MemoryManagement.md

Memory Management

Pointers

A Pointer instance stores reference to a native memory address. As it can represent various data like struct, arrays, java objects, etc. it needs to be used with caution since any illegal access can cause segfaults and JVM crash. The Pointer class provides methods to return different representations of the stored data, for example:

• getInt(long offset): Reads 32-bit int value at given offset
• getPointer(long offset, int size): Reads a pointer at given offset
• array(): Returns an array if it backs this pointer

Runtime

A Runtime instance for the loaded library can be obtained using the Runtime.getRuntime() method. It gives access to important services like ObjectReferenceManager and MemoryManager.

MemoryManager

As the name suggests, it provides various methods to allocate memory for use with native functions.

• allocate: Allocates Java memory
• allocateDirect: Allocates native memory
• allocateTemporary: Allocates transient native memory

The Memory class also provides utility methods to handle memory allocation for common use-cases. It uses MemoryManager internally.

ObjectReferenceManager

Any native memory associated with a Java object is released as soon as the object gets garbage-collected. An ObjectReferenceManager provides handy methods to keep objects strongly-referenced as long as its native memory is in use. This can be helpful while working with function pointers, which are associated with lambda functions on the Java side. Use add to register any object and use remove to dereference the registered object.