step.encoding
Class ConstantStrategy

java.lang.Object
  |
  +--step.encoding.Encoder
        |
        +--step.encoding.Strategy
              |
              +--step.encoding.RegularValueStrategy
                    |
                    +--step.encoding.ConstantStrategy

Direct Known Subclasses:

PConstantStrategy

public class ConstantStrategy

extends RegularValueStrategy

Assume values are mostly the same. If the value remains constant, there is no need to write anything to the output. The decoder simply returns the default value instead of reading from the input.

The "constant" variant of the algorithm throws an exception if an irregular value is encountered. The "default" variant allows deviations from the initial value, signalling the irregularity with an IrregularValueEvent. The "repeat" variant shifts to a new default every time the value differs from the previous, signalling the change with an IrregularValueEvent.

Algorithm:

 if current == default
     then -> nothing
     else if constant
         then ERROR!
         else -> meta:IrregularValueEvent, current
 

Field Summary

static int	CONSTANT_STRATEGY
static String	CONSTANT_STRATEGY_NAME
static int	DEFAULT_STRATEGY
static String	DEFAULT_STRATEGY_NAME
static int	REPEAT_STRATEGY
static String	REPEAT_STRATEGY_NAME

Fields inherited from class step.encoding.RegularValueStrategy

_nextIsRegular

Fields inherited from class step.encoding.Strategy

_baseEncoder

Constructor Summary

ConstantStrategy(Encoder baseEncoder, int strategy)
Create a new constant value strategy.

Method Summary

StepObject	decode(DecodeContext context) Decode a constant value.
void	dump(int level)
void	encode(StepObject o, EncodeContext context) Encode a constant value.
protected int	getStrategyVariant()

Methods inherited from class step.encoding.RegularValueStrategy

setNextIsRegular

Methods inherited from class step.encoding.Strategy

baseDecode, baseEncode, eventMessage

Methods inherited from class step.encoding.Encoder

getFactory, getName, indent, makeFieldName

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

CONSTANT_STRATEGY_NAME

public static final String CONSTANT_STRATEGY_NAME

See Also:

Constant Field Values

DEFAULT_STRATEGY_NAME

public static final String DEFAULT_STRATEGY_NAME

See Also:

Constant Field Values

REPEAT_STRATEGY_NAME

public static final String REPEAT_STRATEGY_NAME

See Also:

Constant Field Values

CONSTANT_STRATEGY

public static final int CONSTANT_STRATEGY

See Also:

Constant Field Values

DEFAULT_STRATEGY

public static final int DEFAULT_STRATEGY

See Also:

Constant Field Values

REPEAT_STRATEGY

public static final int REPEAT_STRATEGY

See Also:

Constant Field Values

Constructor Detail

ConstantStrategy

public ConstantStrategy(Encoder baseEncoder,
                        int strategy)

Create a new constant value strategy.

Parameters:

baseEncoder - the encoder for the values passed to this strategy.

strategy - one of

• CONSTANT_STRATEGY - all values are the same; deviations should generate an error.
• DEFAULT_STRATEGY - values are rarely different from the initial value; deviants are indicated with a meta event.
• REPEAT_STRATEGY - values consist of long sequences of the same value; new default values are indicated with a meta event.

Throws:

IllegalArgumentException - if strategy is invalid.

Method Detail

getStrategyVariant

protected int getStrategyVariant()

encode

public void encode(StepObject o,
                   EncodeContext context)
            throws EncoderException,
                   IOException

Encode a constant value.

Specified by:

encode in class Encoder

Throws:

EncoderException - if the value is different from the default (initial) value and the "constant" option is set.

IOException - if the encode operation encountered an I/O failure.

decode

public StepObject decode(DecodeContext context)
                  throws EncoderException,
                         IOException

Decode a constant value.

Specified by:

decode in class Encoder

Throws:

IOException - if the decode operation encountered an I/O failure.

EncoderException - if the decode operation encountered an error.

dump

public void dump(int level)

Specified by:

dump in class Encoder