1 /*
 2  * Copyright (c) 2024, Oracle and/or its affiliates. All rights reserved.
 3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 4  *
 5  * This code is free software; you can redistribute it and/or modify it
 6  * under the terms of the GNU General Public License version 2 only, as
 7  * published by the Free Software Foundation.  Oracle designates this
 8  * particular file as subject to the "Classpath" exception as provided
 9  * by Oracle in the LICENSE file that accompanied this code.
10  *
11  * This code is distributed in the hope that it will be useful, but WITHOUT
12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14  * version 2 for more details (a copy is included in the LICENSE file that
15  * accompanied this code).
16  *
17  * You should have received a copy of the GNU General Public License version
18  * 2 along with this work; if not, write to the Free Software Foundation,
19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20  *
21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22  * or visit www.oracle.com if you need additional information or have any
23  * questions.
24  */
25 
26 package sun.nio.ch.iouring;
27 
28 import java.io.IOException;
29 import java.lang.foreign.*;
30 import java.lang.invoke.VarHandle;
31 
32 import static sun.nio.ch.iouring.Util.strerror;
33 
34 /**
35  * A context for invoking a system call (typically) which needs
36  * to capture and return errno
37  *
38  * Contexts cannot be shared among threads.
39  */
40 class SystemCallContext {
41     private final Arena confinedArena = Arena.ofConfined();
42     private final Arena autoArena = Arena.ofAuto();
43     private static final Linker.Option ccs =
44             Linker.Option.captureCallState("errno");
45     private static final StructLayout capturedStateLayout =
46             Linker.Option.captureStateLayout();
47     private final VarHandle errnoHandle =
48             capturedStateLayout.varHandle(MemoryLayout.PathElement.groupElement("errno"));
49     private final MemorySegment captureSegment = autoArena.allocate(capturedStateLayout);
50 
51     private static ThreadLocal<SystemCallContext> TL = new ThreadLocal<>() {
52         protected SystemCallContext initialValue() {
53             return new SystemCallContext();
54         }
55     };
56 
57     private SystemCallContext() {
58     }
59 
60     /**
61      * Returns a thread local SystemCallContext
62      */
63     public static SystemCallContext get() {
64         return TL.get();
65     }
66 
67     public static Linker.Option errnoLinkerOption() {
68         return ccs;
69     }
70     public MemorySegment errnoCaptureSegment() {
71         return captureSegment;
72     }
73 
74     /**
75      * If ret < 0 then errno is checked and an IOException thrown
76      * containing the textual description of errno
77      *
78      * @param ret
79      * @throws IOException
80      */
81     public void throwIOExceptionOnError(int ret) throws IOException {
82         if (ret < 0) {
83             ret = (int)errnoHandle().get(captureSegment, 0L);
84             String errmsg = strerror(ret);
85             throw new IOException(errmsg);
86         }
87     }
88     public VarHandle errnoHandle() {
89         return errnoHandle;
90     }
91 
92     protected Arena autoArena() {
93         return autoArena;
94     }
95 
96     protected Arena confinedArena() {return confinedArena;}
97 }