yiguolei commented on code in PR #22694:
URL: https://github.com/apache/doris/pull/22694#discussion_r1287368055
##########
be/src/util/timezone_utils.cpp:
##########
@@ -63,6 +63,172 @@ void TimezoneUtils::load_timezone_names() {
}
}
}
+
+namespace { // functions use only in this file
+
+template <typename T>
+T swapEndianness(T value) {
+ constexpr int numBytes = sizeof(T);
+ T result = 0;
+ for (int i = 0; i < numBytes; ++i) {
+ result = (result << 8) | ((value >> (8 * i)) & 0xFF);
+ }
+ return result;
+}
+
+template <typename T>
+T next_from_charstream(int8_t*& src) {
+ T value = *reinterpret_cast<T*>(src);
+ src += sizeof(T) / sizeof(int8_t);
+ if constexpr (std::endian::native == std::endian::little) {
+ return swapEndianness(
+ value); // timezone information files use network endianess,
which is big-endian
+ } else if (std::endian::native == std::endian::big) {
+ return value;
+ } else {
+ __builtin_unreachable();
+ }
+}
+
+std::pair<int8_t*, int> load_file_to_memory(const std::string& path) {
+ int fd = open(path.c_str(), O_RDONLY);
+ int len = lseek(fd, 0, SEEK_END); // bytes
+
+ int8_t* addr = (int8_t*)mmap(nullptr, len, PROT_READ, MAP_PRIVATE, fd, 0);
+ int8_t* data = new int8_t[len];
+ memcpy(data, addr, len);
+ close(fd);
+ munmap(addr, len);
+
+ return {data, len};
+}
+
+struct alignas(alignof(uint8_t)) ttinfo {
+ uint8_t tt_utoff[4]; // need force cast to int32_t
+ uint8_t tt_isdst;
+ uint8_t tt_desigidx;
+};
+constexpr static int TTINFO_SIZE = sizeof(ttinfo);
+static_assert(TTINFO_SIZE == 6);
+
+struct real_ttinfo {
+ [[maybe_unused]] real_ttinfo() = default; // actually it's used. how
stupid compiler!
+ real_ttinfo(const ttinfo& arg) {
+ diff_seconds = *reinterpret_cast<const int32_t*>(arg.tt_utoff + 0);
+ is_dst = arg.tt_isdst;
+ name_index = arg.tt_desigidx;
+ }
+
+ int32_t diff_seconds; // to UTC
+ bool is_dst;
+ uint8_t name_index;
+};
+
+template <>
+ttinfo next_from_charstream<ttinfo>(int8_t*& src) {
+ ttinfo value = *reinterpret_cast<ttinfo*>(src);
+ src += TTINFO_SIZE;
+ if constexpr (std::endian::native == std::endian::little) {
+ std::swap(value.tt_utoff[0], value.tt_utoff[3]);
+ std::swap(value.tt_utoff[1], value.tt_utoff[2]);
+ }
+ return value;
+}
+
+/*
+ * follow the rule of tzfile(5) which defined in
https://man7.org/linux/man-pages/man5/tzfile.5.html.
+ * should change when it changes.
+ */
+bool parse_load_timezone(vectorized::ZoneList& zone_list, int8_t* data, int
len,
+ bool first_time = true) {
+ int8_t* begin_pos = data;
+ /* HEADERS */
+ if (memcmp(data, "TZif", 4) != 0) [[unlikely]] { // magic number
+ return false;
+ }
+ data += 4;
+
+ // if version = 2, the whole header&data will repeat itself one time.
+ int8_t version = next_from_charstream<int8_t>(data) - '0';
+ data += 15; // null bits
+ int32_t ut_count = next_from_charstream<int32_t>(data);
+ int32_t wall_count = next_from_charstream<int32_t>(data);
+ int32_t leap_count = next_from_charstream<int32_t>(data);
+ int32_t trans_time_count = next_from_charstream<int32_t>(data);
+ int32_t type_count = next_from_charstream<int32_t>(data);
+ int32_t char_count = next_from_charstream<int32_t>(data);
+
+ /* HEADERS end, FIELDS begin*/
+ // transaction time points, which we don't need
+ data += (first_time ? 5 : 9) * trans_time_count;
+
+ // timezones
+ std::vector<real_ttinfo> timezones(type_count);
+ for (int i = 0; i < type_count; i++) {
+ ttinfo tz_data = next_from_charstream<ttinfo>(data);
+ timezones[i] = tz_data; // cast by c'tor
+ }
+
+ // timezone names
+ const char* name_zone = (char*)data;
+ data += char_count;
+
+ // concate names
+ for (auto& tz : timezones) {
+ int len = strlen(name_zone + tz.name_index);
+ zone_list.emplace(std::string {name_zone + tz.name_index, name_zone +
tz.name_index + len},
+
cctz::fixed_time_zone(cctz::seconds(tz.diff_seconds)));
+ }
+
+ // the second part.
+ if (version == 2 && first_time) {
+ // leap seconds, standard/wall indicators, UT/local indicators, which
we don't need
+ data += 4 * leap_count + wall_count + ut_count;
+
+ return (data < begin_pos + len) &&
+ parse_load_timezone(zone_list, data, len - (data - begin_pos),
false);
+ }
+
+ return true;
+}
+
+} // namespace
+
+void TimezoneUtils::load_timezones_to_cache(vectorized::ZoneList& cache_list) {
+ std::string base_str;
+ const char* tzdir = "/usr/share/zoneinfo"; // default
+ // try get from System
Review Comment:
you should make sure, both macos and linux are using /usr/share/zoneinfo
this file to save timezone info.
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