/*

 * Copyright (c) 2015, 2019, 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

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 */

package java.lang;

import java.lang.StackWalker.StackFrame;

import java.util.EnumSet;

import java.util.Set;

import static java.lang.StackWalker.ExtendedOption.LOCALS_AND_OPERANDS;

/**

 * <em>UNSUPPORTED</em> This interface is intended to be package-private

 * or move to an internal package.<p>

 *

 * {@code LiveStackFrame} represents a frame storing data and partial results.

 * Each frame has its own array of local variables (JVMS section 2.6.1),

 * its own operand stack (JVMS section 2.6.2) for a method invocation.

 *

 * @jvms 2.6 Frames

 */

/* package-private */

interface LiveStackFrame extends StackFrame {

    /**

     * Return the monitors held by this stack frame. This method returns

     * an empty array if no monitor is held by this stack frame.

     *

     * @return the monitors held by this stack frames

     */

    public Object[] getMonitors();

    /**

     * Gets the local variable array of this stack frame.

     *

     * <p>A single local variable can hold a value of type boolean, byte, char,

     * short, int, float, reference or returnAddress.  A pair of local variables

     * can hold a value of type long or double (JVMS section 2.6.1).  Primitive

     * locals are represented in the returned array as {@code PrimitiveSlot}s,

     * with longs and doubles occupying a pair of consecutive

     * {@code PrimitiveSlot}s.

     *

     * <p>The current VM implementation does not provide specific type

     * information for primitive locals.  This method simply returns the raw

     * contents of the VM's primitive locals on a best-effort basis, without

     * indicating a specific type.

     *

     * <p>The returned array may contain null entries for local variables that

     * are not live.

     *

     * @implNote

     * <p> The specific subclass of {@code PrimitiveSlot} will reflect the

     * underlying architecture, and will be either {@code PrimitiveSlot32} or

     * {@code PrimitiveSlot64}.

     *

     * <p>How a long or double value is stored in the pair of

     * {@code PrimitiveSlot}s can vary based on the underlying architecture and

     * VM implementation.  On 32-bit architectures, long/double values are split

     * between the two {@code PrimitiveSlot32}s.

     * On 64-bit architectures, the entire value may be stored in one of the

     * {@code PrimitiveSlot64}s, with the other {@code PrimitiveSlot64} being

     * unused.

     *

     * <p>The contents of the unused, high-order portion of a

     * {@code PrimitiveSlot64} (when storing a primitive other than a long or

     * double) is unspecified.  In particular, the unused bits are not

     * necessarily zeroed out.

     *

     * @return  the local variable array of this stack frame.

     */

    public Object[] getLocals();

    /**

     * Gets the operand stack of this stack frame.

     *

     * <p>

     * The 0-th element of the returned array represents the top of the operand stack.

     * This method returns an empty array if the operand stack is empty.

     *

     * <p>Each entry on the operand stack can hold a value of any Java Virtual

     * Machine Type.

     * For a value of primitive type, the element in the returned array is

     * a {@link PrimitiveSlot} object; otherwise, the element is the {@code Object}

     * on the operand stack.

     *

     * @return the operand stack of this stack frame.

     */

    public Object[] getStack();

    /**

     * <em>UNSUPPORTED</em> This interface is intended to be package-private

     * or moved to an internal package.<p>

     *

     * Represents a local variable or an entry on the operand stack whose value is

     * of primitive type.

     */

    public abstract class PrimitiveSlot {

        /**

         * Returns the size, in bytes, of the slot.

         */

        public abstract int size();

        /**

         * Returns the int value if this primitive value is of size 4

         * @return the int value if this primitive value is of size 4

         *

         * @throws UnsupportedOperationException if this primitive value is not

         * of size 4.

         */

        public int intValue() {

            throw new UnsupportedOperationException("this " + size() + "-byte primitive");

        }

        /**

         * Returns the long value if this primitive value is of size 8

         * @return the long value if this primitive value is of size 8

         *

         * @throws UnsupportedOperationException if this primitive value is not

         * of size 8.

         */

        public long longValue() {

            throw new UnsupportedOperationException("this " + size() + "-byte primitive");

        }

    }

    /**

     * Gets {@code StackWalker} that can get locals and operands.

     *

     * @throws SecurityException if the security manager is present and

     * denies access to {@code RuntimePermission("liveStackFrames")}

     */

    public static StackWalker getStackWalker() {

        return getStackWalker(EnumSet.noneOf(StackWalker.Option.class));

    }

    /**

     * Gets a {@code StackWalker} instance with the given options specifying

     * the stack frame information it can access, and which will traverse at most

     * the given {@code maxDepth} number of stack frames.  If no option is

     * specified, this {@code StackWalker} obtains the method name and

     * the class name with all

     * {@linkplain StackWalker.Option#SHOW_HIDDEN_FRAMES hidden frames} skipped.

     * The returned {@code StackWalker} can get locals and operands.

     *

     * @param options stack walk {@link StackWalker.Option options}

     *

     * @throws SecurityException if the security manager is present and

     * it denies access to {@code RuntimePermission("liveStackFrames")};

     * or if the given {@code options} contains

     * {@link StackWalker.Option#RETAIN_CLASS_REFERENCE Option.RETAIN_CLASS_REFERENCE}

     * and it denies access to {@code RuntimePermission("getStackWalkerWithClassReference")}.

     */

    public static StackWalker getStackWalker(Set<StackWalker.Option> options) {

        SecurityManager sm = System.getSecurityManager();

        if (sm != null) {

            sm.checkPermission(new RuntimePermission("liveStackFrames"));

        }

        return StackWalker.newInstance(options, LOCALS_AND_OPERANDS);

    }

}