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 }