[libc++][format] Add basic_format_parse_context.
Implements parts of:
- P0645 Text Formatting
Depends on D92214
Reland with changes:
The format header will only be compiled if the compiler used has support
for concepts. This should fix the issues with the initial version.
Differential Revision: https://reviews.llvm.org/D93166
GitOrigin-RevId: 38ddeade65c50343a7f6a0daec57139b07ec7807
diff --git a/include/format b/include/format
index 833423a..9e41120 100644
--- a/include/format
+++ b/include/format
@@ -19,14 +19,51 @@
explicit format_error(const string& what_arg);
explicit format_error(const char* what_arg);
};
+
+ // [format.parse.ctx], class template basic_format_parse_context
+ template<class charT>
+ class basic_format_parse_context {
+ public:
+ using char_type = charT;
+ using const_iterator = typename basic_string_view<charT>::const_iterator;
+ using iterator = const_iterator;
+
+ private:
+ iterator begin_; // exposition only
+ iterator end_; // exposition only
+ enum indexing { unknown, manual, automatic }; // exposition only
+ indexing indexing_; // exposition only
+ size_t next_arg_id_; // exposition only
+ size_t num_args_; // exposition only
+
+ public:
+ constexpr explicit basic_format_parse_context(basic_string_view<charT> fmt,
+ size_t num_args = 0) noexcept;
+ basic_format_parse_context(const basic_format_parse_context&) = delete;
+ basic_format_parse_context& operator=(const basic_format_parse_context&) = delete;
+
+ constexpr const_iterator begin() const noexcept;
+ constexpr const_iterator end() const noexcept;
+ constexpr void advance_to(const_iterator it);
+
+ constexpr size_t next_arg_id();
+ constexpr void check_arg_id(size_t id);
+ };
+ using format_parse_context = basic_format_parse_context<char>;
+ using wformat_parse_context = basic_format_parse_context<wchar_t>;
}
*/
#include <__config>
#include <stdexcept>
+#include <string_view>
#include <version>
+#ifdef _LIBCPP_NO_EXCEPTIONS
+#include <cstdlib>
+#endif
+
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
#endif
@@ -38,6 +75,12 @@
#if _LIBCPP_STD_VER > 17
+// TODO FMT Remove this once we require compilers with proper C++20 support.
+// If the compiler has no concepts support, the format header will be disabled.
+// Without concepts support enable_if needs to be used and that too much effort
+// to support compilers with partial C++20 support.
+#ifndef _LIBCPP_HAS_NO_CONCEPTS
+
class _LIBCPP_EXCEPTION_ABI format_error : public runtime_error {
public:
_LIBCPP_INLINE_VISIBILITY explicit format_error(const string& __s)
@@ -47,6 +90,89 @@
virtual ~format_error() noexcept;
};
+_LIBCPP_NORETURN inline _LIBCPP_INLINE_VISIBILITY void
+__throw_format_error(const char* __s) {
+#ifndef _LIBCPP_NO_EXCEPTIONS
+ throw format_error(__s);
+#else
+ (void)__s;
+ _VSTD::abort();
+#endif
+}
+
+template <class _CharT>
+class _LIBCPP_TEMPLATE_VIS basic_format_parse_context {
+public:
+ using char_type = _CharT;
+ using const_iterator =
+ typename _VSTD::basic_string_view<_CharT>::const_iterator;
+ using iterator = const_iterator;
+
+public:
+ _LIBCPP_INLINE_VISIBILITY
+ constexpr explicit basic_format_parse_context(
+ _VSTD::basic_string_view<_CharT> __fmt, size_t __num_args = 0) noexcept
+ : __begin_(__fmt.begin()),
+ __end_(__fmt.end()),
+ __indexing_(__unknown),
+ __next_arg_id_(0),
+ __num_args_(__num_args) {}
+
+ basic_format_parse_context(const basic_format_parse_context&) = delete;
+ basic_format_parse_context&
+ operator=(const basic_format_parse_context&) = delete;
+
+ _LIBCPP_INLINE_VISIBILITY constexpr const_iterator begin() const noexcept {
+ return __begin_;
+ }
+ _LIBCPP_INLINE_VISIBILITY constexpr const_iterator end() const noexcept {
+ return __end_;
+ }
+ _LIBCPP_INLINE_VISIBILITY constexpr void advance_to(const_iterator __it) {
+ __begin_ = __it;
+ }
+
+ _LIBCPP_INLINE_VISIBILITY constexpr size_t next_arg_id() {
+ if (__indexing_ == __manual)
+ __throw_format_error("Using automatic argument numbering in manual "
+ "argument numbering mode");
+
+ if (__indexing_ == __unknown)
+ __indexing_ = __automatic;
+ return __next_arg_id_++;
+ }
+ _LIBCPP_INLINE_VISIBILITY constexpr void check_arg_id(size_t __id) {
+ if (__indexing_ == __automatic)
+ __throw_format_error("Using manual argument numbering in automatic "
+ "argument numbering mode");
+
+ if (__indexing_ == __unknown)
+ __indexing_ = __manual;
+
+ // Throws an exception to make the expression a non core constant
+ // expression as required by:
+ // [format.parse.ctx]/11
+ // Remarks: Call expressions where id >= num_args_ are not core constant
+ // expressions ([expr.const]).
+ // Note: the Throws clause [format.parse.ctx]/10 doesn't specify the
+ // behavior when id >= num_args_.
+ if (_VSTD::is_constant_evaluated() && __id >= __num_args_)
+ __throw_format_error("Argument index outside the valid range");
+ }
+
+private:
+ iterator __begin_;
+ iterator __end_;
+ enum _Indexing { __unknown, __manual, __automatic };
+ _Indexing __indexing_;
+ size_t __next_arg_id_;
+ size_t __num_args_;
+};
+
+using format_parse_context = basic_format_parse_context<char>;
+using wformat_parse_context = basic_format_parse_context<wchar_t>;
+
+#endif //_LIBCPP_HAS_NO_CONCEPTS
#endif //_LIBCPP_STD_VER > 17
_LIBCPP_END_NAMESPACE_STD