* Note that this implementation does not calculate StackMapFrame structures * from the method bytecode. If method code is changed or generated from scratch, * then developer is responsible to prepare a correct StackMapFrame structures. *
* The format of the stack map in the class file is given below. In the following, *
* stack_map { // attribute StackMap
* u2 attribute_name_index;
* u4 attribute_length
* uoffset number_of_entries;
* stack_map_frame entries[number_of_entries];
* }
*
* Each stack map frame has the following format:
*
* stack_map_frame {
* uoffset offset;
* ulocalvar number_of_locals;
* verification_type_info locals[number_of_locals];
* ustack number_of_stack_items;
* verification_type_info stack[number_of_stack_items];
* }
*
* The verification_type_info structure consists of a one-byte tag
* followed by zero or more bytes, giving more information about the tag.
* Each verification_type_info structure specifies the verification
* type of one or two locations.
*
* union verification_type_info {
* Top_variable_info;
* Integer_variable_info;
* Float_variable_info;
* Long_variable_info;
* Double_variable_info;
* Null_variable_info;
* UninitializedThis_variable_info;
* Object_variable_info;
* Uninitialized_variable_info;
* }
*
* Top_variable_info {
* u1 tag = ITEM_Top; // 0
* }
*
* Integer_variable_info {
* u1 tag = ITEM_Integer; // 1
* }
*
* Float_variable_info {
* u1 tag = ITEM_Float; // 2
* }
*
* Long_variable_info {
* u1 tag = ITEM_Long; // 4
* }
*
* Double_variable_info {
* u1 tag = ITEM_Double; // 3
* }
*
* Null_variable_info {
* u1 tag = ITEM_Null; // 5
* }
*
* UninitializedThis_variable_info {
* u1 tag = ITEM_UninitializedThis; // 6
* }
*
* Object_variable_info {
* u1 tag = ITEM_Object; // 7
* u2 cpool_index;
* }
*
* Uninitialized_variable_info {
* u1 tag = ITEM_Uninitialized // 8
* uoffset offset;
* }
*
*
* @see JSR 139 : Connected
* Limited Device Configuration 1.1
*
* @author Eugene Kuleshov
*/
public class StackMapAttribute extends Attribute implements Dumpable {
static final int MAX_SIZE = 65535;
public LinkedList frames = new LinkedList();
public StackMapAttribute () {
super("StackMap");
}
public StackMapFrame getFrame (Label label) {
for (int i = 0; i < frames.size(); i++) {
StackMapFrame frame = (StackMapFrame)frames.get(i);
if (frame.label == label) {
return frame;
}
}
return null;
}
protected Attribute read (ClassReader cr, int off, int len,
char[] buf, int codeOff, Label[] labels) {
StackMapAttribute attr = new StackMapAttribute();
// note that this is not the size of Code attribute
int codeSize = cr.readInt(codeOff + 4);
int size = 0;
if (codeSize > MAX_SIZE) {
size = cr.readInt(off);
off += 4;
} else {
size = cr.readShort(off);
off += 2;
}
for (int i = 0; i < size; i++) {
StackMapFrame frame = new StackMapFrame();
off = frame.read(cr, off, buf, codeOff, labels);
attr.frames.add(frame);
}
return attr;
}
protected ByteVector write (ClassWriter cw, byte[] code,
int len, int maxStack, int maxLocals) {
ByteVector bv = new ByteVector();
if (code.length > MAX_SIZE) {
bv.putInt(frames.size());
} else {
bv.putShort(frames.size());
}
for (int i = 0; i < frames.size(); i++) {
((StackMapFrame)frames.get(i)).write(cw, maxStack, maxLocals, bv);
}
return bv;
}
protected Label[] getLabels () {
HashSet labels = new HashSet();
for (int i = 0; i < frames.size(); i++) {
((StackMapFrame)frames.get(i)).getLabels(labels);
}
return (Label[])labels.toArray(new Label[labels.size()]);
}
public void dump (StringBuffer buf, String varName, Map labelNames) {
buf.append("{\n");
buf.append("StackMapAttribute ").append(varName).append("Attr");
buf.append(" = new StackMapAttribute();\n");
if (frames.size() > 0) {
for (int i = 0; i < frames.size(); i++) {
((StackMapFrame)frames.get(i))
.dump(buf, varName + "frame" + i, labelNames);
}
}
buf.append(varName).append(".visitAttribute(").append(varName);
buf.append("Attr);\n}\n");
}
public String toString () {
StringBuffer sb = new StringBuffer("StackMap[");
for (int i = 0; i < frames.size(); i++) {
sb.append('\n').append('[').append(frames.get(i)).append(']');
}
sb.append("\n]");
return sb.toString();
}
}