Package edu.wpi.first.wpilibj

Class Resource

java.lang.Object
edu.wpi.first.wpilibj.Resource
public final class Resource
extends 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 indices 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 Details

    • 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 indices of the resources are 0..size-1.
      Parameters:
      size - The number of blocks to allocate

  • Method Details

    • 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.