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jonathan-gibbonsjonathan-gibbons
committedDec 9, 2019
8234689: facilitate writing additional custom attributes in a class file
Reviewed-by: jlahoda
·
jdk-15+1JEP-429-branchpoint
1 parent 93286c9 commit 589f235

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2 files changed

+184
-7
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2 files changed

+184
-7
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‎src/jdk.compiler/share/classes/com/sun/tools/javac/jvm/ClassWriter.java

+29-7
Original file line numberDiff line numberDiff line change
@@ -30,6 +30,7 @@
3030
import java.util.Map;
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import java.util.Set;
3232
import java.util.LinkedHashSet;
33+
import java.util.function.Function;
3334

3435
import javax.tools.JavaFileManager;
3536
import javax.tools.FileObject;
@@ -113,6 +114,8 @@ public class ClassWriter extends ClassFile {
113114
*/
114115
public boolean multiModuleMode;
115116

117+
private List<Function<Symbol, Integer>> extraAttributeHooks = List.nil();
118+
116119
/** The initial sizes of the data and constant pool buffers.
117120
* Sizes are increased when buffers get full.
118121
*/
@@ -121,7 +124,7 @@ public class ClassWriter extends ClassFile {
121124

122125
/** An output buffer for member info.
123126
*/
124-
ByteBuffer databuf = new ByteBuffer(DATA_BUF_SIZE);
127+
public ByteBuffer databuf = new ByteBuffer(DATA_BUF_SIZE);
125128

126129
/** An output buffer for the constant pool.
127130
*/
@@ -188,6 +191,10 @@ protected ClassWriter(Context context) {
188191
}
189192
}
190193

194+
public void addExtraAttributes(Function<Symbol, Integer> addExtraAttributes) {
195+
extraAttributeHooks = extraAttributeHooks.prepend(addExtraAttributes);
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}
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191198
/******************************************************************
192199
* Diagnostics: dump generated class names and modifiers
193200
******************************************************************/
@@ -276,7 +283,7 @@ public StringOverflow(String s) {
276283
/** Write header for an attribute to data buffer and return
277284
* position past attribute length index.
278285
*/
279-
int writeAttr(Name attrName) {
286+
public int writeAttr(Name attrName) {
280287
int index = poolWriter.putName(attrName);
281288
databuf.appendChar(index);
282289
databuf.appendInt(0);
@@ -285,7 +292,7 @@ int writeAttr(Name attrName) {
285292

286293
/** Fill in attribute length.
287294
*/
288-
void endAttr(int index) {
295+
public void endAttr(int index) {
289296
putInt(databuf, index - 4, databuf.length - index);
290297
}
291298

@@ -942,6 +949,7 @@ void writeField(VarSymbol v) {
942949
acount++;
943950
}
944951
acount += writeMemberAttrs(v, false);
952+
acount += writeExtraAttributes(v);
945953
endAttrs(acountIdx, acount);
946954
}
947955

@@ -988,6 +996,7 @@ void writeMethod(MethodSymbol m) {
988996
acount += writeMemberAttrs(m, false);
989997
if (!m.isLambdaMethod())
990998
acount += writeParameterAttrs(m.params);
999+
acount += writeExtraAttributes(m);
9911000
endAttrs(acountIdx, acount);
9921001
}
9931002

@@ -1605,6 +1614,7 @@ public void writeClassFile(OutputStream out, ClassSymbol c)
16051614
acount += writeFlagAttrs(c.owner.flags() & ~DEPRECATED);
16061615
}
16071616
acount += writeExtraClassAttributes(c);
1617+
acount += writeExtraAttributes(c);
16081618

16091619
poolbuf.appendInt(JAVA_MAGIC);
16101620
if (preview.isEnabled()) {
@@ -1643,14 +1653,26 @@ public void writeClassFile(OutputStream out, ClassSymbol c)
16431653
poolWriter.reset(); // to save space
16441654

16451655
out.write(databuf.elems, 0, databuf.length);
1646-
}
1656+
}
1657+
1658+
/**Allows subclasses to write additional class attributes
1659+
*
1660+
* @return the number of attributes written
1661+
*/
1662+
protected int writeExtraClassAttributes(ClassSymbol c) {
1663+
return 0;
1664+
}
16471665

1648-
/**Allows subclasses to write additional class attributes
1666+
/**Allows friends to write additional attributes
16491667
*
16501668
* @return the number of attributes written
16511669
*/
1652-
protected int writeExtraClassAttributes(ClassSymbol c) {
1653-
return 0;
1670+
protected int writeExtraAttributes(Symbol sym) {
1671+
int i = 0;
1672+
for (Function<Symbol, Integer> hook : extraAttributeHooks) {
1673+
i += hook.apply(sym);
1674+
}
1675+
return i;
16541676
}
16551677

16561678
int adjustFlags(final long flags) {

‎test/langtools/tools/javac/classwriter/ExtraAttributes.java

+155
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,155 @@
1+
/*
2+
* Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
3+
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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+
24+
/*
25+
* @test
26+
* @bug 8234689
27+
* @summary facilitate writing additional custom attributes in a class file
28+
* @library /tools/lib
29+
* @modules jdk.compiler/com.sun.tools.javac.api
30+
* jdk.compiler/com.sun.tools.javac.code
31+
* jdk.compiler/com.sun.tools.javac.jvm
32+
* jdk.compiler/com.sun.tools.javac.main
33+
* jdk.compiler/com.sun.tools.javac.util
34+
* jdk.jdeps/com.sun.tools.javap
35+
* @build toolbox.JarTask toolbox.JavacTask toolbox.JavapTask toolbox.ToolBox
36+
* @run main ExtraAttributes
37+
*/
38+
39+
import java.nio.file.Files;
40+
import java.nio.file.Path;
41+
import java.util.List;
42+
43+
import com.sun.source.util.JavacTask;
44+
import com.sun.source.util.Plugin;
45+
46+
import com.sun.tools.javac.api.BasicJavacTask;
47+
import com.sun.tools.javac.code.Symbol;
48+
import com.sun.tools.javac.jvm.ClassWriter;
49+
import com.sun.tools.javac.util.Context;
50+
import com.sun.tools.javac.util.Name;
51+
import com.sun.tools.javac.util.Names;
52+
53+
import toolbox.JarTask;
54+
import toolbox.JavapTask;
55+
import toolbox.Task;
56+
import toolbox.ToolBox;
57+
58+
59+
public class ExtraAttributes implements Plugin {
60+
public static void main(String... args) throws Exception {
61+
new ExtraAttributes().run();
62+
}
63+
64+
void run() throws Exception {
65+
ToolBox tb = new ToolBox();
66+
Path pluginClasses = Path.of("plugin-classes");
67+
tb.writeFile(pluginClasses.resolve("META-INF").resolve("services").resolve(Plugin.class.getName()),
68+
ExtraAttributes.class.getName() + "\n");
69+
Files.copy(Path.of(ToolBox.testClasses).resolve("ExtraAttributes.class"),
70+
pluginClasses.resolve("ExtraAttributes.class"));
71+
72+
Path pluginJar = Path.of("plugin.jar");
73+
new JarTask(tb, pluginJar)
74+
.baseDir(pluginClasses)
75+
.files(".")
76+
.run();
77+
78+
Path src = Path.of("src");
79+
tb.writeJavaFiles(src,
80+
"public class HelloWorld {\n"
81+
+ " public static String message = \"Hello World!\";\n"
82+
+ " public static void main(String... args) {\n"
83+
+ " System.out.println(message);\n"
84+
+ " }\n"
85+
+ "}\n");
86+
87+
List<String> stdout = new toolbox.JavacTask(tb)
88+
.classpath(pluginJar)
89+
.options("-Xplugin:ExtraAttributes")
90+
.outdir(Files.createDirectories(Path.of("classes")))
91+
.files(tb.findJavaFiles(src))
92+
.run()
93+
.writeAll()
94+
.getOutputLines(Task.OutputKind.STDOUT);
95+
96+
// cannot rely on order of output, so sort it
97+
stdout.sort(CharSequence::compare);
98+
99+
tb.checkEqual(stdout,
100+
List.of(
101+
"Add attributes for <clinit>()",
102+
"Add attributes for HelloWorld",
103+
"Add attributes for HelloWorld()",
104+
"Add attributes for main(java.lang.String...)",
105+
"Add attributes for message"
106+
));
107+
108+
List<String> lines = new JavapTask(tb)
109+
.options("-p",
110+
"-v",
111+
Path.of("classes").resolve("HelloWorld.class").toString())
112+
.run()
113+
.getOutputLines(Task.OutputKind.DIRECT);
114+
115+
long attrs = lines.stream()
116+
.filter(s -> s.contains("testAttr:"))
117+
.count();
118+
if (attrs != 5) {
119+
throw new Exception("expected attributes not found; expected: 5; found: " + attrs);
120+
}
121+
}
122+
123+
// Plugin impl...
124+
125+
private ClassWriter classWriter;
126+
private Names names;
127+
128+
@Override
129+
public String getName() { return "ExtraAttributes"; }
130+
131+
@Override
132+
public void init(JavacTask task, String... args) {
133+
Context c = ((BasicJavacTask) task).getContext();
134+
classWriter = ClassWriter.instance(c);
135+
names = Names.instance(c);
136+
137+
// register callback
138+
classWriter.addExtraAttributes(this::addExtraAttributes);
139+
}
140+
141+
@Override
142+
public boolean autoStart() {
143+
return true;
144+
}
145+
146+
private int addExtraAttributes(Symbol sym) {
147+
System.out.println("Add attributes for " + sym);
148+
Name testAttr = names.fromString("testAttr");
149+
int alenIdx = classWriter.writeAttr(testAttr);
150+
classWriter.databuf.appendChar(42);
151+
classWriter.endAttr(alenIdx);
152+
return 1;
153+
}
154+
}
155+

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