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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
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24 */
25package java.lang;
26
27import java.lang.StackWalker.StackFrame;
28import java.util.EnumSet;
29import java.util.Set;
30
31import static java.lang.StackWalker.ExtendedOption.LOCALS_AND_OPERANDS;
32
33/**
34 * <em>UNSUPPORTED</em> This interface is intended to be package-private
35 * or move to an internal package.<p>
36 *
37 * {@code LiveStackFrame} represents a frame storing data and partial results.
38 * Each frame has its own array of local variables (JVMS section 2.6.1),
39 * its own operand stack (JVMS section 2.6.2) for a method invocation.
40 *
41 * @jvms 2.6 Frames
42 */
43/* package-private */
44interface LiveStackFrame extends StackFrame {
45    /**
46     * Return the monitors held by this stack frame. This method returns
47     * an empty array if no monitor is held by this stack frame.
48     *
49     * @return the monitors held by this stack frames
50     */
51    public Object[] getMonitors();
52
53    /**
54     * Gets the local variable array of this stack frame.
55     *
56     * <p>A single local variable can hold a value of type boolean, byte, char,
57     * short, int, float, reference or returnAddress.  A pair of local variables
58     * can hold a value of type long or double (JVMS section 2.6.1).  Primitive
59     * locals are represented in the returned array as {@code PrimitiveSlot}s,
60     * with longs and doubles occupying a pair of consecutive
61     * {@code PrimitiveSlot}s.
62     *
63     * <p>The current VM implementation does not provide specific type
64     * information for primitive locals.  This method simply returns the raw
65     * contents of the VM's primitive locals on a best-effort basis, without
66     * indicating a specific type.
67     *
68     * <p>The returned array may contain null entries for local variables that
69     * are not live.
70     *
71     * @implNote
72     * <p> The specific subclass of {@code PrimitiveSlot} will reflect the
73     * underlying architecture, and will be either {@code PrimitiveSlot32} or
74     * {@code PrimitiveSlot64}.
75     *
76     * <p>How a long or double value is stored in the pair of
77     * {@code PrimitiveSlot}s can vary based on the underlying architecture and
78     * VM implementation.  On 32-bit architectures, long/double values are split
79     * between the two {@code PrimitiveSlot32}s.
80     * On 64-bit architectures, the entire value may be stored in one of the
81     * {@code PrimitiveSlot64}s, with the other {@code PrimitiveSlot64} being
82     * unused.
83     *
84     * <p>The contents of the unused, high-order portion of a
85     * {@code PrimitiveSlot64} (when storing a primitive other than a long or
86     * double) is unspecified.  In particular, the unused bits are not
87     * necessarily zeroed out.
88     *
89     * @return  the local variable array of this stack frame.
90     */
91    public Object[] getLocals();
92
93    /**
94     * Gets the operand stack of this stack frame.
95     *
96     * <p>
97     * The 0-th element of the returned array represents the top of the operand stack.
98     * This method returns an empty array if the operand stack is empty.
99     *
100     * <p>Each entry on the operand stack can hold a value of any Java Virtual
101     * Machine Type.
102     * For a value of primitive type, the element in the returned array is
103     * a {@link PrimitiveSlot} object; otherwise, the element is the {@code Object}
104     * on the operand stack.
105     *
106     * @return the operand stack of this stack frame.
107     */
108    public Object[] getStack();
109
110    /**
111     * <em>UNSUPPORTED</em> This interface is intended to be package-private
112     * or moved to an internal package.<p>
113     *
114     * Represents a local variable or an entry on the operand stack whose value is
115     * of primitive type.
116     */
117    public abstract class PrimitiveSlot {
118        /**
119         * Returns the size, in bytes, of the slot.
120         */
121        public abstract int size();
122
123        /**
124         * Returns the int value if this primitive value is of size 4
125         * @return the int value if this primitive value is of size 4
126         *
127         * @throws UnsupportedOperationException if this primitive value is not
128         * of size 4.
129         */
130        public int intValue() {
131            throw new UnsupportedOperationException("this " + size() + "-byte primitive");
132        }
133
134        /**
135         * Returns the long value if this primitive value is of size 8
136         * @return the long value if this primitive value is of size 8
137         *
138         * @throws UnsupportedOperationException if this primitive value is not
139         * of size 8.
140         */
141        public long longValue() {
142            throw new UnsupportedOperationException("this " + size() + "-byte primitive");
143        }
144    }
145
146
147    /**
148     * Gets {@code StackWalker} that can get locals and operands.
149     *
150     * @throws SecurityException if the security manager is present and
151     * denies access to {@code RuntimePermission("liveStackFrames")}
152     */
153    public static StackWalker getStackWalker() {
154        return getStackWalker(EnumSet.noneOf(StackWalker.Option.class));
155    }
156
157    /**
158     * Gets a {@code StackWalker} instance with the given options specifying
159     * the stack frame information it can access, and which will traverse at most
160     * the given {@code maxDepth} number of stack frames.  If no option is
161     * specified, this {@code StackWalker} obtains the method name and
162     * the class name with all
163     * {@linkplain StackWalker.Option#SHOW_HIDDEN_FRAMES hidden frames} skipped.
164     * The returned {@code StackWalker} can get locals and operands.
165     *
166     * @param options stack walk {@link StackWalker.Option options}
167     *
168     * @throws SecurityException if the security manager is present and
169     * it denies access to {@code RuntimePermission("liveStackFrames")}; or
170     * or if the given {@code options} contains
171     * {@link StackWalker.Option#RETAIN_CLASS_REFERENCE Option.RETAIN_CLASS_REFERENCE}
172     * and it denies access to {@code RuntimePermission("getStackWalkerWithClassReference")}.
173     */
174    public static StackWalker getStackWalker(Set<StackWalker.Option> options) {
175        SecurityManager sm = System.getSecurityManager();
176        if (sm != null) {
177            sm.checkPermission(new RuntimePermission("liveStackFrames"));
178        }
179        return StackWalker.newInstance(options, LOCALS_AND_OPERANDS);
180    }
181}
182