jtulach@114: package org.apidesign.reentrant;
jtulach@114: 
jtulach@114: import java.util.Collection;
jtulach@114: import java.util.concurrent.atomic.AtomicInteger;
jtulach@114: 
jtulach@114: public class CriticalSectionReentrantImmutable<T extends Comparable<T>> implements CriticalSection<T> {
jtulach@114:     private ImmutableData<T> data = new ImmutableData<T>();
jtulach@114:     
jtulach@114:     public void assignPilot(T pilot) {
jtulach@114:         data = data.newPilot(pilot);
jtulach@114:     }
jtulach@114: 
jtulach@114:     // BEGIN: reentrant.merge.immutable
jtulach@114:     public int sumBigger(Collection<T> args) {
jtulach@114:         for (;;) {
jtulach@210:             ImmutableData<T> previous;
jtulach@210:             synchronized (this) {
jtulach@210:                 previous = this.data;
jtulach@210:             }
jtulach@114:             int[] ret = { 0 };
jtulach@114:             ImmutableData<T> now = doCriticalSection(args, previous, ret);
jtulach@114:             
jtulach@114:             synchronized (this) {
jtulach@114:                 // if there was no parallel or reentrant change, 
jtulach@114:                 // apply and return. Otherwise try once more.
jtulach@114:                 if (previous == this.data) {
jtulach@114:                     this.data = now;
jtulach@114:                     return ret[0];
jtulach@114:                 }
jtulach@114:             }
jtulach@114:         }
jtulach@114:     }
jtulach@114:     // END: reentrant.merge.immutable
jtulach@114:     
jtulach@114:     private ImmutableData<T> doCriticalSection(Collection<T> args, ImmutableData<T> data, int[] result) {
jtulach@114:         result[0] = 0;
jtulach@114:         for (T cmp : args) {
jtulach@114:             if (data.pilot.compareTo(cmp) < 0) {
jtulach@114:                 result[0]++;
jtulach@114:             }
jtulach@114:         }
jtulach@114:         return data.newCnt(data.cnt + result[0]);
jtulach@114:     }
jtulach@114: 
jtulach@114:     public int getCount() {
jtulach@114:         return data.cnt;
jtulach@114:     }
jtulach@114:     
jtulach@114:     private static final class ImmutableData<T> {
jtulach@114:         final T pilot;
jtulach@114:         final int cnt;
jtulach@114:         
jtulach@114:         public ImmutableData() {
jtulach@114:             pilot = null;
jtulach@114:             cnt = 0;
jtulach@114:         }
jtulach@114:         private ImmutableData(T pilot, int cnt) {
jtulach@114:             this.pilot = pilot;
jtulach@114:             this.cnt = cnt;
jtulach@114:         }
jtulach@114:         
jtulach@114:         public ImmutableData<T> newPilot(T pilot) {
jtulach@114:             return new ImmutableData(pilot, this.cnt);
jtulach@114:         }
jtulach@114:         public ImmutableData<T> newCnt(int cnt) {
jtulach@114:             return new ImmutableData(this.pilot, cnt);
jtulach@114:         }
jtulach@114:     }
jtulach@114: }