interpreter.java

java中比较著名的js引擎当属mozilla开源的rhino

    private void addUint8(int value)
    {
        if ((value & ~0xFF) != 0) throw Kit.codeBug();
        byte[] array = itsData.itsICode;
        int top = itsICodeTop;
        if (top == array.length) {
            array = increaseICodeCapasity(1);
        }
        array[top] = (byte)value;
        itsICodeTop = top + 1;
    }

    private void addUint16(int value)
    {
        if ((value & ~0xFFFF) != 0) throw Kit.codeBug();
        byte[] array = itsData.itsICode;
        int top = itsICodeTop;
        if (top + 2 > array.length) {
            array = increaseICodeCapasity(2);
        }
        array[top] = (byte)(value >>> 8);
        array[top + 1] = (byte)value;
        itsICodeTop = top + 2;
    }

    private void addInt(int i)
    {
        byte[] array = itsData.itsICode;
        int top = itsICodeTop;
        if (top + 4 > array.length) {
            array = increaseICodeCapasity(4);
        }
        array[top] = (byte)(i >>> 24);
        array[top + 1] = (byte)(i >>> 16);
        array[top + 2] = (byte)(i >>> 8);
        array[top + 3] = (byte)i;
        itsICodeTop = top + 4;
    }

    private int getDoubleIndex(double num)
    {
        int index = itsDoubleTableTop;
        if (index == 0) {
            itsData.itsDoubleTable = new double[64];
        } else if (itsData.itsDoubleTable.length == index) {
            double[] na = new double[index * 2];
            System.arraycopy(itsData.itsDoubleTable, 0, na, 0, index);
            itsData.itsDoubleTable = na;
        }
        itsData.itsDoubleTable[index] = num;
        itsDoubleTableTop = index + 1;
        return index;
    }

    private void addGotoOp(int gotoOp)
    {
        byte[] array = itsData.itsICode;
        int top = itsICodeTop;
        if (top + 3 > array.length) {
            array = increaseICodeCapasity(3);
        }
        array[top] = (byte)gotoOp;
        // Offset would written later
        itsICodeTop = top + 1 + 2;
    }

    private void addVarOp(int op, int varIndex)
    {
        switch (op) {
          case Token.GETVAR:
          case Token.SETVAR:
            if (varIndex < 128) {
                addIcode(op == Token.GETVAR ? Icode_GETVAR1 : Icode_SETVAR1);
                addUint8(varIndex);
                return;
            }
            // fallthrough
          case Icode_VAR_INC_DEC:
            addIndexOp(op, varIndex);
            return;
        }
        throw Kit.codeBug();
    }

    private void addStringOp(int op, String str)
    {
        addStringPrefix(str);
        if (validIcode(op)) {
            addIcode(op);
        } else {
            addToken(op);
        }
    }

    private void addIndexOp(int op, int index)
    {
        addIndexPrefix(index);
        if (validIcode(op)) {
            addIcode(op);
        } else {
            addToken(op);
        }
    }

    private void addStringPrefix(String str)
    {
        int index = itsStrings.get(str, -1);
        if (index == -1) {
            index = itsStrings.size();
            itsStrings.put(str, index);
        }
        if (index < 4) {
            addIcode(Icode_REG_STR_C0 - index);
        } else if (index <= 0xFF) {
            addIcode(Icode_REG_STR1);
            addUint8(index);
         } else if (index <= 0xFFFF) {
            addIcode(Icode_REG_STR2);
            addUint16(index);
         } else {
            addIcode(Icode_REG_STR4);
            addInt(index);
        }
    }

    private void addIndexPrefix(int index)
    {
        if (index < 0) Kit.codeBug();
        if (index < 6) {
            addIcode(Icode_REG_IND_C0 - index);
        } else if (index <= 0xFF) {
            addIcode(Icode_REG_IND1);
            addUint8(index);
         } else if (index <= 0xFFFF) {
            addIcode(Icode_REG_IND2);
            addUint16(index);
         } else {
            addIcode(Icode_REG_IND4);
            addInt(index);
        }
    }

    private void addExceptionHandler(int icodeStart, int icodeEnd,
                                     int handlerStart, boolean isFinally,
                                     int exceptionObjectLocal, int scopeLocal)
    {
        int top = itsExceptionTableTop;
        int[] table = itsData.itsExceptionTable;
        if (table == null) {
            if (top != 0) Kit.codeBug();
            table = new int[EXCEPTION_SLOT_SIZE * 2];
            itsData.itsExceptionTable = table;
        } else if (table.length == top) {
            table = new int[table.length * 2];
            System.arraycopy(itsData.itsExceptionTable, 0, table, 0, top);
            itsData.itsExceptionTable = table;
        }
        table[top + EXCEPTION_TRY_START_SLOT]  = icodeStart;
        table[top + EXCEPTION_TRY_END_SLOT]    = icodeEnd;
        table[top + EXCEPTION_HANDLER_SLOT]    = handlerStart;
        table[top + EXCEPTION_TYPE_SLOT]       = isFinally ? 1 : 0;
        table[top + EXCEPTION_LOCAL_SLOT]      = exceptionObjectLocal;
        table[top + EXCEPTION_SCOPE_SLOT]      = scopeLocal;

        itsExceptionTableTop = top + EXCEPTION_SLOT_SIZE;
    }

    private byte[] increaseICodeCapasity(int extraSize)
    {
        int capacity = itsData.itsICode.length;
        int top = itsICodeTop;
        if (top + extraSize <= capacity) throw Kit.codeBug();
        capacity *= 2;
        if (top + extraSize > capacity) {
            capacity = top + extraSize;
        }
        byte[] array = new byte[capacity];
        System.arraycopy(itsData.itsICode, 0, array, 0, top);
        itsData.itsICode = array;
        return array;
    }

    private void stackChange(int change)
    {
        if (change <= 0) {
            itsStackDepth += change;
        } else {
            int newDepth = itsStackDepth + change;
            if (newDepth > itsData.itsMaxStack) {
                itsData.itsMaxStack = newDepth;
            }
            itsStackDepth = newDepth;
        }
    }

    private int allocLocal()
    {
        int localSlot = itsLocalTop;
        ++itsLocalTop;
        if (itsLocalTop > itsData.itsMaxLocals) {
            itsData.itsMaxLocals = itsLocalTop;
        }
        return localSlot;
    }

    private void releaseLocal(int localSlot)
    {
        --itsLocalTop;
        if (localSlot != itsLocalTop) Kit.codeBug();
    }

    private static int getShort(byte[] iCode, int pc) {
        return (iCode[pc] << 8) | (iCode[pc + 1] & 0xFF);
    }

    private static int getIndex(byte[] iCode, int pc) {
        return ((iCode[pc] & 0xFF) << 8) | (iCode[pc + 1] & 0xFF);
    }

    private static int getInt(byte[] iCode, int pc) {
        return (iCode[pc] << 24) | ((iCode[pc + 1] & 0xFF) << 16)
               | ((iCode[pc + 2] & 0xFF) << 8) | (iCode[pc + 3] & 0xFF);
    }

    private static int getExceptionHandler(CallFrame frame,
                                           boolean onlyFinally)
    {
        int[] exceptionTable = frame.idata.itsExceptionTable;
        if (exceptionTable == null) {
            // No exception handlers
            return -1;
        }

        // Icode switch in the interpreter increments PC immediately
        // and it is necessary to subtract 1 from the saved PC
        // to point it before the start of the next instruction.
        int pc = frame.pc - 1;

        // OPT: use binary search
        int best = -1, bestStart = 0, bestEnd = 0;
        for (int i = 0; i != exceptionTable.length; i += EXCEPTION_SLOT_SIZE) {
            int start = exceptionTable[i + EXCEPTION_TRY_START_SLOT];
            int end = exceptionTable[i + EXCEPTION_TRY_END_SLOT];
            if (!(start <= pc && pc < end)) {
                continue;
            }
            if (onlyFinally && exceptionTable[i + EXCEPTION_TYPE_SLOT] != 1) {
                continue;
            }
            if (best >= 0) {
                // Since handlers always nest and they never have shared end
                // although they can share start  it is sufficient to compare
                // handlers ends
                if (bestEnd < end) {
                    continue;
                }
                // Check the above assumption
                if (bestStart > start) Kit.codeBug(); // should be nested
                if (bestEnd == end) Kit.codeBug();  // no ens sharing
            }
            best = i;
            bestStart = start;
            bestEnd = end;
        }
        return best;
    }

    private static void dumpICode(InterpreterData idata)
    {
        if (!Token.printICode) {
            return;
        }

        byte iCode[] = idata.itsICode;
        int iCodeLength = iCode.length;
        String[] strings = idata.itsStringTable;
        PrintStream out = System.out;
        out.println("ICode dump, for " + idata.itsName
                    + ", length = " + iCodeLength);
        out.println("MaxStack = " + idata.itsMaxStack);

        int indexReg = 0;
        for (int pc = 0; pc < iCodeLength; ) {
            out.flush();
            out.print(" [" + pc + "] ");
            int token = iCode[pc];
            int icodeLength = bytecodeSpan(token);
            String tname = bytecodeName(token);
            int old_pc = pc;
            ++pc;
            switch (token) {
              default:
                if (icodeLength != 1) Kit.codeBug();
                out.println(tname);
                break;

              case Icode_GOSUB :
              case Token.GOTO :
              case Token.IFEQ :
              case Token.IFNE :
              case Icode_IFEQ_POP :
              case Icode_LEAVEDQ : {
                int newPC = pc + getShort(iCode, pc) - 1;
                out.println(tname + " " + newPC);
                pc += 2;
                break;
              }
              case Icode_VAR_INC_DEC :
              case Icode_NAME_INC_DEC :
              case Icode_PROP_INC_DEC :
              case Icode_ELEM_INC_DEC :
              case Icode_REF_INC_DEC: {
                int incrDecrType = iCode[pc];
                out.println(tname + " " + incrDecrType);
                ++pc;
                break;
              }

              case Icode_CALLSPECIAL : {
                int callType = iCode[pc] & 0xFF;
                boolean isNew =  (iCode[pc + 1] != 0);
                int line = getIndex(iCode, pc+2);
                out.println(tname+" "+callType+" "+isNew+" "+indexReg+" "+line);
                pc += 4;
                break;
              }

              case Token.CATCH_SCOPE:
                {
                    boolean afterFisrtFlag =  (iCode[pc] != 0);
                    out.println(tname+" "+afterFisrtFlag);
                    ++pc;
                }
                break;
              case Token.REGEXP :
                out.println(tname+" "+idata.itsRegExpLiterals[indexReg]);
                break;
              case Token.OBJECTLIT :
              case Icode_SPARE_ARRAYLIT :
                out.println(tname+" "+idata.literalIds[indexReg]);
                break;
              case Icode_CLOSURE_EXPR :
              case Icode_CLOSURE_STMT :
                out.println(tname+" "+idata.itsNestedFunctions[indexReg]);
                break;
              case Token.CALL :
              case Icode_TAIL_CALL :
              case Token.REF_CALL :
              case Token.NEW :
                out.println(tname+' '+indexReg);
                break;
              case Token.THROW : {
                int line = getIndex(iCode, pc);
                out.println(tname + " : " + line);
                pc += 2;
                break;
              }
              case Icode_SHORTNUMBER : {
                int value = getShort(iCode, pc);
                out.println(tname + " " + value);
                pc += 2;
                break;
              }
              case Icode_INTNUMBER : {
                int value = getInt(iCode, pc);
                out.println(tname + " " + value);
                pc += 4;
                break;
              }
              case Token.NUMBER : {
                double value = idata.itsDoubleTable[indexReg];
                out.println(tname + " " + value);
                pc += 2;
                break;
              }
              case Icode_LINE : {
                int line = getIndex(iCode, pc);
                out.println(tname + " : " + line);
                pc += 2;
                break;
              }
              case Icode_REG_STR1: {