CommandParser.java

package com.github.miniyk2012.coding2017.coderising.jvm.cmd;

import com.github.miniyk2012.coding2017.coderising.jvm.clz.ClassFile;

import java.util.LinkedList;
import java.util.List;


public class CommandParser {
	
	public static final String aconst_null = "01";
	public static final String new_object = "BB";
	public static final String lstore = "37";
	public static final String invokespecial = "B7";
	public static final String invokevirtual = "B6";
	public static final String getfield = "B4";
	public static final String putfield = "B5";
	public static final String getstatic = "B2";
	public static final String ldc = "12";
	public static final String dup = "59";
	public static final String bipush = "10";
	public static final String aload_0 = "2A";
	public static final String aload_1 = "2B";
	public static final String aload_2 = "2C";
	public static final String iload = "15";
	public static final String iload_1 = "1B";
	public static final String iload_2 = "1C";
	public static final String iload_3 = "1D";
	public static final String fload_3 = "25";

	public static final String voidreturn = "B1";
	public static final String ireturn = "AC";
	public static final String freturn = "AE";

	public static final String astore_1 = "4C";
	public static final String if_icmp_ge = "A2";
	public static final String if_icmple = "A4";
	public static final String goto_no_condition = "A7";
	public static final String iconst_0 = "03";
	public static final String iconst_1 = "04";
	public static final String istore_1 = "3C";
	public static final String istore_2 = "3D";
	public static final String iadd = "60";
	public static final String iinc = "84";

	public static ByteCodeCommand[] parse(ClassFile clzFile, String codes) {

		CommandIterator cIter = new CommandIterator(codes);
		List<ByteCodeCommand> cmds = new LinkedList<>();
		// 将字符串解析为ByteCodeCommand[]
        while (cIter.hasNext()) {  // todo 重构，1.不应该用这么多的if语句 2.大量重复代码
            String opCode = cIter.next2CharAsString().toUpperCase();
            if (opCode.equalsIgnoreCase(getfield)) {
                GetFieldCmd cmd = new GetFieldCmd(clzFile, opCode);
                cmd.setOprand1(cIter.next2CharAsInt());
                cmd.setOprand2(cIter.next2CharAsInt());
                cmds.add(cmd);
            } else if (opCode.equalsIgnoreCase(getstatic)) {
                GetStaticFieldCmd cmd = new GetStaticFieldCmd(clzFile, opCode);
                cmd.setOprand1(cIter.next2CharAsInt());
                cmd.setOprand2(cIter.next2CharAsInt());
                cmds.add(cmd);
            } else if (opCode.equalsIgnoreCase(invokespecial)) {
                InvokeSpecialCmd cmd = new InvokeSpecialCmd(clzFile, opCode);
                cmd.setOprand1(cIter.next2CharAsInt());
                cmd.setOprand2(cIter.next2CharAsInt());
                cmds.add(cmd);
            } else if (opCode.equalsIgnoreCase(invokevirtual)) {
                InvokeVirtualCmd cmd = new InvokeVirtualCmd(clzFile, opCode);
                cmd.setOprand1(cIter.next2CharAsInt());
                cmd.setOprand2(cIter.next2CharAsInt());
                cmds.add(cmd);
            } else if (opCode.equalsIgnoreCase(ldc)) {
                LdcCmd cmd = new LdcCmd(clzFile, opCode);
                cmd.setOperand(cIter.next2CharAsInt());
                cmds.add(cmd);
            } else if (opCode.equalsIgnoreCase(new_object)) {
                NewObjectCmd cmd = new NewObjectCmd(clzFile, opCode);
                cmd.setOprand1(cIter.next2CharAsInt());
                cmd.setOprand2(cIter.next2CharAsInt());
                cmds.add(cmd);
            } else if (opCode.equalsIgnoreCase(putfield)) {
                PutFieldCmd cmd = new PutFieldCmd(clzFile, opCode);
                cmd.setOprand1(cIter.next2CharAsInt());
                cmd.setOprand2(cIter.next2CharAsInt());
                cmds.add(cmd);
            } else if (opCode.equalsIgnoreCase(bipush)) {
                BiPushCmd cmd = new BiPushCmd(clzFile, opCode);
                cmd.setOperand(cIter.next2CharAsInt());
                cmds.add(cmd);
            } else if (opCode.equalsIgnoreCase(aload_0)
                    || opCode.equalsIgnoreCase(aload_1)
                    || opCode.equalsIgnoreCase(aload_2)
                    || opCode.equalsIgnoreCase(astore_1)
                    || opCode.equalsIgnoreCase(iload_1)
                    || opCode.equalsIgnoreCase(iload_2)
                    || opCode.equalsIgnoreCase(voidreturn)
                    || opCode.equalsIgnoreCase(dup)
                    ) {
                NoOperandCmd cmd = new NoOperandCmd(clzFile, opCode);
                cmds.add(cmd);
            } else {
                throw new RuntimeException("not implement cmd: " + opCode);
            }

        }
        calcuateOffset(cmds);
        ByteCodeCommand[] result = new ByteCodeCommand[cmds.size()];
		cmds.toArray(result);
		return result;
	}

	private static void calcuateOffset(List<ByteCodeCommand> cmds) {

		int offset = 0;
		for (ByteCodeCommand cmd : cmds) {
			cmd.setOffset(offset);
			offset += cmd.getLength();
		}

	}

	private static class CommandIterator {
		String codes = null;
		int pos = 0;

		CommandIterator(String codes) {
			this.codes = codes;
		}

		public boolean hasNext() {
			return pos < this.codes.length();
		}

		public String next2CharAsString() {
			String result = codes.substring(pos, pos + 2);
			pos += 2;
			return result;
		}

		public int next2CharAsInt() {
			String s = this.next2CharAsString();
			return Integer.valueOf(s, 16).intValue();
		}

	}
}