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 * 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

    private String classLoaderName;

    private String moduleName;

    private String moduleVersion;

    private String declaringClass;

    private String methodName;

    private String fileName;

    private int    lineNumber;

    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

     * @spec JPMS

     */

    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

     * @spec JPMS

     */

    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 <i>The Java Virtual Machine Specification</i>, Section

     * 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 <i>The Java Virtual Machine

     * Specification</i>, Section 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

     * @spec JPMS

     * @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

     * @spec JPMS

     * @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

     * @spec JPMS

     * @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 3.9 of <i>The Java Virtual

     * Machine Specification</i>.

     *

     * @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 with

     * 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

     * @spec JPMS

     * @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

     * @spec JPMS

     */

    public boolean equals(Object obj) {

        if (obj==this)

            return true;

        if (!(obj instanceof StackTraceElement))

            return false;

        StackTraceElement e = (StackTraceElement)obj;

        return Objects.equals(classLoaderName, e.classLoaderName) &&

            Objects.equals(moduleName, e.moduleName) &&

            Objects.equals(moduleVersion, e.moduleVersion) &&

            e.declaringClass.equals(declaringClass) &&

            e.lineNumber == lineNumber &&

            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();