szaszm commented on code in PR #1680:
URL: https://github.com/apache/nifi-minifi-cpp/pull/1680#discussion_r1356699329
##########
libminifi/include/utils/StringUtils.h:
##########
@@ -187,48 +187,40 @@ constexpr size_t size(const
std::basic_string_view<CharT>& str) noexcept { retur
namespace detail {
// implementation detail of join_pack
-template<typename CharT>
-struct str_detector {
- template<typename Str>
- using valid_string_t =
decltype(std::declval<std::basic_string<CharT>>().append(std::declval<Str>()));
+template<typename Str, typename CharT>
+concept valid_string = requires(std::basic_string<CharT> left, Str appended) {
+ left.append(appended);
};
-template<typename ResultT, typename CharT, typename... Strs>
-using valid_string_pack_t =
std::enable_if_t<(meta::is_detected_v<str_detector<CharT>::template
valid_string_t, Strs> && ...), ResultT>;
+// normally CharT would be at the end, because we're checking that Strs are
valid strings for CharT,
+// but the syntax needs the parameter pack at the end
+template<typename CharT, typename... Strs>
+concept valid_string_pack = (valid_string<Strs, CharT> && ...);
-template<typename CharT, typename... Strs, valid_string_pack_t<void, CharT,
Strs...>* = nullptr>
-static std::basic_string<CharT> join_pack(const Strs&... strs) {
- std::basic_string<CharT> result;
- result.reserve((size(strs) + ...));
- (result.append(strs), ...);
- return result;
-}
+template<typename Str> struct char_type_of_impl {};
+template<typename CharT> struct char_type_of_impl<std::basic_string<CharT>> :
std::type_identity<CharT> {};
+template<typename CharT> struct char_type_of_impl<CharT*> :
std::type_identity<std::remove_cv_t<CharT>> {};
Review Comment:
`const char*` and `char*` are both considered strings of `char`.
##########
libminifi/include/utils/StringUtils.h:
##########
@@ -187,48 +187,40 @@ constexpr size_t size(const
std::basic_string_view<CharT>& str) noexcept { retur
namespace detail {
// implementation detail of join_pack
-template<typename CharT>
-struct str_detector {
- template<typename Str>
- using valid_string_t =
decltype(std::declval<std::basic_string<CharT>>().append(std::declval<Str>()));
+template<typename Str, typename CharT>
+concept valid_string = requires(std::basic_string<CharT> left, Str appended) {
+ left.append(appended);
};
-template<typename ResultT, typename CharT, typename... Strs>
-using valid_string_pack_t =
std::enable_if_t<(meta::is_detected_v<str_detector<CharT>::template
valid_string_t, Strs> && ...), ResultT>;
+// normally CharT would be at the end, because we're checking that Strs are
valid strings for CharT,
+// but the syntax needs the parameter pack at the end
+template<typename CharT, typename... Strs>
+concept valid_string_pack = (valid_string<Strs, CharT> && ...);
-template<typename CharT, typename... Strs, valid_string_pack_t<void, CharT,
Strs...>* = nullptr>
-static std::basic_string<CharT> join_pack(const Strs&... strs) {
- std::basic_string<CharT> result;
- result.reserve((size(strs) + ...));
- (result.append(strs), ...);
- return result;
-}
+template<typename Str> struct char_type_of_impl {};
+template<typename CharT> struct char_type_of_impl<std::basic_string<CharT>> :
std::type_identity<CharT> {};
+template<typename CharT> struct char_type_of_impl<CharT*> :
std::type_identity<std::remove_cv_t<CharT>> {};
+template<typename CharT> struct
char_type_of_impl<std::basic_string_view<CharT>> : std::type_identity<CharT> {};
+template<typename Str> using char_type_of = typename
char_type_of_impl<std::decay_t<Str>>::type;
Review Comment:
Decay here is intentional: not only do we want to ignore cv-qualifiers and
references, but `char` arrays should be decayed to pointers, to match the
second specialization above.
##########
CPPLINT.cfg:
##########
@@ -1,2 +1,2 @@
set noparent
-filter=-runtime/reference,-runtime/string,-build/c++11,-build/include_subdir,-whitespace/forcolon,-build/namespaces_literals,-readability/check,-build/include_what_you_use,-readability/nolint
+filter=-runtime/reference,-runtime/string,-build/c++11,-build/include_subdir,-whitespace/forcolon,-build/namespaces_literals,-readability/check,-build/include_what_you_use,-readability/nolint,-readability/braces
Review Comment:
Got this after both concept declarations:
```
/home/szaszm/nifi-minifi-cpp-3/libminifi/include/utils/StringUtils.h:193:
You don't need a ; after a } [readability/braces] [4]
```
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