Package libcore.util

Class ZoneInfo.WallTime

  • Enclosing class:
    ZoneInfo
    public static class ZoneInfo.WallTime
extends Object
    A class that represents a "wall time". This class is modeled on the C tm struct and is used to support android.text.format.Time behavior. Unlike the tm struct the year is represented as the full year, not the years since 1900.

    This class contains a rewrite of various native functions that android.text.format.Time once relied on such as mktime_tz and localtime_tz. This replacement does not support leap seconds but does try to preserve behavior around ambiguous date/times found in the BSD version of mktime that was previously used.

    The original native code used a 32-bit value for time_t on 32-bit Android, which was the only variant of Android available at the time. To preserve old behavior this code deliberately uses int rather than long for most things and performs calculations in seconds. This creates deliberate truncation issues for date / times before 1901 and after 2038. This is intentional but might be fixed in future if all the knock-ons can be resolved: Application code may have come to rely on the range so previously values like zero for year could indicate an invalid date but if we move to long the year zero would be valid.

    All offsets are considered to be safe for addition / subtraction / multiplication without worrying about overflow. All absolute time arithmetic is checked for overflow / underflow.

    • Constructor Detail

      • WallTime

        public WallTime()

    • Method Detail

      • localtime

        public void localtime​(int timeSeconds,
                      ZoneInfo zoneInfo)
        Sets the wall time to a point in time using the time zone information provided. This is a replacement for the old native localtime_tz() function.

        When going from an instant to a wall time it is always unambiguous because there is only one offset rule acting at any given instant. We do not consider leap seconds.

      • mktime

        public int mktime​(ZoneInfo zoneInfo)
        Returns the time in seconds since beginning of the Unix epoch for the wall time using the time zone information provided. This is a replacement for an old native mktime_tz() C function.

        When going from a wall time to an instant the answer can be ambiguous. A wall time can map to zero, one or two instants given sane date/time transitions. Sane in this case means that transitions occur less frequently than the offset differences between them (which could cause all sorts of craziness like the skipping out of transitions).

        For example, this is not fully supported:

        • t1 { time = 1, offset = 0 }
        • t2 { time = 2, offset = -1 }
        • t3 { time = 3, offset = -2 }
        A wall time in this case might map to t1, t2 or t3.

        We do not handle leap seconds.

        We assume that no timezone offset transition has an absolute offset > 24 hours.

        We do not assume that adjacent transitions modify the DST state; adjustments can occur for other reasons such as when a zone changes its raw offset.

      • setYear

        public void setYear​(int year)

      • setMonth

        public void setMonth​(int month)

      • setMonthDay

        public void setMonthDay​(int monthDay)

      • setHour

        public void setHour​(int hour)

      • setMinute

        public void setMinute​(int minute)

      • setSecond

        public void setSecond​(int second)

      • setWeekDay

        public void setWeekDay​(int weekDay)

      • setYearDay

        public void setYearDay​(int yearDay)

      • setIsDst

        public void setIsDst​(int isDst)

      • setGmtOffset

        public void setGmtOffset​(int gmtoff)

      • getYear

        public int getYear()

      • getMonth

        public int getMonth()

      • getMonthDay

        public int getMonthDay()

      • getHour

        public int getHour()

      • getMinute

        public int getMinute()

      • getSecond

        public int getSecond()

      • getWeekDay

        public int getWeekDay()

      • getYearDay

        public int getYearDay()

      • getGmtOffset

        public int getGmtOffset()

      • getIsDst

        public int getIsDst()