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Copy pathInMemAOT.java
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72 lines (67 loc) · 2.75 KB
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import javax.tools.*;
import java.io.*;
import java.net.*;
import java.util.*;
import java.util.concurrent.*;
import static java.util.stream.Collectors.*;
public class InMemAOT {
// ----- in-memory source -----
static class StringSource extends SimpleJavaFileObject {
final String code;
StringSource(String name, String code) {
super(URI.create("string:///" + name.replace('.','/') + Kind.SOURCE.extension), Kind.SOURCE);
this.code = code;
}
@Override public CharSequence getCharContent(boolean ignore) { return code; }
}
// ----- in-memory class file -----
static class MemClass extends SimpleJavaFileObject {
final ByteArrayOutputStream bos = new ByteArrayOutputStream();
MemClass(String name) {
super(URI.create("mem:///" + name.replace('.','/') + Kind.CLASS.extension), Kind.CLASS);
}
@Override public OutputStream openOutputStream() { return bos; }
byte[] bytes() { return bos.toByteArray(); }
}
// ----- file manager collecting bytecode -----
static class MemFM extends ForwardingJavaFileManager<JavaFileManager> {
final Map<String,MemClass> classes = new ConcurrentHashMap<>();
MemFM(JavaFileManager fm) { super(fm); }
@Override public JavaFileObject getJavaFileForOutput(Location l, String className, JavaFileObject.Kind k, FileObject sibling) {
var mc = new MemClass(className);
classes.put(className, mc);
return mc;
}
}
// ----- classloader that defines from memory -----
static class MemLoader extends ClassLoader {
Class<?> define(String name, byte[] bytes) { return defineClass(name, bytes, 0, bytes.length); }
}
public static void main(String[] args) throws Exception {
int N = (args.length>0) ? Integer.parseInt(args[0]) : 5000;
var jc = ToolProvider.getSystemJavaCompiler();
var fm = new MemFM(jc.getStandardFileManager(null, null, null));
// generate N tiny classes in package dyn: dyn.Ci#id()
var sources = new ArrayList<JavaFileObject>(N);
for (int i=0;i<N;i++) {
var name = "dyn.C"+i;
var code = "package dyn; public class C"+i+"{ public int id(){ return "+i+"; }}";
sources.add(new StringSource(name, code));
}
// compile all to memory
var opts = List.of("-g:none", "-proc:none");
if (!jc.getTask(null, fm, null, opts, null, sources).call())
throw new RuntimeException("compile failed");
// load + link + invoke to force resolution
var loader = new MemLoader();
long sum = 0;
for (int i=0;i<N;i++) {
var name = "dyn.C"+i;
var bytes = fm.classes.get(name).bytes();
var c = loader.define(name, bytes);
var o = c.getDeclaredConstructor().newInstance();
sum += (int) c.getMethod("id").invoke(o);
}
System.out.println(sum); // prevent dead-code elimination
}
}