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1   /*
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3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4    *
5    * This code is free software; you can redistribute it and/or modify it
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7    * published by the Free Software Foundation.  Oracle designates this
8    * particular file as subject to the "Classpath" exception as provided
9    * by Oracle in the LICENSE file that accompanied this code.
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).
16   *
17   * You should have received a copy of the GNU General Public License version
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19   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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24   */
25  
26  package com.sun.jdi;
27  
28  import java.util.List;
29  import java.util.Map;
30  
31  /**
32   * The state of one method invocation on a thread's call stack.
33   * As a thread executes, stack frames are pushed and popped from
34   * its call stack as methods are invoked and then return. A StackFrame
35   * mirrors one such frame from a target VM at some point in its
36   * thread's execution. The call stack is, then, simply a List of
37   * StackFrame objects. The call stack can be obtained any time a thread
38   * is suspended through a call to {@link ThreadReference#frames}
39   * <p>
40   * StackFrames provide access to a method's local variables and their
41   * current values.
42   * <p>
43   * The lifetime of a StackFrame is very limited. It is available only
44   * for suspended threads and becomes invalid once its thread is resumed.
45   * <p>
46   * Any method on <code>StackFrame</code> which
47   * takes <code>StackFrame</code> as an parameter may throw
48   * {@link com.sun.jdi.VMDisconnectedException} if the target VM is
49   * disconnected and the {@link com.sun.jdi.event.VMDisconnectEvent} has been or is
50   * available to be read from the {@link com.sun.jdi.event.EventQueue}.
51   * <p>
52   * Any method on <code>StackFrame</code> which
53   * takes <code>StackFrame</code> as an parameter may throw
54   * {@link com.sun.jdi.VMOutOfMemoryException} if the target VM has run out of memory.
55   *
56   * @author Robert Field
57   * @author Gordon Hirsch
58   * @author James McIlree
59   * @since  1.3
60   */
61  @jdk.Exported
62  public interface StackFrame extends Mirror, Locatable {
63  
64      /**
65       * Returns the {@link Location} of the current instruction in the frame.
66       * The method for which this frame was created can also be accessed
67       * through the returned location.
68       * For the top frame in the stack, this location identifies the
69       * next instruction to be executed. For all other frames, this
70       * location identifies the instruction that caused the next frame's
71       * method to be invoked.
72       * If the frame represents a native method invocation, the returned
73       * location indicates the class and method, but the code index will
74       * not be valid (-1).
75       *
76       * @return the {@link Location} of the current instruction.
77       * @throws InvalidStackFrameException if this stack frame has become
78       * invalid. Once the frame's thread is resumed, the stack frame is
79       * no longer valid.
80       */
81      Location location();
82  
83      /**
84       * Returns the thread under which this frame's method is running.
85       *
86       * @return a {@link ThreadReference} which mirrors the frame's thread.
87       * @throws InvalidStackFrameException if this stack frame has become
88       * invalid. Once the frame's thread is resumed, the stack frame is
89       * no longer valid.
90       */
91      ThreadReference thread();
92  
93      /**
94       * Returns the value of 'this' for the current frame.
95       * The {@link ObjectReference} for 'this' is only available for
96       * non-native instance methods.
97       *
98       * @return an {@link ObjectReference}, or null if the frame represents
99       * a native or static method.
100      * @throws InvalidStackFrameException if this stack frame has become
101      * invalid. Once the frame's thread is resumed, the stack frame is
102      * no longer valid.
103      */
104     ObjectReference thisObject();
105 
106     /**
107      * Returns a list containing each {@link LocalVariable}
108      * that can be accessed from this frame's location.
109      * <p>
110      * Visibility is based on the code index of the current instruction of
111      * this StackFrame. Each variable has a range of byte code indices in which
112      * it is accessible.
113      * If this stack frame's method
114      * matches this variable's method and if the code index of this
115      * StackFrame is within the variable's byte code range, the variable is
116      * visible.
117      * <p>
118      * A variable's byte code range is at least as large as the scope of
119      * that variable, but can continue beyond the end of the scope under
120      * certain circumstances:
121      * <ul>
122      * <li>the compiler/VM does not immediately reuse the variable's slot.
123      * <li>the compiler/VM is implemented to report the extended range that
124      * would result from the item above.
125      * </ul>
126      * The advantage of an extended range is that variables from recently
127      * exited scopes may remain available for examination (this is especially
128      * useful for loop indices). If, as a result of the extensions above,
129      * the current frame location is contained within the range
130      * of multiple local variables of the same name, the variable with the
131      * highest-starting range is chosen for the returned list.
132      *
133      * @return the list of {@link LocalVariable} objects currently visible;
134      * the list will be empty if there are no visible variables;
135      * specifically, frames in native methods will always return a
136      * zero-length list.
137      * @throws AbsentInformationException if there is no local variable
138      * information for this method.
139      * @throws InvalidStackFrameException if this stack frame has become
140      * invalid. Once the frame's thread is resumed, the stack frame is
141      * no longer valid.
142      * @throws NativeMethodException if the current method is native.
143      */
144     List<LocalVariable> visibleVariables() throws AbsentInformationException;
145 
146     /**
147      * Finds a {@link LocalVariable} that matches the given name and is
148      * visible at the current frame location.
149      * See {@link #visibleVariables} for more information on visibility.
150      *
151      * @param name the variable name to find
152      * @return the matching {@link LocalVariable}, or null if there is no
153      * visible variable with the given name; frames in native methods
154      * will always return null.
155      * @throws AbsentInformationException if there is no local variable
156      * information for this method.
157      * @throws InvalidStackFrameException if this stack frame has become
158      * invalid. Once the frame's thread is resumed, the stack frame is
159      * no longer valid.
160      * @throws NativeMethodException if the current method is native.
161      */
162     LocalVariable visibleVariableByName(String name) throws AbsentInformationException;
163 
164     /**
165      * Gets the {@link Value} of a {@link LocalVariable} in this frame.
166      * The variable must be valid for this frame's method and visible
167      * according to the rules described in {@link #visibleVariables}.
168      *
169      * @param variable the {@link LocalVariable} to be accessed
170      * @return the {@link Value} of the instance field.
171      * @throws java.lang.IllegalArgumentException if the variable is
172      * either invalid for this frame's method or not visible.
173      * @throws InvalidStackFrameException if this stack frame has become
174      * invalid. Once the frame's thread is resumed, the stack frame is
175      * no longer valid.
176      */
177     Value getValue(LocalVariable variable);
178 
179     /**
180      * Returns the values of multiple local variables in this frame.
181      * Each variable must be valid for this frame's method and visible
182      * according to the rules described in {@link #visibleVariables}.
183      *
184      * @param variables a list of {@link LocalVariable} objects to be accessed
185      * @return a map associating each {@link LocalVariable} with
186      * its {@link Value}
187      * @throws java.lang.IllegalArgumentException if any variable is
188      * either invalid for this frame's method or not visible.
189      * @throws InvalidStackFrameException if this stack frame has become
190      * invalid. Once the frame's thread is resumed, the stack frame is
191      * no longer valid.
192      */
193     Map<LocalVariable,Value> getValues(List<? extends LocalVariable> variables);
194 
195     /**
196      * Sets the {@link Value} of a {@link LocalVariable} in this frame.
197      * The variable must be valid for this frame's method and visible
198      * according to the rules described in {@link #visibleVariables}.
199      * <p>
200      * Object values must be assignment compatible with the variable type
201      * (This implies that the variable type must be loaded through the
202      * enclosing class's class loader). Primitive values must be
203      * either assignment compatible with the variable type or must be
204      * convertible to the variable type without loss of information.
205      * See JLS section 5.2 for more information on assignment
206      * compatibility.
207      *
208      * @param variable the field containing the requested value
209      * @param value the new value to assign
210      * @throws java.lang.IllegalArgumentException if the field is not valid for
211      * this object's class.
212      * @throws InvalidTypeException if the value's type does not match
213      * the variable's type.
214      * @throws ClassNotLoadedException if the variable type has not yet been loaded
215      * through the appropriate class loader.
216      * @throws InvalidStackFrameException if this stack frame has become
217      * invalid. Once the frame's thread is resumed, the stack frame is
218      * no longer valid.
219      * @throws VMCannotBeModifiedException if the VirtualMachine is read-only - see {@link VirtualMachine#canBeModified()}.
220      */
221     void setValue(LocalVariable variable, Value value)
222         throws InvalidTypeException, ClassNotLoadedException;
223 
224     /**
225      * Returns the values of all arguments in this frame.  Values are
226      * returned even if no local variable information is present.
227      *
228      * @return a list containing a {@link Value} object for each argument
229      * to this frame, in the order in which the arguments were
230      * declared.  If the method corresponding to this frame has
231      * no arguments, an empty list is returned.
232      *
233      * @throws InvalidStackFrameException if this stack frame has become
234      * invalid. Once the frame's thread is resumed, the stack frame is
235      * no longer valid.
236      * @since 1.6
237      */
238     List<Value> getArgumentValues();
239 
240 }