classfilewriter.java

java中比较著名的js引擎当属mozilla开源的rhino

            case ByteCode.PUTFIELD :
                newStack -= fieldSize;
                break;
            default :
                throw new IllegalArgumentException(
                    "bad opcode for field reference");
        }
        if (newStack < 0 || Short.MAX_VALUE < newStack) badStack(newStack);
        short fieldRefIndex = itsConstantPool.addFieldRef(className,
                                             fieldName, fieldType);
        addToCodeBuffer(theOpCode);
        addToCodeInt16(fieldRefIndex);

        itsStackTop = (short)newStack;
        if (newStack > itsMaxStack) itsMaxStack = (short)newStack;
        if (DEBUGSTACK) {
            System.out.println("After "+bytecodeStr(theOpCode)
                               +" stack = "+itsStackTop);
        }
    }

    public void addInvoke(int theOpCode, String className, String methodName,
                          String methodType)
    {
        if (DEBUGCODE) {
            System.out.println("Add "+bytecodeStr(theOpCode)
                               +", "+className+", "+methodName+", "
                               +methodType);
        }
        int parameterInfo = sizeOfParameters(methodType);
        int parameterCount = parameterInfo >>> 16;
        int stackDiff = (short)parameterInfo;

        int newStack = itsStackTop + stackDiff;
        newStack += stackChange(theOpCode);     // adjusts for 'this'
        if (newStack < 0 || Short.MAX_VALUE < newStack) badStack(newStack);

        switch (theOpCode) {
            case ByteCode.INVOKEVIRTUAL :
            case ByteCode.INVOKESPECIAL :
            case ByteCode.INVOKESTATIC :
            case ByteCode.INVOKEINTERFACE : {
                    addToCodeBuffer(theOpCode);
                    if (theOpCode == ByteCode.INVOKEINTERFACE) {
                        short ifMethodRefIndex
                                    = itsConstantPool.addInterfaceMethodRef(
                                               className, methodName,
                                               methodType);
                        addToCodeInt16(ifMethodRefIndex);
                        addToCodeBuffer(parameterCount + 1);
                        addToCodeBuffer(0);
                    }
                    else {
                        short methodRefIndex = itsConstantPool.addMethodRef(
                                               className, methodName,
                                               methodType);
                        addToCodeInt16(methodRefIndex);
                    }
                }
                break;

            default :
                throw new IllegalArgumentException(
                    "bad opcode for method reference");
        }
        itsStackTop = (short)newStack;
        if (newStack > itsMaxStack) itsMaxStack = (short)newStack;
        if (DEBUGSTACK) {
            System.out.println("After "+bytecodeStr(theOpCode)
                               +" stack = "+itsStackTop);
        }
    }

    /**
     * Generate code to load the given integer on stack.
     *
     * @param k the constant
     */
    public void addPush(int k)
    {
        if ((byte)k == k) {
            if (k == -1) {
                add(ByteCode.ICONST_M1);
            } else if (0 <= k && k <= 5) {
                add((byte)(ByteCode.ICONST_0 + k));
            } else {
                add(ByteCode.BIPUSH, (byte)k);
            }
        } else if ((short)k == k) {
            add(ByteCode.SIPUSH, (short)k);
        } else {
            addLoadConstant(k);
        }
    }

    public void addPush(boolean k)
    {
        add(k ? ByteCode.ICONST_1 : ByteCode.ICONST_0);
    }

    /**
     * Generate code to load the given long on stack.
     *
     * @param k the constant
     */
    public void addPush(long k)
    {
        int ik = (int)k;
        if (ik == k) {
            addPush(ik);
            add(ByteCode.I2L);
        } else {
            addLoadConstant(k);
        }
    }

    /**
     * Generate code to load the given double on stack.
     *
     * @param k the constant
     */
    public void addPush(double k)
    {
        if (k == 0.0) {
            // zero
            add(ByteCode.DCONST_0);
            if (1.0 / k < 0) {
                // Negative zero
                add(ByteCode.DNEG);
            }
        } else if (k == 1.0 || k == -1.0) {
            add(ByteCode.DCONST_1);
            if (k < 0) {
                add(ByteCode.DNEG);
            }
        } else {
            addLoadConstant(k);
        }
    }

    /**
     * Generate the code to leave on stack the given string even if the
     * string encoding exeeds the class file limit for single string constant
     *
     * @param k the constant
     */
    public void addPush(String k) {
        int length = k.length();
        int limit = itsConstantPool.getUtfEncodingLimit(k, 0, length);
        if (limit == length) {
            addLoadConstant(k);
            return;
        }
        // Split string into picies fitting the UTF limit and generate code for
        // StringBuffer sb = new StringBuffer(length);
        // sb.append(loadConstant(piece_1));
        // ...
        // sb.append(loadConstant(piece_N));
        // sb.toString();
        final String SB = "java/lang/StringBuffer";
        add(ByteCode.NEW, SB);
        add(ByteCode.DUP);
        addPush(length);
        addInvoke(ByteCode.INVOKESPECIAL, SB, "<init>", "(I)V");
        int cursor = 0;
        for (;;) {
            add(ByteCode.DUP);
            String s = k.substring(cursor, limit);
            addLoadConstant(s);
            addInvoke(ByteCode.INVOKEVIRTUAL, SB, "append",
                      "(Ljava/lang/String;)Ljava/lang/StringBuffer;");
            add(ByteCode.POP);
            if (limit == length) {
                break;
            }
            cursor = limit;
            limit = itsConstantPool.getUtfEncodingLimit(k, limit, length);
        }
        addInvoke(ByteCode.INVOKEVIRTUAL, SB, "toString",
                  "()Ljava/lang/String;");
    }

    /**
     * Check if k fits limit on string constant size imposed by class file
     * format.
     *
     * @param k the string constant
     */
    public boolean isUnderStringSizeLimit(String k)
    {
        return itsConstantPool.isUnderUtfEncodingLimit(k);
    }

    /**
     * Store integer from stack top into the given local.
     *
     * @param local number of local register
     */
    public void addIStore(int local)
    {
        xop(ByteCode.ISTORE_0, ByteCode.ISTORE, local);
    }

    /**
     * Store long from stack top into the given local.
     *
     * @param local number of local register
     */
    public void addLStore(int local)
    {
        xop(ByteCode.LSTORE_0, ByteCode.LSTORE, local);
    }

    /**
     * Store float from stack top into the given local.
     *
     * @param local number of local register
     */
    public void addFStore(int local)
    {
        xop(ByteCode.FSTORE_0, ByteCode.FSTORE, local);
    }

    /**
     * Store double from stack top into the given local.
     *
     * @param local number of local register
     */
    public void addDStore(int local)
    {
        xop(ByteCode.DSTORE_0, ByteCode.DSTORE, local);
    }

    /**
     * Store object from stack top into the given local.
     *
     * @param local number of local register
     */
    public void addAStore(int local)
    {
        xop(ByteCode.ASTORE_0, ByteCode.ASTORE, local);
    }

    /**
     * Load integer from the given local into stack.
     *
     * @param local number of local register
     */
    public void addILoad(int local)
    {
        xop(ByteCode.ILOAD_0, ByteCode.ILOAD, local);
    }

    /**
     * Load long from the given local into stack.
     *
     * @param local number of local register
     */
    public void addLLoad(int local)
    {
        xop(ByteCode.LLOAD_0, ByteCode.LLOAD, local);
    }

    /**
     * Load float from the given local into stack.
     *
     * @param local number of local register
     */
    public void addFLoad(int local)
    {
        xop(ByteCode.FLOAD_0, ByteCode.FLOAD, local);
    }

    /**
     * Load double from the given local into stack.
     *
     * @param local number of local register
     */
    public void addDLoad(int local)
    {
        xop(ByteCode.DLOAD_0, ByteCode.DLOAD, local);
    }

    /**
     * Load object from the given local into stack.
     *
     * @param local number of local register
     */
    public void addALoad(int local)
    {
        xop(ByteCode.ALOAD_0, ByteCode.ALOAD, local);
    }

    /**
     * Load "this" into stack.
     */
    public void addLoadThis()
    {
        add(ByteCode.ALOAD_0);
    }

    private void xop(int shortOp, int op, int local)
    {
        switch (local) {
          case 0:
            add(shortOp);
            break;
          case 1:
            add(shortOp + 1);
            break;
          case 2:
            add(shortOp + 2);
            break;
          case 3:
            add(shortOp + 3);
            break;
          default:
            add(op, local);
        }
    }

    public int addTableSwitch(int low, int high)
    {
        if (DEBUGCODE) {
            System.out.println("Add "+bytecodeStr(ByteCode.TABLESWITCH)
                               +" "+low+" "+high);
        }
        if (low > high)
            throw new IllegalArgumentException("Bad bounds: "+low+' '+ high);

        int newStack = itsStackTop + stackChange(ByteCode.TABLESWITCH);
        if (newStack < 0 || Short.MAX_VALUE < newStack) badStack(newStack);

        int entryCount = high - low + 1;
        int padSize = 3 & ~itsCodeBufferTop; // == 3 - itsCodeBufferTop % 4

        int N = addReservedCodeSpace(1 + padSize + 4 * (1 + 2 + entryCount));
        int switchStart = N;
        itsCodeBuffer[N++] = (byte)ByteCode.TABLESWITCH;
        while (padSize != 0) {
            itsCodeBuffer[N++] = 0;
            --padSize;
        }
        N += 4; // skip default offset
        N = putInt32(low, itsCodeBuffer, N);
        putInt32(high, itsCodeBuffer, N);

        itsStackTop = (short)newStack;
        if (newStack > itsMaxStack) itsMaxStack = (short)newStack;
        if (DEBUGSTACK) {
            System.out.println("After "+bytecodeStr(ByteCode.TABLESWITCH)
                               +" stack = "+itsStackTop);
        }

        return switchStart;
    }

    public final void markTableSwitchDefault(int switchStart)
    {
        setTableSwitchJump(switchStart, -1, itsCodeBufferTop);
    }

    public final void markTableSwitchCase(int switchStart, int caseIndex)
    {
        setTableSwitchJump(switchStart, caseIndex, itsCodeBufferTop);
    }

    public final void markTableSwitchCase(int switchStart, int caseIndex,
                                          int stackTop)
    {
        if (!(0 <= stackTop && stackTop <= itsMaxStack))
            throw new IllegalArgumentException("Bad stack index: "+stackTop);
        itsStackTop = (short)stackTop;
        setTableSwitchJump(switchStart, caseIndex, itsCodeBufferTop);