scriptruntime.java

java中比较著名的js引擎当属mozilla开源的rhino

                        if ('0' <= digit && digit <= '9')
                            digit -= '0';
                        else if ('a' <= digit && digit <= 'z')
                            digit -= 'a' - 10;
                        else
                            digit -= 'A' - 10;
                        bitShiftInChar = radix;
                    }
                    bitShiftInChar >>= 1;
                    boolean bit = (digit & bitShiftInChar) != 0;

                    switch (state) {
                      case SKIP_LEADING_ZEROS:
                          if (bit) {
                            --exactBitsLimit;
                            sum = 1.0;
                            state = FIRST_EXACT_53_BITS;
                        }
                        break;
                      case FIRST_EXACT_53_BITS:
                           sum *= 2.0;
                        if (bit)
                            sum += 1.0;
                        --exactBitsLimit;
                        if (exactBitsLimit == 0) {
                            bit53 = bit;
                            state = AFTER_BIT_53;
                        }
                        break;
                      case AFTER_BIT_53:
                        bit54 = bit;
                        factor = 2.0;
                        state = ZEROS_AFTER_54;
                        break;
                      case ZEROS_AFTER_54:
                        if (bit) {
                            state = MIXED_AFTER_54;
                        }
                        // fallthrough
                      case MIXED_AFTER_54:
                        factor *= 2;
                        break;
                    }
                }
                switch (state) {
                  case SKIP_LEADING_ZEROS:
                    sum = 0.0;
                    break;
                  case FIRST_EXACT_53_BITS:
                  case AFTER_BIT_53:
                    // do nothing
                    break;
                  case ZEROS_AFTER_54:
                    // x1.1 -> x1 + 1 (round up)
                    // x0.1 -> x0 (round down)
                    if (bit54 & bit53)
                        sum += 1.0;
                    sum *= factor;
                    break;
                  case MIXED_AFTER_54:
                    // x.100...1.. -> x + 1 (round up)
                    // x.0anything -> x (round down)
                    if (bit54)
                        sum += 1.0;
                    sum *= factor;
                    break;
                }
            }
            /* We don't worry about inaccurate numbers for any other base. */
        }
        return sum;
    }


    /**
     * ToNumber applied to the String type
     *
     * See ECMA 9.3.1
     */
    public static double toNumber(String s) {
        int len = s.length();
        int start = 0;
        char startChar;
        for (;;) {
            if (start == len) {
                // Empty or contains only whitespace
                return +0.0;
            }
            startChar = s.charAt(start);
            if (!Character.isWhitespace(startChar))
                break;
            start++;
        }

        if (startChar == '0') {
            if (start + 2 < len) {
                int c1 = s.charAt(start + 1);
                if (c1 == 'x' || c1 == 'X') {
                    // A hexadecimal number
                    return stringToNumber(s, start + 2, 16);
                }
            }
        } else if (startChar == '+' || startChar == '-') {
            if (start + 3 < len && s.charAt(start + 1) == '0') {
                int c2 = s.charAt(start + 2);
                if (c2 == 'x' || c2 == 'X') {
                    // A hexadecimal number with sign
                    double val = stringToNumber(s, start + 3, 16);
                    return startChar == '-' ? -val : val;
                }
            }
        }

        int end = len - 1;
        char endChar;
        while (Character.isWhitespace(endChar = s.charAt(end)))
            end--;
        if (endChar == 'y') {
            // check for "Infinity"
            if (startChar == '+' || startChar == '-')
                start++;
            if (start + 7 == end && s.regionMatches(start, "Infinity", 0, 8))
                return startChar == '-'
                    ? Double.NEGATIVE_INFINITY
                    : Double.POSITIVE_INFINITY;
            return NaN;
        }
        // A non-hexadecimal, non-infinity number:
        // just try a normal floating point conversion
        String sub = s.substring(start, end+1);
        if (MSJVM_BUG_WORKAROUNDS) {
            // The MS JVM will accept non-conformant strings
            // rather than throwing a NumberFormatException
            // as it should.
            for (int i=sub.length()-1; i >= 0; i--) {
                char c = sub.charAt(i);
                if (('0' <= c && c <= '9') || c == '.' ||
                    c == 'e' || c == 'E'  ||
                    c == '+' || c == '-')
                    continue;
                return NaN;
            }
        }
        try {
            return Double.valueOf(sub).doubleValue();
        } catch (NumberFormatException ex) {
            return NaN;
        }
    }

    /**
     * Helper function for builtin objects that use the varargs form.
     * ECMA function formal arguments are undefined if not supplied;
     * this function pads the argument array out to the expected
     * length, if necessary.
     */
    public static Object[] padArguments(Object[] args, int count) {
        if (count < args.length)
            return args;

        int i;
        Object[] result = new Object[count];
        for (i = 0; i < args.length; i++) {
            result[i] = args[i];
        }

        for (; i < count; i++) {
            result[i] = Undefined.instance;
        }

        return result;
    }

    /* Work around Microsoft Java VM bugs. */
    private final static boolean MSJVM_BUG_WORKAROUNDS = true;

    public static String escapeString(String s)
    {
        return escapeString(s, '"');
    }

    /**
     * For escaping strings printed by object and array literals; not quite
     * the same as 'escape.'
     */
    public static String escapeString(String s, char escapeQuote)
    {
        if (!(escapeQuote == '"' || escapeQuote == '\'')) Kit.codeBug();
        StringBuffer sb = null;

        for(int i = 0, L = s.length(); i != L; ++i) {
            int c = s.charAt(i);

            if (' ' <= c && c <= '~' && c != escapeQuote && c != '\\') {
                // an ordinary print character (like C isprint()) and not "
                // or \ .
                if (sb != null) {
                    sb.append((char)c);
                }
                continue;
            }
            if (sb == null) {
                sb = new StringBuffer(L + 3);
                sb.append(s);
                sb.setLength(i);
            }

            int escape = -1;
            switch (c) {
                case '\b':  escape = 'b';  break;
                case '\f':  escape = 'f';  break;
                case '\n':  escape = 'n';  break;
                case '\r':  escape = 'r';  break;
                case '\t':  escape = 't';  break;
                case 0xb:   escape = 'v';  break; // Java lacks \v.
                case ' ':   escape = ' ';  break;
                case '\\':  escape = '\\'; break;
            }
            if (escape >= 0) {
                // an \escaped sort of character
                sb.append('\\');
                sb.append((char)escape);
            } else if (c == escapeQuote) {
                sb.append('\\');
                sb.append(escapeQuote);
            } else {
                int hexSize;
                if (c < 256) {
                    // 2-digit hex
                    sb.append("\\x");
                    hexSize = 2;
                } else {
                    // Unicode.
                    sb.append("\\u");
                    hexSize = 4;
                }
                // append hexadecimal form of c left-padded with 0
                for (int shift = (hexSize - 1) * 4; shift >= 0; shift -= 4) {
                    int digit = 0xf & (c >> shift);
                    int hc = (digit < 10) ? '0' + digit : 'a' - 10 + digit;
                    sb.append((char)hc);
                }
            }
        }
        return (sb == null) ? s : sb.toString();
    }

    static boolean isValidIdentifierName(String s)
    {
        int L = s.length();
        if (L == 0)
            return false;
        if (!Character.isJavaIdentifierStart(s.charAt(0)))
            return false;
        for (int i = 1; i != L; ++i) {
            if (!Character.isJavaIdentifierPart(s.charAt(i)))
                return false;
        }
        return !TokenStream.isKeyword(s);
    }

    /**
     * Convert the value to a string.
     *
     * See ECMA 9.8.
     */
    public static String toString(Object val) {
        for (;;) {
            if (val == null) {
                return "null";
            }
            if (val == Undefined.instance) {
                return "undefined";
            }
            if (val instanceof String) {
                return (String)val;
            }
            if (val instanceof Number) {
                // XXX should we just teach NativeNumber.stringValue()
                // about Numbers?
                return numberToString(((Number)val).doubleValue(), 10);
            }
            if (val instanceof Scriptable) {
                val = ((Scriptable) val).getDefaultValue(StringClass);
                if (val instanceof Scriptable) {
                    throw errorWithClassName("msg.primitive.expected", val);
                }
                continue;
            }
            return val.toString();
        }
    }

    static String defaultObjectToString(Scriptable obj)
    {
        return "[object " + obj.getClassName() + ']';
    }

    public static String toString(Object[] args, int index)
    {
        return (index < args.length) ? toString(args[index]) : "undefined";
    }

    /**
     * Optimized version of toString(Object) for numbers.
     */
    public static String toString(double val) {
        return numberToString(val, 10);
    }

    public static String numberToString(double d, int base) {
        if (d != d)
            return "NaN";
        if (d == Double.POSITIVE_INFINITY)
            return "Infinity";
        if (d == Double.NEGATIVE_INFINITY)
            return "-Infinity";
        if (d == 0.0)
            return "0";

        if ((base < 2) || (base > 36)) {
            throw Context.reportRuntimeError1(
                "msg.bad.radix", Integer.toString(base));
        }

        if (base != 10) {
            return DToA.JS_dtobasestr(base, d);
        } else {
            StringBuffer result = new StringBuffer();
            DToA.JS_dtostr(result, DToA.DTOSTR_STANDARD, 0, d);
            return result.toString();
        }

    }

    static String uneval(Context cx, Scriptable scope, Object value)
    {
        if (value == null) {
            return "null";
        }
        if (value == Undefined.instance) {
            return "undefined";
        }
        if (value instanceof String) {
            String escaped = escapeString((String)value);
            StringBuffer sb = new StringBuffer(escaped.length() + 2);
            sb.append('\"');
            sb.append(escaped);
            sb.append('\"');
            return sb.toString();
        }
        if (value instanceof Number) {
            double d = ((Number)value).doubleValue();
            if (d == 0 && 1 / d < 0) {
                return "-0";
            }
            return toString(d);
        }
        if (value instanceof Boolean) {
            return toString(value);
        }
        if (value instanceof Scriptable) {
            Scriptable obj = (Scriptable)value;
            Object v = ScriptableObject.getProperty(obj, "toSource");
            if (v instanceof Function) {
                Function f = (Function)v;
                return toString(f.call(cx, scope, obj, emptyArgs));
            }
            return toString(value);
        }
        warnAboutNonJSObject(value);
        return value.toString();
    }

    static String defaultObjectToSource(Context cx, Scriptable scope,
                                        Scriptable thisObj, Object[] args)
    {
        boolean toplevel, iterating;
        if (cx.iterating == null) {
            toplevel = true;
            iterating = false;
            cx.iterating = new ObjToIntMap(31);
        } else {
            toplevel = false;
            iterating = cx.iterating.has(thisObj);
        }

        StringBuffer result = new StringBuffer(128);
        if (toplevel) {
            result.append("(");
        }