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	/*
	* Copyright (c) 2000, 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.
	*
	* 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 java.lang;

	import jdk.internal.loader.BuiltinClassLoader;
	import jdk.internal.misc.VM;
	import jdk.internal.module.ModuleHashes;
	import jdk.internal.module.ModuleReferenceImpl;

	import java.lang.module.ModuleDescriptor.Version;
	import java.lang.module.ModuleReference;
	import java.lang.module.ResolvedModule;
	import java.util.HashSet;
	import java.util.Objects;
	import java.util.Optional;
	import java.util.Set;

	/**
	* An element in a stack trace, as returned by {@link
	* Throwable#getStackTrace()}. Each element represents a single stack frame.
	* All stack frames except for the one at the top of the stack represent
	* a method invocation. The frame at the top of the stack represents the
	* execution point at which the stack trace was generated. Typically,
	* this is the point at which the throwable corresponding to the stack trace
	* was created.
	*
	* @since 1.4
	* @author Josh Bloch
	*/
	public final class StackTraceElement implements java.io.Serializable {

	// For Throwables and StackWalker, the VM initially sets this field to a
	// reference to the declaring Class. The Class reference is used to
	// construct the 'format' bitmap, and then is cleared.
	//
	// For STEs constructed using the public constructors, this field is not used.
	private transient Class<?> declaringClassObject;

	// Normally initialized by VM
	/**
	* The name of the class loader.
	*/
	private String classLoaderName;
	/**
	* The module name.
	*/
	private String moduleName;
	/**
	* The module version.
	*/
	private String moduleVersion;
	/**
	* The declaring class.
	*/
	private String declaringClass;
	/**
	* The method name.
	*/
	private String methodName;
	/**
	* The source file name.
	*/
	private String fileName;
	/**
	* The source line number.
	*/
	private int lineNumber;
	/**
	* Control to show full or partial module, package, and class names.
	*/
	private byte format = 0; // Default to show all

	/**
	* Creates a stack trace element representing the specified execution
	* point. The {@link #getModuleName module name} and {@link
	* #getModuleVersion module version} of the stack trace element will
	* be {@code null}.
	*
	* @param declaringClass the fully qualified name of the class containing
	* the execution point represented by the stack trace element
	* @param methodName the name of the method containing the execution point
	* represented by the stack trace element
	* @param fileName the name of the file containing the execution point
	* represented by the stack trace element, or {@code null} if
	* this information is unavailable
	* @param lineNumber the line number of the source line containing the
	* execution point represented by this stack trace element, or
	* a negative number if this information is unavailable. A value
	* of -2 indicates that the method containing the execution point
	* is a native method
	* @throws NullPointerException if {@code declaringClass} or
	* {@code methodName} is null
	* @since 1.5
	* @revised 9
	*/
	public StackTraceElement(String declaringClass, String methodName,
	String fileName, int lineNumber) {
	this(null, null, null, declaringClass, methodName, fileName, lineNumber);
	}

	/**
	* Creates a stack trace element representing the specified execution
	* point.
	*
	* @param classLoaderName the class loader name if the class loader of
	* the class containing the execution point represented by
	* the stack trace is named; otherwise {@code null}
	* @param moduleName the module name if the class containing the
	* execution point represented by the stack trace is in a named
	* module; otherwise {@code null}
	* @param moduleVersion the module version if the class containing the
	* execution point represented by the stack trace is in a named
	* module that has a version; otherwise {@code null}
	* @param declaringClass the fully qualified name of the class containing
	* the execution point represented by the stack trace element
	* @param methodName the name of the method containing the execution point
	* represented by the stack trace element
	* @param fileName the name of the file containing the execution point
	* represented by the stack trace element, or {@code null} if
	* this information is unavailable
	* @param lineNumber the line number of the source line containing the
	* execution point represented by this stack trace element, or
	* a negative number if this information is unavailable. A value
	* of -2 indicates that the method containing the execution point
	* is a native method
	*
	* @throws NullPointerException if {@code declaringClass} is {@code null}
	* or {@code methodName} is {@code null}
	*
	* @since 9
	*/
	public StackTraceElement(String classLoaderName,
	String moduleName, String moduleVersion,
	String declaringClass, String methodName,
	String fileName, int lineNumber) {
	this.classLoaderName = classLoaderName;
	this.moduleName = moduleName;
	this.moduleVersion = moduleVersion;
	this.declaringClass = Objects.requireNonNull(declaringClass, "Declaring class is null");
	this.methodName = Objects.requireNonNull(methodName, "Method name is null");
	this.fileName = fileName;
	this.lineNumber = lineNumber;
	}

	/*
	* Private constructor for the factory methods to create StackTraceElement
	* for Throwable and StackFrameInfo
	*/
	private StackTraceElement() {}

	/**
	* Returns the name of the source file containing the execution point
	* represented by this stack trace element. Generally, this corresponds
	* to the {@code SourceFile} attribute of the relevant {@code class}
	* file (as per <cite>The Java Virtual Machine Specification</cite>, Section
	* {@jvms 4.7.7}). In some systems, the name may refer to some source code unit
	* other than a file, such as an entry in source repository.
	*
	* @return the name of the file containing the execution point
	* represented by this stack trace element, or {@code null} if
	* this information is unavailable.
	*/
	public String getFileName() {
	return fileName;
	}

	/**
	* Returns the line number of the source line containing the execution
	* point represented by this stack trace element. Generally, this is
	* derived from the {@code LineNumberTable} attribute of the relevant
	* {@code class} file (as per <cite>The Java Virtual Machine
	* Specification</cite>, Section {@jvms 4.7.8}).
	*
	* @return the line number of the source line containing the execution
	* point represented by this stack trace element, or a negative
	* number if this information is unavailable.
	*/
	public int getLineNumber() {
	return lineNumber;
	}

	/**
	* Returns the module name of the module containing the execution point
	* represented by this stack trace element.
	*
	* @return the module name of the {@code Module} containing the execution
	* point represented by this stack trace element; {@code null}
	* if the module name is not available.
	* @since 9
	* @see Module#getName()
	*/
	public String getModuleName() {
	return moduleName;
	}

	/**
	* Returns the module version of the module containing the execution point
	* represented by this stack trace element.
	*
	* @return the module version of the {@code Module} containing the execution
	* point represented by this stack trace element; {@code null}
	* if the module version is not available.
	* @since 9
	* @see java.lang.module.ModuleDescriptor.Version
	*/
	public String getModuleVersion() {
	return moduleVersion;
	}

	/**
	* Returns the name of the class loader of the class containing the
	* execution point represented by this stack trace element.
	*
	* @return the name of the class loader of the class containing the execution
	* point represented by this stack trace element; {@code null}
	* if the class loader is not named.
	*
	* @since 9
	* @see java.lang.ClassLoader#getName()
	*/
	public String getClassLoaderName() {
	return classLoaderName;
	}

	/**
	* Returns the fully qualified name of the class containing the
	* execution point represented by this stack trace element.
	*
	* @return the fully qualified name of the {@code Class} containing
	* the execution point represented by this stack trace element.
	*/
	public String getClassName() {
	return declaringClass;
	}

	/**
	* Returns the name of the method containing the execution point
	* represented by this stack trace element. If the execution point is
	* contained in an instance or class initializer, this method will return
	* the appropriate <i>special method name</i>, {@code <init>} or
	* {@code <clinit>}, as per Section {@jvms 3.9} of <cite>The Java Virtual
	* Machine Specification</cite>.
	*
	* @return the name of the method containing the execution point
	* represented by this stack trace element.
	*/
	public String getMethodName() {
	return methodName;
	}

	/**
	* Returns true if the method containing the execution point
	* represented by this stack trace element is a native method.
	*
	* @return {@code true} if the method containing the execution point
	* represented by this stack trace element is a native method.
	*/
	public boolean isNativeMethod() {
	return lineNumber == -2;
	}

	/**
	* Returns a string representation of this stack trace element.
	*
	* @apiNote The format of this string depends on the implementation, but the
	* following examples may be regarded as typical:
	* <ul>
	* <li>
	* "{@code com.foo.loader/foo@9.0/com.foo.Main.run(Main.java:101)}"
	* - See the description below.
	* </li>
	* <li>
	* "{@code com.foo.loader/foo@9.0/com.foo.Main.run(Main.java)}"
	* - The line number is unavailable.
	* </li>
	* <li>
	* "{@code com.foo.loader/foo@9.0/com.foo.Main.run(Unknown Source)}"
	* - Neither the file name nor the line number is available.
	* </li>
	* <li>
	* "{@code com.foo.loader/foo@9.0/com.foo.Main.run(Native Method)}"
	* - The method containing the execution point is a native method.
	* </li>
	* <li>
	* "{@code com.foo.loader//com.foo.bar.App.run(App.java:12)}"
	* - The class of the execution point is defined in the unnamed module of
	* the class loader named {@code com.foo.loader}.
	* </li>
	* <li>
	* "{@code acme@2.1/org.acme.Lib.test(Lib.java:80)}"
	* - The class of the execution point is defined in {@code acme} module
	* loaded by a built-in class loader such as the application class loader.
	* </li>
	* <li>
	* "{@code MyClass.mash(MyClass.java:9)}"
	* - {@code MyClass} class is on the application class path.
	* </li>
	* </ul>
	*
	* <p> The first example shows a stack trace element consisting of
	* three elements, each separated by {@code "/"}, followed by
	* the source file name and the line number of the source line
	* containing the execution point.
	*
	* The first element "{@code com.foo.loader}" is
	* the name of the class loader. The second element "{@code foo@9.0}"
	* is the module name and version. The third element is the method
	* containing the execution point; "{@code com.foo.Main"}" is the
	* fully-qualified class name and "{@code run}" is the name of the method.
	* "{@code Main.java}" is the source file name and "{@code 101}" is
	* the line number.
	*
	* <p> If a class is defined in an <em>unnamed module</em>
	* then the second element is omitted as shown in
	* "{@code com.foo.loader//com.foo.bar.App.run(App.java:12)}".
	*
	* <p> If the class loader is a <a href="ClassLoader.html#builtinLoaders">
	* built-in class loader</a> or is not named then the first element
	* and its following {@code "/"} are omitted as shown in
	* "{@code acme@2.1/org.acme.Lib.test(Lib.java:80)}".
	* If the first element is omitted and the module is an unnamed module,
	* the second element and its following {@code "/"} are also omitted
	* as shown in "{@code MyClass.mash(MyClass.java:9)}".
	*
	* <p> The {@code toString} method may return two different values on two
	* {@code StackTraceElement} instances that are
	* {@linkplain #equals(Object) equal}, for example one created via the
	* constructor, and one obtained from {@link java.lang.Throwable} or
	* {@link java.lang.StackWalker.StackFrame}, where an implementation may
	* choose to omit some element in the returned string.
	*
	* @revised 9
	* @see Throwable#printStackTrace()
	*/
	public String toString() {
	String s = "";
	if (!dropClassLoaderName() && classLoaderName != null &&
	!classLoaderName.isEmpty()) {
	s += classLoaderName + "/";
	}
	if (moduleName != null && !moduleName.isEmpty()) {
	s += moduleName;

	if (!dropModuleVersion() && moduleVersion != null &&
	!moduleVersion.isEmpty()) {
	s += "@" + moduleVersion;
	}
	}
	s = s.isEmpty() ? declaringClass : s + "/" + declaringClass;

	return s + "." + methodName + "(" +
	(isNativeMethod() ? "Native Method)" :
	(fileName != null && lineNumber >= 0 ?
	fileName + ":" + lineNumber + ")" :
	(fileName != null ? ""+fileName+")" : "Unknown Source)")));
	}

	/**
	* Returns true if the specified object is another
	* {@code StackTraceElement} instance representing the same execution
	* point as this instance. Two stack trace elements {@code a} and
	* {@code b} are equal if and only if:
	* <pre>{@code
	* equals(a.getClassLoaderName(), b.getClassLoaderName()) &&
	* equals(a.getModuleName(), b.getModuleName()) &&
	* equals(a.getModuleVersion(), b.getModuleVersion()) &&
	* equals(a.getClassName(), b.getClassName()) &&
	* equals(a.getMethodName(), b.getMethodName())
	* equals(a.getFileName(), b.getFileName()) &&
	* a.getLineNumber() == b.getLineNumber()
	*
	* }</pre>
	* where {@code equals} has the semantics of {@link
	* java.util.Objects#equals(Object, Object) Objects.equals}.
	*
	* @param obj the object to be compared with this stack trace element.
	* @return true if the specified object is another
	* {@code StackTraceElement} instance representing the same
	* execution point as this instance.
	*
	* @revised 9
	*/
	public boolean equals(Object obj) {
	if (obj==this)
	return true;
	return (obj instanceof StackTraceElement e)
	&& e.lineNumber == lineNumber
	&& e.declaringClass.equals(declaringClass)
	&& Objects.equals(classLoaderName, e.classLoaderName)
	&& Objects.equals(moduleName, e.moduleName)
	&& Objects.equals(moduleVersion, e.moduleVersion)
	&& Objects.equals(methodName, e.methodName)
	&& Objects.equals(fileName, e.fileName);
	}

	/**
	* Returns a hash code value for this stack trace element.
	*/
	public int hashCode() {
	int result = 31*declaringClass.hashCode() + methodName.hashCode();
	result = 31*result + Objects.hashCode(classLoaderName);
	result = 31*result + Objects.hashCode(moduleName);
	result = 31*result + Objects.hashCode(moduleVersion);
	result = 31*result + Objects.hashCode(fileName);
	result = 31*result + lineNumber;
	return result;
	}


	/**
	* Called from of() methods to set the 'format' bitmap using the Class
	* reference stored in declaringClassObject, and then clear the reference.
	*
	* <p>
	* If the module is a non-upgradeable JDK module, then set
	* JDK_NON_UPGRADEABLE_MODULE to omit its version string.
	* <p>
	* If the loader is one of the built-in loaders (`boot`, `platform`, or `app`)
	* then set BUILTIN_CLASS_LOADER to omit the first element (`<loader>/`).
	*/
	private synchronized void computeFormat() {
	try {
	Class<?> cls = (Class<?>) declaringClassObject;
	ClassLoader loader = cls.getClassLoader0();
	Module m = cls.getModule();
	byte bits = 0;

	// First element - class loader name
	// Call package-private ClassLoader::name method

	if (loader instanceof BuiltinClassLoader) {
	bits \|= BUILTIN_CLASS_LOADER;
	}

	// Second element - module name and version

	// Omit if is a JDK non-upgradeable module (recorded in the hashes
	// in java.base)
	if (isHashedInJavaBase(m)) {
	bits \|= JDK_NON_UPGRADEABLE_MODULE;
	}
	format = bits;
	} finally {
	// Class reference no longer needed, clear it
	declaringClassObject = null;
	}
	}

	private static final byte BUILTIN_CLASS_LOADER = 0x1;
	private static final byte JDK_NON_UPGRADEABLE_MODULE = 0x2;

	private boolean dropClassLoaderName() {
	return (format & BUILTIN_CLASS_LOADER) == BUILTIN_CLASS_LOADER;
	}

	private boolean dropModuleVersion() {
	return (format & JDK_NON_UPGRADEABLE_MODULE) == JDK_NON_UPGRADEABLE_MODULE;
	}

	/**
	* Returns true if the module is hashed with java.base.
	* <p>
	* This method returns false when running on the exploded image
	* since JDK modules are not hashed. They have no Version attribute
	* and so "@<version>" part will be omitted anyway.
	*/
	private static boolean isHashedInJavaBase(Module m) {
	// return true if module system is not initialized as the code
	// must be in java.base
	if (!VM.isModuleSystemInited())
	return true;

	return ModuleLayer.boot() == m.getLayer() && HashedModules.contains(m);
	}

	/*
	* Finds JDK non-upgradeable modules, i.e. the modules that are
	* included in the hashes in java.base.
	*/
	private static class HashedModules {
	static Set<String> HASHED_MODULES = hashedModules();

	static Set<String> hashedModules() {

	Optional<ResolvedModule> resolvedModule = ModuleLayer.boot()
	.configuration()
	.findModule("java.base");
	assert resolvedModule.isPresent();
	ModuleReference mref = resolvedModule.get().reference();
	assert mref instanceof ModuleReferenceImpl;
	ModuleHashes hashes = ((ModuleReferenceImpl)mref).recordedHashes();
	if (hashes != null) {
	Set<String> names = new HashSet<>(hashes.names());
	names.add("java.base");
	return names;
	}

	return Set.of();
	}

	static boolean contains(Module m) {
	return HASHED_MODULES.contains(m.getName());
	}
	}


	/*
	* Returns an array of StackTraceElements of the given depth
	* filled from the backtrace of a given Throwable.
	*/
	static StackTraceElement[] of(Throwable x, int depth) {
	StackTraceElement[] stackTrace = new StackTraceElement[depth];
	for (int i = 0; i < depth; i++) {
	stackTrace[i] = new StackTraceElement();
	}

	// VM to fill in StackTraceElement
	initStackTraceElements(stackTrace, x);

	// ensure the proper StackTraceElement initialization
	for (StackTraceElement ste : stackTrace) {
	ste.computeFormat();
	}
	return stackTrace;
	}

	/*
	* Returns a StackTraceElement from a given StackFrameInfo.
	*/
	static StackTraceElement of(StackFrameInfo sfi) {
	StackTraceElement ste = new StackTraceElement();
	initStackTraceElement(ste, sfi);

	ste.computeFormat();
	return ste;
	}

	/*
	* Sets the given stack trace elements with the backtrace
	* of the given Throwable.
	*/
	private static native void initStackTraceElements(StackTraceElement[] elements,
	Throwable x);
	/*
	* Sets the given stack trace element with the given StackFrameInfo
	*/
	private static native void initStackTraceElement(StackTraceElement element,
	StackFrameInfo sfi);

	@java.io.Serial
	private static final long serialVersionUID = 6992337162326171013L;
	}

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