/**
* Read the class file header.
*
* @param in The stream from which to read.
* @exception IOException If an error occurs while reading.
*/
void readHeader(DataInputStream in) throws IOException {
int magic = in.readInt();
if (magic != 0xCAFEBABE) {
throw new ClassFormatError("Bad magic number.");
}
int major = in.readUnsignedShort();
int minor = in.readUnsignedShort();
}
/**
* Read a constant from the constant pool.
*
* @param in The stream from which to read.
* @return The constant.
* @exception IOException If an error occurs while reading.
*/
Constant readConstant(DataInputStream in) throws IOException {
int tag = in.readUnsignedByte();
Object value;
switch (tag) {
case Constant.CLASS:
case Constant.STRING:
case Constant.METHOD_TYPE: // @since 1.8
value = Integer.valueOf(in.readUnsignedShort());
break;
case Constant.FIELD_REF:
case Constant.METHOD_REF:
case Constant.INTERFACE_METHOD_REF:
case Constant.NAME_AND_TYPE:
case Constant.INVOKE_DYNAMIC: // @since 1.8
value = new int[2];
((int[]) value)[0] = in.readUnsignedShort();
((int[]) value)[1] = in.readUnsignedShort();
break;
case Constant.INTEGER:
value = Integer.valueOf(in.readInt());
break;
case Constant.FLOAT:
value = Float.valueOf(in.readFloat());
break;
case Constant.LONG:
// Longs take up 2 constant pool entries.
value = Long.valueOf(in.readLong());
break;
case Constant.DOUBLE:
// Doubles take up 2 constant pool entries.
value = Double.valueOf(in.readDouble());
break;
case Constant.UTF8:
value = in.readUTF();
break;
case Constant.METHOD_HANDLE: // @since 1.8
value = new int[2];
((int[]) value)[0] = in.readUnsignedByte();
((int[]) value)[1] = in.readUnsignedShort();
break;
default:
throw new ClassFormatError("Invalid constant tag: " + tag);
}
return new Constant(tag, value);
}
/**
* Read the class's attributes. Since none of the attributes are required, just read the length of
* each attribute and skip that many bytes.
*
* @param in The stream from which to read.
* @exception IOException If an error occurs while reading.
*/
public void readAttributes(DataInputStream in) throws IOException {
int numAttributes = in.readUnsignedShort();
attrs = new Attribute[numAttributes];
for (int i = 0; i < numAttributes; i++) {
int nameIndex = in.readUnsignedShort();
int length = in.readInt();
String name = (String) constants[nameIndex].value();
Attribute a = createAttribute(in, name, nameIndex, length);
if (a != null) {
attrs[i] = a;
} else {
long n = in.skip(length);
if (n != length) {
throw new EOFException();
}
}
}
}