/*
* Copyright (c) 2007, 2012, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package com.sun.max.tele.object;
import com.sun.max.jdwp.vm.proxy.*;
import com.sun.max.tele.*;
import com.sun.max.tele.data.*;
import com.sun.max.tele.field.*;
import com.sun.max.tele.reference.*;
import com.sun.max.unsafe.*;
import com.sun.max.vm.classfile.constant.*;
import com.sun.max.vm.type.*;
/**
* Canonical surrogate for an object of type {@link String} in the VM.
*/
public final class TeleString extends TeleTupleObject implements StringProvider {
private static final TeleInstanceIntFieldAccess String_count;
private static final TeleInstanceIntFieldAccess String_offset;
private static boolean jdk7u6orNewer = true;
static {
/**
* Starting with JDK 7 update 6, the String class no longer has the offset and count fields.
* We want to support both String variants (this is necessary until we drop support for JDK 6).
*/
try {
String.class.getDeclaredField("offset");
jdk7u6orNewer = false;
} catch (NoSuchFieldException e) {
}
if (jdk7u6orNewer) {
String_count = null;
String_offset = null;
} else {
String_count = new TeleInstanceIntFieldAccess(String.class, "count");
String_offset = new TeleInstanceIntFieldAccess(String.class, "offset");
}
}
/**
* Returns a local copy of a Java {@link String} object in the VM's heap, without creating an instance of {@link TeleString}.
* <p>
* <strong>Note:</strong> no check is made that the reference points to a {@link String} object in VM.
*
* @param stringRef assumed to refer to a {@link String} object in the VM.
* @return A local {@link String} duplicating the remote object's contents.
* @throws InvalidReferenceException if the argument does not point a valid heap object.
*/
public static String getString(TeleVM vm, RemoteReference stringRef) throws InvalidReferenceException {
vm.referenceManager().checkReference(stringRef);
try {
final RemoteReference charArrayRef = vm.fields().String_value.readRemoteReference(stringRef);
if (charArrayRef.isZero()) {
return null;
}
vm.referenceManager().checkReference(charArrayRef);
int charCount = 0;
int charOffset = 0;
if (jdk7u6orNewer) {
charCount = vm.objects().unsafeReadArrayLength(charArrayRef);
} else {
charCount = String_count.readInt(stringRef);
charOffset = String_offset.readInt(stringRef);
}
final char[] chars = new char[charCount];
vm.objects().unsafeCopyElements(Kind.CHAR, charArrayRef, charOffset, chars, 0, charCount);
return new String(chars);
} catch (DataIOError dataIOError) {
return null;
}
}
/**
* Returns a local copy of the contents of a {@link String} object in the VM's heap,
* using low level mechanisms and performing no checking that the location
* or object are valid.
* <p>
* The intention is to provide a fast, low-level mechanism for reading strings that
* can be used outside of the AWT event thread without danger of deadlock,
* for example on the canonical reference machinery.
* <p>
* <strong>Unsafe:</strong> this method depends on knowledge of the implementation of
* class {@link String}.
*
* @param origin a {@link String} object in the VM
* @return A local {@link String} duplicating the remote object's contents, null if it can't be read.
*/
public static String getStringUnsafe(TeleVM vm, Address origin) {
// Work only with temporary references that are unsafe across GC
// Do no testing to determine if the reference points to a valid String object in live memory.
try {
final RemoteReference stringRef = vm.referenceManager().makeTemporaryRemoteReference(origin);
final Address charArrayAddress = stringRef.readWord(vm.fields().String_value.fieldActor().offset()).asAddress();
final RemoteReference charArrayRef = vm.referenceManager().makeTemporaryRemoteReference(charArrayAddress);
int charCount = 0;
int charOffset = 0;
if (jdk7u6orNewer) {
charCount = vm.objects().unsafeReadArrayLength(charArrayRef);
} else {
charCount = String_count.readInt(stringRef);
charOffset = String_offset.readInt(stringRef);
}
final char[] chars = new char[charCount];
vm.objects().unsafeCopyElements(Kind.CHAR, charArrayRef, charOffset, chars, 0, charCount);
return new String(chars);
} catch (DataIOError dataIOError) {
return null;
}
}
private String string = null;
public String getString() {
if (status().isLive()) {
String s = getString(vm(), reference());
if (s != null) {
string = SymbolTable.intern(s);
}
}
return string;
}
protected TeleString(TeleVM vm, RemoteReference stringReference) {
super(vm, stringReference);
}
@Override
protected Object createDeepCopy(DeepCopier context) {
// Translate into local equivalent
return getString();
}
@Override
public String maxineRole() {
return "String";
}
@Override
public String maxineTerseRole() {
return "String.";
}
public String stringValue() {
return getString();
}
@Override
public boolean hasTextualVisualization() {
return true;
}
@Override
public String textualVisualization() {
return stringValue();
}
}