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13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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25 
26 package jdk.internal.net.http.common;
27 
28 import java.util.concurrent.CompletableFuture;
29 import java.util.concurrent.CompletionStage;
30 import java.util.concurrent.atomic.AtomicLong;
31 
32 import static java.util.Objects.requireNonNull;
33 
34 /*
35  * A CompletableFuture which does not allow any obtrusion logic.
36  * All methods of CompletionStage return instances of this class.
37  */
38 public final class MinimalFuture<T> extends CompletableFuture<T> {
39 
40     @FunctionalInterface
41     public interface ExceptionalSupplier<U> {
get()42         U get() throws Throwable;
43     }
44 
45     private final static AtomicLong TOKENS = new AtomicLong();
46     private final long id;
47 
completedFuture(U value)48     public static <U> MinimalFuture<U> completedFuture(U value) {
49         MinimalFuture<U> f = new MinimalFuture<>();
50         f.complete(value);
51         return f;
52     }
53 
failedFuture(Throwable ex)54     public static <U> CompletableFuture<U> failedFuture(Throwable ex) {
55         requireNonNull(ex);
56         MinimalFuture<U> f = new MinimalFuture<>();
57         f.completeExceptionally(ex);
58         return f;
59     }
60 
supply(ExceptionalSupplier<U> supplier)61     public static <U> CompletableFuture<U> supply(ExceptionalSupplier<U> supplier) {
62         CompletableFuture<U> cf = new MinimalFuture<>();
63         try {
64             U value = supplier.get();
65             cf.complete(value);
66         } catch (Throwable t) {
67             cf.completeExceptionally(t);
68         }
69         return cf;
70     }
71 
MinimalFuture()72     public MinimalFuture() {
73         super();
74         this.id = TOKENS.incrementAndGet();
75     }
76 
77     @Override
newIncompleteFuture()78     public <U> MinimalFuture<U> newIncompleteFuture() {
79         return new MinimalFuture<>();
80     }
81 
82     @Override
obtrudeValue(T value)83     public void obtrudeValue(T value) {
84         throw new UnsupportedOperationException();
85     }
86 
87     @Override
obtrudeException(Throwable ex)88     public void obtrudeException(Throwable ex) {
89         throw new UnsupportedOperationException();
90     }
91 
92     @Override
toString()93     public String toString() {
94         return super.toString() + " (id=" + id +")";
95     }
96 
of(CompletionStage<U> stage)97     public static <U> MinimalFuture<U> of(CompletionStage<U> stage) {
98         MinimalFuture<U> cf = new MinimalFuture<>();
99         stage.whenComplete((r,t) -> complete(cf, r, t));
100         return cf;
101     }
102 
complete(CompletableFuture<U> cf, U result, Throwable t)103     private static <U> void complete(CompletableFuture<U> cf, U result, Throwable t) {
104         if (t == null) {
105             cf.complete(result);
106         } else {
107             cf.completeExceptionally(t);
108         }
109     }
110 }
111