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/*
* Copyright 2021 Carl Mastrangelo
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package io.perfmark.java15;
import io.perfmark.impl.MarkHolder;
import io.perfmark.impl.MarkHolderProvider;
import java.io.IOException;
import java.io.InputStream;
import java.lang.invoke.MethodHandles;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.util.Arrays;
public final class SecretHiddenClassMarkHolderProvider {
public static final class HiddenClassMarkHolderProvider extends MarkHolderProvider {
private static final int DEFAULT_SIZE = 32768;
private final int[] maxEventsOffsets;
private final int[] maxEventsMaskOffsets;
private final byte[] markHolderClassData;
public HiddenClassMarkHolderProvider() {
try (InputStream classData = getClass().getResourceAsStream("HiddenClassVarHandleMarkHolder.class")) {
markHolderClassData = classData.readAllBytes();
} catch (IOException e) {
throw new RuntimeException(e);
}
ByteBuffer expectedMaxEvents = ByteBuffer.allocate(4).order(ByteOrder.BIG_ENDIAN);
expectedMaxEvents.putInt(HiddenClassVarHandleMarkHolder.MAX_EVENTS);
byte[] maxEvents = expectedMaxEvents.array();
maxEventsOffsets = findOffsets(markHolderClassData, maxEvents);
if (maxEventsOffsets.length != 2) {
throw new RuntimeException("hop");
}
ByteBuffer expectedMaxEventsMask = ByteBuffer.allocate(8).order(ByteOrder.BIG_ENDIAN);
expectedMaxEventsMask.putLong(HiddenClassVarHandleMarkHolder.MAX_EVENTS_MASK);
byte[] maxEventsMax = expectedMaxEventsMask.array();
maxEventsMaskOffsets = findOffsets(markHolderClassData, maxEventsMax);
if (maxEventsMaskOffsets.length != 1) {
throw new RuntimeException("skip");
}
replaceSize(markHolderClassData, DEFAULT_SIZE);
}
@Override
public MarkHolder create(long markHolderId) {
return create(markHolderId, DEFAULT_SIZE);
}
MarkHolder create(long markHolderId, int size) {
final byte[] classData;
if (size != DEFAULT_SIZE) {
classData = Arrays.copyOf(markHolderClassData, markHolderClassData.length);
replaceSize(classData, size);
} else {
classData = markHolderClassData;
}
try {
Class<?> clz = MethodHandles.lookup().defineHiddenClass(classData, true).lookupClass();
return clz.asSubclass(MarkHolder.class).getDeclaredConstructor().newInstance();
} catch (ReflectiveOperationException e) {
throw new RuntimeException(e);
}
}
private void replaceSize(byte[] haystack, int size) {
ByteBuffer buf = ByteBuffer.wrap(haystack).order(ByteOrder.BIG_ENDIAN);
for (int off : maxEventsOffsets) {
buf.putInt(off, size);
}
for (int off : maxEventsMaskOffsets) {
buf.putLong(off, size - 1);
}
}
private static int[] findOffsets(byte[] haystack, byte[] needle) {
int[] matches = new int[0];
outer: for (int i = 0; i < haystack.length - needle.length; i++) {
for (int k = 0; k < needle.length; k++) {
if (haystack[i + k] != needle[k]) {
continue outer;
}
}
matches = Arrays.copyOf(matches, matches.length + 1);
matches[matches.length - 1] = i;
}
return matches;
}
}
private SecretHiddenClassMarkHolderProvider() {}
}
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