net.sf.farrago.fennel.tuple
Class FennelAttributeAccessor

java.lang.Object
  net.sf.farrago.fennel.tuple.FennelAttributeAccessor

Direct Known Subclasses:

FennelAttributeAccessor.FennelBitAccessor, FennelAttributeAccessor.FennelByteAccessor, FennelAttributeAccessor.FennelFixedWidthAccessor, FennelAttributeAccessor.FennelIntAccessor, FennelAttributeAccessor.FennelLongAccessor, FennelAttributeAccessor.FennelShortAccessor, FennelAttributeAccessor.FennelVarWidthAccessor

public abstract class FennelAttributeAccessor
extends Object

FennelAttributeAccessor defines how to efficiently unmarshal the value of an attribute from a stored tuple. Derived classes implement various strategies depending on the storage type.

All data members are defined at this level rather than in derived classes, which only provide method implementations. This makes it possible to write non-polymorphic access code in cases where the entire tuple is being processed, but polymorphic access code in cases where only a small subset of the attributes are being processed. In theory, this hybrid should yield the highest efficiency, but it needs to be benchmarked and tuned. This class is JDK 1.4 compatible.

Nested Class Summary

static class	FennelAttributeAccessor.FennelBitAccessor marshalls a numeric bit
static class	FennelAttributeAccessor.FennelByteAccessor marshalls a numeric byte (signed or unsigned)
static class	FennelAttributeAccessor.FennelFixedWidthAccessor marshalls fixed-width byte arrays.
static class	FennelAttributeAccessor.FennelIntAccessor marshalls a numeric int (signed or unsigned)
static class	FennelAttributeAccessor.FennelLongAccessor marshalls a numeric long (signed or unsigned)
static class	FennelAttributeAccessor.FennelShortAccessor marshalls a numeric short (signed or unsigned)
static class	FennelAttributeAccessor.FennelVarWidthAccessor marshalls any variable width accessor, either first or subsequent.

Field Summary

int	capacity Copied from FennelTupleAttributeDescriptor.storageSize.
int	endIndirectOffset Indirect offset of the end of this attribute within a stored tuple image, or Integer.MAX_VALUE if the end is fixed.
int	fixedOffset Byte offset of this attribute within a stored tuple image, or Integer.MAX_VALUE if the start is variable.
protected byte	nullableBitMask pre-computed offsets and masks for testing bit fields.
protected int	nullableBitOffset pre-computed offsets and masks for testing bit fields.
int	nullBitNdx Index of this attribute's null indicator bit in the tuple's bit array, or Integer.MAX_VALUE for a NOT NULL attribute.
protected byte	valueBitMask pre-computed offsets and masks for testing bit fields.
int	valueBitNdx Index of this attribute's value in the tuple's bit array, or Integer.MAX_VALUE for a non-bit attribute.
protected int	valueBitOffset pre-computed offsets and masks for testing bit fields.

Constructor Summary

protected

FennelAttributeAccessor()

Method Summary

void	computeBitAccessors(int bitfieldOffset) computes bit accessors.
boolean	isPresent(ByteBuffer buf) tests if a field is present in a tuple buffer.
abstract void	marshalValueData(ByteBuffer pDestData, FennelTupleDatum value) Marshalls value data for the attribute.
void	setPresent(ByteBuffer buf, boolean isPresent) sets the presence of a field in a tuple buffer.
abstract void	unmarshalValue(FennelTupleAccessor tupleAccessor, FennelTupleDatum value) Unmarshalls the attribute's value into a tupledatum holder.

Methods inherited from class java.lang.Object

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

Field Detail

nullBitNdx

public int nullBitNdx

Index of this attribute's null indicator bit in the tuple's bit array, or Integer.MAX_VALUE for a NOT NULL attribute.

fixedOffset

public int fixedOffset

Byte offset of this attribute within a stored tuple image, or Integer.MAX_VALUE if the start is variable.

endIndirectOffset

public int endIndirectOffset

Indirect offset of the end of this attribute within a stored tuple image, or Integer.MAX_VALUE if the end is fixed.

valueBitNdx

public int valueBitNdx

Index of this attribute's value in the tuple's bit array, or Integer.MAX_VALUE for a non-bit attribute. NOTE: this is only used for booleans

capacity

public int capacity

Copied from FennelTupleAttributeDescriptor.storageSize. This is not used for anything except assertions.

valueBitOffset

protected int valueBitOffset

pre-computed offsets and masks for testing bit fields.

valueBitMask

protected byte valueBitMask

pre-computed offsets and masks for testing bit fields.

nullableBitOffset

protected int nullableBitOffset

pre-computed offsets and masks for testing bit fields.

nullableBitMask

protected byte nullableBitMask

pre-computed offsets and masks for testing bit fields.

Constructor Detail

FennelAttributeAccessor

protected FennelAttributeAccessor()

Method Detail

computeBitAccessors

public void computeBitAccessors(int bitfieldOffset)

computes bit accessors.

isPresent

public boolean isPresent(ByteBuffer buf)

tests if a field is present in a tuple buffer.

setPresent

public void setPresent(ByteBuffer buf,
                       boolean isPresent)

sets the presence of a field in a tuple buffer.

unmarshalValue

public abstract void unmarshalValue(FennelTupleAccessor tupleAccessor,
                                    FennelTupleDatum value)

Unmarshalls the attribute's value into a tupledatum holder. Unlike the C++ version, this *does* actually copy data.

Parameters:

tupleAccessor - containing FennelTupleAccessor set up with the current tuple image to be accessed

value - receives the reference to the unmarshalled value

marshalValueData

public abstract void marshalValueData(ByteBuffer pDestData,
                                      FennelTupleDatum value)

Marshalls value data for the attribute. Only deals with the data bytes, not length and null indicators.

Parameters:

pDestData - the target address where the data should be marshalled

value - the value to be marshalled