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libstdc++: Refactor filesystem::path string conversions

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This simplifies the logic of converting Source arguments and pairs of
InputIterator arguments into the native string format. For any input
that is a contiguous range of path::value_type (or char8_t for POSIX)
a string view can be created and the conversion can be done directly,
with no intermediate allocation. Previously some cases created a
basic_string unnecessarily, for example construction from a pair of
path::string_type::iterators, or a pair of non-const value_type*
pointers.

	* include/bits/fs_path.h (__detail::_S_range_begin)
	(__detail::_S_range_end, path::_S_string_from_iter): Replace with
	overloaded function template __detail::__effective_range.
	(__detail::__effective_range): New overloaded function template to
	create a basic_string or basic_string_view for an effective range.
	(__detail::__value_type_is_char): Use __detail::__effective_range.
	Do not use remove_const on value type.
	(__detail::__value_type_is_char_or_char8_t): Likewise.
	(path::path(const Source&, format))
	(path::path(const Source&, const locale&))
	(path::operator/=(const Source&), path::append(const Source&))
	(path::concat(const Source&)): Use __detail::__effective_range.
	(path::_S_to_string(InputIterator, InputIterator)): New function
	template to create a string view if possible, or string otherwise.
	(path::_S_convert): Add overloads that convert a string returned
	by __detail::__effective_range. Use if-constexpr to inline conversion
	logic from all overloads of _Cvt::_S_convert.
	(path::_S_convert_loc): Add overload that converts a string. Use
	_S_to_string to avoid allocation when possible.
	(path::_Cvt): Remove.
	(path::operator+=(CharT)): Remove indirection through path::concat.
	* include/experimental/bits/fs_path.h (path::_S_convert_loc): Add
	overload for non-const pointers, to avoid constructing a std::string.
	* src/c++17/fs_path.cc (path::_S_convert_loc): Replace conditional
	compilation with call to _S_convert.
This commit is contained in:
Jonathan Wakely 2020-05-23 09:00:32 +01:00
parent 00c8f2a5e3
commit 584d52b088
4 changed files with 200 additions and 199 deletions
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26
libstdc++-v3/ChangeLog
View file

@ -1,5 +1,31 @@
2020-05-23 Jonathan Wakely <jwakely@redhat.com>
* include/bits/fs_path.h (__detail::_S_range_begin)
(__detail::_S_range_end, path::_S_string_from_iter): Replace with
overloaded function template __detail::__effective_range.
(__detail::__effective_range): New overloaded function template to
create a basic_string or basic_string_view for an effective range.
(__detail::__value_type_is_char): Use __detail::__effective_range.
Do not use remove_const on value type.
(__detail::__value_type_is_char_or_char8_t): Likewise.
(path::path(const Source&, format))
(path::path(const Source&, const locale&))
(path::operator/=(const Source&), path::append(const Source&))
(path::concat(const Source&)): Use __detail::__effective_range.
(path::_S_to_string(InputIterator, InputIterator)): New function
template to create a string view if possible, or string otherwise.
(path::_S_convert): Add overloads that convert a string returned
by __detail::__effective_range. Use if-constexpr to inline conversion
logic from all overloads of _Cvt::_S_convert.
(path::_S_convert_loc): Add overload that converts a string. Use
_S_to_string to avoid allocation when possible.
(path::_Cvt): Remove.
(path::operator+=(CharT)): Remove indirection through path::concat.
* include/experimental/bits/fs_path.h (path::_S_convert_loc): Add
overload for non-const pointers, to avoid constructing a std::string.
* src/c++17/fs_path.cc (path::_S_convert_loc): Replace conditional
compilation with call to _S_convert.
* include/bits/fs_path.h (__detail::_S_range_begin)
(__detail::_S_range_end): Remove unintentional static specifiers.
* include/experimental/bits/fs_path.h (__detail::_S_range_begin)

360
libstdc++-v3/include/bits/fs_path.h
View file

@ -155,56 +155,61 @@ namespace __detail
template<typename _Iter, typename _Tr = __safe_iterator_traits<_Iter>>
using _Path2 = enable_if_t<__is_path_iter_src<_Tr>::value, path>;
template<typename _Source>
_Source
_S_range_begin(_Source __begin) { return __begin; }
struct __null_terminated { };
template<typename _Source>
__null_terminated
_S_range_end(_Source) { return {}; }
// The __effective_range overloads convert a Source parameter into
// either a basic_string_view or basic_string containing the
// effective range of the Source, as defined in [fs.path.req].
template<typename _CharT, typename _Traits, typename _Alloc>
inline const _CharT*
_S_range_begin(const basic_string<_CharT, _Traits, _Alloc>& __str)
{ return __str.data(); }
template<typename _CharT, typename _Traits, typename _Alloc>
inline const _CharT*
_S_range_end(const basic_string<_CharT, _Traits, _Alloc>& __str)
{ return __str.data() + __str.size(); }
inline basic_string_view<_CharT, _Traits>
__effective_range(const basic_string<_CharT, _Traits, _Alloc>& __source)
{ return __source; }
template<typename _CharT, typename _Traits>
inline const _CharT*
_S_range_begin(const basic_string_view<_CharT, _Traits>& __str)
{ return __str.data(); }
inline const basic_string_view<_CharT, _Traits>&
__effective_range(const basic_string_view<_CharT, _Traits>& __source)
{ return __source; }
template<typename _CharT, typename _Traits>
inline const _CharT*
_S_range_end(const basic_string_view<_CharT, _Traits>& __str)
{ return __str.data() + __str.size(); }
template<typename _Source>
inline auto
__effective_range(const _Source& __source)
{
if constexpr (is_pointer_v<decay_t<_Source>>)
return basic_string_view{&*__source};
else
{
// _Source is an input iterator that iterates over an NTCTS.
// Create a basic_string by reading until the null character.
using value_type
= typename iterator_traits<_Source>::value_type;
basic_string<value_type> __str;
_Source __it = __source;
for (value_type __ch = *__it; __ch != value_type(); __ch = *++__it)
__str.push_back(__ch);
return __str;
}
}
template<typename _Tp,
typename _Iter = decltype(_S_range_begin(std::declval<_Tp>())),
typename _Val = typename std::iterator_traits<_Iter>::value_type,
typename _UnqualVal = std::remove_const_t<_Val>>
// The value type of a Source parameter's effective range.
template<typename _Tp>
using __value_t = typename remove_reference_t<
decltype(__detail::__effective_range(std::declval<_Tp>()))>::value_type;
// SFINAE helper to check that an effective range has value_type char,
// as required by path constructors taking a std::locale parameter.
// The type _Tp must have already been checked by _Path<Tp> or _Path2<_Tp>.
template<typename _Tp, typename _Val = __value_t<_Tp>>
using __value_type_is_char
= std::enable_if_t<std::is_same_v<_UnqualVal, char>,
_UnqualVal>;
= std::enable_if_t<std::is_same_v<_Val, char>, _Val>;
template<typename _Tp,
typename _Iter = decltype(_S_range_begin(std::declval<_Tp>())),
typename _Val = typename std::iterator_traits<_Iter>::value_type,
typename _UnqualVal = std::remove_const_t<_Val>>
// As above, but also allows char8_t, as required by u8path
// C++20 [depr.fs.path.factory]
template<typename _Tp, typename _Val = __value_t<_Tp>>
using __value_type_is_char_or_char8_t
= std::enable_if_t<__or_v<
std::is_same<_UnqualVal, char>
= std::enable_if_t<std::is_same_v<_Val, char>
#ifdef _GLIBCXX_USE_CHAR8_T
, std::is_same<_UnqualVal, char8_t>
|| std::is_same_v<_Val, char8_t>
#endif
>,
_UnqualVal>;
, _Val>;
} // namespace __detail
/// @endcond
@ -251,8 +256,7 @@ namespace __detail
template<typename _Source,
typename _Require = __detail::_Path<_Source>>
path(_Source const& __source, format = auto_format)
: _M_pathname(_S_convert(__detail::_S_range_begin(__source),
__detail::_S_range_end(__source)))
: _M_pathname(_S_convert(__detail::__effective_range(__source)))
{ _M_split_cmpts(); }
template<typename _InputIterator,
@ -264,9 +268,8 @@ namespace __detail
template<typename _Source,
typename _Require = __detail::_Path<_Source>,
typename _Require2 = __detail::__value_type_is_char<_Source>>
path(_Source const& __source, const locale& __loc, format = auto_format)
: _M_pathname(_S_convert_loc(__detail::_S_range_begin(__source),
__detail::_S_range_end(__source), __loc))
path(_Source const& __src, const locale& __loc, format = auto_format)
: _M_pathname(_S_convert_loc(__detail::__effective_range(__src), __loc))
{ _M_split_cmpts(); }
template<typename _InputIterator,
@ -309,8 +312,7 @@ namespace __detail
__detail::_Path<_Source>&
operator/=(_Source const& __source)
{
_M_append(_S_convert(__detail::_S_range_begin(__source),
__detail::_S_range_end(__source)));
_M_append(_S_convert(__detail::__effective_range(__source)));
return *this;
}
@ -318,8 +320,7 @@ namespace __detail
__detail::_Path<_Source>&
append(_Source const& __source)
{
_M_append(_S_convert(__detail::_S_range_begin(__source),
__detail::_S_range_end(__source)));
_M_append(_S_convert(__detail::__effective_range(__source)));
return *this;
}
@ -351,8 +352,7 @@ namespace __detail
__detail::_Path<_Source>&
concat(_Source const& __x)
{
_M_concat(_S_convert(__detail::_S_range_begin(__x),
__detail::_S_range_end(__x)));
_M_concat(_S_convert(__detail::__effective_range(__x)));
return *this;
}
@ -523,22 +523,6 @@ namespace __detail
return __result;
}
/// @cond undocumented
// Create a basic_string by reading until a null character.
template<typename _InputIterator,
typename _Traits = std::iterator_traits<_InputIterator>,
typename _CharT
= typename std::remove_cv_t<typename _Traits::value_type>>
static std::basic_string<_CharT>
_S_string_from_iter(_InputIterator __source)
{
std::basic_string<_CharT> __str;
for (_CharT __ch = *__source; __ch != _CharT(); __ch = *++__source)
__str.push_back(__ch);
return __str;
}
/// @endcond
private:
enum class _Type : unsigned char {
_Multi = 0, _Root_name, _Root_dir, _Filename
@ -558,43 +542,67 @@ namespace __detail
pair<const string_type*, size_t> _M_find_extension() const noexcept;
template<typename _CharT>
struct _Cvt;
// Create a string or string view from an iterator range.
template<typename _InputIterator>
static auto
_S_to_string(_InputIterator __first, _InputIterator __last)
{
using _EcharT
= typename std::iterator_traits<_InputIterator>::value_type;
static_assert(__detail::__is_encoded_char<_EcharT>);
static basic_string_view<value_type>
_S_convert(value_type* __src, __detail::__null_terminated)
{ return __src; }
#if __cpp_lib_concepts
constexpr bool __contiguous = std::contiguous_iterator<_InputIterator>;
#else
constexpr bool __contiguous
= is_pointer_v<decltype(std::__niter_base(__first))>;
#endif
if constexpr (__contiguous)
{
// For contiguous iterators we can just return a string view.
const auto* __f = std::__to_address(std::__niter_base(__first));
const auto* __l = std::__to_address(std::__niter_base(__last));
return basic_string_view<_EcharT>(__f, __l - __f);
}
else
// Conversion requires contiguous characters, so create a string.
return basic_string<_EcharT>(__first, __last);
}
static basic_string_view<value_type>
_S_convert(const value_type* __src, __detail::__null_terminated)
{ return __src; }
// path::_S_convert creates a basic_string<value_type> or
// basic_string_view<value_type> from a range (either the effective
// range of a Source parameter, or a pair of InputIterator parameters),
// performing the conversions required by [fs.path.type.cvt].
// If the value_type of the range value type is path::value_type,
// no encoding conversion is performed. If the range is contiguous
// a string_view
static basic_string_view<value_type>
_S_convert(value_type* __first, value_type* __last)
{ return {__first, __last - __first}; }
static string_type
_S_convert(string_type __str)
{ return __str; }
static basic_string_view<value_type>
_S_convert(const value_type* __first, const value_type* __last)
{ return {__first, __last - __first}; }
template<typename _Tp>
static auto
_S_convert(const _Tp& __str)
{
if constexpr (is_same_v<_Tp, string_type>)
return __str;
else if constexpr (is_same_v<_Tp, basic_string_view<value_type>>)
return __str;
else if constexpr (is_same_v<typename _Tp::value_type, value_type>)
return basic_string_view<value_type>(__str.data(), __str.size());
else
return _S_convert(__str.data(), __str.data() + __str.size());
}
template<typename _EcharT>
static auto
_S_convert(const _EcharT* __first, const _EcharT* __last);
template<typename _Iter>
static string_type
static auto
_S_convert(_Iter __first, _Iter __last)
{
using __value_type = typename std::iterator_traits<_Iter>::value_type;
return _Cvt<typename remove_cv<__value_type>::type>::
_S_convert(__first, __last);
}
template<typename _InputIterator>
static string_type
_S_convert(_InputIterator __src, __detail::__null_terminated)
{
// Read from iterator into basic_string until a null value is seen:
auto __s = _S_string_from_iter(__src);
// Convert (if needed) from iterator's value type to path::value_type:
return string_type(_S_convert(__s.data(), __s.data() + __s.size()));
}
{ return _S_convert(_S_to_string(__first, __last)); }
static string_type
_S_convert_loc(const char* __first, const char* __last,
@ -604,16 +612,14 @@ namespace __detail
static string_type
_S_convert_loc(_Iter __first, _Iter __last, const std::locale& __loc)
{
const std::string __str(__first, __last);
return _S_convert_loc(__str.data(), __str.data()+__str.size(), __loc);
const auto __s = _S_to_string(__first, __last);
return _S_convert_loc(__s.data(), __s.data() + __s.size(), __loc);
}
template<typename _InputIterator>
template<typename _Tp>
static string_type
_S_convert_loc(_InputIterator __src, __detail::__null_terminated,
const std::locale& __loc)
_S_convert_loc(const _Tp& __s, const std::locale& __loc)
{
const std::string __s = _S_string_from_iter(__src);
return _S_convert_loc(__s.data(), __s.data() + __s.size(), __loc);
}
@ -803,100 +809,66 @@ namespace __detail
size_t _M_pos;
};
// specialize _Cvt for degenerate 'noconv' case
template<>
struct path::_Cvt<path::value_type>
template<typename _EcharT>
auto
path::_S_convert(const _EcharT* __f, const _EcharT* __l)
{
template<typename _Iter>
static string_type
_S_convert(_Iter __first, _Iter __last)
{ return string_type{__first, __last}; }
};
static_assert(__detail::__is_encoded_char<_EcharT>);
#if !defined _GLIBCXX_FILESYSTEM_IS_WINDOWS && defined _GLIBCXX_USE_CHAR8_T
// For POSIX converting from char8_t to char is also 'noconv'
template<>
struct path::_Cvt<char8_t>
{
template<typename _Iter>
static string_type
_S_convert(_Iter __first, _Iter __last)
{ return string_type(__first, __last); }
};
if constexpr (is_same_v<_EcharT, value_type>)
return basic_string_view<value_type>(__f, __l - __f);
#if !defined _GLIBCXX_FILESYSTEM_IS_WINDOWS && defined _GLIBCXX_USE_CHAR8_T
else if constexpr (is_same_v<_EcharT, char8_t>)
// For POSIX converting from char8_t to char is also 'noconv'
return string_view(reinterpret_cast<const char*>(__f), __l - __f);
#endif
template<typename _CharT>
struct path::_Cvt
{
static string_type
_S_convert(const _CharT* __f, const _CharT* __l)
{
#ifdef _GLIBCXX_FILESYSTEM_IS_WINDOWS
std::wstring __wstr;
if constexpr (is_same_v<_CharT, char>)
{
struct _UCvt : std::codecvt<wchar_t, char, std::mbstate_t>
{ } __cvt;
if (__str_codecvt_in_all(__f, __l, __wstr, __cvt))
return __wstr;
}
#ifdef _GLIBCXX_USE_CHAR8_T
else if constexpr (is_same_v<_CharT, char8_t>)
{
const char* __f2 = (const char*)__f;
const char* __l2 = (const char*)__l;
std::codecvt_utf8_utf16<wchar_t> __wcvt;
if (__str_codecvt_in_all(__f2, __l2, __wstr, __wcvt))
return __wstr;
}
#endif
else // char16_t or char32_t
{
struct _UCvt : std::codecvt<_CharT, char, std::mbstate_t>
{ } __cvt;
std::string __str;
if (__str_codecvt_out_all(__f, __l, __str, __cvt))
{
const char* __f2 = __str.data();
const char* __l2 = __f2 + __str.size();
std::codecvt_utf8_utf16<wchar_t> __wcvt;
if (__str_codecvt_in_all(__f2, __l2, __wstr, __wcvt))
return __wstr;
}
}
#else // ! windows
struct _UCvt : std::codecvt<_CharT, char, std::mbstate_t>
{ } __cvt;
std::string __str;
if (__str_codecvt_out_all(__f, __l, __str, __cvt))
return __str;
#endif
_GLIBCXX_THROW_OR_ABORT(filesystem_error(
"Cannot convert character sequence",
std::make_error_code(errc::illegal_byte_sequence)));
}
static string_type
_S_convert(_CharT* __f, _CharT* __l)
{
return _S_convert(const_cast<const _CharT*>(__f),
const_cast<const _CharT*>(__l));
}
template<typename _Iter>
static string_type
_S_convert(_Iter __first, _Iter __last)
else
{
const std::basic_string<_CharT> __str(__first, __last);
return _S_convert(__str.data(), __str.data() + __str.size());
#ifdef _GLIBCXX_FILESYSTEM_IS_WINDOWS
std::wstring __wstr;
if constexpr (is_same_v<_EcharT, char>)
{
struct _UCvt : std::codecvt<wchar_t, char, std::mbstate_t>
{ } __cvt;
if (__str_codecvt_in_all(__f, __l, __wstr, __cvt))
return __wstr;
}
#ifdef _GLIBCXX_USE_CHAR8_T
else if constexpr (is_same_v<_EcharT, char8_t>)
{
const char* __f2 = (const char*)__f;
const char* __l2 = (const char*)__l;
std::codecvt_utf8_utf16<wchar_t> __wcvt;
if (__str_codecvt_in_all(__f2, __l2, __wstr, __wcvt))
return __wstr;
}
#endif
else // char16_t or char32_t
{
struct _UCvt : std::codecvt<_EcharT, char, std::mbstate_t>
{ } __cvt;
std::string __str;
if (__str_codecvt_out_all(__f, __l, __str, __cvt))
{
const char* __f2 = __str.data();
const char* __l2 = __f2 + __str.size();
std::codecvt_utf8_utf16<wchar_t> __wcvt;
if (__str_codecvt_in_all(__f2, __l2, __wstr, __wcvt))
return __wstr;
}
}
#else // ! windows
struct _UCvt : std::codecvt<_EcharT, char, std::mbstate_t>
{ } __cvt;
std::string __str;
if (__str_codecvt_out_all(__f, __l, __str, __cvt))
return __str;
#endif
_GLIBCXX_THROW_OR_ABORT(filesystem_error(
"Cannot convert character sequence",
std::make_error_code(errc::illegal_byte_sequence)));
}
template<typename _Iter, typename _Cont>
static string_type
_S_convert(__gnu_cxx::__normal_iterator<_Iter, _Cont> __first,
__gnu_cxx::__normal_iterator<_Iter, _Cont> __last)
{ return _S_convert(__first.base(), __last.base()); }
};
}
/// @endcond
@ -1030,10 +1002,10 @@ namespace __detail
template<typename _CharT>
inline __detail::_Path2<_CharT*>&
path::operator+=(_CharT __x)
path::operator+=(const _CharT __x)
{
auto* __addr = std::__addressof(__x);
return concat(__addr, __addr + 1);
_M_concat(_S_convert(&__x, &__x + 1));
return *this;
}
inline path&

7
libstdc++-v3/include/experimental/bits/fs_path.h
View file

@ -495,6 +495,13 @@ namespace __detail
_S_convert_loc(const char* __first, const char* __last,
const std::locale& __loc);
static string_type
_S_convert_loc(char* __first, char* __last, const std::locale& __loc)
{
return _S_convert_loc(const_cast<const char*>(__first),
const_cast<const char*>(__last), __loc);
}
template<typename _Iter>
static string_type
_S_convert_loc(_Iter __first, _Iter __last, const std::locale& __loc)

6
libstdc++-v3/src/c++17/fs_path.cc
View file

@ -1949,11 +1949,7 @@ path::_S_convert_loc(const char* __first, const char* __last,
_GLIBCXX_THROW_OR_ABORT(filesystem_error(
"Cannot convert character sequence",
std::make_error_code(errc::illegal_byte_sequence)));
#ifdef _GLIBCXX_FILESYSTEM_IS_WINDOWS
return __ws;
#else
return _Cvt<wchar_t>::_S_convert(__ws.data(), __ws.data() + __ws.size());
#endif
return _S_convert(std::move(__ws));
#else
return {__first, __last};
#endif