First Commit

ext/libpqxx-7.7.3/install/ubuntu22.04/arm64/include/pqxx/time.hxx

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+/** Support for date/time values.
+ *
+ * At the moment this supports dates, but not times.
+ */
+#ifndef PQXX_H_TIME
+#define PQXX_H_TIME
+
+#if !defined(PQXX_HEADER_PRE)
+#  error "Include libpqxx headers as <pqxx/header>, not <pqxx/header.hxx>."
+#endif
+
+#include <chrono>
+#include <cstdlib>
+
+#include "pqxx/internal/concat.hxx"
+#include "pqxx/strconv.hxx"
+
+
+#if defined(PQXX_HAVE_YEAR_MONTH_DAY)
+
+namespace pqxx
+{
+using namespace std::literals;
+
+template<>
+struct nullness<std::chrono::year_month_day>
+        : no_null<std::chrono::year_month_day>
+{};
+
+
+/// String representation for a Gregorian date in ISO-8601 format.
+/** @warning Experimental.  There may still be design problems, particularly
+ * when it comes to BC years.
+ *
+ * PostgreSQL supports a choice of date formats, but libpqxx does not.  The
+ * other formats in turn support a choice of "month before day" versus "day
+ * before month," meaning that it's not necessarily known which format a given
+ * date is supposed to be.  So I repeat: ISO-8601-style format only!
+ *
+ * Invalid dates will not convert.  This includes February 29 on non-leap
+ * years, which is why it matters that `year_month_day` represents a
+ * _Gregorian_ date.
+ *
+ * The range of years is limited.  At the time of writing, PostgreSQL 14
+ * supports years from 4713 BC to 294276 AD inclusive, and C++20 supports
+ * a range of 32767 BC to 32767 AD inclusive.  So in practice, years must fall
+ * between 4713 BC and 32767 AD, inclusive.
+ *
+ * @warning Support for BC (or BCE) years is still experimental.  I still need
+ * confirmation on this issue: it looks as if C++ years are astronomical years,
+ * which means they have a Year Zero.  Regular BC/AD years do not have a year
+ * zero, so the year 1 AD follows directly after 1 BC.
+ *
+ * So, what to our calendars (and to PostgreSQL) is the year "0001 BC" seems to
+ * count as year "0" in a `std::chrono::year_month_day`.  The year 0001 AD is
+ * still equal to 1 as you'd expect, and all AD years work normally, but all
+ * years before then are shifted by one.  For instance, the year 543 BC would
+ * be -542 in C++.
+ */
+template<> struct PQXX_LIBEXPORT string_traits<std::chrono::year_month_day>
+{
+  [[nodiscard]] static zview
+  to_buf(char *begin, char *end, std::chrono::year_month_day const &value)
+  {
+    return generic_to_buf(begin, end, value);
+  }
+
+  static char *
+  into_buf(char *begin, char *end, std::chrono::year_month_day const &value);
+
+  [[nodiscard]] static std::chrono::year_month_day
+  from_string(std::string_view text);
+
+  [[nodiscard]] static std::size_t
+  size_buffer(std::chrono::year_month_day const &) noexcept
+  {
+    static_assert(int{(std::chrono::year::min)()} >= -99999);
+    static_assert(int{(std::chrono::year::max)()} <= 99999);
+    return 5 + 1 + 2 + 1 + 2 + std::size(s_bc) + 1;
+  }
+
+private:
+  /// The "BC" suffix for years before 1 AD.
+  static constexpr std::string_view s_bc{" BC"sv};
+};
+} // namespace pqxx
+#endif // PQXX_HAVE_YEAR_MONTH_DAY
+#endif