pitrou commented on code in PR #48601:
URL: https://github.com/apache/arrow/pull/48601#discussion_r2660768172
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cpp/src/arrow/compute/kernels/scalar_temporal_test.cc:
##########
@@ -38,6 +39,10 @@ using internal::StringFormatter;
namespace compute {
+TEST(ChronoConfig, LogChronoBackend) {
Review Comment:
Do we want to keep this?
##########
cpp/src/arrow/util/chrono_internal.h:
##########
@@ -0,0 +1,269 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements. See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership. The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License. You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied. See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+#pragma once
+
+/// \file chrono_internal.h
+/// \brief Abstraction layer for C++20 chrono calendar/timezone APIs
+///
+/// This header provides a unified interface for chrono calendar and timezone
+/// functionality. On compilers with full C++20 chrono support, it uses
+/// std::chrono. On other compilers, it falls back to the vendored Howard
Hinnant
+/// date library.
+///
+/// The main benefit is on Windows where std::chrono uses the system timezone
+/// database, eliminating the need for users to install IANA tzdata separately.
+
+#include <chrono>
+#include <string>
+#include <string_view>
+
+// Feature detection for C++20 chrono timezone support
+// We only enable for compilers with FULL support (not partial)
+//
https://en.cppreference.com/w/cpp/compiler_support/20.html#cpp_lib_chrono_201907L
+//
+// MSVC 19.29+ (VS16.10+): Full C++20 chrono support, uses Windows internal TZ
database.
+// GCC libstdc++ has a bug where DST state is incorrectly reset when a timezone
+// transitions between rule sets in tzdata.zi (e.g., Australia/Broken_Hill
around
+// 2000-02-29 23:23:24).
+// Until this is fixed, we use the vendored date.h library for GCC.
+
+#if defined(_MSC_VER) && defined(__cpp_lib_chrono) && __cpp_lib_chrono >=
201907L
+# define ARROW_USE_STD_CHRONO 1
+#else
+# define ARROW_USE_STD_CHRONO 0
+#endif
+
+#if ARROW_USE_STD_CHRONO
+// Use C++20 standard library chrono
+# include <format>
+# include <iterator>
+# include <ostream>
+#else
+// Use vendored Howard Hinnant date library
+# include "arrow/vendored/datetime.h"
+#endif
+
+namespace arrow::internal::chrono {
+
+#if ARROW_USE_STD_CHRONO
+
+// ============================================================================
+// C++20 std::chrono backend
+// ============================================================================
+
+// Duration types
+using days = std::chrono::days;
+using weeks = std::chrono::weeks;
+using months = std::chrono::months;
+using years = std::chrono::years;
+
+// Time point types
+template <typename Duration>
+using sys_time = std::chrono::sys_time<Duration>;
+using sys_days = std::chrono::sys_days;
+using sys_seconds = std::chrono::sys_seconds;
+
+template <typename Duration>
+using local_time = std::chrono::local_time<Duration>;
+using local_days = std::chrono::local_days;
+using local_seconds = std::chrono::local_seconds;
+
+// Calendar types
+using year = std::chrono::year;
+using month = std::chrono::month;
+using day = std::chrono::day;
+using weekday = std::chrono::weekday;
+using year_month_day = std::chrono::year_month_day;
+using year_month_weekday = std::chrono::year_month_weekday;
+
+template <typename Duration>
+using hh_mm_ss = std::chrono::hh_mm_ss<Duration>;
+
+// Timezone types
+using time_zone = std::chrono::time_zone;
+using sys_info = std::chrono::sys_info;
+using local_info = std::chrono::local_info;
+using choose = std::chrono::choose;
+
+template <typename Duration, typename TimeZonePtr = const time_zone*>
+using zoned_time = std::chrono::zoned_time<Duration, TimeZonePtr>;
+
+template <typename TimeZonePtr>
+using zoned_traits = std::chrono::zoned_traits<TimeZonePtr>;
+
+// Exceptions
+using nonexistent_local_time = std::chrono::nonexistent_local_time;
+using ambiguous_local_time = std::chrono::ambiguous_local_time;
+
+// Weekday constants
+using std::chrono::Monday;
+using std::chrono::Sunday;
+
+// Rounding functions
+using std::chrono::ceil;
+using std::chrono::floor;
+using std::chrono::round;
+
+// trunc (truncation toward zero) is not in std::chrono, only floor/ceil/round
+template <typename ToDuration, typename Rep, typename Period>
+constexpr ToDuration trunc(const std::chrono::duration<Rep, Period>& d) {
+ auto floored = std::chrono::floor<ToDuration>(d);
+ // floor rounds toward -infinity; for negative values with remainder, add 1
to get
+ // toward zero
+ if (d.count() < 0 && (d - floored).count() != 0) {
+ return floored + ToDuration{1};
+ }
+ return floored;
+}
+
+// Timezone lookup
+inline const time_zone* locate_zone(std::string_view tz_name) {
+ return std::chrono::locate_zone(tz_name);
+}
+
+inline const time_zone* current_zone() { return std::chrono::current_zone(); }
+
+// Formatting support - streams directly using C++20 std::vformat_to
+// Provides: direct streaming, stream state preservation, chaining, rich
format specifiers
+template <typename CharT, typename Traits, typename Duration, typename
TimeZonePtr>
+std::basic_ostream<CharT, Traits>& to_stream(
+ std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
+ const std::chrono::zoned_time<Duration, TimeZonePtr>& zt) {
+ std::vformat_to(std::ostreambuf_iterator<CharT>(os), std::string("{:") + fmt
+ "}",
+ std::make_format_args(zt));
+ return os;
+}
+
+// Format a duration using strftime-like format specifiers
+// Converts "%H%M" style to C++20's "{:%H%M}" style and uses std::vformat
+template <typename Duration>
+std::string format(const char* fmt, const Duration& d) {
+ return std::vformat(std::string("{:") + fmt + "}", std::make_format_args(d));
+}
+
+// Literals namespace
+namespace literals {
Review Comment:
Is there any particular reason to expose this in a `literals` nested
namespace rather than in `chrono` itself?
##########
cpp/src/arrow/util/chrono_internal.h:
##########
@@ -0,0 +1,269 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements. See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership. The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License. You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied. See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+#pragma once
+
+/// \file chrono_internal.h
+/// \brief Abstraction layer for C++20 chrono calendar/timezone APIs
+///
+/// This header provides a unified interface for chrono calendar and timezone
+/// functionality. On compilers with full C++20 chrono support, it uses
+/// std::chrono. On other compilers, it falls back to the vendored Howard
Hinnant
+/// date library.
+///
+/// The main benefit is on Windows where std::chrono uses the system timezone
+/// database, eliminating the need for users to install IANA tzdata separately.
+
+#include <chrono>
+#include <string>
+#include <string_view>
+
+// Feature detection for C++20 chrono timezone support
+// We only enable for compilers with FULL support (not partial)
+//
https://en.cppreference.com/w/cpp/compiler_support/20.html#cpp_lib_chrono_201907L
+//
+// MSVC 19.29+ (VS16.10+): Full C++20 chrono support, uses Windows internal TZ
database.
+// GCC libstdc++ has a bug where DST state is incorrectly reset when a timezone
+// transitions between rule sets in tzdata.zi (e.g., Australia/Broken_Hill
around
+// 2000-02-29 23:23:24).
+// Until this is fixed, we use the vendored date.h library for GCC.
+
+#if defined(_MSC_VER) && defined(__cpp_lib_chrono) && __cpp_lib_chrono >=
201907L
+# define ARROW_USE_STD_CHRONO 1
+#else
+# define ARROW_USE_STD_CHRONO 0
+#endif
+
+#if ARROW_USE_STD_CHRONO
+// Use C++20 standard library chrono
+# include <format>
+# include <iterator>
+# include <ostream>
+#else
+// Use vendored Howard Hinnant date library
+# include "arrow/vendored/datetime.h"
+#endif
+
+namespace arrow::internal::chrono {
+
+#if ARROW_USE_STD_CHRONO
+
+// ============================================================================
+// C++20 std::chrono backend
+// ============================================================================
+
+// Duration types
+using days = std::chrono::days;
+using weeks = std::chrono::weeks;
+using months = std::chrono::months;
+using years = std::chrono::years;
+
+// Time point types
+template <typename Duration>
+using sys_time = std::chrono::sys_time<Duration>;
+using sys_days = std::chrono::sys_days;
+using sys_seconds = std::chrono::sys_seconds;
+
+template <typename Duration>
+using local_time = std::chrono::local_time<Duration>;
+using local_days = std::chrono::local_days;
+using local_seconds = std::chrono::local_seconds;
+
+// Calendar types
+using year = std::chrono::year;
+using month = std::chrono::month;
+using day = std::chrono::day;
+using weekday = std::chrono::weekday;
+using year_month_day = std::chrono::year_month_day;
+using year_month_weekday = std::chrono::year_month_weekday;
+
+template <typename Duration>
+using hh_mm_ss = std::chrono::hh_mm_ss<Duration>;
+
+// Timezone types
+using time_zone = std::chrono::time_zone;
+using sys_info = std::chrono::sys_info;
+using local_info = std::chrono::local_info;
+using choose = std::chrono::choose;
+
+template <typename Duration, typename TimeZonePtr = const time_zone*>
+using zoned_time = std::chrono::zoned_time<Duration, TimeZonePtr>;
+
+template <typename TimeZonePtr>
+using zoned_traits = std::chrono::zoned_traits<TimeZonePtr>;
+
+// Exceptions
+using nonexistent_local_time = std::chrono::nonexistent_local_time;
+using ambiguous_local_time = std::chrono::ambiguous_local_time;
+
+// Weekday constants
+using std::chrono::Monday;
+using std::chrono::Sunday;
+
+// Rounding functions
+using std::chrono::ceil;
+using std::chrono::floor;
+using std::chrono::round;
+
+// trunc (truncation toward zero) is not in std::chrono, only floor/ceil/round
+template <typename ToDuration, typename Rep, typename Period>
+constexpr ToDuration trunc(const std::chrono::duration<Rep, Period>& d) {
+ auto floored = std::chrono::floor<ToDuration>(d);
+ // floor rounds toward -infinity; for negative values with remainder, add 1
to get
+ // toward zero
+ if (d.count() < 0 && (d - floored).count() != 0) {
+ return floored + ToDuration{1};
+ }
+ return floored;
+}
+
+// Timezone lookup
+inline const time_zone* locate_zone(std::string_view tz_name) {
+ return std::chrono::locate_zone(tz_name);
+}
+
+inline const time_zone* current_zone() { return std::chrono::current_zone(); }
+
+// Formatting support - streams directly using C++20 std::vformat_to
+// Provides: direct streaming, stream state preservation, chaining, rich
format specifiers
+template <typename CharT, typename Traits, typename Duration, typename
TimeZonePtr>
+std::basic_ostream<CharT, Traits>& to_stream(
+ std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
+ const std::chrono::zoned_time<Duration, TimeZonePtr>& zt) {
+ std::vformat_to(std::ostreambuf_iterator<CharT>(os), std::string("{:") + fmt
+ "}",
+ std::make_format_args(zt));
+ return os;
+}
+
+// Format a duration using strftime-like format specifiers
+// Converts "%H%M" style to C++20's "{:%H%M}" style and uses std::vformat
+template <typename Duration>
+std::string format(const char* fmt, const Duration& d) {
+ return std::vformat(std::string("{:") + fmt + "}", std::make_format_args(d));
+}
+
+// Literals namespace
+namespace literals {
+// Month literals
+inline constexpr std::chrono::month jan = std::chrono::January;
+inline constexpr std::chrono::month dec = std::chrono::December;
+
+// Weekday literals
+inline constexpr std::chrono::weekday sun = std::chrono::Sunday;
+inline constexpr std::chrono::weekday mon = std::chrono::Monday;
+inline constexpr std::chrono::weekday wed = std::chrono::Wednesday;
+inline constexpr std::chrono::weekday thu = std::chrono::Thursday;
Review Comment:
I'm curious, why expose only a subset of them?
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