codegen.java

Javassist是一个开源的分析、编辑和创建Java字节码的类库。是由东京技术学院的数学和计算机科学系的 Shigeru Chiba 所创建的。它已加入了开放源代码JBoss 应用服务器项目,通过使

        int pc3 = bytecode.currentPc();
        if (update != null)
            update.accept(this);

        bytecode.addOpcode(Opcode.GOTO);
        bytecode.addIndex(pc - bytecode.currentPc() + 1);

        int pc4 = bytecode.currentPc();
        if (expr != null)
            bytecode.write16bit(pc2, pc4 - pc2 + 1);

        patchGoto(breakList, pc4);
        patchGoto(continueList, pc3);
        continueList = prevContList;
        breakList = prevBreakList;
        hasReturned = false;
    }

    private void atSwitchStmnt(Stmnt st) throws CompileError {
        compileExpr(st.head());

        ArrayList prevBreakList = breakList;
        breakList = new ArrayList();
        int opcodePc = bytecode.currentPc();
        bytecode.addOpcode(LOOKUPSWITCH);
        int npads = 3 - (opcodePc & 3);
        while (npads-- > 0)
            bytecode.add(0);

        Stmnt body = (Stmnt)st.tail();
        int npairs = 0;
        for (ASTList list = body; list != null; list = list.tail())
            if (((Stmnt)list.head()).getOperator() == CASE)
                ++npairs;

        // opcodePc2 is the position at which the default jump offset is.
        int opcodePc2 = bytecode.currentPc();
        bytecode.addGap(4);
        bytecode.add32bit(npairs);
        bytecode.addGap(npairs * 8);

        long[] pairs = new long[npairs];
        int ipairs = 0;
        int defaultPc = -1;
        for (ASTList list = body; list != null; list = list.tail()) {
            Stmnt label = (Stmnt)list.head();
            int op = label.getOperator();
            if (op == DEFAULT)
                defaultPc = bytecode.currentPc();
            else if (op != CASE)
                fatal();
            else {
                pairs[ipairs++]
                    = ((long)computeLabel(label.head()) << 32) + 
                      ((long)(bytecode.currentPc() - opcodePc) & 0xffffffff);
            }

            hasReturned = false;
            ((Stmnt)label.tail()).accept(this);
        }

        Arrays.sort(pairs);
        int pc = opcodePc2 + 8;
        for (int i = 0; i < npairs; ++i) {
            bytecode.write32bit(pc, (int)(pairs[i] >>> 32));
            bytecode.write32bit(pc + 4, (int)pairs[i]);
            pc += 8;
        } 

        if (defaultPc < 0 || breakList.size() > 0)
            hasReturned = false;

        int endPc = bytecode.currentPc();
        if (defaultPc < 0)
            defaultPc = endPc;

        bytecode.write32bit(opcodePc2, defaultPc - opcodePc);

        patchGoto(breakList, endPc);
        breakList = prevBreakList;
    }

    private int computeLabel(ASTree expr) throws CompileError {
        doTypeCheck(expr);
        expr = TypeChecker.stripPlusExpr(expr);
        if (expr instanceof IntConst)
            return (int)((IntConst)expr).get();
        else
            throw new CompileError("bad case label");
    }

    private void atBreakStmnt(Stmnt st, boolean notCont)
        throws CompileError
    {
        if (st.head() != null)
            throw new CompileError(
                        "sorry, not support labeled break or continue");

        bytecode.addOpcode(Opcode.GOTO);
        Integer pc = new Integer(bytecode.currentPc());
        bytecode.addIndex(0);
        if (notCont)
            breakList.add(pc);
        else
            continueList.add(pc);
    }

    protected void atReturnStmnt(Stmnt st) throws CompileError {
        atReturnStmnt2(st.getLeft());
    }

    protected final void atReturnStmnt2(ASTree result) throws CompileError {
        int op;
        if (result == null)
            op = Opcode.RETURN;
        else {
            compileExpr(result);
            if (arrayDim > 0)
                op = ARETURN;
            else {
                int type = exprType;
                if (type == DOUBLE)
                    op = DRETURN;
                else if (type == FLOAT)
                    op = FRETURN;
                else if (type == LONG)
                    op = LRETURN;
                else if (isRefType(type))
                    op = ARETURN;
                else
                    op = IRETURN;
            }
        }

        for (ReturnHook har = returnHooks; har != null; har = har.next)
            har.doit(bytecode, op);

        bytecode.addOpcode(op);
        hasReturned = true;
    }

    private void atThrowStmnt(Stmnt st) throws CompileError {
        ASTree e = st.getLeft();
        compileExpr(e);
        if (exprType != CLASS || arrayDim > 0)
            throw new CompileError("bad throw statement");

        bytecode.addOpcode(ATHROW);
        hasReturned = true;
    }

    /* overridden in MemberCodeGen
     */
    protected void atTryStmnt(Stmnt st) throws CompileError {
        hasReturned = false;
    }

    private void atSyncStmnt(Stmnt st) throws CompileError {
        int nbreaks = getListSize(breakList);
        int ncontinues = getListSize(continueList);

        compileExpr(st.head());
        if (exprType != CLASS && arrayDim == 0)
            throw new CompileError("bad type expr for synchronized block");

        Bytecode bc = bytecode;
        final int var = bc.getMaxLocals();
        bc.incMaxLocals(1);
        bc.addOpcode(DUP);
        bc.addAstore(var);
        bc.addOpcode(MONITORENTER);

        ReturnHook rh = new ReturnHook(this) {
            protected void doit(Bytecode b, int opcode) {
                b.addAload(var);
                b.addOpcode(MONITOREXIT);
            }
        };

        int pc = bc.currentPc();
        Stmnt body = (Stmnt)st.tail();
        if (body != null)
            body.accept(this);

        int pc2 = bc.currentPc();
        int pc3 = 0;
        if (!hasReturned) {
            rh.doit(bc, 0);     // the 2nd arg is ignored.
            bc.addOpcode(Opcode.GOTO);
            pc3 = bc.currentPc();
            bc.addIndex(0);
        }

        int pc4 = bc.currentPc();
        rh.doit(bc, 0);         // the 2nd arg is ignored.
        bc.addOpcode(ATHROW);
        bc.addExceptionHandler(pc, pc2, pc4, 0);
        if (!hasReturned)
            bc.write16bit(pc3, bc.currentPc() - pc3 + 1);

        rh.remove(this);

        if (getListSize(breakList) != nbreaks
            || getListSize(continueList) != ncontinues)
            throw new CompileError(
                "sorry, cannot break/continue in synchronized block");
    }

    private static int getListSize(ArrayList list) {
        return list == null ? 0 : list.size();
    }

    private static boolean isPlusPlusExpr(ASTree expr) {
        if (expr instanceof Expr) {
            int op = ((Expr)expr).getOperator();
            return op == PLUSPLUS || op == MINUSMINUS;
        }

        return false;
    }

    public void atDeclarator(Declarator d) throws CompileError {
        d.setLocalVar(getMaxLocals());
        d.setClassName(resolveClassName(d.getClassName()));

        int size;
        if (is2word(d.getType(), d.getArrayDim()))
            size = 2;
        else
            size = 1;

        incMaxLocals(size);

        /*  NOTE: Array initializers has not been supported.
         */
        ASTree init = d.getInitializer();
        if (init != null) {
            doTypeCheck(init);
            atVariableAssign(null, '=', null, d, init, false);
        }
    }

    public abstract void atNewExpr(NewExpr n) throws CompileError;

    public abstract void atArrayInit(ArrayInit init) throws CompileError;

    public void atAssignExpr(AssignExpr expr) throws CompileError {
        atAssignExpr(expr, true);
    }

    protected void atAssignExpr(AssignExpr expr, boolean doDup)
        throws CompileError
    {
        // =, %=, &=, *=, /=, +=, -=, ^=, |=, <<=, >>=, >>>=
        int op = expr.getOperator();
        ASTree left = expr.oprand1();
        ASTree right = expr.oprand2();
        if (left instanceof Variable)
            atVariableAssign(expr, op, (Variable)left,
                             ((Variable)left).getDeclarator(),
                             right, doDup);
        else {
            if (left instanceof Expr) {
                Expr e = (Expr)left;
                if (e.getOperator() == ARRAY) {
                    atArrayAssign(expr, op, (Expr)left, right, doDup);
                    return;
                }
            }

            atFieldAssign(expr, op, left, right, doDup);
        }
    }

    protected static void badAssign(Expr expr) throws CompileError {
        String msg;
        if (expr == null)
            msg = "incompatible type for assignment";
        else
            msg = "incompatible type for " + expr.getName();

        throw new CompileError(msg);
    }

    /* op is either =, %=, &=, *=, /=, +=, -=, ^=, |=, <<=, >>=, or >>>=.
     *
     * expr and var can be null.
     */
    private void atVariableAssign(Expr expr, int op, Variable var,
                                  Declarator d, ASTree right,
                                  boolean doDup) throws CompileError
    {
        int varType = d.getType();
        int varArray = d.getArrayDim();
        String varClass = d.getClassName();
        int varNo = getLocalVar(d);

        if (op != '=')
            atVariable(var);

        // expr is null if the caller is atDeclarator().
        if (expr == null && right instanceof ArrayInit)
            atArrayVariableAssign((ArrayInit)right, varType, varArray, varClass);
        else
            atAssignCore(expr, op, right, varType, varArray, varClass);

        if (doDup)
            if (is2word(varType, varArray))
                bytecode.addOpcode(DUP2);
            else
                bytecode.addOpcode(DUP);

        if (varArray > 0)
            bytecode.addAstore(varNo);
        else if (varType == DOUBLE)
            bytecode.addDstore(varNo);
        else if (varType == FLOAT)
            bytecode.addFstore(varNo);
        else if (varType == LONG)
            bytecode.addLstore(varNo);
        else if (isRefType(varType))
            bytecode.addAstore(varNo);
        else
            bytecode.addIstore(varNo);

        exprType = varType;
        arrayDim = varArray;
        className = varClass;
    }

    protected abstract void atArrayVariableAssign(ArrayInit init,
            int varType, int varArray, String varClass) throws CompileError;

    private void atArrayAssign(Expr expr, int op, Expr array,
                        ASTree right, boolean doDup) throws CompileError
    {
        arrayAccess(array.oprand1(), array.oprand2());

        if (op != '=') {
            bytecode.addOpcode(DUP2);
            bytecode.addOpcode(getArrayReadOp(exprType, arrayDim));
        }

        int aType = exprType;
        int aDim = arrayDim;
        String cname = className;

        atAssignCore(expr, op, right, aType, aDim, cname);

        if (doDup)
            if (is2word(aType, aDim))
                bytecode.addOpcode(DUP2_X2);
            else
                bytecode.addOpcode(DUP_X2);

        bytecode.addOpcode(getArrayWriteOp(aType, aDim));
        exprType = aType;
        arrayDim = aDim;
        className = cname;
    }

    protected abstract void atFieldAssign(Expr expr, int op, ASTree left,
                        ASTree right, boolean doDup) throws CompileError;

    protected void atAssignCore(Expr expr, int op, ASTree right,
                                int type, int dim, String cname)
        throws CompileError
    {
        if (op == PLUS_E && dim == 0 && type == CLASS)
            atStringPlusEq(expr, type, dim, cname, right);
        else {
            right.accept(this);
            if (invalidDim(exprType, arrayDim, className, type, dim, cname,
                           false) || (op != '=' && dim > 0))
                badAssign(expr);

            if (op != '=') {
                int token = assignOps[op - MOD_E];
                int k = lookupBinOp(token);
                if (k < 0)
                    fatal();

                atArithBinExpr(expr, token, k, type);
            }
        }

        if (op != '=' || (dim == 0 && !isRefType(type)))
            atNumCastExpr(exprType, type);

        // type check should be done here.
    }

    private void atStringPlusEq(Expr expr, int type, int dim, String cname,
                                ASTree right)
        throws CompileError
    {
        if (!jvmJavaLangString.equals(cname))
            badAssign(expr);

        convToString(type, dim);    // the value might be null.
        right.accept(this);
        convToString(exprType, arrayDim);
        bytecode.addInvokevirtual(javaLangString, "concat",
                                "(Ljava/lang/String;)Ljava/lang/String;");
        exprType = CLASS;
        arrayDim = 0;
        className = jvmJavaLangString;
    }

    private boolean invalidDim(int srcType, int srcDim, String srcClass,
                               int destType, int destDim, String destClass,
                               boolean isCast)
    {
        if (srcDim != destDim)
            if (srcType == NULL)
                return false;
            else if (destDim == 0 && destType == CLASS
                     && jvmJavaLangObject.equals(destClass))
                return false;
            else if (isCast && srcDim == 0 && srcType == CLASS
                     && jvmJavaLangObject.equals(srcClass))
                return false;
            else
                return true;

        return false;
    }

    public void atCondExpr(CondExpr expr) throws CompileError {
        booleanExpr(false, expr.condExpr());
        int pc = bytecode.currentPc();
        bytecode.addIndex(0);   // correct later
        expr.thenExpr().accept(this);
        int dim1 = arrayDim;
        bytecode.addOpcode(Opcode.GOTO);
        int pc2 = bytecode.currentPc();
        bytecode.addIndex(0);
        bytecode.write16bit(pc, bytecode.currentPc() - pc + 1);
        expr.elseExpr().accept(this);
        if (dim1 != arrayDim)
            throw new CompileError("type mismatch in ?:");

        bytecode.write16bit(pc2, bytecode.currentPc() - pc2 + 1);
    }

    static final int[] binOp = {
        '+', DADD, FADD, LADD, IADD,
        '-', DSUB, FSUB, LSUB, ISUB,
        '*', DMUL, FMUL, LMUL, IMUL,
        '/', DDIV, FDIV, LDIV, IDIV,
        '%', DREM, FREM, LREM, IREM,
        '|', NOP,  NOP,  LOR,  IOR,
        '^', NOP,  NOP,  LXOR, IXOR,
        '&', NOP,  NOP,  LAND, IAND,
        LSHIFT, NOP, NOP, LSHL, ISHL,
        RSHIFT, NOP, NOP, LSHR, ISHR,
        ARSHIFT, NOP, NOP, LUSHR, IUSHR };

    static int lookupBinOp(int token) {
        int[] code = binOp;
        int s = code.length;
        for (int k = 0; k < s; k = k + 5)
            if (code[k] == token)
                return k;

        return -1;
    }

    public void atBinExpr(BinExpr expr) throws CompileError {
        int token = expr.getOperator();

        /* arithmetic operators: +, -, *, /, %, |, ^, &, <<, >>, >>>
         */
        int k = lookupBinOp(token);