrdiff_t __cap = __last - __first;
int __n = __width(__value);
if (__n > __cap)
return {__last, errc::value_too_large};
__last = __first + __n;
char* __p = __last;
unsigned __divisor = 64;
while (__value > __divisor) {
unsigned __c = __value % __divisor;
__value /= __divisor;
__p -= 2;
std::copy_n(&__base_8_lut[2 * __c], 2, __p);
}
do {
unsigned __c = __value % 8;
__value /= 8;
*--__p = "01234567"[__c];
} while (__value != 0);
return {__last, errc(0)};
}
};
template <>
struct _LIBCPP_HIDDEN __integral<16> {
template <typename _Tp>
_LIBCPP_HIDE_FROM_ABI static constexpr int __width(_Tp __value) noexcept {
// If value == 0 still need one digit. If the value != this has no
// effect since the code scans for the most significat bit set. (Note
// that __libcpp_clz doesn't work for 0.)
return (numeric_limits<_Tp>::digits - std::__libcpp_clz(__value | 1) + 3) / 4;
}
template <typename _Tp>
_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI static to_chars_result __to_chars(char* __first, char* __last, _Tp __value) {
ptrdiff_t __cap = __last - __first;
int __n = __width(__value);
if (__n > __cap)
return {__last, errc::value_too_large};
__last = __first + __n;
char* __p = __last;
unsigned __divisor = 256;
while (__value > __divisor) {
unsigned __c = __value % __divisor;
__value /= __divisor;
__p -= 2;
std::copy_n(&__base_16_lut[2 * __c], 2, __p);
}
if (__first != __last)
do {
unsigned __c = __value % 16;
__value /= 16;
*--__p = "0123456789abcdef"[__c];
} while (__value != 0);
return {__last, errc(0)};
}
};
} // namespace __itoa
template <unsigned _Base, typename _Tp,
typename enable_if<(sizeof(_Tp) >= sizeof(unsigned)), int>::type = 0>
_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI int
__to_chars_integral_width(_Tp __value) {
return __itoa::__integral<_Base>::__width(__value);
}
template <unsigned _Base, typename _Tp,
typename enable_if<(sizeof(_Tp) < sizeof(unsigned)), int>::type = 0>
_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI int
__to_chars_integral_width(_Tp __value) {
return std::__to_chars_integral_width<_Base>(static_cast<unsigned>(__value));
}
template <unsigned _Base, typename _Tp,
typename enable_if<(sizeof(_Tp) >= sizeof(unsigned)), int>::type = 0>
_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
__to_chars_integral(char* __first, char* __last, _Tp __value) {
return __itoa::__integral<_Base>::__to_chars(__first, __last, __value);
}
template <unsigned _Base, typename _Tp,
typename enable_if<(sizeof(_Tp) < sizeof(unsigned)), int>::type = 0>
_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
__to_chars_integral(char* __first, char* __last, _Tp __value) {
return std::__to_chars_integral<_Base>(__first, __last, static_cast<unsigned>(__value));
}
template <typename _Tp>
_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI int
__to_chars_integral_width(_Tp __value, unsigned __base) {
_LIBCPP_ASSERT(__value >= 0, "The function requires a non-negative value.");
unsigned __base_2 = __base * __base;
unsigned __base_3 = __base_2 * __base;
unsigned __base_4 = __base_2 * __base_2;
int __r = 0;
while (true) {
if (__value < __base)
return __r + 1;
if (__value < __base_2)
return __r + 2;
if (__value < __base_3)
return __r + 3;
if (__value < __base_4)
return __r + 4;
__value /= __base_4;
__r += 4;
}
__libcpp_unreachable();
}
template <typename _Tp>
inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
__to_chars_integral(char* __first, char* __last, _Tp __value, int __base,
false_type)
{
if (__base == 10) [[likely]]
return std::__to_chars_itoa(__first, __last, __value, false_type());
switch (__base) {
case 2:
return std::__to_chars_integral<2>(__first, __last, __value);
case 8:
return std::__to_chars_integral<8>(__first, __last, __value);
case 16:
return std::__to_chars_integral<16>(__first, __last, __value);
}
ptrdiff_t __cap = __last - __first;
int __n = std::__to_chars_integral_width(__value, __base);
if (__n > __cap)
return {__last, errc::value_too_large};
__last = __first + __n;
char* __p = __last;
do {
unsigned __c = __value % __base;
__value /= __base;
*--__p = "0123456789abcdefghijklmnopqrstuvwxyz"[__c];
} while (__value != 0);
return {__last, errc(0)};
}
template <typename _Tp, typename enable_if<is_integral<_Tp>::value, int>::type = 0>
inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
to_chars(char* __first, char* __last, _Tp __value)
{
using _Type = __make_32_64_or_128_bit_t<_Tp>;
static_assert(!is_same<_Type, void>::value, "unsupported integral type used in to_chars");
return std::__to_chars_itoa(__first, __last, static_cast<_Type>(__value), is_signed<_Tp>());
}
template <typename _Tp, typename enable_if<is_integral<_Tp>::value, int>::type = 0>
inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
to_chars(char* __first, char* __last, _Tp __value, int __base)
{
_LIBCPP_ASSERT(2 <= __base && __base <= 36, "base not in [2, 36]");
using _Type = __make_32_64_or_128_bit_t<_Tp>;
return std::__to_chars_integral(__first, __last, static_cast<_Type>(__value), __base, is_signed<_Tp>());
}
philnikUnsubmitted
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I think we should put these and the floating point overloads in a __fwd/to_chars.h header to avoid having a different overload set depending on what file is included. A linker error is a lot better than a program that compiler but is subtly wrong.

philnik: I think we should put these and the floating point overloads in a `__fwd/to_chars.h` header to…
MordanteAuthorUnsubmitted
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I did this on purpose, when I use the floating point formatter, I can include that light header. I don't see a huge issue with this approach. This is only used in the library internally.

Mordante: I did this on purpose, when I use the floating point formatter, I can include that light header.
philnikUnsubmitted
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Adding two forward declarations doesn't make this much heavier. My concern is that someone might rely on this being included transitively, and they get unexpected behaviour.

philnik: Adding two forward declarations doesn't make this much heavier. My concern is that someone…
MordanteAuthorUnsubmitted
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I tried it, but then Clang (rightfully) complains about duplicated default arguments. It also pulls in some headers for the floating-point case. So for now I keep it as is.

Mordante: I tried it, but then Clang (rightfully) complains about duplicated default arguments. It also…
philnikUnsubmitted
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The default arguments shouldn't be a problem. Simply set the defaults in the forward declaration and include the forward-declaration header when you define them.
What headers are pulled in by that? If it's just __type_traits/enable_if.h and __type_traits/is_integral.h, I don't think that's a real problem. These headers are tiny.

philnik: The default arguments shouldn't be a problem. Simply set the defaults in the forward…
MordanteAuthorUnsubmitted
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I just dislike that solution where we have two declarations.

Instead I added a new to_chars.h private header including them both. So you can pick that one or if you know what you're doing the even more specialized ones.

Mordante: I just dislike that solution where we have two declarations. Instead I added a new `to_chars.
philnikUnsubmitted
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I really don't get why you are so vehemently against this. It's really not a lot of work and could easily fix super subtle bugs. I also don't think that adding another header is a fix for this. It still splits up the interface.

philnik: I really don't get why you are so vehemently against this. It's really not a lot of work and…
#endif // _LIBCPP_STD_VER >= 17
_LIBCPP_END_NAMESPACE_STD
_LIBCPP_POP_MACROS
#endif // _LIBCPP___CHARCONV_TO_CHARS_INTEGRAL_H