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/*
* Copyright (c) 2015, 2020, 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. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* 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.
*
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package java.lang;
import jdk.internal.reflect.MethodAccessor;
import jdk.internal.reflect.ConstructorAccessor;
import java.lang.StackWalker.Option;
import java.lang.StackWalker.StackFrame;
import java.lang.annotation.Native;
import java.lang.reflect.Method;
import java.lang.reflect.Constructor;
import java.util.HashSet;
import java.util.NoSuchElementException;
import java.util.Objects;
import java.util.Set;
import java.util.Spliterator;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;
import sun.security.action.GetPropertyAction;
import static java.lang.StackStreamFactory.WalkerState.*;
/**
* StackStreamFactory class provides static factory methods
* to get different kinds of stack walker/traverser.
*
* AbstractStackWalker provides the basic stack walking support
* fetching stack frames from VM in batches.
*
* AbstractStackWalker subclass is specialized for a specific kind of stack traversal
* to avoid overhead of Stream/Lambda
* 1. Support traversing Stream
* 2. StackWalker::getCallerClass
* 3. AccessControlContext getting ProtectionDomain
*/
final class StackStreamFactory {
private StackStreamFactory() {}
// Stack walk implementation classes to be excluded during stack walking
// lazily add subclasses when they are loaded.
private static final Set> stackWalkImplClasses = init();
private static final int SMALL_BATCH = 8;
private static final int BATCH_SIZE = 32;
private static final int LARGE_BATCH_SIZE = 256;
private static final int MIN_BATCH_SIZE = SMALL_BATCH;
// These flags must match the values maintained in the VM
@Native private static final int DEFAULT_MODE = 0x0;
@Native private static final int FILL_CLASS_REFS_ONLY = 0x2;
@Native private static final int GET_CALLER_CLASS = 0x4;
@Native private static final int SHOW_HIDDEN_FRAMES = 0x20; // LambdaForms are hidden by the VM
@Native private static final int FILL_LIVE_STACK_FRAMES = 0x100;
/*
* For Throwable to use StackWalker, set useNewThrowable to true.
* Performance work and extensive testing is needed to replace the
* VM built-in backtrace filled in Throwable with the StackWalker.
*/
static final boolean isDebug =
"true".equals(GetPropertyAction.privilegedGetProperty("stackwalk.debug"));
static StackFrameTraverser
makeStackTraverser(StackWalker walker, Function, ? extends T> function)
{
if (walker.hasLocalsOperandsOption())
return new LiveStackInfoTraverser<>(walker, function);
else
return new StackFrameTraverser<>(walker, function);
}
/**
* Gets a stack stream to find caller class.
*/
static CallerClassFinder makeCallerFinder(StackWalker walker) {
return new CallerClassFinder(walker);
}
enum WalkerState {
NEW, // the stream is new and stack walking has not started
OPEN, // the stream is open when it is being traversed.
CLOSED; // the stream is closed when the stack walking is done
}
/**
* Subclass of AbstractStackWalker implements a specific stack walking logic.
* It needs to set up the frame buffer and stack walking mode.
*
* It initiates the VM stack walking via the callStackWalk method that serves
* as the anchored frame and VM will call up to AbstractStackWalker::doStackWalk.
*
* @param the type of the result returned from stack walking
* @param the type of the data gathered for each frame.
* For example, StackFrameInfo for StackWalker::walk or
* Class for StackWalker::getCallerClass
*/
static abstract class AbstractStackWalker {
protected final StackWalker walker;
protected final Thread thread;
protected final int maxDepth;
protected final long mode;
protected int depth; // traversed stack depth
protected FrameBuffer frameBuffer;
protected long anchor;
// buffers to fill in stack frame information
protected AbstractStackWalker(StackWalker walker, int mode) {
this(walker, mode, Integer.MAX_VALUE);
}
protected AbstractStackWalker(StackWalker walker, int mode, int maxDepth) {
this.thread = Thread.currentThread();
this.mode = toStackWalkMode(walker, mode);
this.walker = walker;
this.maxDepth = maxDepth;
this.depth = 0;
}
private int toStackWalkMode(StackWalker walker, int mode) {
int newMode = mode;
if (walker.hasOption(Option.SHOW_HIDDEN_FRAMES) &&
(mode & FILL_CLASS_REFS_ONLY) != FILL_CLASS_REFS_ONLY)
newMode |= SHOW_HIDDEN_FRAMES;
if (walker.hasLocalsOperandsOption())
newMode |= FILL_LIVE_STACK_FRAMES;
return newMode;
}
/**
* A callback method to consume the stack frames. This method is invoked
* once stack walking begins (i.e. it is only invoked when walkFrames is called).
*
* Each specialized AbstractStackWalker subclass implements the consumeFrames method
* to control the following:
* 1. fetch the subsequent batches of stack frames
* 2. reuse or expand the allocated buffers
* 3. create specialized StackFrame objects
*
* @return the number of consumed frames
*/
protected abstract R consumeFrames();
/**
* Initialize FrameBuffer. Subclass should implement this method to
* create its custom frame buffers.
*/
protected abstract void initFrameBuffer();
/**
* Returns the suggested next batch size.
*
* Subclass should override this method to change the batch size
*
* @param lastBatchFrameCount number of frames in the last batch; or zero
* @return suggested batch size
*/
protected abstract int batchSize(int lastBatchFrameCount);
/*
* Returns the next batch size, always >= minimum batch size (32)
*
* Subclass may override this method if the minimum batch size is different.
*/
protected int getNextBatchSize() {
int lastBatchSize = depth == 0 ? 0 : frameBuffer.curBatchFrameCount();
int nextBatchSize = batchSize(lastBatchSize);
if (isDebug) {
System.err.println("last batch size = " + lastBatchSize +
" next batch size = " + nextBatchSize);
}
return nextBatchSize >= MIN_BATCH_SIZE ? nextBatchSize : MIN_BATCH_SIZE;
}
/*
* Checks if this stream is in the given state. Otherwise, throws IllegalStateException.
*
* VM also validates this stream if it's anchored for stack walking
* when stack frames are fetched for each batch.
*/
final void checkState(WalkerState state) {
if (thread != Thread.currentThread()) {
throw new IllegalStateException("Invalid thread walking this stack stream: " +
Thread.currentThread().getName() + " " + thread.getName());
}
switch (state) {
case NEW:
if (anchor != 0) {
throw new IllegalStateException("This stack stream is being reused.");
}
break;
case OPEN:
if (anchor == 0 || anchor == -1L) {
throw new IllegalStateException("This stack stream is not valid for walking.");
}
break;
case CLOSED:
if (anchor != -1L) {
throw new IllegalStateException("This stack stream is not closed.");
}
}
}
/*
* Close this stream. This stream becomes invalid to walk.
*/
private void close() {
this.anchor = -1L;
}
/*
* Walks stack frames until {@link #consumeFrames} is done consuming
* the frames it is interested in.
*/
final R walk() {
checkState(NEW);
try {
// VM will need to stabilize the stack before walking. It will invoke
// the AbstractStackWalker::doStackWalk method once it fetches the first batch.
// the callback will be invoked within the scope of the callStackWalk frame.
return beginStackWalk();
} finally {
close(); // done traversal; close the stream
}
}
private boolean skipReflectionFrames() {
return !walker.hasOption(Option.SHOW_REFLECT_FRAMES) &&
!walker.hasOption(Option.SHOW_HIDDEN_FRAMES);
}
/*
* Returns {@code Class} object at the current frame;
* or {@code null} if no more frame. If advanceToNextBatch is true,
* it will only fetch the next batch.
*/
final Class peekFrame() {
while (frameBuffer.isActive() && depth < maxDepth) {
if (frameBuffer.isEmpty()) {
// fetch another batch of stack frames
getNextBatch();
} else {
Class c = frameBuffer.get();
if (skipReflectionFrames() && isReflectionFrame(c)) {
if (isDebug)
System.err.println(" skip: frame " + frameBuffer.getIndex() + " " + c);
frameBuffer.next();
depth++;
continue;
} else {
return c;
}
}
}
return null;
}
/*
* This method is only invoked by VM.
*
* It will invoke the consumeFrames method to start the stack walking
* with the first batch of stack frames. Each specialized AbstractStackWalker
* subclass implements the consumeFrames method to control the following:
* 1. fetch the subsequent batches of stack frames
* 2. reuse or expand the allocated buffers
* 3. create specialized StackFrame objects
*/
private Object doStackWalk(long anchor, int skipFrames, int batchSize,
int bufStartIndex, int bufEndIndex) {
checkState(NEW);
frameBuffer.check(skipFrames);
if (isDebug) {
System.err.format("doStackWalk: skip %d start %d end %d%n",
skipFrames, bufStartIndex, bufEndIndex);
}
this.anchor = anchor; // set anchor for this bulk stack frame traversal
frameBuffer.setBatch(depth, bufStartIndex, bufEndIndex);
// traverse all frames and perform the action on the stack frames, if specified
return consumeFrames();
}
/*
* Get next batch of stack frames.
*/
private int getNextBatch() {
int nextBatchSize = Math.min(maxDepth - depth, getNextBatchSize());
if (!frameBuffer.isActive() || nextBatchSize <= 0) {
if (isDebug) {
System.out.format(" more stack walk done%n");
}
frameBuffer.freeze(); // stack walk done
return 0;
}
return fetchStackFrames(nextBatchSize);
}
/*
* This method traverses the next stack frame and returns the Class
* invoking that stack frame.
*
* This method can only be called during the walk method. This is intended
* to be used to walk the stack frames in one single invocation and
* this stack stream will be invalidated once walk is done.
*
* @see #tryNextFrame
*/
final Class nextFrame() {
if (!hasNext()) {
return null;
}
Class c = frameBuffer.next();
depth++;
return c;
}
/*
* Returns true if there is next frame to be traversed.
* This skips hidden frames unless this StackWalker has
* {@link Option#SHOW_REFLECT_FRAMES}
*/
final boolean hasNext() {
return peekFrame() != null;
}
/**
* Begin stack walking - pass the allocated arrays to the VM to fill in
* stack frame information.
*
* VM first anchors the frame of the current thread. A traversable stream
* on this thread's stack will be opened. The VM will fetch the first batch
* of stack frames and call AbstractStackWalker::doStackWalk to invoke the
* stack walking function on each stack frame.
*
* If all fetched stack frames are traversed, AbstractStackWalker::fetchStackFrames will
* fetch the next batch of stack frames to continue.
*/
private R beginStackWalk() {
// initialize buffers for VM to fill the stack frame info
initFrameBuffer();
return callStackWalk(mode, 0,
frameBuffer.curBatchFrameCount(),
frameBuffer.startIndex(),
frameBuffer.frames());
}
/*
* Fetches stack frames.
*
* @params batchSize number of elements of the frame buffers for this batch
* @returns number of frames fetched in this batch
*/
private int fetchStackFrames(int batchSize) {
int startIndex = frameBuffer.startIndex();
frameBuffer.resize(startIndex, batchSize);
int endIndex = fetchStackFrames(mode, anchor, batchSize,
startIndex,
frameBuffer.frames());
if (isDebug) {
System.out.format(" more stack walk requesting %d got %d to %d frames%n",
batchSize, frameBuffer.startIndex(), endIndex);
}
int numFrames = endIndex - startIndex;
if (numFrames == 0) {
frameBuffer.freeze(); // done stack walking
} else {
frameBuffer.setBatch(depth, startIndex, endIndex);
}
return numFrames;
}
/**
* Begins stack walking. This method anchors this frame and invokes
* AbstractStackWalker::doStackWalk after fetching the first batch of stack frames.
*
* @param mode mode of stack walking
* @param skipframes number of frames to be skipped before filling the frame buffer.
* @param batchSize the batch size, max. number of elements to be filled in the frame buffers.
* @param startIndex start index of the frame buffers to be filled.
* @param frames Either a Class array, if mode is {@link #FILL_CLASS_REFS_ONLY}
* or a {@link StackFrameInfo} (or derivative) array otherwise.
* @return Result of AbstractStackWalker::doStackWalk
*/
private native R callStackWalk(long mode, int skipframes,
int batchSize, int startIndex,
T[] frames);
/**
* Fetch the next batch of stack frames.
*
* @param mode mode of stack walking
* @param anchor
* @param batchSize the batch size, max. number of elements to be filled in the frame buffers.
* @param startIndex start index of the frame buffers to be filled.
* @param frames Either a Class array, if mode is {@link #FILL_CLASS_REFS_ONLY}
* or a {@link StackFrameInfo} (or derivative) array otherwise.
*
* @return the end index to the frame buffers
*/
private native int fetchStackFrames(long mode, long anchor,
int batchSize, int startIndex,
T[] frames);
}
/*
* This StackFrameTraverser supports {@link Stream} traversal.
*
* This class implements Spliterator::forEachRemaining and Spliterator::tryAdvance.
*/
static class StackFrameTraverser extends AbstractStackWalker
implements Spliterator
{
static {
stackWalkImplClasses.add(StackFrameTraverser.class);
}
private static final int CHARACTERISTICS = Spliterator.ORDERED | Spliterator.IMMUTABLE;
final class StackFrameBuffer extends FrameBuffer {
private StackFrameInfo[] stackFrames;
StackFrameBuffer(int initialBatchSize) {
super(initialBatchSize);
this.stackFrames = new StackFrameInfo[initialBatchSize];
for (int i = START_POS; i < initialBatchSize; i++) {
stackFrames[i] = new StackFrameInfo(walker);
}
}
@Override
StackFrameInfo[] frames() {
return stackFrames;
}
@Override
void resize(int startIndex, int elements) {
if (!isActive())
throw new IllegalStateException("inactive frame buffer can't be resized");
assert startIndex == START_POS :
"bad start index " + startIndex + " expected " + START_POS;
int size = startIndex+elements;
if (stackFrames.length < size) {
StackFrameInfo[] newFrames = new StackFrameInfo[size];
// copy initial magic...
System.arraycopy(stackFrames, 0, newFrames, 0, startIndex);
stackFrames = newFrames;
}
for (int i = startIndex; i < size; i++) {
stackFrames[i] = new StackFrameInfo(walker);
}
currentBatchSize = size;
}
@Override
StackFrameInfo nextStackFrame() {
if (isEmpty()) {
throw new NoSuchElementException("origin=" + origin + " fence=" + fence);
}
StackFrameInfo frame = stackFrames[origin];
origin++;
return frame;
}
@Override
final Class at(int index) {
return stackFrames[index].declaringClass();
}
}
final Function, ? extends T> function; // callback
StackFrameTraverser(StackWalker walker,
Function, ? extends T> function) {
this(walker, function, DEFAULT_MODE);
}
StackFrameTraverser(StackWalker walker,
Function, ? extends T> function,
int mode) {
super(walker, mode);
this.function = function;
}
/**
* Returns next StackFrame object in the current batch of stack frames;
* or null if no more stack frame.
*/
StackFrame nextStackFrame() {
if (!hasNext()) {
return null;
}
StackFrameInfo frame = frameBuffer.nextStackFrame();
depth++;
return frame;
}
@Override
protected T consumeFrames() {
checkState(OPEN);
Stream stream = StreamSupport.stream(this, false);
if (function != null) {
return function.apply(stream);
} else
throw new UnsupportedOperationException();
}
@Override
protected void initFrameBuffer() {
this.frameBuffer = new StackFrameBuffer(getNextBatchSize());
}
@Override
protected int batchSize(int lastBatchFrameCount) {
if (lastBatchFrameCount == 0) {
// First batch, use estimateDepth if not exceed the large batch size
// and not too small
int initialBatchSize = Math.max(walker.estimateDepth(), SMALL_BATCH);
return Math.min(initialBatchSize, LARGE_BATCH_SIZE);
} else {
if (lastBatchFrameCount > BATCH_SIZE) {
return lastBatchFrameCount;
} else {
return Math.min(lastBatchFrameCount*2, BATCH_SIZE);
}
}
}
// ------- Implementation of Spliterator
@Override
public Spliterator trySplit() {
return null; // ordered stream and do not allow to split
}
@Override
public long estimateSize() {
return maxDepth;
}
@Override
public int characteristics() {
return CHARACTERISTICS;
}
@Override
public void forEachRemaining(Consumer action) {
checkState(OPEN);
for (int n = 0; n < maxDepth; n++) {
StackFrame frame = nextStackFrame();
if (frame == null) break;
action.accept(frame);
}
}
@Override
public boolean tryAdvance(Consumer action) {
checkState(OPEN);
int index = frameBuffer.getIndex();
if (hasNext()) {
StackFrame frame = nextStackFrame();
action.accept(frame);
if (isDebug) {
System.err.println("tryAdvance: " + index + " " + frame);
}
return true;
}
if (isDebug) {
System.err.println("tryAdvance: " + index + " NO element");
}
return false;
}
}
/*
* CallerClassFinder is specialized to return Class for each stack frame.
* StackFrame is not requested.
*/
static final class CallerClassFinder extends AbstractStackWalker> {
static {
stackWalkImplClasses.add(CallerClassFinder.class);
}
private Class caller;
CallerClassFinder(StackWalker walker) {
super(walker, FILL_CLASS_REFS_ONLY|GET_CALLER_CLASS);
}
static final class ClassBuffer extends FrameBuffer> {
Class[] classes; // caller class for fast path
ClassBuffer(int batchSize) {
super(batchSize);
classes = new Class[batchSize];
}
@Override
Class[] frames() { return classes;}
@Override
final Class at(int index) { return classes[index];}
// ------ subclass may override the following methods -------
/**
* Resizes the buffers for VM to fill in the next batch of stack frames.
* The next batch will start at the given startIndex with the maximum number
* of elements.
*
* Subclass may override this method to manage the allocated buffers.
*
* @param startIndex the start index for the first frame of the next batch to fill in.
* @param elements the number of elements for the next batch to fill in.
*
*/
@Override
void resize(int startIndex, int elements) {
if (!isActive())
throw new IllegalStateException("inactive frame buffer can't be resized");
assert startIndex == START_POS :
"bad start index " + startIndex + " expected " + START_POS;
int size = startIndex+elements;
if (classes.length < size) {
// copy the elements in classes array to the newly allocated one.
// classes[0] is a Thread object
Class[] prev = classes;
classes = new Class[size];
System.arraycopy(prev, 0, classes, 0, startIndex);
}
currentBatchSize = size;
}
}
Class findCaller() {
walk();
return caller;
}
@Override
protected Integer consumeFrames() {
checkState(OPEN);
int n = 0;
Class[] frames = new Class[2];
// skip the API calling this getCallerClass method
// 0: StackWalker::getCallerClass
// 1: caller-sensitive method
// 2: caller class
while (n < 2 && (caller = nextFrame()) != null) {
if (isMethodHandleFrame(caller)) { continue; }
if (isReflectionFrame(caller)) { continue; }
frames[n++] = caller;
}
if (frames[1] == null) {
throw new IllegalCallerException("no caller frame");
}
return n;
}
@Override
protected void initFrameBuffer() {
this.frameBuffer = new ClassBuffer(getNextBatchSize());
}
@Override
protected int batchSize(int lastBatchFrameCount) {
return MIN_BATCH_SIZE;
}
@Override
protected int getNextBatchSize() {
return MIN_BATCH_SIZE;
}
}
static final class LiveStackInfoTraverser extends StackFrameTraverser {
static {
stackWalkImplClasses.add(LiveStackInfoTraverser.class);
}
// VM will fill in all method info and live stack info directly in StackFrameInfo
final class LiveStackFrameBuffer extends FrameBuffer {
private LiveStackFrameInfo[] stackFrames;
LiveStackFrameBuffer(int initialBatchSize) {
super(initialBatchSize);
this.stackFrames = new LiveStackFrameInfo[initialBatchSize];
for (int i = START_POS; i < initialBatchSize; i++) {
stackFrames[i] = new LiveStackFrameInfo(walker);
}
}
@Override
LiveStackFrameInfo[] frames() {
return stackFrames;
}
@Override
void resize(int startIndex, int elements) {
if (!isActive()) {
throw new IllegalStateException("inactive frame buffer can't be resized");
}
assert startIndex == START_POS :
"bad start index " + startIndex + " expected " + START_POS;
int size = startIndex + elements;
if (stackFrames.length < size) {
LiveStackFrameInfo[] newFrames = new LiveStackFrameInfo[size];
// copy initial magic...
System.arraycopy(stackFrames, 0, newFrames, 0, startIndex);
stackFrames = newFrames;
}
for (int i = startIndex(); i < size; i++) {
stackFrames[i] = new LiveStackFrameInfo(walker);
}
currentBatchSize = size;
}
@Override
LiveStackFrameInfo nextStackFrame() {
if (isEmpty()) {
throw new NoSuchElementException("origin=" + origin + " fence=" + fence);
}
LiveStackFrameInfo frame = stackFrames[origin];
origin++;
return frame;
}
@Override
final Class at(int index) {
return stackFrames[index].declaringClass();
}
}
LiveStackInfoTraverser(StackWalker walker,
Function, ? extends T> function) {
super(walker, function, DEFAULT_MODE);
}
@Override
protected void initFrameBuffer() {
this.frameBuffer = new LiveStackFrameBuffer(getNextBatchSize());
}
}
/*
* Frame buffer
*
* Each specialized AbstractStackWalker subclass may subclass the FrameBuffer.
*/
static abstract class FrameBuffer {
static final int START_POS = 2; // 0th and 1st elements are reserved
// buffers for VM to fill stack frame info
int currentBatchSize; // current batch size
int origin; // index to the current traversed stack frame
int fence; // index to the last frame in the current batch
FrameBuffer(int initialBatchSize) {
if (initialBatchSize < MIN_BATCH_SIZE) {
throw new IllegalArgumentException(initialBatchSize +
" < minimum batch size: " + MIN_BATCH_SIZE);
}
this.origin = START_POS;
this.fence = 0;
this.currentBatchSize = initialBatchSize;
}
/**
* Returns an array of frames that may be used to store frame objects
* when walking the stack.
*
* May be an array of {@code Class} if the {@code AbstractStackWalker}
* mode is {@link #FILL_CLASS_REFS_ONLY}, or an array of
* {@link StackFrameInfo} (or derivative) array otherwise.
*
* @return An array of frames that may be used to store frame objects
* when walking the stack. Must not be null.
*/
abstract F[] frames(); // must not return null
/**
* Resizes the buffers for VM to fill in the next batch of stack frames.
* The next batch will start at the given startIndex with the maximum number
* of elements.
*
* Subclass may override this method to manage the allocated buffers.
*
* @param startIndex the start index for the first frame of the next batch to fill in.
* @param elements the number of elements for the next batch to fill in.
*
*/
abstract void resize(int startIndex, int elements);
/**
* Return the class at the given position in the current batch.
* @param index the position of the frame.
* @return the class at the given position in the current batch.
*/
abstract Class at(int index);
// ------ subclass may override the following methods -------
/*
* Returns the start index for this frame buffer is refilled.
*
* This implementation reuses the allocated buffer for the next batch
* of stack frames. For subclass to retain the fetched stack frames,
* it should override this method to return the index at which the frame
* should be filled in for the next batch.
*/
int startIndex() {
return START_POS;
}
/**
* Returns next StackFrame object in the current batch of stack frames
*/
F nextStackFrame() {
throw new InternalError("should not reach here");
}
// ------ FrameBuffer implementation ------
final int curBatchFrameCount() {
return currentBatchSize-START_POS;
}
/*
* Tests if this frame buffer is empty. All frames are fetched.
*/
final boolean isEmpty() {
return origin >= fence || (origin == START_POS && fence == 0);
}
/*
* Freezes this frame buffer. The stack stream source is done fetching.
*/
final void freeze() {
origin = 0;
fence = 0;
}
/*
* Tests if this frame buffer is active. It is inactive when
* it is done for traversal. All stack frames have been traversed.
*/
final boolean isActive() {
return origin > 0 && (fence == 0 || origin < fence || fence == currentBatchSize);
}
/**
* Gets the class at the current frame and move to the next frame.
*/
final Class next() {
if (isEmpty()) {
throw new NoSuchElementException("origin=" + origin + " fence=" + fence);
}
Class c = at(origin);
origin++;
if (isDebug) {
int index = origin-1;
System.out.format(" next frame at %d: %s (origin %d fence %d)%n", index,
Objects.toString(c), index, fence);
}
return c;
}
/**
* Gets the class at the current frame.
*/
final Class get() {
if (isEmpty()) {
throw new NoSuchElementException("origin=" + origin + " fence=" + fence);
}
return at(origin);
}
/*
* Returns the index of the current frame.
*/
final int getIndex() {
return origin;
}
/*
* Set the start and end index of a new batch of stack frames that have
* been filled in this frame buffer.
*/
final void setBatch(int depth, int startIndex, int endIndex) {
if (startIndex <= 0 || endIndex <= 0)
throw new IllegalArgumentException("startIndex=" + startIndex
+ " endIndex=" + endIndex);
this.origin = startIndex;
this.fence = endIndex;
if (depth == 0 && fence > 0) {
// filter the frames due to the stack stream implementation
for (int i = START_POS; i < fence; i++) {
Class c = at(i);
if (isDebug) System.err.format(" frame %d: %s%n", i, c);
if (filterStackWalkImpl(c)) {
origin++;
} else {
break;
}
}
}
}
/*
* Checks if the origin is the expected start index.
*/
final void check(int skipFrames) {
int index = skipFrames + START_POS;
if (origin != index) {
// stack walk must continue with the previous frame depth
throw new IllegalStateException("origin " + origin + " != " + index);
}
}
}
private static native boolean checkStackWalkModes();
// avoid loading other subclasses as they may not be used
private static Set> init() {
if (!checkStackWalkModes()) {
throw new InternalError("StackWalker mode values do not match with JVM");
}
Set> classes = new HashSet<>();
classes.add(StackWalker.class);
classes.add(StackStreamFactory.class);
classes.add(AbstractStackWalker.class);
return classes;
}
private static boolean filterStackWalkImpl(Class c) {
return stackWalkImplClasses.contains(c) ||
c.getName().startsWith("java.util.stream.");
}
// MethodHandle frames are not hidden and CallerClassFinder has
// to filter them out
private static boolean isMethodHandleFrame(Class c) {
return c.getName().startsWith("java.lang.invoke.");
}
private static boolean isReflectionFrame(Class c) {
// ## should filter all @Hidden frames?
return c == Method.class ||
c == Constructor.class ||
MethodAccessor.class.isAssignableFrom(c) ||
ConstructorAccessor.class.isAssignableFrom(c) ||
c.getName().startsWith("java.lang.invoke.LambdaForm");
}
}