jdk/src/share/classes/sun/security/util/DerValue.java
changeset 2 90ce3da70b43
child 2065 d0bafa066816
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/share/classes/sun/security/util/DerValue.java	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,934 @@
+/*
+ * Copyright 1996-2006 Sun Microsystems, Inc.  All Rights Reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Sun designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Sun in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ */
+
+package sun.security.util;
+
+import java.io.*;
+import java.math.BigInteger;
+import java.util.Date;
+
+/**
+ * Represents a single DER-encoded value.  DER encoding rules are a subset
+ * of the "Basic" Encoding Rules (BER), but they only support a single way
+ * ("Definite" encoding) to encode any given value.
+ *
+ * <P>All DER-encoded data are triples <em>{type, length, data}</em>.  This
+ * class represents such tagged values as they have been read (or constructed),
+ * and provides structured access to the encoded data.
+ *
+ * <P>At this time, this class supports only a subset of the types of DER
+ * data encodings which are defined.  That subset is sufficient for parsing
+ * most X.509 certificates, and working with selected additional formats
+ * (such as PKCS #10 certificate requests, and some kinds of PKCS #7 data).
+ *
+ * A note with respect to T61/Teletex strings: From RFC 1617, section 4.1.3
+ * and RFC 3280, section 4.1.2.4., we assume that this kind of string will
+ * contain ISO-8859-1 characters only.
+ *
+ *
+ * @author David Brownell
+ * @author Amit Kapoor
+ * @author Hemma Prafullchandra
+ */
+public class DerValue {
+    /** The tag class types */
+    public static final byte TAG_UNIVERSAL = (byte)0x000;
+    public static final byte TAG_APPLICATION = (byte)0x040;
+    public static final byte TAG_CONTEXT = (byte)0x080;
+    public static final byte TAG_PRIVATE = (byte)0x0c0;
+
+    /** The DER tag of the value; one of the tag_ constants. */
+    public byte                 tag;
+
+    protected DerInputBuffer    buffer;
+
+    /**
+     * The DER-encoded data of the value.
+     */
+    public final DerInputStream data;
+
+    private int                 length;
+
+    /*
+     * The type starts at the first byte of the encoding, and
+     * is one of these tag_* values.  That may be all the type
+     * data that is needed.
+     */
+
+    /*
+     * These tags are the "universal" tags ... they mean the same
+     * in all contexts.  (Mask with 0x1f -- five bits.)
+     */
+
+    /** Tag value indicating an ASN.1 "BOOLEAN" value. */
+    public final static byte    tag_Boolean = 0x01;
+
+    /** Tag value indicating an ASN.1 "INTEGER" value. */
+    public final static byte    tag_Integer = 0x02;
+
+    /** Tag value indicating an ASN.1 "BIT STRING" value. */
+    public final static byte    tag_BitString = 0x03;
+
+    /** Tag value indicating an ASN.1 "OCTET STRING" value. */
+    public final static byte    tag_OctetString = 0x04;
+
+    /** Tag value indicating an ASN.1 "NULL" value. */
+    public final static byte    tag_Null = 0x05;
+
+    /** Tag value indicating an ASN.1 "OBJECT IDENTIFIER" value. */
+    public final static byte    tag_ObjectId = 0x06;
+
+    /** Tag value including an ASN.1 "ENUMERATED" value */
+    public final static byte    tag_Enumerated = 0x0A;
+
+    /** Tag value indicating an ASN.1 "UTF8String" value. */
+    public final static byte    tag_UTF8String = 0x0C;
+
+    /** Tag value including a "printable" string */
+    public final static byte    tag_PrintableString = 0x13;
+
+    /** Tag value including a "teletype" string */
+    public final static byte    tag_T61String = 0x14;
+
+    /** Tag value including an ASCII string */
+    public final static byte    tag_IA5String = 0x16;
+
+    /** Tag value indicating an ASN.1 "UTCTime" value. */
+    public final static byte    tag_UtcTime = 0x17;
+
+    /** Tag value indicating an ASN.1 "GeneralizedTime" value. */
+    public final static byte    tag_GeneralizedTime = 0x18;
+
+    /** Tag value indicating an ASN.1 "GenerallString" value. */
+    public final static byte    tag_GeneralString = 0x1B;
+
+    /** Tag value indicating an ASN.1 "UniversalString" value. */
+    public final static byte    tag_UniversalString = 0x1C;
+
+    /** Tag value indicating an ASN.1 "BMPString" value. */
+    public final static byte    tag_BMPString = 0x1E;
+
+    // CONSTRUCTED seq/set
+
+    /**
+     * Tag value indicating an ASN.1
+     * "SEQUENCE" (zero to N elements, order is significant).
+     */
+    public final static byte    tag_Sequence = 0x30;
+
+    /**
+     * Tag value indicating an ASN.1
+     * "SEQUENCE OF" (one to N elements, order is significant).
+     */
+    public final static byte    tag_SequenceOf = 0x30;
+
+    /**
+     * Tag value indicating an ASN.1
+     * "SET" (zero to N members, order does not matter).
+     */
+    public final static byte    tag_Set = 0x31;
+
+    /**
+     * Tag value indicating an ASN.1
+     * "SET OF" (one to N members, order does not matter).
+     */
+    public final static byte    tag_SetOf = 0x31;
+
+    /*
+     * These values are the high order bits for the other kinds of tags.
+     */
+
+    /**
+     * Returns true if the tag class is UNIVERSAL.
+     */
+    public boolean isUniversal()      { return ((tag & 0x0c0) == 0x000); }
+
+    /**
+     * Returns true if the tag class is APPLICATION.
+     */
+    public boolean isApplication()    { return ((tag & 0x0c0) == 0x040); }
+
+    /**
+     * Returns true iff the CONTEXT SPECIFIC bit is set in the type tag.
+     * This is associated with the ASN.1 "DEFINED BY" syntax.
+     */
+    public boolean isContextSpecific() { return ((tag & 0x0c0) == 0x080); }
+
+    /**
+     * Returns true iff the CONTEXT SPECIFIC TAG matches the passed tag.
+     */
+    public boolean isContextSpecific(byte cntxtTag) {
+        if (!isContextSpecific()) {
+            return false;
+        }
+        return ((tag & 0x01f) == cntxtTag);
+    }
+
+    boolean isPrivate()        { return ((tag & 0x0c0) == 0x0c0); }
+
+    /** Returns true iff the CONSTRUCTED bit is set in the type tag. */
+    public boolean isConstructed()    { return ((tag & 0x020) == 0x020); }
+
+    /**
+     * Returns true iff the CONSTRUCTED TAG matches the passed tag.
+     */
+    public boolean isConstructed(byte constructedTag) {
+        if (!isConstructed()) {
+            return false;
+        }
+        return ((tag & 0x01f) == constructedTag);
+    }
+
+    /**
+     * Creates a PrintableString or UTF8string DER value from a string
+     */
+    public DerValue(String value) throws IOException {
+        boolean isPrintableString = true;
+        for (int i = 0; i < value.length(); i++) {
+            if (!isPrintableStringChar(value.charAt(i))) {
+                isPrintableString = false;
+                break;
+            }
+        }
+
+        data = init(isPrintableString ? tag_PrintableString : tag_UTF8String, value);
+    }
+
+    /**
+     * Creates a string type DER value from a String object
+     * @param stringTag the tag for the DER value to create
+     * @param value the String object to use for the DER value
+     */
+    public DerValue(byte stringTag, String value) throws IOException {
+        data = init(stringTag, value);
+    }
+
+    /**
+     * Creates a DerValue from a tag and some DER-encoded data.
+     *
+     * @param tag the DER type tag
+     * @param data the DER-encoded data
+     */
+    public DerValue(byte tag, byte[] data) {
+        this.tag = tag;
+        buffer = new DerInputBuffer(data.clone());
+        length = data.length;
+        this.data = new DerInputStream(buffer);
+        this.data.mark(Integer.MAX_VALUE);
+    }
+
+    /*
+     * package private
+     */
+    DerValue(DerInputBuffer in) throws IOException {
+        // XXX must also parse BER-encoded constructed
+        // values such as sequences, sets...
+
+        tag = (byte)in.read();
+        byte lenByte = (byte)in.read();
+        length = DerInputStream.getLength((lenByte & 0xff), in);
+        if (length == -1) {  // indefinite length encoding found
+            DerInputBuffer inbuf = in.dup();
+            int readLen = inbuf.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(inbuf);
+            dis.readFully(indefData, offset, readLen);
+            dis.close();
+            DerIndefLenConverter derIn = new DerIndefLenConverter();
+            inbuf = new DerInputBuffer(derIn.convert(indefData));
+            if (tag != inbuf.read())
+                throw new IOException
+                        ("Indefinite length encoding not supported");
+            length = DerInputStream.getLength(inbuf);
+            buffer = inbuf.dup();
+            buffer.truncate(length);
+            data = new DerInputStream(buffer);
+            // indefinite form is encoded by sending a length field with a
+            // length of 0. - i.e. [1000|0000].
+            // the object is ended by sending two zero bytes.
+            in.skip(length + offset);
+        } else {
+
+            buffer = in.dup();
+            buffer.truncate(length);
+            data = new DerInputStream(buffer);
+
+            in.skip(length);
+        }
+    }
+
+    /**
+     * Get an ASN.1/DER encoded datum from a buffer.  The
+     * entire buffer must hold exactly one datum, including
+     * its tag and length.
+     *
+     * @param buf buffer holding a single DER-encoded datum.
+     */
+    public DerValue(byte[] buf) throws IOException {
+        data = init(true, new ByteArrayInputStream(buf));
+    }
+
+    /**
+     * Get an ASN.1/DER encoded datum from part of a buffer.
+     * That part of the buffer must hold exactly one datum, including
+     * its tag and length.
+     *
+     * @param buf the buffer
+     * @param offset start point of the single DER-encoded dataum
+     * @param length how many bytes are in the encoded datum
+     */
+    public DerValue(byte[] buf, int offset, int len) throws IOException {
+        data = init(true, new ByteArrayInputStream(buf, offset, len));
+    }
+
+    /**
+     * Get an ASN1/DER encoded datum from an input stream.  The
+     * stream may have additional data following the encoded datum.
+     * In case of indefinite length encoded datum, the input stream
+     * must hold only one datum.
+     *
+     * @param in the input stream holding a single DER datum,
+     *  which may be followed by additional data
+     */
+    public DerValue(InputStream in) throws IOException {
+        data = init(false, in);
+    }
+
+    private DerInputStream init(byte stringTag, String value) throws IOException {
+        String enc = null;
+
+        tag = stringTag;
+
+        switch (stringTag) {
+        case tag_PrintableString:
+        case tag_IA5String:
+        case tag_GeneralString:
+            enc = "ASCII";
+            break;
+        case tag_T61String:
+            enc = "ISO-8859-1";
+            break;
+        case tag_BMPString:
+            enc = "UnicodeBigUnmarked";
+            break;
+        case tag_UTF8String:
+            enc = "UTF8";
+            break;
+            // TBD: Need encoder for UniversalString before it can
+            // be handled.
+        default:
+            throw new IllegalArgumentException("Unsupported DER string type");
+        }
+
+        byte[] buf = value.getBytes(enc);
+        length = buf.length;
+        buffer = new DerInputBuffer(buf);
+        DerInputStream result = new DerInputStream(buffer);
+        result.mark(Integer.MAX_VALUE);
+        return result;
+    }
+
+    /*
+     * helper routine
+     */
+    private DerInputStream init(boolean fullyBuffered, InputStream in)
+            throws IOException {
+
+        tag = (byte)in.read();
+        byte lenByte = (byte)in.read();
+        length = DerInputStream.getLength((lenByte & 0xff), in);
+        if (length == -1) { // indefinite length encoding found
+            int readLen = in.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(in);
+            dis.readFully(indefData, offset, readLen);
+            dis.close();
+            DerIndefLenConverter derIn = new DerIndefLenConverter();
+            in = new ByteArrayInputStream(derIn.convert(indefData));
+            if (tag != in.read())
+                throw new IOException
+                        ("Indefinite length encoding not supported");
+            length = DerInputStream.getLength(in);
+        }
+        if (length == 0)
+            return null;
+
+        if (fullyBuffered && in.available() != length)
+            throw new IOException("extra data given to DerValue constructor");
+
+        byte[] bytes = new byte[length];
+
+        // n.b. readFully not needed in normal fullyBuffered case
+        DataInputStream dis = new DataInputStream(in);
+
+        dis.readFully(bytes);
+        buffer = new DerInputBuffer(bytes);
+        return new DerInputStream(buffer);
+    }
+
+    /**
+     * Encode an ASN1/DER encoded datum onto a DER output stream.
+     */
+    public void encode(DerOutputStream out)
+    throws IOException {
+        out.write(tag);
+        out.putLength(length);
+        // XXX yeech, excess copies ... DerInputBuffer.write(OutStream)
+        if (length > 0) {
+            byte[] value = new byte[length];
+            // always synchronized on data
+            synchronized (data) {
+                buffer.reset();
+                if (buffer.read(value) != length) {
+                    throw new IOException("short DER value read (encode)");
+                }
+                out.write(value);
+            }
+        }
+    }
+
+    public final DerInputStream getData() {
+        return data;
+    }
+
+    public final byte getTag() {
+        return tag;
+    }
+
+    /**
+     * Returns an ASN.1 BOOLEAN
+     *
+     * @return the boolean held in this DER value
+     */
+    public boolean getBoolean() throws IOException {
+        if (tag != tag_Boolean) {
+            throw new IOException("DerValue.getBoolean, not a BOOLEAN " + tag);
+        }
+        if (length != 1) {
+            throw new IOException("DerValue.getBoolean, invalid length "
+                                        + length);
+        }
+        if (buffer.read() != 0) {
+            return true;
+        }
+        return false;
+    }
+
+    /**
+     * Returns an ASN.1 OBJECT IDENTIFIER.
+     *
+     * @return the OID held in this DER value
+     */
+    public ObjectIdentifier getOID() throws IOException {
+        if (tag != tag_ObjectId)
+            throw new IOException("DerValue.getOID, not an OID " + tag);
+        return new ObjectIdentifier(buffer);
+    }
+
+    private byte[] append(byte[] a, byte[] b) {
+        if (a == null)
+            return b;
+
+        byte[] ret = new byte[a.length + b.length];
+        System.arraycopy(a, 0, ret, 0, a.length);
+        System.arraycopy(b, 0, ret, a.length, b.length);
+
+        return ret;
+    }
+
+    /**
+     * Returns an ASN.1 OCTET STRING
+     *
+     * @return the octet string held in this DER value
+     */
+    public byte[] getOctetString() throws IOException {
+        byte[] bytes;
+
+        if (tag != tag_OctetString && !isConstructed(tag_OctetString)) {
+            throw new IOException(
+                "DerValue.getOctetString, not an Octet String: " + tag);
+        }
+        bytes = new byte[length];
+        if (buffer.read(bytes) != length)
+            throw new IOException("short read on DerValue buffer");
+        if (isConstructed()) {
+            DerInputStream in = new DerInputStream(bytes);
+            bytes = null;
+            while (in.available() != 0) {
+                bytes = append(bytes, in.getOctetString());
+            }
+        }
+        return bytes;
+    }
+
+    /**
+     * Returns an ASN.1 INTEGER value as an integer.
+     *
+     * @return the integer held in this DER value.
+     */
+    public int getInteger() throws IOException {
+        if (tag != tag_Integer) {
+            throw new IOException("DerValue.getInteger, not an int " + tag);
+        }
+        return buffer.getInteger(data.available());
+    }
+
+    /**
+     * Returns an ASN.1 INTEGER value as a BigInteger.
+     *
+     * @return the integer held in this DER value as a BigInteger.
+     */
+    public BigInteger getBigInteger() throws IOException {
+        if (tag != tag_Integer)
+            throw new IOException("DerValue.getBigInteger, not an int " + tag);
+        return buffer.getBigInteger(data.available(), false);
+    }
+
+    /**
+     * Returns an ASN.1 INTEGER value as a positive BigInteger.
+     * This is just to deal with implementations that incorrectly encode
+     * some values as negative.
+     *
+     * @return the integer held in this DER value as a BigInteger.
+     */
+    public BigInteger getPositiveBigInteger() throws IOException {
+        if (tag != tag_Integer)
+            throw new IOException("DerValue.getBigInteger, not an int " + tag);
+        return buffer.getBigInteger(data.available(), true);
+    }
+
+    /**
+     * Returns an ASN.1 ENUMERATED value.
+     *
+     * @return the integer held in this DER value.
+     */
+    public int getEnumerated() throws IOException {
+        if (tag != tag_Enumerated) {
+            throw new IOException("DerValue.getEnumerated, incorrect tag: "
+                                  + tag);
+        }
+        return buffer.getInteger(data.available());
+    }
+
+    /**
+     * Returns an ASN.1 BIT STRING value.  The bit string must be byte-aligned.
+     *
+     * @return the bit string held in this value
+     */
+    public byte[] getBitString() throws IOException {
+        if (tag != tag_BitString)
+            throw new IOException(
+                "DerValue.getBitString, not a bit string " + tag);
+
+        return buffer.getBitString();
+    }
+
+    /**
+     * Returns an ASN.1 BIT STRING value that need not be byte-aligned.
+     *
+     * @return a BitArray representing the bit string held in this value
+     */
+    public BitArray getUnalignedBitString() throws IOException {
+        if (tag != tag_BitString)
+            throw new IOException(
+                "DerValue.getBitString, not a bit string " + tag);
+
+        return buffer.getUnalignedBitString();
+    }
+
+    /**
+     * Returns the name component as a Java string, regardless of its
+     * encoding restrictions (ASCII, T61, Printable, IA5, BMP, UTF8).
+     */
+    // TBD: Need encoder for UniversalString before it can be handled.
+    public String getAsString() throws IOException {
+        if (tag == tag_UTF8String)
+            return getUTF8String();
+        else if (tag == tag_PrintableString)
+            return getPrintableString();
+        else if (tag == tag_T61String)
+            return getT61String();
+        else if (tag == tag_IA5String)
+            return getIA5String();
+        /*
+          else if (tag == tag_UniversalString)
+          return getUniversalString();
+        */
+        else if (tag == tag_BMPString)
+            return getBMPString();
+        else if (tag == tag_GeneralString)
+            return getGeneralString();
+        else
+            return null;
+    }
+
+    /**
+     * Returns an ASN.1 BIT STRING value, with the tag assumed implicit
+     * based on the parameter.  The bit string must be byte-aligned.
+     *
+     * @params tagImplicit if true, the tag is assumed implicit.
+     * @return the bit string held in this value
+     */
+    public byte[] getBitString(boolean tagImplicit) throws IOException {
+        if (!tagImplicit) {
+            if (tag != tag_BitString)
+                throw new IOException("DerValue.getBitString, not a bit string "
+                                       + tag);
+            }
+        return buffer.getBitString();
+    }
+
+    /**
+     * Returns an ASN.1 BIT STRING value, with the tag assumed implicit
+     * based on the parameter.  The bit string need not be byte-aligned.
+     *
+     * @params tagImplicit if true, the tag is assumed implicit.
+     * @return the bit string held in this value
+     */
+    public BitArray getUnalignedBitString(boolean tagImplicit)
+    throws IOException {
+        if (!tagImplicit) {
+            if (tag != tag_BitString)
+                throw new IOException("DerValue.getBitString, not a bit string "
+                                       + tag);
+            }
+        return buffer.getUnalignedBitString();
+    }
+
+    /**
+     * Helper routine to return all the bytes contained in the
+     * DerInputStream associated with this object.
+     */
+    public byte[] getDataBytes() throws IOException {
+        byte[] retVal = new byte[length];
+        synchronized (data) {
+            data.reset();
+            data.getBytes(retVal);
+        }
+        return retVal;
+    }
+
+    /**
+     * Returns an ASN.1 STRING value
+     *
+     * @return the printable string held in this value
+     */
+    public String getPrintableString()
+    throws IOException {
+        if (tag != tag_PrintableString)
+            throw new IOException(
+                "DerValue.getPrintableString, not a string " + tag);
+
+        return new String(getDataBytes(), "ASCII");
+    }
+
+    /**
+     * Returns an ASN.1 T61 (Teletype) STRING value
+     *
+     * @return the teletype string held in this value
+     */
+    public String getT61String() throws IOException {
+        if (tag != tag_T61String)
+            throw new IOException(
+                "DerValue.getT61String, not T61 " + tag);
+
+        return new String(getDataBytes(), "ISO-8859-1");
+    }
+
+    /**
+     * Returns an ASN.1 IA5 (ASCII) STRING value
+     *
+     * @return the ASCII string held in this value
+     */
+    public String getIA5String() throws IOException {
+        if (tag != tag_IA5String)
+            throw new IOException(
+                "DerValue.getIA5String, not IA5 " + tag);
+
+        return new String(getDataBytes(), "ASCII");
+    }
+
+    /**
+     * Returns the ASN.1 BMP (Unicode) STRING value as a Java string.
+     *
+     * @return a string corresponding to the encoded BMPString held in
+     * this value
+     */
+    public String getBMPString() throws IOException {
+        if (tag != tag_BMPString)
+            throw new IOException(
+                "DerValue.getBMPString, not BMP " + tag);
+
+        // BMPString is the same as Unicode in big endian, unmarked
+        // format.
+        return new String(getDataBytes(), "UnicodeBigUnmarked");
+    }
+
+    /**
+     * Returns the ASN.1 UTF-8 STRING value as a Java String.
+     *
+     * @return a string corresponding to the encoded UTF8String held in
+     * this value
+     */
+    public String getUTF8String() throws IOException {
+        if (tag != tag_UTF8String)
+            throw new IOException(
+                "DerValue.getUTF8String, not UTF-8 " + tag);
+
+        return new String(getDataBytes(), "UTF8");
+    }
+
+    /**
+     * Returns the ASN.1 GENERAL STRING value as a Java String.
+     *
+     * @return a string corresponding to the encoded GeneralString held in
+     * this value
+     */
+    public String getGeneralString() throws IOException {
+        if (tag != tag_GeneralString)
+            throw new IOException(
+                "DerValue.getGeneralString, not GeneralString " + tag);
+
+        return new String(getDataBytes(), "ASCII");
+    }
+
+    /**
+     * Returns a Date if the DerValue is UtcTime.
+     *
+     * @return the Date held in this DER value
+     */
+    public Date getUTCTime() throws IOException {
+        if (tag != tag_UtcTime) {
+            throw new IOException("DerValue.getUTCTime, not a UtcTime: " + tag);
+        }
+        return buffer.getUTCTime(data.available());
+    }
+
+    /**
+     * Returns a Date if the DerValue is GeneralizedTime.
+     *
+     * @return the Date held in this DER value
+     */
+    public Date getGeneralizedTime() throws IOException {
+        if (tag != tag_GeneralizedTime) {
+            throw new IOException(
+                "DerValue.getGeneralizedTime, not a GeneralizedTime: " + tag);
+        }
+        return buffer.getGeneralizedTime(data.available());
+    }
+
+    /**
+     * Returns true iff the other object is a DER value which
+     * is bitwise equal to this one.
+     *
+     * @param other the object being compared with this one
+     */
+    public boolean equals(Object other) {
+        if (other instanceof DerValue)
+            return equals((DerValue)other);
+        else
+            return false;
+    }
+
+    /**
+     * Bitwise equality comparison.  DER encoded values have a single
+     * encoding, so that bitwise equality of the encoded values is an
+     * efficient way to establish equivalence of the unencoded values.
+     *
+     * @param other the object being compared with this one
+     */
+    public boolean equals(DerValue other) {
+        if (this == other) {
+            return true;
+        }
+        if (tag != other.tag) {
+            return false;
+        }
+        if (data == other.data) {
+            return true;
+        }
+
+        // make sure the order of lock is always consistent to avoid a deadlock
+        return (System.identityHashCode(this.data)
+                > System.identityHashCode(other.data)) ?
+                doEquals(this, other):
+                doEquals(other, this);
+    }
+
+    /**
+     * Helper for public method equals()
+     */
+    private static boolean doEquals(DerValue d1, DerValue d2) {
+        synchronized (d1.data) {
+            synchronized (d2.data) {
+                d1.data.reset();
+                d2.data.reset();
+                return d1.buffer.equals(d2.buffer);
+            }
+        }
+    }
+
+    /**
+     * Returns a printable representation of the value.
+     *
+     * @return printable representation of the value
+     */
+    public String toString() {
+        try {
+
+            String str = getAsString();
+            if (str != null)
+                return "\"" + str + "\"";
+            if (tag == tag_Null)
+                return "[DerValue, null]";
+            if (tag == tag_ObjectId)
+                return "OID." + getOID();
+
+            // integers
+            else
+                return "[DerValue, tag = " + tag
+                        + ", length = " + length + "]";
+        } catch (IOException e) {
+            throw new IllegalArgumentException("misformatted DER value");
+        }
+    }
+
+    /**
+     * Returns a DER-encoded value, such that if it's passed to the
+     * DerValue constructor, a value equivalent to "this" is returned.
+     *
+     * @return DER-encoded value, including tag and length.
+     */
+    public byte[] toByteArray() throws IOException {
+        DerOutputStream out = new DerOutputStream();
+
+        encode(out);
+        data.reset();
+        return out.toByteArray();
+    }
+
+    /**
+     * For "set" and "sequence" types, this function may be used
+     * to return a DER stream of the members of the set or sequence.
+     * This operation is not supported for primitive types such as
+     * integers or bit strings.
+     */
+    public DerInputStream toDerInputStream() throws IOException {
+        if (tag == tag_Sequence || tag == tag_Set)
+            return new DerInputStream(buffer);
+        throw new IOException("toDerInputStream rejects tag type " + tag);
+    }
+
+    /**
+     * Get the length of the encoded value.
+     */
+    public int length() {
+        return length;
+    }
+
+    /**
+     * Determine if a character is one of the permissible characters for
+     * PrintableString:
+     * A-Z, a-z, 0-9, space, apostrophe (39), left and right parentheses,
+     * plus sign, comma, hyphen, period, slash, colon, equals sign,
+     * and question mark.
+     *
+     * Characters that are *not* allowed in PrintableString include
+     * exclamation point, quotation mark, number sign, dollar sign,
+     * percent sign, ampersand, asterisk, semicolon, less than sign,
+     * greater than sign, at sign, left and right square brackets,
+     * backslash, circumflex (94), underscore, back quote (96),
+     * left and right curly brackets, vertical line, tilde,
+     * and the control codes (0-31 and 127).
+     *
+     * This list is based on X.680 (the ASN.1 spec).
+     */
+    public static boolean isPrintableStringChar(char ch) {
+        if ((ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z') ||
+            (ch >= '0' && ch <= '9')) {
+            return true;
+        } else {
+            switch (ch) {
+                case ' ':       /* space */
+                case '\'':      /* apostrophe */
+                case '(':       /* left paren */
+                case ')':       /* right paren */
+                case '+':       /* plus */
+                case ',':       /* comma */
+                case '-':       /* hyphen */
+                case '.':       /* period */
+                case '/':       /* slash */
+                case ':':       /* colon */
+                case '=':       /* equals */
+                case '?':       /* question mark */
+                    return true;
+                default:
+                    return false;
+            }
+        }
+    }
+
+    /**
+     * Create the tag of the attribute.
+     *
+     * @params class the tag class type, one of UNIVERSAL, CONTEXT,
+     *               APPLICATION or PRIVATE
+     * @params form if true, the value is constructed, otherwise it
+     * is primitive.
+     * @params val the tag value
+     */
+    public static byte createTag(byte tagClass, boolean form, byte val) {
+        byte tag = (byte)(tagClass | val);
+        if (form) {
+            tag |= (byte)0x20;
+        }
+        return (tag);
+    }
+
+    /**
+     * Set the tag of the attribute. Commonly used to reset the
+     * tag value used for IMPLICIT encodings.
+     *
+     * @params tag the tag value
+     */
+    public void resetTag(byte tag) {
+        this.tag = tag;
+    }
+
+    /**
+     * Returns a hashcode for this DerValue.
+     *
+     * @return a hashcode for this DerValue.
+     */
+    public int hashCode() {
+        return toString().hashCode();
+    }
+}