Package uk.gov.gchq.gaffer.time.serialisation

Class DeltaLongTimeSeriesSerialiser

java.lang.Object

uk.gov.gchq.gaffer.time.serialisation.DeltaLongTimeSeriesSerialiser

All Implemented Interfaces:

Serializable, Serialiser<LongTimeSeries,byte[]>, ToBytesSerialiser<LongTimeSeries>

public class DeltaLongTimeSeriesSerialiser
extends Object
implements ToBytesSerialiser<LongTimeSeries>

Serialises a LongTimeSeries by writing out the deltas between consecutive values in the timeseries. The same approach is used, independently, for both the timestamps and the values. This should store the time series compactly when there is some regularity in the spacing of the keys or values.

If the values of the time series are extreme, i.e. greater than half of Long.MAX_VALUE in absolute size, then the deltas might overflow. In this case, a simpler serialisation is used where the timestamps and values are simply written out directly.

See Also:

Serialized Form

Field Summary

Fields inherited from interface uk.gov.gchq.gaffer.serialisation.ToBytesSerialiser

EMPTY_BYTES

Constructor Summary

Constructors

Constructor	Description
DeltaLongTimeSeriesSerialiser()

Method Summary

Modifier and Type	Method	Description
boolean	canHandle(Class clazz)	Check whether the serialiser can serialise a particular class.
LongTimeSeries	deserialise(byte[] bytes)	Deserialise an array of bytes into the original object.
LongTimeSeries	deserialise(byte[] allBytes, int offset, int length)
LongTimeSeries	deserialiseEmpty()	Handle an empty byte array and reconstruct an appropriate representation in T form.
boolean	equals(Object obj)
int	hashCode()
boolean	isConsistent()	Indicates whether the serialisation process produces a predictable, consistent OUTPUT, from a given INPUT, ie the same object should always serialise in the same way for this to be true.
boolean	preservesObjectOrdering()	Indicates whether the serialisation process preserves the ordering of the T, i.e.
byte[]	serialise(LongTimeSeries timeSeries)	Serialise some object and returns the raw bytes of the serialised form.

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface uk.gov.gchq.gaffer.serialisation.ToBytesSerialiser

serialiseNull

Constructor Detail

DeltaLongTimeSeriesSerialiser

public DeltaLongTimeSeriesSerialiser()

Method Detail

canHandle

public boolean canHandle(Class clazz)

Description copied from interface: Serialiser

Check whether the serialiser can serialise a particular class.

//Warning: Due to erasure you may get false positives. e.g.

 
 Set<Foo> set = Sets.newHashSet();
 boolean b = new Serialiser<Set<Bar>, byte[]>().canHandle(set.getClass());
 b will incorrectly be true because of type erasure between Set<Foo> Set<Bar>
 
 

Specified by:

canHandle in interface Serialiser<LongTimeSeries,byte[]>

Parameters:

clazz - the object class to serialise

Returns:

boolean true if it can be handled

serialise

public byte[] serialise(LongTimeSeries timeSeries)
                 throws SerialisationException

Description copied from interface: ToBytesSerialiser

Serialise some object and returns the raw bytes of the serialised form.

Specified by:

serialise in interface Serialiser<LongTimeSeries,byte[]>

Specified by:

serialise in interface ToBytesSerialiser<LongTimeSeries>

Parameters:

timeSeries - the object to be serialised

Returns:

byte[] the serialised bytes

Throws:

SerialisationException - if the object fails to serialise

deserialise

public LongTimeSeries deserialise(byte[] allBytes,
                                  int offset,
                                  int length)
                           throws SerialisationException

Specified by:

deserialise in interface ToBytesSerialiser<LongTimeSeries>

Parameters:

allBytes - The bytes to be decoded into characters

offset - The index of the first byte to decode

length - The number of bytes to decode

Returns:

T the deserialised object

Throws:

SerialisationException - issues during deserialisation

deserialise

public LongTimeSeries deserialise(byte[] bytes)
                           throws SerialisationException

Description copied from interface: ToBytesSerialiser

Deserialise an array of bytes into the original object.

Specified by:

deserialise in interface Serialiser<LongTimeSeries,byte[]>

Specified by:

deserialise in interface ToBytesSerialiser<LongTimeSeries>

Parameters:

bytes - the bytes to deserialise

Returns:

T the deserialised object

Throws:

SerialisationException - if the object fails to deserialise

Note that this implementation is less efficient than using deserialise with an offset and a length, but may still be used if necessary. It has been marked deprecated but will not be removed as it is needed in the Serialiser interface.

See Also:

ToBytesSerialiser.deserialise(byte[], int, int)

deserialiseEmpty

public LongTimeSeries deserialiseEmpty()
                                throws SerialisationException

Description copied from interface: ToBytesSerialiser

Handle an empty byte array and reconstruct an appropriate representation in T form.

Specified by:

deserialiseEmpty in interface Serialiser<LongTimeSeries,byte[]>

Specified by:

deserialiseEmpty in interface ToBytesSerialiser<LongTimeSeries>

Returns:

T the deserialised object

Throws:

SerialisationException - if the object fails to deserialise

preservesObjectOrdering

public boolean preservesObjectOrdering()

Description copied from interface: ToBytesSerialiser

Indicates whether the serialisation process preserves the ordering of the T, i.e. if x and y are objects of class T, and x is less than y, then this method should return true if the serialised form of x is guaranteed to be less than the serialised form of y (using the standard ordering of byte arrays). If T is not Comparable then this test makes no sense and false should be returned.

Specified by:

preservesObjectOrdering in interface Serialiser<LongTimeSeries,byte[]>

Specified by:

preservesObjectOrdering in interface ToBytesSerialiser<LongTimeSeries>

Returns:

true if the serialisation will preserve the order of the T, otherwise false.

isConsistent

public boolean isConsistent()

Description copied from interface: Serialiser

Indicates whether the serialisation process produces a predictable, consistent OUTPUT, from a given INPUT, ie the same object should always serialise in the same way for this to be true.

Specified by:

isConsistent in interface Serialiser<LongTimeSeries,byte[]>

Returns:

true if serialisation is consistent for a given object, otherwise false.

equals

public boolean equals(Object obj)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object