Merge pull request #6862 from realm/je/fix-timestamp

CHANGELOG.md

@@ -7,6 +7,7 @@
 ### Fixed
 * <How do the end-user experience this issue? what was the impact?> ([#????](https://github.com/realm/realm-core/issues/????), since v?.?.?)
 * Fix failed assertion for unknown app server errors ([#6758](https://github.com/realm/realm-core/issues/6758), since v12.9.0).
+* Change JSON selialization format back to follow ISO 8601 - and add output of nanoseconds ([#6855](https://github.com/realm/realm-core/issues/6855), since 13.17.0)
 
 ### Breaking changes
 * None.

src/realm/obj.cpp

@@ -922,7 +922,7 @@ void out_mixed_json(std::ostream& out, const Mixed& val)
         }
         case type_Timestamp:
             out << "\"";
-            out << util::serializer::print_value<Timestamp>(val.get_timestamp());
+            out << val.get<Timestamp>();
             out << "\"";
             break;
         case type_Decimal:

src/realm/timestamp.hpp

@@ -182,6 +182,9 @@ class Timestamp {
         return size_t(m_seconds) ^ size_t(m_nanoseconds);
     }
 
+    // Buffer must be at least 32 bytes long
+    const char* to_string(char* buffer) const;
+
     template <class Ch, class Tr>
     friend std::basic_ostream<Ch, Tr>& operator<<(std::basic_ostream<Ch, Tr>& out, const Timestamp&);
     static constexpr int32_t nanoseconds_per_second = 1000000000;
@@ -196,26 +199,8 @@ class Timestamp {
 template <class C, class T>
 inline std::basic_ostream<C, T>& operator<<(std::basic_ostream<C, T>& out, const Timestamp& d)
 {
-    if (d.is_null()) {
-        out << "null";
-        return out;
-    }
-    auto seconds = time_t(d.get_seconds());
-    struct tm buf;
-#ifdef _MSC_VER
-    bool success = gmtime_s(&buf, &seconds) == 0;
-#else
-    bool success = gmtime_r(&seconds, &buf) != nullptr;
-#endif
-    if (success) {
-        // We need a buffer for formatting dates.
-        // Max size is 20 bytes (incl terminating zero) "YYYY-MM-DD HH:MM:SS"\0
-        char buffer[30];
-        if (strftime(buffer, sizeof(buffer), "%Y-%m-%d %H:%M:%S", &buf)) {
-            out << buffer;
-        }
-    }
-
+    char buffer[32];
+    out << d.to_string(buffer);
     return out;
 }
 // LCOV_EXCL_STOP

src/realm/util/serializer.cpp

@@ -32,7 +32,103 @@
 #include <cctype>
 #include <cmath>
 
+
 namespace realm {
+
+/* Uses Fliegel & Van Flandern algorithm */
+static constexpr long date_to_julian(int y, int m, int d)
+{
+    return (1461 * (y + 4800 + (m - 14) / 12)) / 4 + (367 * (m - 2 - 12 * ((m - 14) / 12))) / 12 -
+           (3 * ((y + 4900 + (m - 14) / 12) / 100)) / 4 + d - 32075;
+}
+
+static void julian_to_date(int jd, int* y, int* m, int* d)
+{
+    int L = jd + 68569;
+    int n = (4 * L) / 146097;
+    int i, j;
+
+    L = L - (146097 * n + 3) / 4;
+    i = (4000 * (L + 1)) / 1461001;
+    L = L - (1461 * i) / 4 + 31;
+    j = (80 * L) / 2447;
+    *d = L - (2447 * j) / 80;
+    L = j / 11;
+    *m = j + 2 - (12 * L);
+    *y = 100 * (n - 49) + i + L;
+}
+
+// Confirmed to work for all val < 16389
+static void out_dec(char** buffer, unsigned val, int width)
+{
+    int w = width;
+    char* p = *buffer;
+    while (width > 0) {
+        width--;
+        unsigned div10 = (val * 6554) >> 16;
+        p[width] = char(val - div10 * 10) + '0';
+        val = div10;
+    }
+    *buffer += w;
+}
+
+static constexpr long epoc_julian_days = date_to_julian(1970, 1, 1); // 2440588
+static constexpr int seconds_in_a_day = 24 * 60 * 60;
+
+const char* Timestamp::to_string(char* buffer) const
+{
+    if (is_null()) {
+        return "null";
+    }
+    int64_t seconds = get_seconds();
+    int32_t nano = get_nanoseconds();
+    if (nano < 0) {
+        nano += Timestamp::nanoseconds_per_second;
+        seconds--;
+    }
+
+    int64_t days = seconds / seconds_in_a_day;
+    int julian_days = int(days + epoc_julian_days);
+
+    int seconds_in_day = int(seconds - days * seconds_in_a_day);
+    if (seconds_in_day < 0) {
+        seconds_in_day += seconds_in_a_day;
+        julian_days--;
+    }
+
+    int year;
+    int month;
+    int day;
+    int hours = seconds_in_day / 3600;
+    int remainingSeconds = seconds_in_day - hours * 3600;
+    int minutes = remainingSeconds / 60;
+    int secs = remainingSeconds - minutes * 60;
+
+    julian_to_date(julian_days, &year, &month, &day);
+
+    char* p = buffer;
+    if (year < 0) {
+        *p++ = '-';
+        year = -year;
+    }
+    out_dec(&p, year, 4);
+    *p++ = '-';
+    out_dec(&p, month, 2);
+    *p++ = '-';
+    out_dec(&p, day, 2);
+    *p++ = ' ';
+    out_dec(&p, hours, 2);
+    *p++ = ':';
+    out_dec(&p, minutes, 2);
+    *p++ = ':';
+    out_dec(&p, secs, 2);
+    *p = '\0';
+    if (nano) {
+        snprintf(p, 32 - (p - buffer), ".%09d", nano);
+    }
+    return buffer;
+}
+
 namespace util {
 namespace serializer {