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Implement operator<< for cuda::std::string_view #4736

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275c887
Implement `operator<<` for `cuda::std::string_view`
davebayer May 19, 2025
545c4d9
add interoperability with `std::string_view`
davebayer May 19, 2025
576a28c
fix review, simplify implementation
davebayer May 20, 2025
12ebede
fix typo
davebayer May 20, 2025
d8346ae
add missing `typename`
davebayer May 20, 2025
2974a4f
try to fix compilation
davebayer May 20, 2025
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10 changes: 10 additions & 0 deletions libcudacxx/include/cuda/std/__string/helper_functions.h
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,7 @@

_LIBCUDACXX_BEGIN_NAMESPACE_STD

_CCCL_EXEC_CHECK_DISABLE
template <class _CharT, class _SizeT, class _Traits, _SizeT __npos>
Comment on lines 34 to 36
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Adding _CCCL_EXEC_CHECK_DISABLE is necessary to allow using e. g. host only char_traits

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I am a bit torn here, we should use host only char_traits as they will crash.

I believe the solution with just casting to ::std::string_view is the better solution

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The problem is that the user can pass any type traits he wants, they might be host only, or device only..

_LIBCUDACXX_HIDE_FROM_ABI constexpr _SizeT
__cccl_str_find(const _CharT* __p, _SizeT __sz, _CharT __c, _SizeT __pos) noexcept
Expand All @@ -48,6 +49,7 @@ __cccl_str_find(const _CharT* __p, _SizeT __sz, _CharT __c, _SizeT __pos) noexce
return static_cast<_SizeT>(__r - __p);
}

_CCCL_EXEC_CHECK_DISABLE
template <class _CharT, class _Traits>
_LIBCUDACXX_HIDE_FROM_ABI constexpr const _CharT*
__cccl_search_substring(const _CharT* __first1, const _CharT* __last1, const _CharT* __first2, const _CharT* __last2)
Expand Down Expand Up @@ -121,6 +123,7 @@ __cccl_str_find(const _CharT* __p, _SizeT __sz, const _CharT* __s, _SizeT __pos,
return static_cast<_SizeT>(__r - __p);
}

_CCCL_EXEC_CHECK_DISABLE
template <class _CharT, class _SizeT, class _Traits, _SizeT __npos>
_LIBCUDACXX_HIDE_FROM_ABI constexpr _SizeT
__cccl_str_rfind(const _CharT* __p, _SizeT __sz, _CharT __c, _SizeT __pos) noexcept
Expand All @@ -147,6 +150,7 @@ __cccl_str_rfind(const _CharT* __p, _SizeT __sz, _CharT __c, _SizeT __pos) noexc
return __npos;
}

_CCCL_EXEC_CHECK_DISABLE
template <class _CharT, class _SizeT, class _Traits, _SizeT __npos>
_LIBCUDACXX_HIDE_FROM_ABI constexpr _SizeT
__cccl_str_rfind(const _CharT* __p, _SizeT __sz, const _CharT* __s, _SizeT __pos, _SizeT __n) noexcept
Expand All @@ -169,6 +173,7 @@ __cccl_str_rfind(const _CharT* __p, _SizeT __sz, const _CharT* __s, _SizeT __pos
return static_cast<_SizeT>(__r - __p);
}

_CCCL_EXEC_CHECK_DISABLE
template <class _CharT, class _SizeT, class _Traits, _SizeT __npos>
_LIBCUDACXX_HIDE_FROM_ABI constexpr _SizeT
__cccl_str_find_first_of(const _CharT* __p, _SizeT __sz, const _CharT* __s, _SizeT __pos, _SizeT __n) noexcept
Expand All @@ -185,6 +190,7 @@ __cccl_str_find_first_of(const _CharT* __p, _SizeT __sz, const _CharT* __s, _Siz
return static_cast<_SizeT>(__r - __p);
}

_CCCL_EXEC_CHECK_DISABLE
template <class _CharT, class _SizeT, class _Traits, _SizeT __npos>
_LIBCUDACXX_HIDE_FROM_ABI constexpr _SizeT
__cccl_str_find_last_of(const _CharT* __p, _SizeT __sz, const _CharT* __s, _SizeT __pos, _SizeT __n) noexcept
Expand All @@ -211,6 +217,7 @@ __cccl_str_find_last_of(const _CharT* __p, _SizeT __sz, const _CharT* __s, _Size
return __npos;
}

_CCCL_EXEC_CHECK_DISABLE
template <class _CharT, class _SizeT, class _Traits, _SizeT __npos>
_LIBCUDACXX_HIDE_FROM_ABI constexpr _SizeT
__cccl_str_find_first_not_of(const _CharT* __p, _SizeT __sz, const _CharT* __s, _SizeT __pos, _SizeT __n) noexcept
Expand All @@ -230,6 +237,7 @@ __cccl_str_find_first_not_of(const _CharT* __p, _SizeT __sz, const _CharT* __s,
return __npos;
}

_CCCL_EXEC_CHECK_DISABLE
template <class _CharT, class _SizeT, class _Traits, _SizeT __npos>
_LIBCUDACXX_HIDE_FROM_ABI constexpr _SizeT
__cccl_str_find_first_not_of(const _CharT* __p, _SizeT __sz, _CharT __c, _SizeT __pos) noexcept
Expand All @@ -248,6 +256,7 @@ __cccl_str_find_first_not_of(const _CharT* __p, _SizeT __sz, _CharT __c, _SizeT
return __npos;
}

_CCCL_EXEC_CHECK_DISABLE
template <class _CharT, class _SizeT, class _Traits, _SizeT __npos>
_LIBCUDACXX_HIDE_FROM_ABI constexpr _SizeT
__cccl_str_find_last_not_of(const _CharT* __p, _SizeT __sz, const _CharT* __s, _SizeT __pos, _SizeT __n) noexcept
Expand All @@ -270,6 +279,7 @@ __cccl_str_find_last_not_of(const _CharT* __p, _SizeT __sz, const _CharT* __s, _
return __npos;
}

_CCCL_EXEC_CHECK_DISABLE
template <class _CharT, class _SizeT, class _Traits, _SizeT __npos>
_LIBCUDACXX_HIDE_FROM_ABI constexpr _SizeT
__cccl_str_find_last_not_of(const _CharT* __p, _SizeT __sz, _CharT __c, _SizeT __pos) noexcept
Expand Down
66 changes: 61 additions & 5 deletions libcudacxx/include/cuda/std/string_view
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Original file line number Diff line number Diff line change
Expand Up @@ -57,7 +57,7 @@
#include <cuda/std/version>

#if !_CCCL_COMPILER(NVRTC)
# include <iosfwd>
# include <string_view>
#endif // !_CCCL_COMPILER(NVRTC)

#include <cuda/std/__cccl/prologue.h>
Expand Down Expand Up @@ -105,6 +105,7 @@ public:

_CCCL_HIDE_FROM_ABI basic_string_view& operator=(const basic_string_view&) noexcept = default;

_CCCL_EXEC_CHECK_DISABLE
_LIBCUDACXX_HIDE_FROM_ABI constexpr basic_string_view(const _CharT* __s) noexcept
: __data_{__s}
, __size_{_Traits::length(__s)}
Expand Down Expand Up @@ -146,6 +147,21 @@ public:
, __size_{_CUDA_VRANGES::size(__r)}
{}

#if !_CCCL_COMPILER(NVRTC)
_CCCL_HIDE_FROM_ABI constexpr basic_string_view(::std::basic_string_view<_CharT, _Traits> __sv) noexcept
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This forces use of the same char_traits than this string_view is using. We should templatize this so that we can construct from a ::std::string_view

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This is intentional, the idea is that both char traits types must match with an exception of std::char_traits that are mapped to cuda::std::char_traits. That means that:

  • cuda::std::basic_string_view<CharT, cuda::std::char_traits<CharT>> can be constructed (converted) from (to) both std::basic_string_view<CharT, std::char_traits<CharT>> and std::basic_string_view<CharT, cuda::std::char_traits<CharT>>
  • cuda::std::basic_string_view<CharT, Traits> can be constructed (converted) from (to) std::basic_string_view<CharT, Traits>

Do you think this is wrong?

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I believe then should have 2 constructors,

  • basic_string_view(::std::basic_string_view<_CharT, _Traits> __sv)
  • basic_string_view(::std::basic_string_view<_CharT, ::std::char_traits<_CharT>> __sv)

We can then omit the constraint on the second constructor

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That's what we have now. But I don't think we can omit the constraint, because we must ensure that the current type traits are cuda::std::char_traits, otherwise we would allow something like:

cuda::std::basic_string_view<my_char, my_char_traits>{std::basic_string_view<my_char, std::char_traits<my_char>>{...}};

which is wrong

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I dont think so, the incoming type traits are correct and its the users responsibility to ensure that their char_traits are conforming.

Also no one writes their own char_traits, so I believe its more of a theoretical question

: __data_{__sv.data()}
, __size_{__sv.size()}
{}

_CCCL_TEMPLATE(bool = true)
_CCCL_REQUIRES(is_same_v<_Traits, char_traits<_CharT>>)
_CCCL_HIDE_FROM_ABI constexpr basic_string_view(
::std::basic_string_view<_CharT, ::std::char_traits<_CharT>> __sv) noexcept
: __data_{__sv.data()}
, __size_{__sv.size()}
{}
#endif // !_CCCL_COMPILER(NVRTC)

[[nodiscard]] _LIBCUDACXX_HIDE_FROM_ABI constexpr const_iterator begin() const noexcept
{
return const_iterator{__data_};
Expand Down Expand Up @@ -262,6 +278,7 @@ public:
__other.__size_ = __sz;
}

_CCCL_EXEC_CHECK_DISABLE
_LIBCUDACXX_HIDE_FROM_ABI constexpr size_type copy(_CharT* __s, size_type __n, size_type __pos = 0) const
{
if (__pos > __size_)
Expand All @@ -288,6 +305,7 @@ public:

// compare

_CCCL_EXEC_CHECK_DISABLE
[[nodiscard]] _LIBCUDACXX_HIDE_FROM_ABI constexpr int compare(basic_string_view __sv) const noexcept
{
const auto __rlen = _CUDA_VSTD::min(__size_, __sv.__size_);
Expand Down Expand Up @@ -350,6 +368,7 @@ public:
return _CUDA_VSTD::__cccl_str_find<value_type, size_type, traits_type, npos>(__data_, __size_, __s, __pos, __n);
}

_CCCL_EXEC_CHECK_DISABLE
[[nodiscard]] _LIBCUDACXX_HIDE_FROM_ABI constexpr size_type find(const _CharT* __s, size_type __pos = 0) const noexcept
{
_CCCL_ASSERT(__s != nullptr, "string_view::find(): received nullptr");
Expand Down Expand Up @@ -379,6 +398,7 @@ public:
return _CUDA_VSTD::__cccl_str_rfind<value_type, size_type, traits_type, npos>(__data_, __size_, __s, __pos, __n);
}

_CCCL_EXEC_CHECK_DISABLE
[[nodiscard]] _LIBCUDACXX_HIDE_FROM_ABI constexpr size_type
rfind(const _CharT* __s, size_type __pos = npos) const noexcept
{
Expand Down Expand Up @@ -411,6 +431,7 @@ public:
__data_, __size_, __s, __pos, __n);
}

_CCCL_EXEC_CHECK_DISABLE
[[nodiscard]] _LIBCUDACXX_HIDE_FROM_ABI constexpr size_type
find_first_of(const _CharT* __s, size_type __pos = 0) const noexcept
{
Expand Down Expand Up @@ -443,6 +464,7 @@ public:
__data_, __size_, __s, __pos, __n);
}

_CCCL_EXEC_CHECK_DISABLE
[[nodiscard]] _LIBCUDACXX_HIDE_FROM_ABI constexpr size_type
find_last_of(const _CharT* __s, size_type __pos = npos) const noexcept
{
Expand Down Expand Up @@ -476,6 +498,7 @@ public:
__data_, __size_, __s, __pos, __n);
}

_CCCL_EXEC_CHECK_DISABLE
[[nodiscard]] _LIBCUDACXX_HIDE_FROM_ABI constexpr size_type
find_first_not_of(const _CharT* __s, size_type __pos = 0) const noexcept
{
Expand Down Expand Up @@ -509,6 +532,7 @@ public:
__data_, __size_, __s, __pos, __n);
}

_CCCL_EXEC_CHECK_DISABLE
[[nodiscard]] _LIBCUDACXX_HIDE_FROM_ABI constexpr size_type
find_last_not_of(const _CharT* __s, size_type __pos = npos) const noexcept
{
Expand All @@ -524,6 +548,7 @@ public:
return (__size_ >= __s.__size_) && compare(0, __s.__size_, __s) == 0;
}

_CCCL_EXEC_CHECK_DISABLE
[[nodiscard]] _LIBCUDACXX_HIDE_FROM_ABI constexpr bool starts_with(value_type __c) const noexcept
{
return (__size_ > 0) && _Traits::eq(front(), __c);
Expand All @@ -541,6 +566,7 @@ public:
return (__size_ >= __s.__size_) && compare(__size_ - __s.__size_, npos, __s) == 0;
}

_CCCL_EXEC_CHECK_DISABLE
[[nodiscard]] _LIBCUDACXX_HIDE_FROM_ABI constexpr bool ends_with(value_type __c) const noexcept
{
return (__size_ > 0) && _Traits::eq(back(), __c);
Expand Down Expand Up @@ -711,6 +737,20 @@ public:
return __lhs.compare(__rhs) >= 0;
}

#if !_CCCL_COMPILER(NVRTC)
_CCCL_HIDE_FROM_ABI constexpr operator ::std::basic_string_view<_CharT, _Traits>() const noexcept
{
return ::std::basic_string_view<_CharT, _Traits>{__data_, __size_};
}

_CCCL_TEMPLATE(bool = true)
_CCCL_REQUIRES(is_same_v<_Traits, char_traits<_CharT>>)
_CCCL_HIDE_FROM_ABI constexpr operator ::std::basic_string_view<_CharT, ::std::char_traits<_CharT>>() const noexcept
{
return ::std::basic_string_view<_CharT, ::std::char_traits<_CharT>>{__data_, __size_};
}
#endif // !_CCCL_COMPILER(NVRTC)

private:
enum class __assume_valid
{
Expand Down Expand Up @@ -738,16 +778,32 @@ _CCCL_TEMPLATE(class _Range)
_CCCL_REQUIRES(_CUDA_VRANGES::contiguous_range<_Range>)
_CCCL_HOST_DEVICE basic_string_view(_Range&&) -> basic_string_view<_CUDA_VRANGES::range_value_t<_Range>>;

#if !_CCCL_COMPILER(NVRTC)
_CCCL_TEMPLATE(class _CharT, class _Traits)
_CCCL_HOST_DEVICE basic_string_view(::std::basic_string_view<_CharT, _Traits>) -> basic_string_view<_CharT, _Traits>;

_CCCL_TEMPLATE(class _CharT)
_CCCL_HOST_DEVICE basic_string_view(::std::basic_string_view<_CharT, ::std::char_traits<_CharT>>)
-> basic_string_view<_CharT, char_traits<_CharT>>;
#endif // !_CCCL_COMPILER(NVRTC)

// operator <<

#if 0 // todo: we need to implement char_traits stream types & functions
#if !_CCCL_COMPILER(NVRTC)
template <class _CharT, class _Traits>
_LIBCUDACXX_HIDE_FROM_ABI ::std::basic_ostream<_CharT, _Traits>&
_CCCL_HIDE_FROM_ABI _CCCL_HOST ::std::basic_ostream<_CharT, _Traits>&
operator<<(::std::basic_ostream<_CharT, _Traits>& __os, basic_string_view<_CharT, _Traits> __str)
{
return __os.write(__str.data(), static_cast<::std::streamsize>(__str.size()));
return __os << ::std::basic_string_view<_CharT, _Traits>{__str};
}
#endif // 0

template <class _CharT>
_CCCL_HIDE_FROM_ABI _CCCL_HOST ::std::basic_ostream<_CharT, ::std::char_traits<_CharT>>& operator<<(
::std::basic_ostream<_CharT, ::std::char_traits<_CharT>>& __os, basic_string_view<_CharT, char_traits<_CharT>> __str)
{
return __os << ::std::basic_string_view<_CharT, ::std::char_traits<_CharT>>{__str};
}
#endif // !_CCCL_COMPILER(NVRTC)

// literals

Expand Down
5 changes: 1 addition & 4 deletions libcudacxx/include/cuda/std/version
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -143,7 +143,7 @@
// # define __cccl_lib_shared_mutex 201505L
// # define __cccl_lib_shared_ptr_arrays 201611L
// # define __cccl_lib_shared_ptr_weak_type 201606L
// # define __cccl_lib_string_view 201606L
#define __cccl_lib_string_view 201803L
// # define __cccl_lib_to_chars 201611L
// # define __cccl_lib_uncaught_exceptions 201411L
// # define __cccl_lib_unordered_map_try_emplace 201411L
Expand Down Expand Up @@ -173,7 +173,6 @@
// # define __cccl_lib_constexpr_misc 201811L
// # define __cccl_lib_constexpr_numeric 201911L
// # define __cccl_lib_constexpr_string 201907L
// # define __cccl_lib_constexpr_string_view 201811L
// # define __cccl_lib_constexpr_swap_algorithms 201806L
// # define __cccl_lib_constexpr_tuple 201811L
// # define __cccl_lib_constexpr_utility 201811L
Expand Down Expand Up @@ -206,8 +205,6 @@
// # define __cccl_lib_source_location 201907L
// # define __cccl_lib_ssize 201902L
// # define __cccl_lib_starts_ends_with 201711L
// # undef __cccl_lib_string_view
// # define __cccl_lib_string_view 201803L
// # define __cccl_lib_syncbuf 201803L
// # define __cccl_lib_three_way_comparison 201907L
# define __cccl_lib_unwrap_ref 201811L
Expand Down
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