Implement an extended semaphore

[yruslan]

Background

Classic semaphore uses 2 methods:

• P() - decrement and wait
• V() - increment.

While a semaphore provides good means of controlling shared resource usage, issues like 'the dining philosophers problem' can arise when a thread needs to consume more than one resource to function.

Feature

Create an extended semaphore that provides

• P(n) - consume n items or wait until they are available
• V(n) - return n items

This can only work if waiting threads wait for resources in FIFO order. Otherwise, threads that require only 1 resource will take precedence and can create liveness issues for threads that require more than 1.

[yruslan]

Standard Java semaphores support this it seems.