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25 
26 package sun.nio.ch;
27 
28 import java.lang.annotation.Native;
29 
30 // Constants for reporting I/O status
31 
32 public final class IOStatus {
33 
IOStatus()34     private IOStatus() { }
35 
36     @Native public static final int EOF = -1;              // End of file
37     @Native public static final int UNAVAILABLE = -2;      // Nothing available (non-blocking)
38     @Native public static final int INTERRUPTED = -3;      // System call interrupted
39     @Native public static final int UNSUPPORTED = -4;      // Operation not supported
40     @Native public static final int THROWN = -5;           // Exception thrown in JNI code
41     @Native public static final int UNSUPPORTED_CASE = -6; // This case not supported
42 
43     // The following two methods are for use in try/finally blocks where a
44     // status value needs to be normalized before being returned to the invoker
45     // but also checked for illegal negative values before the return
46     // completes, like so:
47     //
48     //     int n = 0;
49     //     try {
50     //         begin();
51     //         n = op(fd, buf, ...);
52     //         return IOStatus.normalize(n);    // Converts UNAVAILABLE to zero
53     //     } finally {
54     //         end(n > 0);
55     //         assert IOStatus.check(n);        // Checks other negative values
56     //     }
57     //
58 
normalize(int n)59     public static int normalize(int n) {
60         if (n == UNAVAILABLE)
61             return 0;
62         return n;
63     }
64 
check(int n)65     public static boolean check(int n) {
66         return (n >= UNAVAILABLE);
67     }
68 
normalize(long n)69     public static long normalize(long n) {
70         if (n == UNAVAILABLE)
71             return 0;
72         return n;
73     }
74 
check(long n)75     public static boolean check(long n) {
76         return (n >= UNAVAILABLE);
77     }
78 
79     // Return true iff n is not one of the IOStatus values
checkAll(long n)80     public static boolean checkAll(long n) {
81         return ((n > EOF) || (n < UNSUPPORTED_CASE));
82     }
83 
84 }
85