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comparison jvmci/jdk.vm.ci.common/src/jdk/vm/ci/common/UnsafeUtil.java @ 23392:b3a816d3b844

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Backed out changeset: a920338dd4d4
author Doug Simon <doug.simon@oracle.com>
date Thu, 12 May 2016 11:06:49 +0200
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23391:dd9f3badc978 23392:b3a816d3b844
1 /*
2 * Copyright (c) 2012, 2012, 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.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 */
23 package jdk.vm.ci.common;
24
25 import sun.misc.Unsafe;
26
27 /**
28 * Utilities for operating on raw memory with {@link Unsafe}.
29 */
30 public class UnsafeUtil {
31
32 /**
33 * Copies the contents of a {@link String} to a native memory buffer as a {@code '\0'}
34 * terminated C string. The native memory buffer is allocated via
35 * {@link Unsafe#allocateMemory(long)}. The caller is responsible for releasing the buffer when
36 * it is no longer needed via {@link Unsafe#freeMemory(long)}.
37 *
38 * @return the native memory pointer of the C string created from {@code s}
39 */
40 public static long createCString(Unsafe unsafe, String s) {
41 return writeCString(unsafe, s, unsafe.allocateMemory(s.length() + 1));
42 }
43
44 /**
45 * Reads a {@code '\0'} terminated C string from native memory and converts it to a
46 * {@link String}.
47 *
48 * @return a Java string
49 */
50 public static String readCString(Unsafe unsafe, long address) {
51 if (address == 0) {
52 return null;
53 }
54 StringBuilder sb = new StringBuilder();
55 for (int i = 0;; i++) {
56 char c = (char) unsafe.getByte(address + i);
57 if (c == 0) {
58 break;
59 }
60 sb.append(c);
61 }
62 return sb.toString();
63 }
64
65 /**
66 * Writes the contents of a {@link String} to a native memory buffer as a {@code '\0'}
67 * terminated C string. The caller is responsible for ensuring the buffer is at least
68 * {@code s.length() + 1} bytes long. The caller is also responsible for releasing the buffer
69 * when it is no longer.
70 *
71 * @return the value of {@code buf}
72 */
73 public static long writeCString(Unsafe unsafe, String s, long buf) {
74 int size = s.length();
75 for (int i = 0; i < size; i++) {
76 unsafe.putByte(buf + i, (byte) s.charAt(i));
77 }
78 unsafe.putByte(buf + size, (byte) '\0');
79 return buf;
80 }
81 }