edu.wpi.first.wpilibj

Class Resource

java.lang.Object

edu.wpi.first.wpilibj.Resource

public final class Resource
extends java.lang.Object

Track resources in the program. The Resource class is a convenient way of keeping track of allocated arbitrary resources in the program. Resources are just indicies that have an lower and upper bound that are tracked by this class. In the library they are used for tracking allocation of hardware channels but this is purely arbitrary. The resource class does not do any actual allocation, but simply tracks if a given index is currently in use.

WARNING: this should only be statically allocated. When the program loads into memory all the static constructors are called. At that time a linked list of all the "Resources" is created. Then when the program actually starts - in the Robot constructor, all resources are initialized. This ensures that the program is restartable in memory without having to unload/reload.

Constructor Summary

Constructors

Constructor and Description
Resource(int size) Allocate storage for a new instance of Resource.

Method Summary

Modifier and Type	Method and Description
int	allocate() Allocate a resource.
int	allocate(int index) Allocate a specific resource value.
void	free(int index) Free an allocated resource.
static void	restartProgram() Clears all allocated resources.

Methods inherited from class java.lang.Object

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

Constructor Detail

Resource

public Resource(int size)

Allocate storage for a new instance of Resource. Allocate a bool array of values that will get initialized to indicate that no resources have been allocated yet. The indicies of the resources are 0..size-1.

Parameters:

size - The number of blocks to allocate

Method Detail

restartProgram

public static void restartProgram()

Clears all allocated resources.

allocate

public int allocate()
             throws CheckedAllocationException

Allocate a resource. When a resource is requested, mark it allocated. In this case, a free resource value within the range is located and returned after it is marked allocated.

Returns:

The index of the allocated block.

Throws:

CheckedAllocationException - If there are no resources available to be allocated.

allocate

public int allocate(int index)
             throws CheckedAllocationException

Allocate a specific resource value. The user requests a specific resource value, i.e. channel number and it is verified unallocated, then returned.

Parameters:

index - The resource to allocate

Returns:

The index of the allocated block

Throws:

CheckedAllocationException - If there are no resources available to be allocated.

free

public void free(int index)

Free an allocated resource. After a resource is no longer needed, for example a destructor is called for a channel assignment class, Free will release the resource value so it can be reused somewhere else in the program.

Parameters:

index - The index of the resource to free.