de.schlichtherle.util.zip
Class DateTimeConverter

java.lang.Object
  de.schlichtherle.util.zip.DateTimeConverter

public abstract class DateTimeConverter
extends Object

Converts Java time values to DOS date/time values and vice versa. This class has been introduced in order to enhance interoperability between different flavours of the ZIP file format specification when converting date/time from the serialized DOS format in a ZIP file to the local system time, which is represented by a UNIX-like encoding by the Java API.

This class is thread-safe.

Since:

TrueZIP 6.7

Author:

Christian Schlichtherle

JAR

public static final DateTimeConverter JAR

This instance applies the schedule for Daylight Saving Time (DST), i.e. all time conversions will apply DST where appropriate to a particular date.

This behaviour provides best interoperability with:

• Java SE: jar utility and java.util.zip package
• Info-ZIP: unzip

ZIP

public static final DateTimeConverter ZIP

This instance ignores the schedule for Daylight Saving Time (DST), i.e. all time conversions will use the same raw offset and current DST savings, regardless of whether DST savings should be applied to a particular date or not.

This behavior provides best interoperability with:

• Windows Vista Explorer (as of June 30^th, 2009)
• WinZip 12.0
• 7-Zip 4.65

MIN_DOS_TIME

static final long MIN_DOS_TIME

Smallest supported DOS date/time value in a ZIP file, which is January 1^st, 1980 AD 00:00:00 local time.

See Also:

Constant Field Values

MAX_DOS_TIME

static final long MAX_DOS_TIME

Largest supported DOS date/time value in a ZIP file, which is December 31^st, 2107 AD 23:59:58 local time.

See Also:

Constant Field Values

calendar

private final ThreadLocal calendar

A thread local lenient gregorian calendar for date/time conversion which has its timezone set to the return value of #newTimeZone().

DateTimeConverter

public DateTimeConverter()

createTimeZone

protected abstract TimeZone createTimeZone()

Returns a new timezone to use for date/time conversion. All returned instances must have the same rules.

Returns:

A new timezone for date/time conversion - never null.

roundUp

protected abstract boolean roundUp(long jTime)

Returns whether the given Java time should be rounded up or down to the next two second interval when converting it to a DOS date/time.

Parameters:

jTime - The number of milliseconds since midnight, January 1st, 1970 AD UTC (called epoch alias Java time).

Returns:

true for round-up, false for round-down.

getGregorianCalendar

private GregorianCalendar getGregorianCalendar()

Returns a thread local lenient gregorian calendar for date/time conversion which has its timezone set to the return value of #newTimeZone().

Returns:

A thread local lenient gregorian calendar.

toDosTime

final long toDosTime(long jTime)

Converts a Java time value to a DOS date/time value. The returned value is rounded up or down to even seconds, depending on roundUp(long). If the Java time value is earlier than January 1^st, 1980 AD 00:00:00 local time, then this value is returned instead.

This method uses a lenient DateTimeConverter.ThreadLocalGregorianCalendar for the date/time conversion which has its timezone set to the return value of #newTimeZone().

Parameters:

jTime - The number of milliseconds since midnight, January 1st, 1970 AD UTC (called the epoch alias Java time).

Returns:

A DOS date/time value reflecting the local time zone and rounded down to even seconds which is minimum January 1^st, 1980 AD 00:00:00.

Throws:

RuntimeException - If jTime is negative or later than 2107 AD.

See Also:

toJavaTime(long), #newTimeZone()

toJavaTime

final long toJavaTime(long dTime)

Converts a 32 bit integer encoded DOS date/time value to a Java time value.

Note that not all 32 bit integers are valid DOS date/time values. If an invalid DOS date/time value is provided, it gets adjusted by overflowing the respective field value as if using a lenient calendar. This feature is provided in order to read bogus ZIP archive files created by third party tools. However, the returned Java time may differ from its intended value at the time of the creation of the ZIP archive file and when converting it back again, the resulting DOS date/time value will not be the same as dTime.

This method uses a lenient DateTimeConverter.ThreadLocalGregorianCalendar for the date/time conversion which has its timezone set to the return value of #newTimeZone().

Parameters:

dTime - The DOS date/time value.

Returns:

The number of milliseconds since midnight, January 1st, 1970 AD UTC (called epoch alias Java time).

Throws:

IllegalArgumentException - If dTime is earlier than 1980 AD or greater than 0xffffffffL.

See Also:

toDosTime(long), #newTimeZone()