derinputstream.java

来自「This is a resource based on j2me embedde」· Java 代码 · 共 583 行 · 第 1/2 页

        return readVector(startLen);
    }

    /**
     * Return a set of encoded entities.  ASN.1 sets are unordered,
     * though DER may specify an order for some kinds of sets (such
     * as the attributes in an X.500 relative distinguished name)
     * to facilitate binary comparisons of encoded values.
     *
     * @param startLen guess about how large the set will be
     *          (used to initialize an auto-growing data structure)
     * @param implicit if true tag is assumed implicit.
     * @return array of the values in the sequence
     */
    public DerValue[] getSet(int startLen, boolean implicit)
        throws IOException {
        tag = (byte)buffer.read();
        if (!implicit) {
            if (tag != DerValue.tag_Set) {
                throw new IOException("Set tag error");
            }
        }
        return (readVector(startLen));
    }

    /*
     * Read a "vector" of values ... set or sequence have the
     * same encoding, except for the initial tag, so both use
     * this same helper routine.
     */
    protected DerValue[] readVector(int startLen) throws IOException {
        DerInputStream  newstr;

        byte lenByte = (byte)buffer.read();
        int len = getLength((lenByte & 0xff), buffer);

        if (len == -1) {
           // indefinite length encoding found
           int readLen = buffer.available();
           int offset = 2;     // for tag and length bytes
           byte[] indefData = new byte[readLen + offset];
           indefData[0] = tag;
           indefData[1] = lenByte;
           DataInputStream dis = new DataInputStream(buffer);
           dis.readFully(indefData, offset, readLen);
           dis.close();
           DerIndefLenConverter derIn = new DerIndefLenConverter();
           buffer = new DerInputBuffer(derIn.convert(indefData));
           if (tag != buffer.read()) {
                throw new IOException("Indefinite length encoding" +
                                      " not supported");
           }
           len = DerInputStream.getLength(buffer);
        }

        if (len == 0)
            // return empty array instead of null, which should be
            // used only for missing optionals
            return new DerValue[0];

        /*
         * Create a temporary stream from which to read the data,
         * unless it's not really needed.
         */
        if (buffer.available() == len) {
            newstr = this;
        } else {
            newstr = subStream(len, true);
        }

        /*
         * Pull values out of the stream.
         */
        Vector vec = new Vector(startLen);
        DerValue value;

        do {
            value = new DerValue(newstr.buffer);
            vec.addElement(value);
        } while (newstr.available() > 0);

        if (newstr.available() != 0) {
            throw new IOException("extra data at end of vector");
        }

        /*
         * Now stick them into the array we're returning.
         */
        int             i, max = vec.size();
        DerValue[]      retval = new DerValue[max];

        for (i = 0; i < max; i++) {
            retval[i] = (DerValue)vec.elementAt(i);
        }

        return retval;
    }

    /**
     * Get a single DER-encoded value from the input stream.
     * It can often be useful to pull a value from the stream
     * and defer parsing it.  For example, you can pull a nested
     * sequence out with one call, and only examine its elements
     * later when you really need to.
     */
    public DerValue getDerValue() throws IOException {
        return new DerValue(buffer);
    }

    /**
     * Read a string that was encoded as a UTF8String DER value.
     */
    public String getUTF8String() throws IOException {
        return readString(DerValue.tag_UTF8String, "UTF-8", "UTF-8");
    }

    /**
     * Read a string that was encoded as a PrintableString DER value.
     */
    public String getPrintableString() throws IOException {
        return readString(DerValue.tag_PrintableString, "Printable",
                          "US_ASCII");
    }

    /**
     * Read a string that was encoded as a T61String DER value.
     */
    public String getT61String() throws IOException {
        /*
         * Works for common characters between T61 and ASCII.
         */
        return readString(DerValue.tag_T61String, "T61", "ISO-8859-1");
    }

    /**
     * Read a string that was encoded as a IA5tring DER value.
     */
    public String getIA5String() throws IOException {
        return readString(DerValue.tag_IA5String, "IA5", "US_ASCII");
    }

    /**
     * Read a string that was encoded as a BMPString DER value.
     */
    public String getBMPString() throws IOException {
        return readString(DerValue.tag_BMPString, "BMP",
                          "UnicodeBigUnmarked");
    }

    /**
     * Read a string that was encoded as a GeneralString DER value.
     */
    public String getGeneralString() throws IOException {
        return readString(DerValue.tag_GeneralString, "General",
                          "US_ASCII");
    }

    /**
     * Private helper routine to read an encoded string from the input
     * stream.
     * @param stringTag the tag for the type of string to read
     * @param stringName a name to display in error messages
     * @param enc the encoder to use to interpret the data. Should
     * correspond to the stringTag above.
     */
    private String readString(byte stringTag, String stringName,
                              String enc) throws IOException {

        if (buffer.read() != stringTag) {
            throw new IOException("DER input not a " +
                                  stringName + " string");
        }

        int length = getLength(buffer);
        byte[] retval = new byte[length];
        if ((length != 0) && (buffer.read(retval) != length)) {
            throw new IOException("short read of DER " +
                                  stringName + " string");
        }

        return new String(retval, enc);
    }

    /**
     * Get a UTC encoded time value from the input stream.
     */
    public Date getUTCTime() throws IOException {
        if (buffer.read() != DerValue.tag_UtcTime) {
            throw new IOException("DER input, UTCtime tag invalid ");
        }
        return buffer.getUTCTime(getLength(buffer));
    }

    /**
     * Get a Generalized encoded time value from the input stream.
     */
    public Date getGeneralizedTime() throws IOException {
        if (buffer.read() != DerValue.tag_GeneralizedTime) {
            throw new IOException("DER input, GeneralizedTime tag invalid ");
        }
        return buffer.getGeneralizedTime(getLength(buffer));
    }

    /*
     * Get a byte from the input stream.
     */
    // package private
    int getByte() throws IOException {
        return (0x00ff & buffer.read());
    }

    public int peekByte() throws IOException {
        return buffer.peek();
    }

    // package private
    int getLength() throws IOException {
        return getLength(buffer);
    }

    /*
     * Get a length from the input stream, allowing for at most 32 bits of
     * encoding to be used.  (Not the same as getting a tagged integer!)
     *
     * @return the length or -1 if indefinite length found.
     * @exception IOException on parsing error or unsupported lengths.
     */
    static int getLength(InputStream in) throws IOException {
        return getLength(in.read(), in);
    }

    /**
     * Get a length from the input stream, allowing for at most 32 bits of
     * encoding to be used.  (Not the same as getting a tagged integer!)
     *
     * @return the length or -1 if indefinite length found.
     * @exception IOException on parsing error or unsupported lengths.
     */
    static int getLength(int lenByte, InputStream in) throws IOException {
        int value, tmp;

        tmp = lenByte;
        if ((tmp & 0x080) == 0x00) { // short form, 1 byte datum
            value = tmp;
        } else {                     // long form or indefinite
            tmp &= 0x07f;

            /*
             * NOTE:  tmp == 0 indicates indefinite length encoded data.
             * tmp > 4 indicates more than 4Gb of data.
             */
            if (tmp == 0) {
                return -1;
            }
            if (tmp < 0 || tmp > 4) {
                throw new IOException("DerInputStream.getLength(): lengthTag="
                    + tmp + ", "
                    + ((tmp < 0) ? "incorrect DER encoding." : "too big."));
            }

            for (value = 0; tmp > 0; tmp --) {
                value <<= 8;
                value += 0x0ff & in.read();
            }
        }
        return value;
    }

    /**
     * Mark the current position in the buffer, so that
     * a later call to <code>reset</code> will return here.
     */
    public void mark(int value) { buffer.mark(value); }


    /**
     * Return to the position of the last <code>mark</code>
     * call.  A mark is implicitly set at the beginning of
     * the stream when it is created.
     */
    public void reset() { buffer.reset(); }


    /**
     * Returns the number of bytes available for reading.
     * This is most useful for testing whether the stream is
     * empty.
     */
    public int available() { return buffer.available(); }
}