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 }