1 package serp.bytecode;
2
3 import java.io.*;
4 import java.util.*;
5
6 import serp.bytecode.lowlevel.*;
7 import serp.bytecode.visitor.*;
8
9 /***
10 * Abstract superclass for all bytecode entities that hold attributes.
11 *
12 * @author Abe White
13 */
14 public abstract class Attributes implements BCEntity {
15 /***
16 * Return all the attributes owned by this entity.
17 *
18 * @return all owned attributes, or empty array if none
19 */
20 public Attribute[] getAttributes() {
21 Collection attrs = getAttributesHolder();
22 return (Attribute[]) attrs.toArray(new Attribute[attrs.size()]);
23 }
24
25 /***
26 * Return the attribute with the given name. If multiple attributes
27 * share the name, which is returned is undefined.
28 */
29 public Attribute getAttribute(String name) {
30 Collection attrs = getAttributesHolder();
31 Attribute attr;
32 for (Iterator itr = attrs.iterator(); itr.hasNext();) {
33 attr = (Attribute) itr.next();
34 if (attr.getName().equals(name))
35 return attr;
36 }
37 return null;
38 }
39
40 /***
41 * Return all attributes with the given name.
42 *
43 * @return the matching attributes, or empty array if none
44 */
45 public Attribute[] getAttributes(String name) {
46 List matches = new LinkedList();
47 Collection attrs = getAttributesHolder();
48 Attribute attr;
49 for (Iterator itr = attrs.iterator(); itr.hasNext();) {
50 attr = (Attribute) itr.next();
51 if (attr.getName().equals(name))
52 matches.add(attr);
53 }
54 return (Attribute[]) matches.toArray(new Attribute[matches.size()]);
55 }
56
57 /***
58 * Set the attributes for this entity; this method is useful for importing
59 * all attributes from another entity. Set to null or empty array if none.
60 */
61 public void setAttributes(Attribute[] attrs) {
62 clearAttributes();
63 if (attrs != null)
64 for (int i = 0; i < attrs.length; i++)
65 addAttribute(attrs[i]);
66 }
67
68 /***
69 * Import an attribute from another entity, or make a copy of one
70 * on this entity.
71 */
72 public Attribute addAttribute(Attribute attr) {
73 Attribute newAttr = addAttribute(attr.getName());
74 newAttr.read(attr);
75 return newAttr;
76 }
77
78 /***
79 * Add an attribute of the given type.
80 */
81 public Attribute addAttribute(String name) {
82 Attribute attr = Attribute.create(name, this);
83 getAttributesHolder().add(attr);
84 return attr;
85 }
86
87 /***
88 * Clear all attributes from this entity.
89 */
90 public void clearAttributes() {
91 Collection attrs = getAttributesHolder();
92 Attribute attr;
93 for (Iterator itr = attrs.iterator(); itr.hasNext();) {
94 attr = (Attribute) itr.next();
95 itr.remove();
96 attr.invalidate();
97 }
98 }
99
100 /***
101 * Remove all attributes with the given name from this entity.
102 *
103 * @return true if an attribute was removed, false otherwise
104 */
105 public boolean removeAttribute(String name) {
106 return removeAttribute(getAttribute(name));
107 }
108
109 /***
110 * Remove the given attribute. After being removed, the attribute
111 * is invalid, and the result of any operations on it are undefined.
112 *
113 * @return true if the attribute was removed, false otherwise
114 */
115 public boolean removeAttribute(Attribute attribute) {
116 if ((attribute == null) || !getAttributesHolder().remove(attribute))
117 return false;
118 attribute.invalidate();
119 return true;
120 }
121
122 /***
123 * Convenience method to be called by BCEntities when being visited
124 * by a {@link BCVisitor}; this method will allow the visitor to visit all
125 * attributes of this entity.
126 */
127 void visitAttributes(BCVisitor visit) {
128 Attribute attr;
129 for (Iterator itr = getAttributesHolder().iterator(); itr.hasNext();) {
130 attr = (Attribute) itr.next();
131 visit.enterAttribute(attr);
132 attr.acceptVisit(visit);
133 visit.exitAttribute(attr);
134 }
135 }
136
137 /***
138 * Build the attribute list from the given stream.
139 * Relies on the ability of attributes to read themselves, and
140 * requires access to the constant pool, which must already by read.
141 */
142 void readAttributes(DataInput in) throws IOException {
143 Collection attrs = getAttributesHolder();
144 attrs.clear();
145
146 Attribute attribute;
147 String name;
148 for (int i = in.readUnsignedShort(); i > 0; i--) {
149 name = ((UTF8Entry) getPool().getEntry(in.readUnsignedShort())).
150 getValue();
151 attribute = addAttribute(name);
152 attribute.read(in, in.readInt());
153 }
154 }
155
156 /***
157 * Writes all the owned attributes to the given stream.
158 * Relies on the ability of attributes to write themselves.
159 */
160 void writeAttributes(DataOutput out) throws IOException {
161 Collection attrs = getAttributesHolder();
162 out.writeShort(attrs.size());
163
164 Attribute attribute;
165 int length;
166 for (Iterator itr = attrs.iterator(); itr.hasNext();) {
167 attribute = (Attribute) itr.next();
168 out.writeShort(attribute.getNameIndex());
169 length = attribute.getLength();
170 out.writeInt(length);
171 attribute.write(out, length);
172 }
173 }
174
175 /***
176 * Return the collection used to hold the attributes of this entity.
177 */
178 abstract Collection getAttributesHolder();
179 }