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Java > Open Source Codes > com > tc > asm > Attribute


1 /***
2  * ASM: a very small and fast Java bytecode manipulation framework
3  * Copyright (c) 2000-2005 INRIA, France Telecom
4  * All rights reserved.
5  *
6  * Redistribution and use in source and binary forms, with or without
7  * modification, are permitted provided that the following conditions
8  * are met:
9  * 1. Redistributions of source code must retain the above copyright
10  * notice, this list of conditions and the following disclaimer.
11  * 2. Redistributions in binary form must reproduce the above copyright
12  * notice, this list of conditions and the following disclaimer in the
13  * documentation and/or other materials provided with the distribution.
14  * 3. Neither the name of the copyright holders nor the names of its
15  * contributors may be used to endorse or promote products derived from
16  * this software without specific prior written permission.
17  *
18  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
19  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
22  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
23  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
24  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
25  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
26  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
27  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
28  * THE POSSIBILITY OF SUCH DAMAGE.
29  */

30 package com.tc.asm;
31
32 /**
33  * A non standard class, field, method or code attribute.
34  *
35  * @author Eric Bruneton
36  * @author Eugene Kuleshov
37  */

38 public class Attribute {
39
40     /**
41      * The type of this attribute.
42      */

43     public final String JavaDoc type;
44
45     /**
46      * The raw value of this attribute, used only for unknown attributes.
47      */

48     byte[] value;
49     
50     /**
51      * The next attribute in this attribute list. May be <tt>null</tt>.
52      */

53     Attribute next;
54
55     /**
56      * Constructs a new empty attribute.
57      *
58      * @param type the type of the attribute.
59      */

60     protected Attribute(final String JavaDoc type) {
61         this.type = type;
62     }
63
64     /**
65      * Returns <tt>true</tt> if this type of attribute is unknown. The default
66      * implementation of this method always returns <tt>true</tt>.
67      *
68      * @return <tt>true</tt> if this type of attribute is unknown.
69      */

70     public boolean isUnknown() {
71         return true;
72     }
73
74     /**
75      * Returns <tt>true</tt> if this type of attribute is a code attribute.
76      *
77      * @return <tt>true</tt> if this type of attribute is a code attribute.
78      */

79     public boolean isCodeAttribute() {
80         return false;
81     }
82
83     /**
84      * Returns the labels corresponding to this attribute.
85      *
86      * @return the labels corresponding to this attribute, or <tt>null</tt> if
87      * this attribute is not a code attribute that contains labels.
88      */

89     protected Label[] getLabels() {
90         return null;
91     }
92
93     /**
94      * Reads a {@link #type type} attribute. This method must return a <i>new</i>
95      * {@link Attribute} object, of type {@link #type type}, corresponding to
96      * the <tt>len</tt> bytes starting at the given offset, in the given class
97      * reader.
98      *
99      * @param cr the class that contains the attribute to be read.
100      * @param off index of the first byte of the attribute's content in {@link
101      * ClassReader#b cr.b}. The 6 attribute header bytes, containing the
102      * type and the length of the attribute, are not taken into account
103      * here.
104      * @param len the length of the attribute's content.
105      * @param buf buffer to be used to call
106      * {@link ClassReader#readUTF8 readUTF8},
107      * {@link ClassReader#readClass(int,char[]) readClass} or
108      * {@link ClassReader#readConst readConst}.
109      * @param codeOff index of the first byte of code's attribute content in
110      * {@link ClassReader#b cr.b}, or -1 if the attribute to be read is
111      * not a code attribute. The 6 attribute header bytes, containing the
112      * type and the length of the attribute, are not taken into account
113      * here.
114      * @param labels the labels of the method's code, or <tt>null</tt> if the
115      * attribute to be read is not a code attribute.
116      * @return a <i>new</i> {@link Attribute} object corresponding to the given
117      * bytes.
118      */

119     protected Attribute read(
120         ClassReader cr,
121         int off,
122         int len,
123         char[] buf,
124         int codeOff,
125         Label[] labels)
126     {
127         Attribute attr = new Attribute(type);
128         attr.value = new byte[len];
129         System.arraycopy(cr.b, off, attr.value, 0, len);
130         return attr;
131     }
132
133     /**
134      * Returns the byte array form of this attribute.
135      *
136      * @param cw the class to which this attribute must be added. This parameter
137      * can be used to add to the constant pool of this class the items
138      * that corresponds to this attribute.
139      * @param code the bytecode of the method corresponding to this code
140      * attribute, or <tt>null</tt> if this attribute is not a code
141      * attributes.
142      * @param len the length of the bytecode of the method corresponding to this
143      * code attribute, or <tt>null</tt> if this attribute is not a code
144      * attribute.
145      * @param maxStack the maximum stack size of the method corresponding to
146      * this code attribute, or -1 if this attribute is not a code
147      * attribute.
148      * @param maxLocals the maximum number of local variables of the method
149      * corresponding to this code attribute, or -1 if this attribute is
150      * not a code attribute.
151      * @return the byte array form of this attribute.
152      */

153     protected ByteVector write(
154         ClassWriter cw,
155         byte[] code,
156         int len,
157         int maxStack,
158         int maxLocals)
159     {
160         ByteVector v = new ByteVector();
161         v.data = value;
162         v.length = value.length;
163         return v;
164     }
165
166     /**
167      * Returns the length of the attribute list that begins with this attribute.
168      *
169      * @return the length of the attribute list that begins with this attribute.
170      */

171     final int getCount() {
172         int count = 0;
173         Attribute attr = this;
174         while (attr != null) {
175             count += 1;
176             attr = attr.next;
177         }
178         return count;
179     }
180
181     /**
182      * Returns the size of all the attributes in this attribute list.
183      *
184      * @param cw the class writer to be used to convert the attributes into byte
185      * arrays, with the {@link #write write} method.
186      * @param code the bytecode of the method corresponding to these code
187      * attributes, or <tt>null</tt> if these attributes are not code
188      * attributes.
189      * @param len the length of the bytecode of the method corresponding to
190      * these code attributes, or <tt>null</tt> if these attributes are
191      * not code attributes.
192      * @param maxStack the maximum stack size of the method corresponding to
193      * these code attributes, or -1 if these attributes are not code
194      * attributes.
195      * @param maxLocals the maximum number of local variables of the method
196      * corresponding to these code attributes, or -1 if these attributes
197      * are not code attributes.
198      * @return the size of all the attributes in this attribute list. This size
199      * includes the size of the attribute headers.
200      */

201     final int getSize(
202         final ClassWriter cw,
203         final byte[] code,
204         final int len,
205         final int maxStack,
206         final int maxLocals)
207     {
208         Attribute attr = this;
209         int size = 0;
210         while (attr != null) {
211             cw.newUTF8(attr.type);
212             size += attr.write(cw, code, len, maxStack, maxLocals).length + 6;
213             attr = attr.next;
214         }
215         return size;
216     }
217
218     /**
219      * Writes all the attributes of this attribute list in the given byte
220      * vector.
221      *
222      * @param cw the class writer to be used to convert the attributes into byte
223      * arrays, with the {@link #write write} method.
224      * @param code the bytecode of the method corresponding to these code
225      * attributes, or <tt>null</tt> if these attributes are not code
226      * attributes.
227      * @param len the length of the bytecode of the method corresponding to
228      * these code attributes, or <tt>null</tt> if these attributes are
229      * not code attributes.
230      * @param maxStack the maximum stack size of the method corresponding to
231      * these code attributes, or -1 if these attributes are not code
232      * attributes.
233      * @param maxLocals the maximum number of local variables of the method
234      * corresponding to these code attributes, or -1 if these attributes
235      * are not code attributes.
236      * @param out where the attributes must be written.
237      */

238     final void put(
239         final ClassWriter cw,
240         final byte[] code,
241         final int len,
242         final int maxStack,
243         final int maxLocals,
244         final ByteVector out)
245     {
246         Attribute attr = this;
247         while (attr != null) {
248             ByteVector b = attr.write(cw, code, len, maxStack, maxLocals);
249             out.putShort(cw.newUTF8(attr.type)).putInt(b.length);
250             out.putByteArray(b.data, 0, b.length);
251             attr = attr.next;
252         }
253     }
254 }
255
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