#JavaLang This module provides marshalling, de-marshalling and handling of thread safe off heap memory through ByteBuffers.
This module is available on maven central as
<dependency>
<groupId>net.openhft</groupId>
<artifactId>lang</artifactId>
<version><!--replace with the latest version--></version>
</dependency>
The version 6.x signifies that it is build for Java 6+. (It requires Java 6 update 18 or later to build)
Check out our documentation at [JavaDoc] (http://openhft.github.io/Java-Lang/apidocs/)
Java-Lang 6.1 adds support for basic off heap data structures. More collections types and more complex data types will be added in future versions.
public interface DataType {
// add getters and setters here
}
// can create an array of any size (provided you have the memory) off heap.
HugeArray<DataType> array = HugeCollections.newArray(DataType.class, 10*1000*1000*1000L);
DataType dt = array.get(1111111111);
// set data on dt
array.recycle(dt); // recycle the reference (or discard it)
// create a ring writeBuffer
HugeQueue<DataType> queue = HugeCollections.newQueue(DataType.class, 10*1000*1000L);
// give me a reference to an object to populate
DataType dt2 = queue.offer();
// set the values od dt2
queue.recycle(dt2);
DataType dt3 = queue.take();
// get values
queue.recycle(dt3);
This is designed to be largely GC-less and you can queue millions of entries with 32 MB heap and not trigger GCs.
To work with buffers there is a several options:
- ByteBufferBytes which wraps java.nio.ByteBuffer
- DirectBytes which is slices/records of DirectStore - own implementation for offheap storage
Both classes provide functionality:
- write\read operations for primitives (writeLong(long n), readLong() etc.)
- locking in native memory, so you can add thread safe constructs to your native record.
- CAS operations for int and long boolean compareAndSwapInt(long offset, int expected, int x), boolean compareAndSwapLong(long offset, long expected, long x)
- addAndGetInt and getAndAddInt operations
####Example ByteBuffer byteBuffer = ByteBuffer.allocate(SIZE); ByteBufferBytes bytes = new ByteBufferBytes(byteBuffer); for (long i = 0; i < bytes.maximumLimit(); i++) bytes.writeLong(i); for (long i = bytes.maximumLimit()-8; i >= 0; i -= 8) { int j = bytes.readLong(i); assert i == j; }
#Building for eclipse
Download Java-Lang zip from git https://github.com/OpenHFT/Java-Lang/archive/master.zip
Unzip master.zip, Java-Lang-master folder will be extracted from zip.
cd Java-Lang-master
mvn eclipse:eclipse
Now you have an eclipse project, import project into Eclipse
If your Eclipse configuration is not UTF-8, after importing the project you may see some errors and strange characters in some .java files. To get rid of this problem change character enconding to UTF-8: project->properties->resource->text file encoding->utf8