TimeZone.cpp 5.3 KB

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  1. /*
  2. * Copyright (c) 2022, Tim Flynn <trflynn89@serenityos.org>
  3. *
  4. * SPDX-License-Identifier: BSD-2-Clause
  5. */
  6. #include <AK/String.h>
  7. #include <LibTimeZone/TimeZone.h>
  8. #include <stdio.h>
  9. #include <time.h>
  10. namespace TimeZone {
  11. // NOTE: Without ENABLE_TIME_ZONE_DATA LibTimeZone operates in a UTC-only mode and only recognizes
  12. // the 'UTC' time zone, which is slightly more useful than a bunch of dummy functions that
  13. // can't do anything. When we build with time zone data, these weakly linked functions are
  14. // replaced with their proper counterparts.
  15. #if !ENABLE_TIME_ZONE_DATA
  16. enum class TimeZone : u16 {
  17. UTC,
  18. };
  19. #endif
  20. class TimeZoneFile {
  21. public:
  22. TimeZoneFile(char const* mode)
  23. : m_file(fopen("/etc/timezone", mode))
  24. {
  25. if (m_file)
  26. flockfile(m_file);
  27. }
  28. ~TimeZoneFile()
  29. {
  30. if (m_file) {
  31. funlockfile(m_file);
  32. fclose(m_file);
  33. }
  34. }
  35. ErrorOr<String> read_time_zone()
  36. {
  37. if (!m_file)
  38. return Error::from_string_literal("Could not open /etc/timezone");
  39. Array<u8, 128> buffer;
  40. size_t bytes = fread(buffer.data(), 1, buffer.size(), m_file);
  41. if (bytes == 0)
  42. return Error::from_string_literal("Could not read time zone from /etc/timezone");
  43. return String(buffer.span().slice(0, bytes)).trim_whitespace();
  44. }
  45. ErrorOr<void> write_time_zone(StringView time_zone)
  46. {
  47. if (!m_file)
  48. return Error::from_string_literal("Could not open /etc/timezone");
  49. auto bytes = fwrite(time_zone.characters_without_null_termination(), 1, time_zone.length(), m_file);
  50. if (bytes != time_zone.length())
  51. return Error::from_string_literal("Could not write new time zone to /etc/timezone");
  52. return {};
  53. }
  54. private:
  55. FILE* m_file { nullptr };
  56. };
  57. StringView system_time_zone()
  58. {
  59. TimeZoneFile time_zone_file("r");
  60. // FIXME: Propagate the error to existing callers.
  61. if (auto time_zone = time_zone_file.read_time_zone(); !time_zone.is_error())
  62. return canonicalize_time_zone(time_zone.value()).value_or("UTC"sv);
  63. return "UTC"sv;
  64. }
  65. StringView current_time_zone()
  66. {
  67. return canonicalize_time_zone(tzname[0]).value_or("UTC"sv);
  68. }
  69. ErrorOr<void> change_time_zone([[maybe_unused]] StringView time_zone)
  70. {
  71. #ifdef __serenity__
  72. TimeZoneFile time_zone_file("w");
  73. if (auto new_time_zone = canonicalize_time_zone(time_zone); new_time_zone.has_value())
  74. return time_zone_file.write_time_zone(*new_time_zone);
  75. return Error::from_string_literal("Provided time zone is not supported");
  76. #else
  77. // Do not even attempt to change the time zone of someone's host machine.
  78. return {};
  79. #endif
  80. }
  81. Span<StringView const> __attribute__((weak)) all_time_zones()
  82. {
  83. #if !ENABLE_TIME_ZONE_DATA
  84. static constexpr auto utc = Array { "UTC"sv };
  85. return utc;
  86. #else
  87. return {};
  88. #endif
  89. }
  90. Optional<TimeZone> __attribute__((weak)) time_zone_from_string([[maybe_unused]] StringView time_zone)
  91. {
  92. #if !ENABLE_TIME_ZONE_DATA
  93. if (time_zone.equals_ignoring_case("UTC"sv))
  94. return TimeZone::UTC;
  95. #endif
  96. return {};
  97. }
  98. StringView __attribute__((weak)) time_zone_to_string([[maybe_unused]] TimeZone time_zone)
  99. {
  100. #if !ENABLE_TIME_ZONE_DATA
  101. VERIFY(time_zone == TimeZone::UTC);
  102. return "UTC"sv;
  103. #else
  104. return {};
  105. #endif
  106. }
  107. Optional<StringView> canonicalize_time_zone(StringView time_zone)
  108. {
  109. auto maybe_time_zone = time_zone_from_string(time_zone);
  110. if (!maybe_time_zone.has_value())
  111. return {};
  112. auto canonical_time_zone = time_zone_to_string(*maybe_time_zone);
  113. if (canonical_time_zone.is_one_of("Etc/UTC"sv, "Etc/GMT"sv))
  114. return "UTC"sv;
  115. return canonical_time_zone;
  116. }
  117. Optional<DaylightSavingsRule> __attribute__((weak)) daylight_savings_rule_from_string(StringView) { return {}; }
  118. StringView __attribute__((weak)) daylight_savings_rule_to_string(DaylightSavingsRule) { return {}; }
  119. Optional<Offset> __attribute__((weak)) get_time_zone_offset([[maybe_unused]] TimeZone time_zone, AK::Time)
  120. {
  121. #if !ENABLE_TIME_ZONE_DATA
  122. VERIFY(time_zone == TimeZone::UTC);
  123. return Offset {};
  124. #else
  125. return {};
  126. #endif
  127. }
  128. Optional<Offset> get_time_zone_offset(StringView time_zone, AK::Time time)
  129. {
  130. if (auto maybe_time_zone = time_zone_from_string(time_zone); maybe_time_zone.has_value())
  131. return get_time_zone_offset(*maybe_time_zone, time);
  132. return {};
  133. }
  134. Optional<Array<NamedOffset, 2>> __attribute__((weak)) get_named_time_zone_offsets([[maybe_unused]] TimeZone time_zone, AK::Time)
  135. {
  136. #if !ENABLE_TIME_ZONE_DATA
  137. VERIFY(time_zone == TimeZone::UTC);
  138. NamedOffset utc_offset {};
  139. utc_offset.name = "UTC"sv;
  140. return Array { utc_offset, utc_offset };
  141. #else
  142. return {};
  143. #endif
  144. }
  145. Optional<Array<NamedOffset, 2>> get_named_time_zone_offsets(StringView time_zone, AK::Time time)
  146. {
  147. if (auto maybe_time_zone = time_zone_from_string(time_zone); maybe_time_zone.has_value())
  148. return get_named_time_zone_offsets(*maybe_time_zone, time);
  149. return {};
  150. }
  151. Optional<Location> __attribute__((weak)) get_time_zone_location(TimeZone) { return {}; }
  152. Optional<Location> get_time_zone_location(StringView time_zone)
  153. {
  154. if (auto maybe_time_zone = time_zone_from_string(time_zone); maybe_time_zone.has_value())
  155. return get_time_zone_location(*maybe_time_zone);
  156. return {};
  157. }
  158. }