1 /*
2 * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.
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
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 */
23 package org.graalvm.compiler.replacements.classfile;
24
25 import java.io.DataInputStream;
26 import java.io.IOException;
27 import java.lang.reflect.Modifier;
28 import java.util.ArrayList;
29 import java.util.List;
30
31 import org.graalvm.compiler.replacements.classfile.ClassfileConstant.Utf8;
32
33 import jdk.vm.ci.meta.ResolvedJavaMethod;
34 import jdk.vm.ci.meta.ResolvedJavaType;
35
36 /**
37 * Container for objects representing the {@code Code} attributes parsed from a class file.
38 *
39 * @see <a href="https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.7.3">Code
40 * attributes</a>
41 * @see <a href="https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.4">Constant
42 * Pool</a>
43 */
44 public class Classfile {
45
46 private final ResolvedJavaType type;
47 private final List<ClassfileBytecode> codeAttributes;
48
49 private static final int MAJOR_VERSION_JAVA7 = 51;
50 private static final int MAJOR_VERSION_JAVA9 = 53;
51
52 /**
53 * Creates a {@link Classfile} by parsing the class file bytes for {@code type} loadable from
54 * {@code context}.
55 *
56 * @throws NoClassDefFoundError if there is an IO error while parsing the class file
57 */
58 public Classfile(ResolvedJavaType type, DataInputStream stream, ClassfileBytecodeProvider context) throws IOException {
59 this.type = type;
60
61 // magic
62 int magic = stream.readInt();
63 assert magic == 0xCAFEBABE;
64
65 int minor = stream.readUnsignedShort();
66 int major = stream.readUnsignedShort();
67 if (major < MAJOR_VERSION_JAVA7 || major > MAJOR_VERSION_JAVA9) {
68 throw new UnsupportedClassVersionError("Unsupported class file version: " + major + "." + minor);
69 }
70
71 ClassfileConstantPool cp = new ClassfileConstantPool(stream, context);
72
73 // access_flags, this_class, super_class
74 skipFully(stream, 6);
75
76 // interfaces
77 skipFully(stream, stream.readUnsignedShort() * 2);
78
79 // fields
80 skipFields(stream);
81
82 // methods
83 codeAttributes = readMethods(stream, cp);
84
85 // attributes
86 skipAttributes(stream);
87 }
88
89 public ClassfileBytecode getCode(String name, String descriptor) {
90 for (ClassfileBytecode code : codeAttributes) {
91 ResolvedJavaMethod method = code.getMethod();
92 if (method.getName().equals(name) && method.getSignature().toMethodDescriptor().equals(descriptor)) {
93 return code;
94 }
95 }
96 throw new NoSuchMethodError(type.toJavaName() + "." + name + descriptor);
97 }
98
99 private static void skipAttributes(DataInputStream stream) throws IOException {
100 int attributesCount;
101 attributesCount = stream.readUnsignedShort();
102 for (int i = 0; i < attributesCount; i++) {
103 skipFully(stream, 2); // name_index
104 int attributeLength = stream.readInt();
105 skipFully(stream, attributeLength);
106 }
107 }
108
109 static void skipFully(DataInputStream stream, int n) throws IOException {
110 long skipped = 0;
111 do {
112 long s = stream.skip(n - skipped);
113 skipped += s;
114 if (s == 0 && skipped != n) {
115 // Check for EOF (i.e., truncated class file)
116 if (stream.read() == -1) {
117 throw new IOException("truncated stream");
118 }
119 skipped++;
120 }
121 } while (skipped != n);
122 }
123
124 private ClassfileBytecode findCodeAttribute(DataInputStream stream, ClassfileConstantPool cp, String name, String descriptor, boolean isStatic) throws IOException {
125 int attributesCount;
126 attributesCount = stream.readUnsignedShort();
127 ClassfileBytecode code = null;
128 for (int i = 0; i < attributesCount; i++) {
129 String attributeName = cp.get(Utf8.class, stream.readUnsignedShort()).value;
130 int attributeLength = stream.readInt();
131 if (code == null && attributeName.equals("Code")) {
132 ResolvedJavaMethod method = ClassfileBytecodeProvider.findMethod(type, name, descriptor, isStatic);
133 // Even if we will discard the Code attribute (see below), we still
134 // need to parse it to reach the following class file content.
135 code = new ClassfileBytecode(method, stream, cp);
136 if (method == null) {
137 // This is a method hidden from reflection
138 // (see sun.reflect.Reflection.filterMethods)
139 code = null;
140 }
141 } else {
142 skipFully(stream, attributeLength);
143 }
144 }
145 return code;
146 }
147
148 private static void skipFields(DataInputStream stream) throws IOException {
149 int count = stream.readUnsignedShort();
150 for (int i = 0; i < count; i++) {
151 skipFully(stream, 6); // access_flags, name_index, descriptor_index
152 skipAttributes(stream);
153 }
154 }
155
156 private List<ClassfileBytecode> readMethods(DataInputStream stream, ClassfileConstantPool cp) throws IOException {
157 int count = stream.readUnsignedShort();
158 List<ClassfileBytecode> result = new ArrayList<>(count);
159 for (int i = 0; i < count; i++) {
160 int accessFlags = stream.readUnsignedShort();
161 boolean isStatic = Modifier.isStatic(accessFlags);
162 String name = cp.get(Utf8.class, stream.readUnsignedShort()).value;
163 String descriptor = cp.get(Utf8.class, stream.readUnsignedShort()).value;
164 ClassfileBytecode code = findCodeAttribute(stream, cp, name, descriptor, isStatic);
165 if (code != null) {
166 result.add(code);
167 }
168 }
169 return result;
170 }
171
172 @Override
173 public String toString() {
174 return getClass().getSimpleName() + "<" + type.toJavaName() + ">";
175 }
176 }