/*
 * Copyright (c) 1996, 2017, Oracle and/or its affiliates. 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.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 */

package sun.security.util;

import java.io.*;
import java.math.BigInteger;
import java.util.Arrays;

Represent an ISO Object Identifier.
Object Identifiers are arbitrary length hierarchical identifiers.
The individual components are numbers, and they define paths from the
root of an ISO-managed identifier space.  You will sometimes see a
string name used instead of (or in addition to) the numerical id.
These are synonyms for the numerical IDs, but are not widely used
since most sites do not know all the requisite strings, while all
sites can parse the numeric forms.
So for example, JavaSoft has the sole authority to assign the
meaning to identifiers below the 1.3.6.1.4.1.42.2.17 node in the
hierarchy, and other organizations can easily acquire the ability
to assign such unique identifiers.
Author:
David Brownell, Amit Kapoor, Hemma Prafullchandra/**
 * Represent an ISO Object Identifier.
 *
 * <P>Object Identifiers are arbitrary length hierarchical identifiers.
 * The individual components are numbers, and they define paths from the
 * root of an ISO-managed identifier space.  You will sometimes see a
 * string name used instead of (or in addition to) the numerical id.
 * These are synonyms for the numerical IDs, but are not widely used
 * since most sites do not know all the requisite strings, while all
 * sites can parse the numeric forms.
 *
 * <P>So for example, JavaSoft has the sole authority to assign the
 * meaning to identifiers below the 1.3.6.1.4.1.42.2.17 node in the
 * hierarchy, and other organizations can easily acquire the ability
 * to assign such unique identifiers.
 *
 * @author David Brownell
 * @author Amit Kapoor
 * @author Hemma Prafullchandra
 */

public final
class ObjectIdentifier implements Serializable
{
    
We use the DER value (no tag, no length) as the internal format
@serial
/**
     * We use the DER value (no tag, no length) as the internal format
     * @serial
     */
    private byte[] encoding = null;

    private transient volatile String stringForm;

    /*
     * IMPORTANT NOTES FOR CODE CHANGES (bug 4811968) IN JDK 1.7.0
     * ===========================================================
     *
     * (Almost) serialization compatibility with old versions:
     *
     * serialVersionUID is unchanged. Old field "component" is changed to
     * type Object so that "poison" (unknown object type for old versions)
     * can be put inside if there are huge components that cannot be saved
     * as integers.
     *
     * New version use the new filed "encoding" only.
     *
     * Below are all 4 cases in a serialization/deserialization process:
     *
     * 1. old -> old: Not covered here
     * 2. old -> new: There's no "encoding" field, new readObject() reads
     *    "components" and "componentLen" instead and inits correctly.
     * 3. new -> new: "encoding" field exists, new readObject() uses it
     *    (ignoring the other 2 fields) and inits correctly.
     * 4. new -> old: old readObject() only recognizes "components" and
     *    "componentLen" fields. If no huge components are involved, they
     *    are serialized as legal values and old object can init correctly.
     *    Otherwise, old object cannot recognize the form (component not int[])
     *    and throw a ClassNotFoundException at deserialization time.
     *
     * Therfore, for the first 3 cases, exact compatibility is preserved. In
     * the 4th case, non-huge OID is still supportable in old versions, while
     * huge OID is not.
     */
    private static final long serialVersionUID = 8697030238860181294L;

    
Changed to Object
@serial
/**
     * Changed to Object
     * @serial
     */
    private Object      components   = null;          // path from root
    
@serial
/**
     * @serial
     */
    private int         componentLen = -1;            // how much is used.

    // Is the components field calculated?
    private transient boolean   componentsCalculated = false;

    private void readObject(ObjectInputStream is)
            throws IOException, ClassNotFoundException {
        is.defaultReadObject();

        if (encoding == null) {  // from an old version
            int[] comp = (int[])components;
            if (componentLen > comp.length) {
                componentLen = comp.length;
            }
            init(comp, componentLen);
        }
    }

    private void writeObject(ObjectOutputStream os)
            throws IOException {
        if (!componentsCalculated) {
            int[] comps = toIntArray();
            if (comps != null) {    // every one understands this
                components = comps;
                componentLen = comps.length;
            } else {
                components = HugeOidNotSupportedByOldJDK.theOne;
            }
            componentsCalculated = true;
        }
        os.defaultWriteObject();
    }

    static class HugeOidNotSupportedByOldJDK implements Serializable {
        private static final long serialVersionUID = 1L;
        static HugeOidNotSupportedByOldJDK theOne = new HugeOidNotSupportedByOldJDK();
    }

    
Constructs, from a string.  This string should be of the form 1.23.56.
Validity check included.
/**
     * Constructs, from a string.  This string should be of the form 1.23.56.
     * Validity check included.
     */
    public ObjectIdentifier (String oid) throws IOException
    {
        int ch = '.';
        int start = 0;
        int end = 0;

        int pos = 0;
        byte[] tmp = new byte[oid.length()];
        int first = 0, second;
        int count = 0;

        try {
            String comp = null;
            do {
                int length = 0; // length of one section
                end = oid.indexOf(ch,start);
                if (end == -1) {
                    comp = oid.substring(start);
                    length = oid.length() - start;
                } else {
                    comp = oid.substring(start,end);
                    length = end - start;
                }

                if (length > 9) {
                    BigInteger bignum = new BigInteger(comp);
                    if (count == 0) {
                        checkFirstComponent(bignum);
                        first = bignum.intValue();
                    } else {
                        if (count == 1) {
                            checkSecondComponent(first, bignum);
                            bignum = bignum.add(BigInteger.valueOf(40*first));
                        } else {
                            checkOtherComponent(count, bignum);
                        }
                        pos += pack7Oid(bignum, tmp, pos);
                    }
                } else {
                    int num = Integer.parseInt(comp);
                    if (count == 0) {
                        checkFirstComponent(num);
                        first = num;
                    } else {
                        if (count == 1) {
                            checkSecondComponent(first, num);
                            num += 40 * first;
                        } else {
                            checkOtherComponent(count, num);
                        }
                        pos += pack7Oid(num, tmp, pos);
                    }
                }
                start = end + 1;
                count++;
            } while (end != -1);

            checkCount(count);
            encoding = new byte[pos];
            System.arraycopy(tmp, 0, encoding, 0, pos);
            this.stringForm = oid;
        } catch (IOException ioe) { // already detected by checkXXX
            throw ioe;
        } catch (Exception e) {
            throw new IOException("ObjectIdentifier() -- Invalid format: "
                    + e.toString(), e);
        }
    }

    
Constructor, from an array of integers.
Validity check included.
/**
     * Constructor, from an array of integers.
     * Validity check included.
     */
    public ObjectIdentifier(int[] values) throws IOException
    {
        checkCount(values.length);
        checkFirstComponent(values[0]);
        checkSecondComponent(values[0], values[1]);
        for (int i=2; i<values.length; i++)
            checkOtherComponent(i, values[i]);
        init(values, values.length);
    }

    
Constructor, from an ASN.1 encoded input stream.
Validity check NOT included.
The encoding of the ID in the stream uses "DER", a BER/1 subset.
In this case, that means a triple { typeId, length, data }.
NOTE:  When an exception is thrown, the
input stream has not been returned to its "initial" state.
Params:
in – DER-encoded data holding an object ID
Throws:
IOException – indicates a decoding error/**
     * Constructor, from an ASN.1 encoded input stream.
     * Validity check NOT included.
     * The encoding of the ID in the stream uses "DER", a BER/1 subset.
     * In this case, that means a triple { typeId, length, data }.
     *
     * <P><STRONG>NOTE:</STRONG>  When an exception is thrown, the
     * input stream has not been returned to its "initial" state.
     *
     * @param in DER-encoded data holding an object ID
     * @exception IOException indicates a decoding error
     */
    public ObjectIdentifier (DerInputStream in) throws IOException
    {
        byte    type_id;
        int     bufferEnd;

        /*
         * Object IDs are a "universal" type, and their tag needs only
         * one byte of encoding.  Verify that the tag of this datum
         * is that of an object ID.
         *
         * Then get and check the length of the ID's encoding.  We set
         * up so that we can use in.available() to check for the end of
         * this value in the data stream.
         */
        type_id = (byte) in.getByte ();
        if (type_id != DerValue.tag_ObjectId)
            throw new IOException (
                "ObjectIdentifier() -- data isn't an object ID"
                + " (tag = " +  type_id + ")"
                );

        int len = in.getDefiniteLength();
        if (len > in.available()) {
            throw new IOException("ObjectIdentifier() -- length exceeds" +
                    "data available.  Length: " + len + ", Available: " +
                    in.available());
        }
        encoding = new byte[len];
        in.getBytes(encoding);
        check(encoding);
    }

    /*
     * Constructor, from the rest of a DER input buffer;
     * the tag and length have been removed/verified
     * Validity check NOT included.
     */
    ObjectIdentifier (DerInputBuffer buf) throws IOException
    {
        DerInputStream in = new DerInputStream(buf);
        encoding = new byte[in.available()];
        in.getBytes(encoding);
        check(encoding);
    }

    private void init(int[] components, int length) {
        int pos = 0;
        byte[] tmp = new byte[length*5+1];  // +1 for empty input

        if (components[1] < Integer.MAX_VALUE - components[0]*40)
            pos += pack7Oid(components[0]*40+components[1], tmp, pos);
        else {
            BigInteger big = BigInteger.valueOf(components[1]);
            big = big.add(BigInteger.valueOf(components[0]*40));
            pos += pack7Oid(big, tmp, pos);
        }

        for (int i=2; i<length; i++) {
            pos += pack7Oid(components[i], tmp, pos);
        }
        encoding = new byte[pos];
        System.arraycopy(tmp, 0, encoding, 0, pos);
    }

    
This method is kept for compatibility reasons. The new implementation
does the check and conversion. All around the JDK, the method is called
in static blocks to initialize pre-defined ObjectIdentifieies. No
obvious performance hurt will be made after this change.
Old doc: Create a new ObjectIdentifier for internal use. The values are
neither checked nor cloned.
/**
     * This method is kept for compatibility reasons. The new implementation
     * does the check and conversion. All around the JDK, the method is called
     * in static blocks to initialize pre-defined ObjectIdentifieies. No
     * obvious performance hurt will be made after this change.
     *
     * Old doc: Create a new ObjectIdentifier for internal use. The values are
     * neither checked nor cloned.
     */
    public static ObjectIdentifier newInternal(int[] values) {
        try {
            return new ObjectIdentifier(values);
        } catch (IOException ex) {
            throw new RuntimeException(ex);
            // Should not happen, internal calls always uses legal values.
        }
    }

    /*
     * n.b. the only public interface is DerOutputStream.putOID()
     */
    void encode (DerOutputStream out) throws IOException
    {
        out.write (DerValue.tag_ObjectId, encoding);
    }

    
Compares this identifier with another, for equality.
Returns:
true iff the names are identical./**
     * Compares this identifier with another, for equality.
     *
     * @return true iff the names are identical.
     */
    @Override
    public boolean equals(Object obj) {
        if (this == obj) {
            return true;
        }
        if (obj instanceof ObjectIdentifier == false) {
            return false;
        }
        ObjectIdentifier other = (ObjectIdentifier)obj;
        return Arrays.equals(encoding, other.encoding);
    }

    @Override
    public int hashCode() {
        return Arrays.hashCode(encoding);
    }

    
Private helper method for serialization. To be compatible with old
versions of JDK.
Returns:
components in an int array, if all the components are less than
        Integer.MAX_VALUE. Otherwise, null./**
     * Private helper method for serialization. To be compatible with old
     * versions of JDK.
     * @return components in an int array, if all the components are less than
     *         Integer.MAX_VALUE. Otherwise, null.
     */
    private int[] toIntArray() {
        int length = encoding.length;
        int[] result = new int[20];
        int which = 0;
        int fromPos = 0;
        for (int i = 0; i < length; i++) {
            if ((encoding[i] & 0x80) == 0) {
                // one section [fromPos..i]
                if (i - fromPos + 1 > 4) {
                    BigInteger big = new BigInteger(pack(encoding, fromPos, i-fromPos+1, 7, 8));
                    if (fromPos == 0) {
                        result[which++] = 2;
                        BigInteger second = big.subtract(BigInteger.valueOf(80));
                        if (second.compareTo(BigInteger.valueOf(Integer.MAX_VALUE)) == 1) {
                            return null;
                        } else {
                            result[which++] = second.intValue();
                        }
                    } else {
                        if (big.compareTo(BigInteger.valueOf(Integer.MAX_VALUE)) == 1) {
                            return null;
                        } else {
                            result[which++] = big.intValue();
                        }
                    }
                } else {
                    int retval = 0;
                    for (int j = fromPos; j <= i; j++) {
                        retval <<= 7;
                        byte tmp = encoding[j];
                        retval |= (tmp & 0x07f);
                    }
                    if (fromPos == 0) {
                        if (retval < 80) {
                            result[which++] = retval / 40;
                            result[which++] = retval % 40;
                        } else {
                            result[which++] = 2;
                            result[which++] = retval - 80;
                        }
                    } else {
                        result[which++] = retval;
                    }
                }
                fromPos = i+1;
            }
            if (which >= result.length) {
                result = Arrays.copyOf(result, which + 10);
            }
        }
        return Arrays.copyOf(result, which);
    }

    
Returns a string form of the object ID.  The format is the
conventional "dot" notation for such IDs, without any
user-friendly descriptive strings, since those strings
will not be understood everywhere.
/**
     * Returns a string form of the object ID.  The format is the
     * conventional "dot" notation for such IDs, without any
     * user-friendly descriptive strings, since those strings
     * will not be understood everywhere.
     */
    @Override
    public String toString() {
        String s = stringForm;
        if (s == null) {
            int length = encoding.length;
            StringBuilder sb = new StringBuilder(length * 4);

            int fromPos = 0;
            for (int i = 0; i < length; i++) {
                if ((encoding[i] & 0x80) == 0) {
                    // one section [fromPos..i]
                    if (fromPos != 0) {  // not the first segment
                        sb.append('.');
                    }
                    if (i - fromPos + 1 > 4) { // maybe big integer
                        BigInteger big = new BigInteger(pack(encoding, fromPos, i-fromPos+1, 7, 8));
                        if (fromPos == 0) {
                            // first section encoded with more than 4 bytes,
                            // must be 2.something
                            sb.append("2.");
                            sb.append(big.subtract(BigInteger.valueOf(80)));
                        } else {
                            sb.append(big);
                        }
                    } else { // small integer
                        int retval = 0;
                        for (int j = fromPos; j <= i; j++) {
                            retval <<= 7;
                            byte tmp = encoding[j];
                            retval |= (tmp & 0x07f);
                        }
                        if (fromPos == 0) {
                            if (retval < 80) {
                                sb.append(retval/40);
                                sb.append('.');
                                sb.append(retval%40);
                            } else {
                                sb.append("2.");
                                sb.append(retval - 80);
                            }
                        } else {
                            sb.append(retval);
                        }
                    }
                    fromPos = i+1;
                }
            }
            s = sb.toString();
            stringForm = s;
        }
        return s;
    }

    
Repack all bits from input to output. On the both sides, only a portion
(from the least significant bit) of the 8 bits in a byte is used. This
number is defined as the number of useful bits (NUB) for the array. All the
used bits from the input byte array and repacked into the output in the
exactly same order. The output bits are aligned so that the final bit of
the input (the least significant bit in the last byte), when repacked as
the final bit of the output, is still at the least significant position.
Zeroes will be padded on the left side of the first output byte if
necessary. All unused bits in the output are also zeroed.
For example: if the input is 01001100 with NUB 8, the output which
has a NUB 6 will look like:
     00000001 00001100
The first 2 bits of the output bytes are unused bits. The other bits
turn out to be 000001 001100. While the 8 bits on the right are from
the input, the left 4 zeroes are padded to fill the 6 bits space.
Params:
in –        the input byte array
ioffset –   start point inside in
ilength –   number of bytes to repack
iw –        NUB for input
ow –        NUB for output
Returns:
         the repacked bytes/**
     * Repack all bits from input to output. On the both sides, only a portion
     * (from the least significant bit) of the 8 bits in a byte is used. This
     * number is defined as the number of useful bits (NUB) for the array. All the
     * used bits from the input byte array and repacked into the output in the
     * exactly same order. The output bits are aligned so that the final bit of
     * the input (the least significant bit in the last byte), when repacked as
     * the final bit of the output, is still at the least significant position.
     * Zeroes will be padded on the left side of the first output byte if
     * necessary. All unused bits in the output are also zeroed.
     *
     * For example: if the input is 01001100 with NUB 8, the output which
     * has a NUB 6 will look like:
     *      00000001 00001100
     * The first 2 bits of the output bytes are unused bits. The other bits
     * turn out to be 000001 001100. While the 8 bits on the right are from
     * the input, the left 4 zeroes are padded to fill the 6 bits space.
     *
     * @param in        the input byte array
     * @param ioffset   start point inside <code>in</code>
     * @param ilength   number of bytes to repack
     * @param iw        NUB for input
     * @param ow        NUB for output
     * @return          the repacked bytes
     */
    private static byte[] pack(byte[] in, int ioffset, int ilength, int iw, int ow) {
        assert (iw > 0 && iw <= 8): "input NUB must be between 1 and 8";
        assert (ow > 0 && ow <= 8): "output NUB must be between 1 and 8";

        if (iw == ow) {
            return in.clone();
        }

        int bits = ilength * iw;    // number of all used bits
        byte[] out = new byte[(bits+ow-1)/ow];

        // starting from the 0th bit in the input
        int ipos = 0;

        // the number of padding 0's needed in the output, skip them
        int opos = (bits+ow-1)/ow*ow-bits;

        while(ipos < bits) {
            int count = iw - ipos%iw;   // unpacked bits in current input byte
            if (count > ow - opos%ow) { // free space available in output byte
                count = ow - opos%ow;   // choose the smaller number
            }
            // and move them!
            out[opos/ow] |=                         // paste!
                (((in[ioffset+ipos/iw]+256)         // locate the byte (+256 so that it's never negative)
                    >> (iw-ipos%iw-count))          // move to the end of a byte
                        & ((1 << (count))-1))       // zero out all other bits
                            << (ow-opos%ow-count);  // move to the output position
            ipos += count;  // advance
            opos += count;  // advance
        }
        return out;
    }

    
Repack from NUB 8 to a NUB 7 OID sub-identifier, remove all
unnecessary 0 headings, set the first bit of all non-tail
output bytes to 1 (as ITU-T Rec. X.690 8.19.2 says), and
paste it into an existing byte array.
Params:
out – the existing array to be pasted into
ooffset – the starting position to paste
Returns:
the number of bytes pasted/**
     * Repack from NUB 8 to a NUB 7 OID sub-identifier, remove all
     * unnecessary 0 headings, set the first bit of all non-tail
     * output bytes to 1 (as ITU-T Rec. X.690 8.19.2 says), and
     * paste it into an existing byte array.
     * @param out the existing array to be pasted into
     * @param ooffset the starting position to paste
     * @return the number of bytes pasted
     */
    private static int pack7Oid(byte[] in, int ioffset, int ilength, byte[] out, int ooffset) {
        byte[] pack = pack(in, ioffset, ilength, 8, 7);
        int firstNonZero = pack.length-1;   // paste at least one byte
        for (int i=pack.length-2; i>=0; i--) {
            if (pack[i] != 0) {
                firstNonZero = i;
            }
            pack[i] |= 0x80;
        }
        System.arraycopy(pack, firstNonZero, out, ooffset, pack.length-firstNonZero);
        return pack.length-firstNonZero;
    }

    
Repack from NUB 7 to NUB 8, remove all unnecessary 0
headings, and paste it into an existing byte array.
Params:
out – the existing array to be pasted into
ooffset – the starting position to paste
Returns:
the number of bytes pasted/**
     * Repack from NUB 7 to NUB 8, remove all unnecessary 0
     * headings, and paste it into an existing byte array.
     * @param out the existing array to be pasted into
     * @param ooffset the starting position to paste
     * @return the number of bytes pasted
     */
    private static int pack8(byte[] in, int ioffset, int ilength, byte[] out, int ooffset) {
        byte[] pack = pack(in, ioffset, ilength, 7, 8);
        int firstNonZero = pack.length-1;   // paste at least one byte
        for (int i=pack.length-2; i>=0; i--) {
            if (pack[i] != 0) {
                firstNonZero = i;
            }
        }
        System.arraycopy(pack, firstNonZero, out, ooffset, pack.length-firstNonZero);
        return pack.length-firstNonZero;
    }

    
Pack the int into a OID sub-identifier DER encoding
/**
     * Pack the int into a OID sub-identifier DER encoding
     */
    private static int pack7Oid(int input, byte[] out, int ooffset) {
        byte[] b = new byte[4];
        b[0] = (byte)(input >> 24);
        b[1] = (byte)(input >> 16);
        b[2] = (byte)(input >> 8);
        b[3] = (byte)(input);
        return pack7Oid(b, 0, 4, out, ooffset);
    }

    
Pack the BigInteger into a OID subidentifier DER encoding
/**
     * Pack the BigInteger into a OID subidentifier DER encoding
     */
    private static int pack7Oid(BigInteger input, byte[] out, int ooffset) {
        byte[] b = input.toByteArray();
        return pack7Oid(b, 0, b.length, out, ooffset);
    }

    /**
     * Private methods to check validity of OID. They must be --
     * 1. at least 2 components
     * 2. all components must be non-negative
     * 3. the first must be 0, 1 or 2
     * 4. if the first is 0 or 1, the second must be <40
     */

    
Check the DER encoding. Since DER encoding defines that the integer bits
are unsigned, so there's no need to check the MSB.
/**
     * Check the DER encoding. Since DER encoding defines that the integer bits
     * are unsigned, so there's no need to check the MSB.
     */
    private static void check(byte[] encoding) throws IOException {
        int length = encoding.length;
        if (length < 1 ||      // too short
                (encoding[length - 1] & 0x80) != 0) {  // not ended
            throw new IOException("ObjectIdentifier() -- " +
                    "Invalid DER encoding, not ended");
        }
        for (int i=0; i<length; i++) {
            // 0x80 at the beginning of a subidentifier
            if (encoding[i] == (byte)0x80 &&
                    (i==0 || (encoding[i-1] & 0x80) == 0)) {
                throw new IOException("ObjectIdentifier() -- " +
                        "Invalid DER encoding, useless extra octet detected");
            }
        }
    }
    private static void checkCount(int count) throws IOException {
        if (count < 2) {
            throw new IOException("ObjectIdentifier() -- " +
                    "Must be at least two oid components ");
        }
    }
    private static void checkFirstComponent(int first) throws IOException {
        if (first < 0 || first > 2) {
            throw new IOException("ObjectIdentifier() -- " +
                    "First oid component is invalid ");
        }
    }
    private static void checkFirstComponent(BigInteger first) throws IOException {
        if (first.signum() == -1 || first.compareTo(BigInteger.TWO) > 0) {
            throw new IOException("ObjectIdentifier() -- " +
                    "First oid component is invalid ");
        }
    }
    private static void checkSecondComponent(int first, int second) throws IOException {
        if (second < 0 || first != 2 && second > 39) {
            throw new IOException("ObjectIdentifier() -- " +
                    "Second oid component is invalid ");
        }
    }
    private static void checkSecondComponent(int first, BigInteger second) throws IOException {
        if (second.signum() == -1 ||
                first != 2 &&
                second.compareTo(BigInteger.valueOf(39)) == 1) {
            throw new IOException("ObjectIdentifier() -- " +
                    "Second oid component is invalid ");
        }
    }
    private static void checkOtherComponent(int i, int num) throws IOException {
        if (num < 0) {
            throw new IOException("ObjectIdentifier() -- " +
                    "oid component #" + (i+1) + " must be non-negative ");
        }
    }
    private static void checkOtherComponent(int i, BigInteger num) throws IOException {
        if (num.signum() == -1) {
            throw new IOException("ObjectIdentifier() -- " +
                    "oid component #" + (i+1) + " must be non-negative ");
        }
    }
}