Timestamp.java
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.arrow.flatbuf;
import com.google.flatbuffers.BaseVector;
import com.google.flatbuffers.BooleanVector;
import com.google.flatbuffers.ByteVector;
import com.google.flatbuffers.Constants;
import com.google.flatbuffers.DoubleVector;
import com.google.flatbuffers.FlatBufferBuilder;
import com.google.flatbuffers.FloatVector;
import com.google.flatbuffers.IntVector;
import com.google.flatbuffers.LongVector;
import com.google.flatbuffers.ShortVector;
import com.google.flatbuffers.StringVector;
import com.google.flatbuffers.Struct;
import com.google.flatbuffers.Table;
import com.google.flatbuffers.UnionVector;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
/**
* Timestamp is a 64-bit signed integer representing an elapsed time since a
* fixed epoch, stored in either of four units: seconds, milliseconds,
* microseconds or nanoseconds, and is optionally annotated with a timezone.
*
* Timestamp values do not include any leap seconds (in other words, all
* days are considered 86400 seconds long).
*
* Timestamps with a non-empty timezone
* ------------------------------------
*
* If a Timestamp column has a non-empty timezone value, its epoch is
* 1970-01-01 00:00:00 (January 1st 1970, midnight) in the *UTC* timezone
* (the Unix epoch), regardless of the Timestamp's own timezone.
*
* Therefore, timestamp values with a non-empty timezone correspond to
* physical points in time together with some additional information about
* how the data was obtained and/or how to display it (the timezone).
*
* For example, the timestamp value 0 with the timezone string "Europe/Paris"
* corresponds to "January 1st 1970, 00h00" in the UTC timezone, but the
* application may prefer to display it as "January 1st 1970, 01h00" in
* the Europe/Paris timezone (which is the same physical point in time).
*
* One consequence is that timestamp values with a non-empty timezone
* can be compared and ordered directly, since they all share the same
* well-known point of reference (the Unix epoch).
*
* Timestamps with an unset / empty timezone
* -----------------------------------------
*
* If a Timestamp column has no timezone value, its epoch is
* 1970-01-01 00:00:00 (January 1st 1970, midnight) in an *unknown* timezone.
*
* Therefore, timestamp values without a timezone cannot be meaningfully
* interpreted as physical points in time, but only as calendar / clock
* indications ("wall clock time") in an unspecified timezone.
*
* For example, the timestamp value 0 with an empty timezone string
* corresponds to "January 1st 1970, 00h00" in an unknown timezone: there
* is not enough information to interpret it as a well-defined physical
* point in time.
*
* One consequence is that timestamp values without a timezone cannot
* be reliably compared or ordered, since they may have different points of
* reference. In particular, it is *not* possible to interpret an unset
* or empty timezone as the same as "UTC".
*
* Conversion between timezones
* ----------------------------
*
* If a Timestamp column has a non-empty timezone, changing the timezone
* to a different non-empty value is a metadata-only operation:
* the timestamp values need not change as their point of reference remains
* the same (the Unix epoch).
*
* However, if a Timestamp column has no timezone value, changing it to a
* non-empty value requires to think about the desired semantics.
* One possibility is to assume that the original timestamp values are
* relative to the epoch of the timezone being set; timestamp values should
* then adjusted to the Unix epoch (for example, changing the timezone from
* empty to "Europe/Paris" would require converting the timestamp values
* from "Europe/Paris" to "UTC", which seems counter-intuitive but is
* nevertheless correct).
*
* Guidelines for encoding data from external libraries
* ----------------------------------------------------
*
* Date & time libraries often have multiple different data types for temporal
* data. In order to ease interoperability between different implementations the
* Arrow project has some recommendations for encoding these types into a Timestamp
* column.
*
* An "instant" represents a physical point in time that has no relevant timezone
* (for example, astronomical data). To encode an instant, use a Timestamp with
* the timezone string set to "UTC", and make sure the Timestamp values
* are relative to the UTC epoch (January 1st 1970, midnight).
*
* A "zoned date-time" represents a physical point in time annotated with an
* informative timezone (for example, the timezone in which the data was
* recorded). To encode a zoned date-time, use a Timestamp with the timezone
* string set to the name of the timezone, and make sure the Timestamp values
* are relative to the UTC epoch (January 1st 1970, midnight).
*
* (There is some ambiguity between an instant and a zoned date-time with the
* UTC timezone. Both of these are stored the same in Arrow. Typically,
* this distinction does not matter. If it does, then an application should
* use custom metadata or an extension type to distinguish between the two cases.)
*
* An "offset date-time" represents a physical point in time combined with an
* explicit offset from UTC. To encode an offset date-time, use a Timestamp
* with the timezone string set to the numeric timezone offset string
* (e.g. "+03:00"), and make sure the Timestamp values are relative to
* the UTC epoch (January 1st 1970, midnight).
*
* A "naive date-time" (also called "local date-time" in some libraries)
* represents a wall clock time combined with a calendar date, but with
* no indication of how to map this information to a physical point in time.
* Naive date-times must be handled with care because of this missing
* information, and also because daylight saving time (DST) may make
* some values ambiguous or nonexistent. A naive date-time may be
* stored as a struct with Date and Time fields. However, it may also be
* encoded into a Timestamp column with an empty timezone. The timestamp
* values should be computed "as if" the timezone of the date-time values
* was UTC; for example, the naive date-time "January 1st 1970, 00h00" would
* be encoded as timestamp value 0.
*/
@SuppressWarnings("unused")
public final class Timestamp extends Table {
public static void ValidateVersion() { Constants.FLATBUFFERS_24_3_25(); }
public static Timestamp getRootAsTimestamp(ByteBuffer _bb) { return getRootAsTimestamp(_bb, new Timestamp()); }
public static Timestamp getRootAsTimestamp(ByteBuffer _bb, Timestamp obj) { _bb.order(ByteOrder.LITTLE_ENDIAN); return (obj.__assign(_bb.getInt(_bb.position()) + _bb.position(), _bb)); }
public void __init(int _i, ByteBuffer _bb) { __reset(_i, _bb); }
public Timestamp __assign(int _i, ByteBuffer _bb) { __init(_i, _bb); return this; }
public short unit() { int o = __offset(4); return o != 0 ? bb.getShort(o + bb_pos) : 0; }
/**
* The timezone is an optional string indicating the name of a timezone,
* one of:
*
* * As used in the Olson timezone database (the "tz database" or
* "tzdata"), such as "America/New_York".
* * An absolute timezone offset of the form "+XX:XX" or "-XX:XX",
* such as "+07:30".
*
* Whether a timezone string is present indicates different semantics about
* the data (see above).
*/
public String timezone() { int o = __offset(6); return o != 0 ? __string(o + bb_pos) : null; }
public ByteBuffer timezoneAsByteBuffer() { return __vector_as_bytebuffer(6, 1); }
public ByteBuffer timezoneInByteBuffer(ByteBuffer _bb) { return __vector_in_bytebuffer(_bb, 6, 1); }
public static int createTimestamp(FlatBufferBuilder builder,
short unit,
int timezoneOffset) {
builder.startTable(2);
Timestamp.addTimezone(builder, timezoneOffset);
Timestamp.addUnit(builder, unit);
return Timestamp.endTimestamp(builder);
}
public static void startTimestamp(FlatBufferBuilder builder) { builder.startTable(2); }
public static void addUnit(FlatBufferBuilder builder, short unit) { builder.addShort(0, unit, 0); }
public static void addTimezone(FlatBufferBuilder builder, int timezoneOffset) { builder.addOffset(1, timezoneOffset, 0); }
public static int endTimestamp(FlatBufferBuilder builder) {
int o = builder.endTable();
return o;
}
public static final class Vector extends BaseVector {
public Vector __assign(int _vector, int _element_size, ByteBuffer _bb) { __reset(_vector, _element_size, _bb); return this; }
public Timestamp get(int j) { return get(new Timestamp(), j); }
public Timestamp get(Timestamp obj, int j) { return obj.__assign(__indirect(__element(j), bb), bb); }
}
}