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Scala example source code file (JStackMapTableAttribute.java)
This example Scala source code file (JStackMapTableAttribute.java) is included in the DevDaily.com
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The Scala JStackMapTableAttribute.java source code
/* FJBG -- Fast Java Bytecode Generator
* Copyright 2002-2011 LAMP/EPFL
* @author Michel Schinz
*/
package ch.epfl.lamp.fjbg;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
/**
*
* @author Stephane Micheloud
* @version 1.0
*/
public class JStackMapTableAttribute extends JAttribute {
/** Constant pool of the current classfile. */
private JConstantPool pool;
/** StackMapTable entries */
protected final List/*<Frame>*/ entries = new ArrayList();
protected int entriesSize = 0;
protected boolean usesU2;
public JStackMapTableAttribute(FJBGContext context,
JClass clazz,
JCode code) {
super(context, clazz);
this.pool = clazz.pool;
assert code.getOwner().getOwner() == clazz;
}
public JStackMapTableAttribute(FJBGContext context,
JClass clazz,
Object owner,
String name,
int size,
DataInputStream stream)
throws IOException {
super(context, clazz, name);
this.pool = clazz.pool;
int count = stream.readShort();
this.usesU2 = count < 65536;
for (int i = 0; i < count; ++i)
this.entries.add(new Frame(stream));
this.entriesSize = computeSize();
assert name.equals(getName());
}
public String getName() { return "StackMapTable"; }
// Follows javap output format for StackMapTable attribute.
/*@Override*/ public String toString() {
Frame frame = null;
StringBuffer buf = new StringBuffer(" StackMapTable: number_of_entries = ");
buf.append(entries.size());
Iterator it = entries.iterator();
while (it.hasNext()) {
frame = (Frame)it.next();
buf.append("\n frame_type = ");
buf.append(frame.tag);
buf.append(" /* ");
buf.append(getFrameType(frame.tag));
buf.append(" */");
if (frame.offsetDelta != -1)
buf.append("\n offset_delta = "+frame.offsetDelta);
if (frame.locals != null)
appendTypeInfoArray(buf, "locals", frame.locals);
if (frame.stackItems != null)
appendTypeInfoArray(buf, "stack", frame.stackItems);
}
buf.append("\n");
return buf.toString();
}
protected int getSize() {
return entriesSize;
}
protected void writeContentsTo(DataOutputStream stream) throws IOException {
stream.writeShort(entriesSize);
Iterator it = entries.iterator();
while (it.hasNext()) {
Frame frame = (Frame)it.next();
frame.writeContentsTo(stream);
}
}
private class TypeInfo {
final int tag;
final int poolIndexOrOffset; // tag == 7 => poolIndex, tag = 8 => offset
private int bytes;
TypeInfo(DataInputStream stream) throws IOException {
int size = 1;
this.tag = stream.readByte();
if (tag == 7) { // ITEM_Object; // 7
poolIndexOrOffset = stream.readShort();
size += 2;
} else if (tag == 8) { // ITEM_Uninitialized // 8
poolIndexOrOffset = (usesU2) ? stream.readShort() : stream.readInt();
size += (usesU2) ? 2 : 4;
} else
poolIndexOrOffset = -1;
this.bytes += size;
}
int getSize() { return bytes; }
void writeContentsTo(DataOutputStream stream) throws IOException {
stream.writeByte(tag);
if (tag == 7) { // ITEM_Object; // 7
stream.writeShort(poolIndexOrOffset);
} else if (tag == 8) { // ITEM_Uninitialized // 8
if (usesU2) stream.writeShort(poolIndexOrOffset);
else stream.writeInt(poolIndexOrOffset);
}
}
/*@Override*/ public String toString() {
switch (tag) {
case 0: // ITEM_Top
return "<top>";
case 1: // ITEM_Integer
return "int";
case 2: // ITEM_Float
return "float";
case 3: // ITEM_Double
return "double";
case 4: // ITEM_Long
return "long";
case 5: // ITEM_Null
return "null";
case 6: // ITEM_UninializedThis
return "this";
case 7: // ITEM_Object
String name = pool.lookupClass(poolIndexOrOffset);
if (name.startsWith("[")) name = "\""+name+"\"";
return "class "+name;
case 8: // ITEM_Uninitialized
return "<uninitialized>";
default:
return String.valueOf(tag);
}
}
}
private class Frame {
final int tag;
int offsetDelta = -1;
TypeInfo[] stackItems = null;
TypeInfo[] locals = null;
private int bytes;
Frame(DataInputStream stream) throws IOException {
// The stack_map_frame structure consists of a one-byte tag
// followed by zero or more bytes.
this.tag = stream.readUnsignedByte();
if (tag < 64) { // SAME; // 0-63
//done
} else if (tag < 128) { // SAME_LOCALS_1_STACK_ITEM; // 64-127
this.offsetDelta = tag - 64;
readStackItems(stream, 1);
} else if (tag < 248) { // reserved for future use.
assert false : "Tags in the range [128-247] are reserved for future use.";
} else if (tag < 251) { // CHOP; // 248-250
int k = 251 - tag;
readOffsetDelta(stream);
} else if (tag == 251) { // SAME_FRAME_EXTENDED
readOffsetDelta(stream);
} else if (tag < 255) { // APPEND; // 252-254
readOffsetDelta(stream);
readLocals(stream, tag - 251);
} else { // FULL_FRAME; // 255
readOffsetDelta(stream);
readLocals(stream);
readStackItems(stream);
}
}
int getSize() { return bytes; }
void readOffsetDelta(DataInputStream stream) throws IOException {
this.offsetDelta = (usesU2) ? stream.readShort() : stream.readInt();
this.bytes += (usesU2) ? 2 : 4;
}
int getOffsetDelta() { return offsetDelta; }
void readStackItems(DataInputStream stream, int k) throws IOException {
this.stackItems = new TypeInfo[k];
for (int i = 0; i < k; ++i) {
stackItems[i] = new TypeInfo(stream);
this.bytes += stackItems[i].getSize();
}
}
void readStackItems(DataInputStream stream) throws IOException {
int k = (usesU2) ? stream.readShort() : stream.readInt();
this.bytes += (usesU2) ? 2 : 4;
readStackItems(stream, k);
}
void readLocals(DataInputStream stream, int k) throws IOException {
this.locals = new TypeInfo[k];
for (int i = 0; i < k; ++i) {
locals[i] = new TypeInfo(stream);
this.bytes += locals[i].getSize();
}
}
void readLocals(DataInputStream stream) throws IOException {
int k = (usesU2) ? stream.readShort() : stream.readInt();
this.bytes += (usesU2) ? 2 : 4;
readLocals(stream, k);
}
void writeContentsTo(DataOutputStream stream) throws IOException {
stream.writeByte(tag);
if (tag < 64) {
//done
} else if (tag < 128) { // SAME; // 0-63
assert stackItems.length == 1;
stackItems[0].writeContentsTo(stream);
} else if (tag < 248) {
assert false : "Tags in the range [128-247] are reserved for future use.";
} else if (tag < 251) {
if (usesU2) stream.writeShort(offsetDelta);
else stream.writeInt(offsetDelta);
} else if (tag == 251) {
if (usesU2) stream.writeShort(offsetDelta);
else stream.writeInt(offsetDelta);
} else if (tag < 255) { // APPEND; // 252-254
if (usesU2) stream.writeShort(offsetDelta);
else stream.writeInt(offsetDelta);
for (int i = 0; i < locals.length; ++i)
locals[i].writeContentsTo(stream);
} else {
if (usesU2) stream.writeShort(offsetDelta);
else stream.writeInt(offsetDelta);
for (int i = 0; i < locals.length; ++i)
locals[i].writeContentsTo(stream);
for (int i = 0; i < stackItems.length; ++i)
stackItems[i].writeContentsTo(stream);
}
}
}
private int computeSize() {
int size = (usesU2) ? 2 : 4; // number of frames
Iterator it = entries.iterator();
while (it.hasNext()) {
Frame frame = (Frame)it.next();
size += frame.getSize();
}
return size;
}
private static final String getFrameType(int tag) {
if (tag < 64) return "same";
else if (tag < 128) return "same locals 1 stack item";
else if (tag < 248) return "
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