Module org.apache.jena.serviceplugins

Package org.apache.jena.sparql.service.enhancer.slice.api

Interface SliceAccessor<A>

Type Parameters:

A - The array type for transferring data in blocks

All Superinterfaces:

AutoCloseable

All Known Implementing Classes:

SliceAccessorImpl

public interface SliceAccessor<A>
extends AutoCloseable

Abstraction over a sequence of pages to view their content as consecutive items. The underlying pages may be claimed by multiple page ranges held by different clients. Clients must eventually close pages ranges in order to allow for resources to be freed. Note: The page range abstraction enables consumers and producers to claim the same pages independently. A consumer does not have to wait for the producers to advertise pages they are working on, instead the (low-level/internal) consumer can simply claim the pages it wants to read in advance and then schedule any needed executors. The claim range can be mutated which performs only the necessary (un)claim operations.

Method Summary

Modifier and Type	Method	Description
default void	addEvictionGuard(com.google.common.collect.Range<Long> range)
void	addEvictionGuard(com.google.common.collect.RangeSet<Long> ranges)	Adds an eviction guard (if the slice supports it) and binds its life cycle to this accessor.
void	claimByOffsetRange(long startOffset, long endOffset)	Set or update the claimed range - this will immediately request references to any pages providing the data for that range.
void	close()	Closes the page range.
Slice<A>	getSlice()
void	lock()	Lock the range for writing
void	releaseAll()	Releases all currently held pages.
void	unlock()	Unlock the range
int	unsafeRead(A tgt, int tgtOffset, long srcOffset, int length)	Read operation that assumes a prior check for available ranges has been performed.
void	write(long offset, A arrayWithItemsOfTypeT, int arrOffset, int arrLength)	Put a sequence of items into the claimed range Attempts to put items outside of the claimed range raises an IndexOutOfBoundsException The page range should be locked when calling this method.

Method Details

getSlice

Slice<A> getSlice()

addEvictionGuard

void addEvictionGuard(com.google.common.collect.RangeSet<Long> ranges)

Adds an eviction guard (if the slice supports it) and binds its life cycle to this accessor. Closing an accessor thus also removes all eviction guards created by it. This method must be called after acquiring a read lock on the slice's metadata.

Parameters:

ranges - The set of ranges which to protected from eviction

addEvictionGuard

default void addEvictionGuard(com.google.common.collect.Range<Long> range)

claimByOffsetRange

void claimByOffsetRange(long startOffset,
 long endOffset)

Set or update the claimed range - this will immediately request references to any pages providing the data for that range. Pages outside of that range are considered as no longer needed pages will immediately be released. This method prepares the pages which can be subsequently locked. Calling this method while the page range is locked (lock()) raises an IllegalStateException.

Parameters:

startOffset -

endOffset -

lock

void lock()

Lock the range for writing

write

void write(long offset,
 A arrayWithItemsOfTypeT,
 int arrOffset,
 int arrLength)
    throws IOException

Put a sequence of items into the claimed range Attempts to put items outside of the claimed range raises an IndexOutOfBoundsException The page range should be locked when calling this method.

Throws:

IOException

unsafeRead

int unsafeRead(A tgt,
 int tgtOffset,
 long srcOffset,
 int length)
        throws IOException

Read operation that assumes a prior check for available ranges has been performed. Only use this method after locking.

Throws:

IOException

unlock

void unlock()

Unlock the range

releaseAll

void releaseAll()

Releases all currently held pages. Future requests via claimByOffsetRange(long, long) are allowed.

close

void close()

Closes the page range. Implementations of this method should call {releaseAll() and an addition prevent any further claims.

Specified by:

close in interface AutoCloseable