Java tutorial
package org.bouncycastle.asn1; import java.io.ByteArrayOutputStream; import java.io.IOException; import java.math.BigInteger; import java.util.concurrent.ConcurrentHashMap; import java.util.concurrent.ConcurrentMap; import org.bouncycastle.util.Arrays; /** * Class representing the ASN.1 OBJECT IDENTIFIER type. */ public class ASN1ObjectIdentifier extends ASN1Primitive { private final String identifier; private byte[] body; /** * Return an OID from the passed in object * * @param obj an ASN1ObjectIdentifier or an object that can be converted into one. * @return an ASN1ObjectIdentifier instance, or null. * @throws IllegalArgumentException if the object cannot be converted. */ public static ASN1ObjectIdentifier getInstance(Object obj) { if (obj == null || obj instanceof ASN1ObjectIdentifier) { return (ASN1ObjectIdentifier) obj; } if (obj instanceof ASN1Encodable) { ASN1Primitive primitive = ((ASN1Encodable) obj).toASN1Primitive(); if (primitive instanceof ASN1ObjectIdentifier) { return (ASN1ObjectIdentifier) primitive; } } if (obj instanceof byte[]) { byte[] enc = (byte[]) obj; try { return (ASN1ObjectIdentifier) fromByteArray(enc); } catch (IOException e) { throw new IllegalArgumentException( "failed to construct object identifier from byte[]: " + e.getMessage()); } } throw new IllegalArgumentException("illegal object in getInstance: " + obj.getClass().getName()); } /** * Return an OBJECT IDENTIFIER from a tagged object. * * @param obj the tagged object holding the object we want * @param explicit true if the object is meant to be explicitly * tagged false otherwise. * @return an ASN1ObjectIdentifier instance, or null. * @throws IllegalArgumentException if the tagged object cannot * be converted. */ public static ASN1ObjectIdentifier getInstance(ASN1TaggedObject obj, boolean explicit) { ASN1Primitive o = obj.getObject(); if (explicit || o instanceof ASN1ObjectIdentifier) { return getInstance(o); } else { return ASN1ObjectIdentifier.fromOctetString(ASN1OctetString.getInstance(o).getOctets()); } } private static final long LONG_LIMIT = (Long.MAX_VALUE >> 7) - 0x7f; ASN1ObjectIdentifier(byte[] bytes) { StringBuffer objId = new StringBuffer(); long value = 0; BigInteger bigValue = null; boolean first = true; for (int i = 0; i != bytes.length; i++) { int b = bytes[i] & 0xff; if (value <= LONG_LIMIT) { value += (b & 0x7f); if ((b & 0x80) == 0) // end of number reached { if (first) { if (value < 40) { objId.append('0'); } else if (value < 80) { objId.append('1'); value -= 40; } else { objId.append('2'); value -= 80; } first = false; } objId.append('.'); objId.append(value); value = 0; } else { value <<= 7; } } else { if (bigValue == null) { bigValue = BigInteger.valueOf(value); } bigValue = bigValue.or(BigInteger.valueOf(b & 0x7f)); if ((b & 0x80) == 0) { if (first) { objId.append('2'); bigValue = bigValue.subtract(BigInteger.valueOf(80)); first = false; } objId.append('.'); objId.append(bigValue); bigValue = null; value = 0; } else { bigValue = bigValue.shiftLeft(7); } } } this.identifier = objId.toString(); this.body = Arrays.clone(bytes); } /** * Create an OID based on the passed in String. * * @param identifier a string representation of an OID. */ public ASN1ObjectIdentifier(String identifier) { if (identifier == null) { throw new NullPointerException("'identifier' cannot be null"); } if (!isValidIdentifier(identifier)) { throw new IllegalArgumentException("string " + identifier + " not an OID"); } this.identifier = identifier; } /** * Create an OID that creates a branch under the current one. * * @param branchID node numbers for the new branch. * @return the OID for the new created branch. */ ASN1ObjectIdentifier(ASN1ObjectIdentifier oid, String branchID) { if (!isValidBranchID(branchID, 0)) { throw new IllegalArgumentException("string " + branchID + " not a valid OID branch"); } this.identifier = oid.getId() + "." + branchID; } /** * Return the OID as a string. * * @return the string representation of the OID carried by this object. */ public String getId() { return identifier; } /** * Return an OID that creates a branch under the current one. * * @param branchID node numbers for the new branch. * @return the OID for the new created branch. */ public ASN1ObjectIdentifier branch(String branchID) { return new ASN1ObjectIdentifier(this, branchID); } /** * Return true if this oid is an extension of the passed in branch - stem. * * @param stem the arc or branch that is a possible parent. * @return true if the branch is on the passed in stem, false otherwise. */ public boolean on(ASN1ObjectIdentifier stem) { String id = getId(), stemId = stem.getId(); return id.length() > stemId.length() && id.charAt(stemId.length()) == '.' && id.startsWith(stemId); } private void writeField(ByteArrayOutputStream out, long fieldValue) { byte[] result = new byte[9]; int pos = 8; result[pos] = (byte) ((int) fieldValue & 0x7f); while (fieldValue >= (1L << 7)) { fieldValue >>= 7; result[--pos] = (byte) ((int) fieldValue & 0x7f | 0x80); } out.write(result, pos, 9 - pos); } private void writeField(ByteArrayOutputStream out, BigInteger fieldValue) { int byteCount = (fieldValue.bitLength() + 6) / 7; if (byteCount == 0) { out.write(0); } else { BigInteger tmpValue = fieldValue; byte[] tmp = new byte[byteCount]; for (int i = byteCount - 1; i >= 0; i--) { tmp[i] = (byte) ((tmpValue.intValue() & 0x7f) | 0x80); tmpValue = tmpValue.shiftRight(7); } tmp[byteCount - 1] &= 0x7f; out.write(tmp, 0, tmp.length); } } private void doOutput(ByteArrayOutputStream aOut) { OIDTokenizer tok = new OIDTokenizer(identifier); int first = Integer.parseInt(tok.nextToken()) * 40; String secondToken = tok.nextToken(); if (secondToken.length() <= 18) { writeField(aOut, first + Long.parseLong(secondToken)); } else { writeField(aOut, new BigInteger(secondToken).add(BigInteger.valueOf(first))); } while (tok.hasMoreTokens()) { String token = tok.nextToken(); if (token.length() <= 18) { writeField(aOut, Long.parseLong(token)); } else { writeField(aOut, new BigInteger(token)); } } } private synchronized byte[] getBody() { if (body == null) { ByteArrayOutputStream bOut = new ByteArrayOutputStream(); doOutput(bOut); body = bOut.toByteArray(); } return body; } boolean isConstructed() { return false; } int encodedLength() throws IOException { int length = getBody().length; return 1 + StreamUtil.calculateBodyLength(length) + length; } void encode(ASN1OutputStream out, boolean withTag) throws IOException { out.writeEncoded(withTag, BERTags.OBJECT_IDENTIFIER, getBody()); } public int hashCode() { return identifier.hashCode(); } boolean asn1Equals(ASN1Primitive o) { if (o == this) { return true; } if (!(o instanceof ASN1ObjectIdentifier)) { return false; } return identifier.equals(((ASN1ObjectIdentifier) o).identifier); } public String toString() { return getId(); } private static boolean isValidBranchID(String branchID, int start) { int digitCount = 0; int pos = branchID.length(); while (--pos >= start) { char ch = branchID.charAt(pos); if (ch == '.') { if (0 == digitCount || (digitCount > 1 && branchID.charAt(pos + 1) == '0')) { return false; } digitCount = 0; } else if ('0' <= ch && ch <= '9') { ++digitCount; } else { return false; } } if (0 == digitCount || (digitCount > 1 && branchID.charAt(pos + 1) == '0')) { return false; } return true; } private static boolean isValidIdentifier(String identifier) { if (identifier.length() < 3 || identifier.charAt(1) != '.') { return false; } char first = identifier.charAt(0); if (first < '0' || first > '2') { return false; } return isValidBranchID(identifier, 2); } /** * Intern will return a reference to a pooled version of this object, unless it * is not present in which case intern will add it. * <p> * The pool is also used by the ASN.1 parsers to limit the number of duplicated OID * objects in circulation. * </p> * * @return a reference to the identifier in the pool. */ public ASN1ObjectIdentifier intern() { final OidHandle hdl = new OidHandle(getBody()); ASN1ObjectIdentifier oid = pool.get(hdl); if (oid == null) { oid = pool.putIfAbsent(hdl, this); if (oid == null) { oid = this; } } return oid; } private static final ConcurrentMap<OidHandle, ASN1ObjectIdentifier> pool = new ConcurrentHashMap<OidHandle, ASN1ObjectIdentifier>(); private static class OidHandle { private final int key; private final byte[] enc; OidHandle(byte[] enc) { this.key = Arrays.hashCode(enc); this.enc = enc; } public int hashCode() { return key; } public boolean equals(Object o) { if (o instanceof OidHandle) { return Arrays.areEqual(enc, ((OidHandle) o).enc); } return false; } } static ASN1ObjectIdentifier fromOctetString(byte[] enc) { final OidHandle hdl = new OidHandle(enc); ASN1ObjectIdentifier oid = pool.get(hdl); if (oid == null) { return new ASN1ObjectIdentifier(enc); } return oid; } }