/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * 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 dalvik.system;

import dalvik.annotation.optimization.FastNative;

/**
 * Provides a limited interface to the Dalvik VM stack. This class is mostly
 * used for implementing security checks.
 *
 * @hide
 */
public final class VMStack {
    /**
     * Returns the defining class loader of the caller's caller.
     *
     * @return the requested class loader, or {@code null} if this is the
     *         bootstrap class loader.
     */
    @FastNative
    native public static ClassLoader getCallingClassLoader();

    /**
     * Returns the class of the caller's caller.
     *
     * @return the requested class, or {@code null}.
     */
    public static Class<?> getStackClass1() {
        return getStackClass2();
    }

    /**
     * Returns the class of the caller's caller's caller.
     *
     * @return the requested class, or {@code null}.
     */
    @FastNative
    native public static Class<?> getStackClass2();

    /**
     * Returns the first ClassLoader on the call stack that isn't the
     * bootstrap class loader.
     */
    @FastNative
    public native static ClassLoader getClosestUserClassLoader();

    /**
     * Retrieves the stack trace from the specified thread.
     *
     * @param t
     *      thread of interest
     * @return an array of stack trace elements, or null if the thread
     *      doesn't have a stack trace (e.g. because it exited)
     */
    @FastNative
    native public static StackTraceElement[] getThreadStackTrace(Thread t);

    /**
     * Retrieves a partial stack trace from the specified thread into
     * the provided array.
     *
     * @param t
     *      thread of interest
     * @param stackTraceElements
     *      preallocated array for use when only the top of stack is
     *      desired. Unused elements will be filled with null values.
     * @return the number of elements filled
     */
    @FastNative
    native public static int fillStackTraceElements(Thread t,
        StackTraceElement[] stackTraceElements);
}