1 cananian 1.1.2.7 // ConstPointer.java, created Sat Mar 27 17:05:07 1999 by duncan
2 cananian 1.1.2.6 // Copyright (C) 1998 Duncan Bryce <duncan@lcs.mit.edu>
3 cananian 1.1.2.6 // Licensed under the terms of the GNU GPL; see COPYING for details.
4 duncan 1.1.2.1 package harpoon.Interpret.Tree;
5 duncan 1.1.2.1
6 duncan 1.1.2.1 import harpoon.ClassFile.HClass;
7 duncan 1.1.2.1 import harpoon.Util.Tuple;
8 duncan 1.1.2.1 import harpoon.Util.Util;
9 duncan 1.1.2.1 import harpoon.Temp.Label;
10 duncan 1.1.2.1
11 duncan 1.1.2.1 /**
12 duncan 1.1.2.1 * The <code>ConstPointer</code> class is used to represent
13 duncan 1.1.2.1 * pointers that can be resolved statically. Unlike the other pointer
14 duncan 1.1.2.1 * classes, <code>ConstPointer</code>s have no offsets. Their base
15 duncan 1.1.2.1 * is simply a <code>Label</code> object.
16 duncan 1.1.2.1 *
17 duncan 1.1.2.1 * @author Duncan Bryce <duncan@lcs.mit.edu>
18 cananian 1.2 * @version $Id: ConstPointer.java,v 1.2 2002/02/25 21:05:50 cananian Exp $
19 duncan 1.1.2.1 */
20 duncan 1.1.2.1 class ConstPointer extends Pointer {
21 duncan 1.1.2.1 private final StaticState ss;
22 duncan 1.1.2.4
23 duncan 1.1.2.4 public static final ConstPointer NULL_POINTER =
24 duncan 1.1.2.4 new ConstPointer(null, null);
25 duncan 1.1.2.1
26 duncan 1.1.2.1 /** Class constructor. */
27 duncan 1.1.2.1 ConstPointer(Label label, StaticState ss) {
28 duncan 1.1.2.1 super(new Object[] { label } );
29 duncan 1.1.2.1 this.ss = ss;
30 duncan 1.1.2.1 }
31 duncan 1.1.2.1
32 duncan 1.1.2.1 /** Throws an <code>Error</code>. <code>ConstPointer</code>s must
33 duncan 1.1.2.1 * remain constant */
34 duncan 1.1.2.1 public Pointer add(long offset) {
35 duncan 1.1.2.1 throw new Error("Can't add to a ConstPointer!");
36 duncan 1.1.2.1 }
37 duncan 1.1.2.1
38 duncan 1.1.2.1 /** Returns true if <code>obj</code> is a <code>ConstPointer</code> which
39 duncan 1.1.2.1 * points to the same location as this <code>ConstPointer</code>.
40 duncan 1.1.2.1 */
41 duncan 1.1.2.1 public boolean equals(Object obj) {
42 cananian 1.1.2.3 ConstPointer ptr;
43 cananian 1.1.2.3 if (this==obj) return true;
44 cananian 1.1.2.3 if (null==obj) return false;
45 duncan 1.1.2.4 if (this==NULL_POINTER || obj==NULL_POINTER) return false;
46 cananian 1.1.2.3 try { ptr = (ConstPointer)obj; }
47 cananian 1.1.2.3 catch (ClassCastException e) { return false; }
48 cananian 1.1.2.3 return ((Label)getBase()).toString().
49 cananian 1.1.2.3 equals(((Label)ptr.getBase()).toString());
50 duncan 1.1.2.1 }
51 duncan 1.1.2.1
52 duncan 1.1.2.1 /** Returns a <code>Label</code> representing the base of this
53 duncan 1.1.2.1 * <code>ConstPointer</code>.
54 duncan 1.1.2.1 */
55 duncan 1.1.2.1 public Object getBase() { return (Label)proj(0); }
56 duncan 1.1.2.1
57 duncan 1.1.2.1 /** Throws an <code>Error</code>. Since <code>ConstPointer</code>s
58 duncan 1.1.2.1 * have no offsets, it is incorrect to try to access their offsets.
59 duncan 1.1.2.1 */
60 duncan 1.1.2.1 public long getOffset() {
61 duncan 1.1.2.1 throw new Error("ConstPointers have no offsets");
62 duncan 1.1.2.1 }
63 duncan 1.1.2.1
64 duncan 1.1.2.1 /** Returns the value obtained by dereferencing this
65 duncan 1.1.2.1 * <code>ConstPointer</code>.
66 duncan 1.1.2.1 */
67 duncan 1.1.2.1 public Object getValue() {
68 duncan 1.1.2.5 return (this==NULL_POINTER) ?
69 duncan 1.1.2.5 Method.toNonNativeFormat(null) :
70 duncan 1.1.2.5 Method.toNonNativeFormat(ss.getValue(this));
71 duncan 1.1.2.1 }
72 duncan 1.1.2.1
73 duncan 1.1.2.1 /** Always returns true. */
74 duncan 1.1.2.1 public boolean isConst() { return true; }
75 duncan 1.1.2.1
76 duncan 1.1.2.1 /** Always returns false. */
77 duncan 1.1.2.1 public boolean isDerived() { return false; }
78 duncan 1.1.2.4
79 duncan 1.1.2.4 /** Returns an integer enumeration of the kind of this Pointer. The
80 duncan 1.1.2.4 enumerated values are public fields of the Pointer class.
81 duncan 1.1.2.4 */
82 duncan 1.1.2.4 public int kind() { return Pointer.CONST_PTR; }
83 duncan 1.1.2.1
84 duncan 1.1.2.1 /** If this <code>ConstPointer</code> points to a static field, then
85 duncan 1.1.2.1 * returns the type of this static field. Otherwise throws an
86 duncan 1.1.2.1 * <code>Error</code>.
87 duncan 1.1.2.1 */
88 duncan 1.1.2.1 public HClass getType() {
89 duncan 1.1.2.1 return ss.getField(this).getType();
90 duncan 1.1.2.1 }
91 duncan 1.1.2.1
92 duncan 1.1.2.1 /** If this <code>ConstPointer</code> points to a static field, then
93 duncan 1.1.2.1 * updates the value of this static field. Otherwise throws an
94 duncan 1.1.2.1 * <code>Error</code>.
95 duncan 1.1.2.1 */
96 duncan 1.1.2.1 public void updateValue(Object value) {
97 duncan 1.1.2.1 ss.updateFieldValue(this, Method.toNativeFormat(value, getType()));
98 duncan 1.1.2.1 }
99 duncan 1.1.2.1
100 duncan 1.1.2.1 /** Returns a human-readable representation of this
101 duncan 1.1.2.1 * <code>ConstPointer</code>.
102 duncan 1.1.2.1 */
103 duncan 1.1.2.1 public String toString() {
104 duncan 1.1.2.1 StringBuffer sb = new StringBuffer("ConstPtr: < ");
105 duncan 1.1.2.4 if (this==NULL_POINTER)
106 duncan 1.1.2.4 sb.append("null");
107 duncan 1.1.2.4 else
108 duncan 1.1.2.4 sb.append(getBase().toString());
109 duncan 1.1.2.1 sb.append(" >");
110 duncan 1.1.2.1 return sb.toString();
111 duncan 1.1.2.1 }
112 duncan 1.1.2.1
113 duncan 1.1.2.1 }
114 duncan 1.1.2.2
115 duncan 1.1.2.2
116 cananian 1.2