Method.java

package week08.jvm.method;

import week08.jvm.clz.ClassFile;
import week08.jvm.cmd.ByteCodeCommand;
import week08.jvm.method.Method;

import java.util.ArrayList;
import java.util.List;

import week08.jvm.attr.AttributeInfo;
import week08.jvm.attr.CodeAttr;
import week08.jvm.constant.ConstantPool;
import week08.jvm.constant.UTF8Info;
import week08.jvm.loader.ByteCodeIterator;

public class Method {

	private int accessFlag;
	private int nameIndex;
	private int descriptorIndex;

	private CodeAttr codeAttr;

	private ClassFile clzFile;

	public ClassFile getClzFile() {
		return clzFile;
	}

	public int getNameIndex() {
		return nameIndex;
	}

	public int getDescriptorIndex() {
		return descriptorIndex;
	}

	public CodeAttr getCodeAttr() {
		return codeAttr;
	}

	public void setCodeAttr(CodeAttr code) {
		this.codeAttr = code;
	}

	public Method(ClassFile clzFile, int accessFlag, int nameIndex, int descriptorIndex) {
		this.clzFile = clzFile;
		this.accessFlag = accessFlag;
		this.nameIndex = nameIndex;
		this.descriptorIndex = descriptorIndex;
	}

	public String toString() {

		ConstantPool pool = this.clzFile.getConstantPool();
		StringBuilder buffer = new StringBuilder();

		String name = ((UTF8Info) pool.getConstantInfo(this.nameIndex)).getValue();

		String desc = ((UTF8Info) pool.getConstantInfo(this.descriptorIndex)).getValue();

		buffer.append(name).append(":").append(desc).append("\n");

		buffer.append(this.codeAttr.toString(pool));

		return buffer.toString();
	}

	public static Method parse(ClassFile clzFile, ByteCodeIterator iter) {
		int accessFlag = iter.nextU2ToInt();
		int nameIndex = iter.nextU2ToInt();
		int descIndex = iter.nextU2ToInt();
		int attribCount = iter.nextU2ToInt();

		Method m = new Method(clzFile, accessFlag, nameIndex, descIndex);

		for (int i = 1; i <= attribCount; i++) {
			int attrNameIndex = iter.nextU2ToInt();
			String attrName = clzFile.getConstantPool().getUTF8String(attrNameIndex);
			iter.back(2);

			if (AttributeInfo.CODE.equalsIgnoreCase(attrName)) {
				CodeAttr codeAttr = CodeAttr.parse(clzFile, iter);
				m.setCodeAttr(codeAttr);
			} else {
				throw new RuntimeException("only CODE attribute is implemented");
			}
		}
		return m;

	}

	public ByteCodeCommand[] getCmds() {
		return this.getCodeAttr().getCmds();
	}

	public List<String> getParameterList() {
		
		// e.g. (Ljava/util/List;Ljava/lang/String;II)V
		String paramAndType = getParamAndReturnType();
		
		int first = paramAndType.indexOf("(");
		int last = paramAndType.lastIndexOf(")");
		// e.g. Ljava/util/List;Ljava/lang/String;II
		String param = paramAndType.substring(first+1, last);		
		
		List<String> paramList = new ArrayList<String>();
		
		if((null == param) || "".equals(param)){
			return paramList;
		}
		
		while(!param.equals("")){
			
			int pos = 0;
			// 这是一个对象类型
			if(param.charAt(pos) == 'L'){
				
				int end = param.indexOf(";");
				
				if(end == -1){
					throw new RuntimeException("can't find the ; for a object type");
				}
				paramList.add(param.substring(pos+1,end));
				
				pos = end + 1; 				
				
			} 
			else if(param.charAt(pos) == 'I'){
				// int
				paramList.add("I");
				pos ++;
				
			}
			else if(param.charAt(pos) == 'F'){
				// float
				paramList.add("F");
				pos ++;
				
			} else{
				throw new RuntimeException("the param has unsupported type:" + param);
			}
			
			param = param.substring(pos);
			
		}
		return paramList;
	}

	private String getParamAndReturnType() {
		UTF8Info  nameAndTypeInfo = (UTF8Info)this.getClzFile()
				.getConstantPool().getConstantInfo(this.getDescriptorIndex());
		return nameAndTypeInfo.getValue();
	}
}