package at.gv.egovernment.moa.id.util;

import iaik.ixsil.util.URI;

import iaik.security.ecc.ecdsa.ECDSAParameter;
import iaik.security.ecc.ecdsa.ECPublicKey;
//import iaik.security.ecc.interfaces.ECDSAPublicKey;
import iaik.security.ecc.math.ecgroup.ECGroupFactory;
import iaik.security.ecc.math.ecgroup.ECPoint;
import iaik.security.ecc.math.ecgroup.EllipticCurve;
import iaik.security.ecc.math.ecgroup.ProjectiveCoordinate;
//import iaik.security.ecc.math.field.BinaryField;
//import iaik.security.ecc.math.field.BinaryFieldValue;
import iaik.security.ecc.math.field.Field;
import iaik.security.ecc.math.field.FieldElement;
import iaik.security.ecc.math.field.FieldFactory;
import iaik.security.ecc.math.field.Value;
import iaik.security.ecc.parameter.ECCParameterFactory;
import iaik.security.ecc.spec.ECCParameterSpec;

import java.math.BigInteger;
import java.security.PublicKey;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Vector;

import org.w3c.dom.Attr;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

//import at.gv.cio.identitylink.init.Constants;
import at.gv.egovernment.moa.id.util.ECDSAConstants;

public class ECDSAKeyValueConverter
{ 
    
    
  //TODO enhance javadoc
 
  /**
   * converter class which can be used to convert ECDSA keys encoded in XML 
   * to a PublicKey data structure 
   * @param keyValueElem ECDSAKeyValue Element  
   * @return ECPublicKey encoded in PublicKey data structure
   * @throws Exception
   * 
   * @author gregor karlinger
   */
public static PublicKey element2ECDSAPublicKey(Element keyValueElem) throws Exception
  {
    String ecdsaNS = ECDSAConstants.NAMESPACE_ECDSAKEYVALUE_;

    // Domain parameters
    Element domainParams = getChildElement(keyValueElem, ecdsaNS, "DomainParameters", 1);
    if (domainParams == null) throw new Exception("Domain parameters must not be implicit.");

    Element namedCurve = getChildElement(domainParams, ecdsaNS, "NamedCurve", 1);
    ECCParameterSpec eccParameterSpec;

    if (namedCurve != null)
    {
      URI curveNameURN = new URI(namedCurve.getAttributeNS(null, "URN"));
      ECCParameterFactory eccParamFactory = ECCParameterFactory.getInstance();
      eccParameterSpec = eccParamFactory.getParameterByOID(curveNameURN.getPath().substring(4));
    }
    else
    {
      Element excplicitParams = getChildElement(domainParams, ecdsaNS, "ExplicitParams", 1);
      Element fieldParams = getChildElement(excplicitParams, ecdsaNS, "FieldParams", 1);
      Element curveParams = getChildElement(excplicitParams, ecdsaNS, "CurveParams", 1);
      Element basePointParams = getChildElement(excplicitParams, ecdsaNS, "BasePointParams", 1);

      // Field parameters
      String fieldParamsTypeStr = fieldParams.getAttributeNS(ECDSAConstants.NAMESPACE_XSI_, "type");
      String ecdsaNSPrefix = getECDSANSPrefix(fieldParams);
      BigInteger p = null;
      int fieldParamsType = 0;
      final int FIELD_TYPE_PRIME = 1;
      final int FIELD_TYPE_TNB = 2;
      final int FIELD_TYPE_PNB = 3;
      int m = -1, k = -1, k1 = -1, k2 = -1, k3 = -1;
      if (fieldParamsTypeStr.equals(ecdsaNSPrefix + ":PrimeFieldParamsType"))
      {
        fieldParamsType = FIELD_TYPE_PRIME;
        String pStr = getChildElementText(fieldParams, ecdsaNS, "P", 1);
        p = new BigInteger(pStr, 10);
      }
      else if (fieldParamsTypeStr.equals(ecdsaNSPrefix + ":TnBFieldParamsType"))
      {
        fieldParamsType = FIELD_TYPE_TNB;
        String mStr = getChildElementText(fieldParams, ecdsaNS, "M", 1);
        m = Integer.parseInt(mStr);
        String kStr = getChildElementText(fieldParams, ecdsaNS, "K", 1);
        k = Integer.parseInt(kStr);
      }
      else if (fieldParamsTypeStr.equals(ecdsaNSPrefix + ":PnBFieldParamsType"))
      {
        fieldParamsType = FIELD_TYPE_PNB;
        String mStr = getChildElementText(fieldParams, ecdsaNS, "M", 1);
        m = Integer.parseInt(mStr);
        String k1Str = getChildElementText(fieldParams, ecdsaNS, "K1", 1);
        k1 = Integer.parseInt(k1Str);
        String k2Str = getChildElementText(fieldParams, ecdsaNS, "K2", 1);
        k2 = Integer.parseInt(k2Str);
        String k3Str = getChildElementText(fieldParams, ecdsaNS, "K3", 1);
        k3 = Integer.parseInt(k3Str);
      }
      else throw new Exception("Unknown field parameters.");

      // Curve parameters
      Element aElem = getChildElement(curveParams, ecdsaNS, "A", 1);
      String aStr = aElem.getAttributeNS(null, "Value");
      Element bElem = getChildElement(curveParams, ecdsaNS, "B", 1);
      String bStr = bElem.getAttributeNS(null, "Value");
      String seedStr = getChildElementText(curveParams, ecdsaNS, "Seed", 1);
      BigInteger seed = (seedStr != null) ? new BigInteger(seedStr, 10) : null;

      // Base point parameters
      Element basePoint = getChildElement(basePointParams, ecdsaNS, "BasePoint", 1);
      Element basePointXElem = getChildElement(basePoint, ecdsaNS, "X", 1);
      String basePointXStr = basePointXElem.getAttributeNS(null, "Value");
      Element basePointYElem = getChildElement(basePoint, ecdsaNS, "Y", 1);
      String basePointYStr = basePointYElem.getAttributeNS(null, "Value");
      String orderStr =  getChildElementText(basePointParams, ecdsaNS, "Order", 1);
      BigInteger order = new BigInteger(orderStr, 10);
      String cofactorStr = getChildElementText(basePointParams, ecdsaNS, "Cofactor", 1);
      BigInteger cofactor = (cofactorStr != null) ? new BigInteger(cofactorStr, 10) : null;

      if (fieldParamsType == FIELD_TYPE_PRIME)
      {
        BigInteger a = new BigInteger(aStr, 10);
        BigInteger b = new BigInteger(bStr, 10);
        BigInteger basePointX = new BigInteger(basePointXStr, 10);
        BigInteger basePointY = new BigInteger(basePointYStr, 10);
        eccParameterSpec = new ECCParameterSpec(p, cofactor, order, seed, null, a, b, basePointX,
          basePointY, null);
      }
      else
      {
        int[] irreducible = new int[m/32 + ((m % 32 != 0) ? 1 : 0)];
        if (fieldParamsType == FIELD_TYPE_TNB)
        {
          irreducible[m/32] = 1 << m % 32;
          irreducible[k/32] += 1 << k % 32;
          irreducible[0] += 1;
        }
        else
        {
          irreducible[m/32] = 1 << m % 32;
          irreducible[k3/32] += 1 << k3 % 32;
          irreducible[k2/32] += 1 << k2 % 32;
          irreducible[k1/32] += 1 << k1 % 32;
          irreducible[0] += 1;
        }
        eccParameterSpec = new ECCParameterSpec(irreducible, cofactor, order, octetString2IntArray(aStr),
          octetString2IntArray(bStr), octetString2IntArray(basePointXStr),
          octetString2IntArray(basePointYStr), null);
      }
    }

    // Public key
    Element publicKeyElem = getChildElement(keyValueElem, ecdsaNS, "PublicKey", 1);
    Element publicKeyXElem = getChildElement(publicKeyElem, ecdsaNS, "X", 1);
    String publicKeyXStr = publicKeyXElem.getAttributeNS(null, "Value");
    Element publicKeyYElem = getChildElement(publicKeyElem, ecdsaNS, "Y", 1);
    String publicKeyYStr = publicKeyYElem.getAttributeNS(null, "Value");

    ECDSAParameter ecdsaParams = new ECDSAParameter(eccParameterSpec, false);
    ECGroupFactory ecGroupFactory = ECGroupFactory.getInstance();
    EllipticCurve eCurve = ecGroupFactory.getCurveWithProjective(eccParameterSpec.getA(),
      eccParameterSpec.getB(), eccParameterSpec.getR());
    Field field = eCurve.getField();

    // Detect type of public key field elements
    String elementType = publicKeyXElem.getAttributeNS(ECDSAConstants.NAMESPACE_XSI_, "type");
    String elementTypeLocalName = elementType.substring(elementType.indexOf(':') + 1);
    int FIELD_TYPE_PRIME = 1, FIELD_TYPE_CHAR_TWO = 2;
    int fieldElemType = ("PrimeFieldElemType".equals(elementTypeLocalName))
      ? FIELD_TYPE_PRIME
      : FIELD_TYPE_CHAR_TWO;

    FieldElement publicKeyPointX, publicKeyPointY;
    if (fieldElemType == FIELD_TYPE_PRIME)
    {
      Value xValue = FieldFactory.getInstance().getPrimeFieldValue(new BigInteger(publicKeyXStr, 10));
      publicKeyPointX = field.newElement(xValue);
      Value yValue = FieldFactory.getInstance().getPrimeFieldValue(new BigInteger(publicKeyYStr, 10));
      publicKeyPointY = field.newElement(yValue);
    }
    else
    {
      publicKeyPointX = field.newElement(octetString2ByteArray(publicKeyXStr));
      publicKeyPointY = field.newElement(octetString2ByteArray(publicKeyYStr));
    }
    ProjectiveCoordinate publicKeyPointCoordinate = new ProjectiveCoordinate(publicKeyPointX,
      publicKeyPointY, field.getONEelement());
    ECPoint publicKeyPoint = eCurve.newPoint(publicKeyPointCoordinate);
    ECPublicKey publicKey = new ECPublicKey(ecdsaParams, publicKeyPoint);

    return publicKey;
  }

  /* ---------------------------------------------------------------------------------------------------- */

  /*
  public static Element publicKey2ECDSAKeyValueElement(boolean implParams, String curveOID,
    ECDSAPublicKey publicKey, Document factoryDoc)
  {
    String ecdsaNS = ECDSAConstants.NAMESPACE_ECDSAKEYVALUE_;
    String ecdsaNSP = ECDSAConstants.NS_PREFIX_ECDSAKEYVALUE_;
    String nsNS = ECDSAConstants.NAMESPACE_NAMESPACES_;
    String xsiNS = ECDSAConstants.NAMESPACE_XSI_;
    String xsiNSP = ECDSAConstants.NS_PREFIX_XSI_;

    ECDSAParameter params = (ECDSAParameter)publicKey.getParameter();
    EllipticCurve curve = params.getG().getCurve();
    Field field = curve.getField();
    int fieldId = curve.getField().getFieldId();

    Element eCDSAKeyValue = factoryDoc.createElementNS(ecdsaNS, ecdsaNSP + ":ECDSAKeyValue");
    eCDSAKeyValue.setAttributeNS(nsNS, "xmlns:" + ecdsaNSP, ecdsaNS);
    eCDSAKeyValue.setAttributeNS(nsNS, "xmlns:" + xsiNSP, xsiNS);

    // Detect field type
    int coeffPositions[] = new int[3];
    int fieldType = 0;
    String fieldElemTypeString = null;
    final int FT_PRIME = 1, FT_TNB = 2, FT_PNB = 3;
    if (fieldId == Field.PRIME_FIELD)
    {
      fieldType = FT_PRIME;
      fieldElemTypeString = ecdsaNSP + ":PrimeFieldElemType";
    }
    else
    {
      // Get irreducible polynomal
      BinaryField binaryField = (BinaryField)field;
      BinaryFieldValue irreducible = binaryField.getIrreducible();

      // Get coefficients of irreducible polynomal
      int order = irreducible.getOrder();
      int coeffCount = 2;
      for (int i = 1; i < order - 1; i++)
      {
        if (irreducible.testBit(i))
        {
          coeffPositions[coeffCount - 2] = i;
          coeffCount++;
          if (coeffCount == 5) break;
        }
      }

      // Set polynomal type (TNB or
      fieldType = (coeffCount == 3) ? FT_TNB : FT_PNB;
      fieldElemTypeString = ecdsaNSP + ":CharTwoFieldElemType";
    }

    if (!implParams)
    {
      Element domainParameters = factoryDoc.createElementNS(ecdsaNS, ecdsaNSP + ":DomainParameters");
      eCDSAKeyValue.appendChild(factoryDoc.createTextNode("\n          "));
      eCDSAKeyValue.appendChild(domainParameters);

      if (curveOID != null)
      {
        // Named curve
        Element namedCurve = factoryDoc.createElementNS(ecdsaNS, ecdsaNSP + ":NamedCurve");
        namedCurve.setAttributeNS(null, "URN", "urn:oid:" + curveOID);
        domainParameters.appendChild(factoryDoc.createTextNode("\n            "));
        domainParameters.appendChild(namedCurve);
        domainParameters.appendChild(factoryDoc.createTextNode("\n          "));
      }
      else
      {
        // Explicit parameters
        Element explicitParams = factoryDoc.createElementNS(ecdsaNS, ecdsaNSP + ":ExplicitParams");

        // Field parameters
        Element fieldParams = factoryDoc.createElementNS(ecdsaNS, ecdsaNSP + ":FieldParams");
        explicitParams.appendChild(factoryDoc.createTextNode("\n              "));
        explicitParams.appendChild(fieldParams);

        if (fieldType == FT_PRIME)
        {
          fieldParams.setAttributeNS(xsiNS, xsiNSP + ":type", ecdsaNSP + ":PrimeFieldParamsType");
          Element p = factoryDoc.createElementNS(ecdsaNS, ecdsaNSP + ":P");
          p.appendChild(factoryDoc.createTextNode(curve.getField().getSize().toString(10)));
          fieldParams.appendChild(factoryDoc.createTextNode("\n                "));
          fieldParams.appendChild(p);
          fieldParams.appendChild(factoryDoc.createTextNode("\n              "));
        }
        else if (fieldType == FT_TNB)
        {
          fieldParams.setAttributeNS(xsiNS, xsiNSP + ":type", ecdsaNSP + ":TnBFieldParamsType");
          Element m = factoryDoc.createElementNS(ecdsaNS, ecdsaNSP + ":M");
          m.appendChild(factoryDoc.createTextNode(Integer.toString(curve.getField().getOrder())));
          fieldParams.appendChild(factoryDoc.createTextNode("\n                "));
          fieldParams.appendChild(m);

          Element k = factoryDoc.createElementNS(ecdsaNS, ecdsaNSP + ":K");
          k.appendChild(factoryDoc.createTextNode(Integer.toString(coeffPositions[0], 10)));
          fieldParams.appendChild(factoryDoc.createTextNode("\n                "));
          fieldParams.appendChild(k);
          fieldParams.appendChild(factoryDoc.createTextNode("\n              "));
        }
        else
        {
          fieldParams.setAttributeNS(xsiNS, xsiNSP + ":type", ecdsaNSP + ":PnBFieldParamsType");
          Element m = factoryDoc.createElementNS(ecdsaNS, ecdsaNSP + ":M");
          m.appendChild(factoryDoc.createTextNode(Integer.toString(curve.getField().getOrder())));
          fieldParams.appendChild(factoryDoc.createTextNode("\n                "));
          fieldParams.appendChild(m);

          Element k1 = factoryDoc.createElementNS(ecdsaNS, ecdsaNSP + ":K1");
          k1.appendChild(factoryDoc.createTextNode(Integer.toString(coeffPositions[0])));
          fieldParams.appendChild(factoryDoc.createTextNode("\n                "));
          fieldParams.appendChild(k1);

          Element k2 = factoryDoc.createElementNS(ecdsaNS, ecdsaNSP + ":K2");
          k2.appendChild(factoryDoc.createTextNode(Integer.toString(coeffPositions[1])));
          fieldParams.appendChild(factoryDoc.createTextNode("\n                "));
          fieldParams.appendChild(k2);

          Element k3 = factoryDoc.createElementNS(ecdsaNS, ecdsaNSP + ":K3");
          k3.appendChild(factoryDoc.createTextNode(Integer.toString(coeffPositions[2])));
          fieldParams.appendChild(factoryDoc.createTextNode("\n                "));
          fieldParams.appendChild(k3);
          fieldParams.appendChild(factoryDoc.createTextNode("\n              "));
        }

        // Curve parameters
        Element curveParams = factoryDoc.createElementNS(ecdsaNS, ecdsaNSP + ":CurveParams");
        explicitParams.appendChild(factoryDoc.createTextNode("\n              "));
        explicitParams.appendChild(curveParams);

        Element a = factoryDoc.createElementNS(ecdsaNS, ecdsaNSP + ":A");
        a.setAttributeNS(xsiNS, xsiNSP + ":type", fieldElemTypeString);
        a.setAttributeNS(null, "Value",
          (fieldId == Field.PRIME_FIELD)
            ? curve.getA().getValue().toBigInt().toString(10)
            : evenStringLength(curve.getA().getValue().toBigInt().toString(16)));
        curveParams.appendChild(factoryDoc.createTextNode("\n                "));
        curveParams.appendChild(a);

        Element b = factoryDoc.createElementNS(ecdsaNS, ecdsaNSP + ":B");
        b.setAttributeNS(xsiNS, xsiNSP + ":type", fieldElemTypeString);
        b.setAttributeNS(null, "Value",
          (fieldId == Field.PRIME_FIELD)
            ? curve.getB().getValue().toBigInt().toString(10)
            : evenStringLength(curve.getB().getValue().toBigInt().toString(16)));
        curveParams.appendChild(factoryDoc.createTextNode("\n                "));
        curveParams.appendChild(b);

        if (params.getS() != null)
        {
          Element seed = factoryDoc.createElementNS(ecdsaNS, ecdsaNSP + ":Seed");
          seed.appendChild(factoryDoc.createTextNode(evenStringLength(params.getS().toString(16))));
          curveParams.appendChild(factoryDoc.createTextNode("\n                "));
          curveParams.appendChild(seed);
        }

        curveParams.appendChild(factoryDoc.createTextNode("\n              "));

        // Base point params
        Element basePointParams = factoryDoc.createElementNS(ecdsaNS, ecdsaNSP + ":BasePointParams");
        explicitParams.appendChild(factoryDoc.createTextNode("\n              "));
        explicitParams.appendChild(basePointParams);

        Element basePoint = factoryDoc.createElementNS(ecdsaNS, ecdsaNSP + ":BasePoint");
        basePointParams.appendChild(factoryDoc.createTextNode("\n                "));
        basePointParams.appendChild(basePoint);

        Element x = factoryDoc.createElementNS(ecdsaNS, ecdsaNSP + ":X");
        x.setAttributeNS(xsiNS, xsiNSP + ":type", fieldElemTypeString);
        x.setAttributeNS(null, "Value",
          (fieldId == Field.PRIME_FIELD)
            ? params.getG().getCoordinates().getX().getValue().toBigInt().toString(10)
            : evenStringLength(params.getG().getCoordinates().getX().getValue().toBigInt().toString(16)));
        basePoint.appendChild(factoryDoc.createTextNode("\n                "));
        basePoint.appendChild(x);

        Element y = factoryDoc.createElementNS(ecdsaNS, ecdsaNSP + ":Y");
        y.setAttributeNS(xsiNS, xsiNSP + ":type", fieldElemTypeString);
        y.setAttributeNS(null, "Value",
          (fieldId == Field.PRIME_FIELD)
            ? params.getG().getCoordinates().getY().getValue().toBigInt().toString(10)
            : evenStringLength(params.getG().getCoordinates().getY().getValue().toBigInt().toString(16)));
        basePoint.appendChild(factoryDoc.createTextNode("\n                "));
        basePoint.appendChild(y);
        basePoint.appendChild(factoryDoc.createTextNode("\n              "));

        Element order = factoryDoc.createElementNS(ecdsaNS, ecdsaNSP + ":Order");
        order.appendChild(factoryDoc.createTextNode(params.getR().toString(10)));
        basePointParams.appendChild(factoryDoc.createTextNode("\n                "));
        basePointParams.appendChild(order);

        if (params.getK() != null)
        {
          Element cofactor = factoryDoc.createElementNS(ecdsaNS, ecdsaNSP + ":Cofactor");
          cofactor.appendChild(factoryDoc.createTextNode(params.getK().toString(10)));
          basePointParams.appendChild(factoryDoc.createTextNode("\n                "));
          basePointParams.appendChild(cofactor);
        }

        basePointParams.appendChild(factoryDoc.createTextNode("\n              "));
        explicitParams.appendChild(factoryDoc.createTextNode("\n            "));

        domainParameters.appendChild(factoryDoc.createTextNode("\n            "));
        domainParameters.appendChild(explicitParams);
        domainParameters.appendChild(factoryDoc.createTextNode("\n          "));
      }
    }

    // Public key point
    Element publicKeyPoint = factoryDoc.createElementNS(ecdsaNS, ecdsaNSP + ":PublicKey");

    Element publicKeyX = factoryDoc.createElementNS(ecdsaNS, ecdsaNSP + ":X");
    publicKeyX.setAttributeNS(xsiNS, xsiNSP + ":type", fieldElemTypeString);
    publicKeyX.setAttributeNS(null, "Value",
      (fieldId == Field.PRIME_FIELD)
        ? publicKey.getW().getCoordinates().getX().getValue().toBigInt().toString(10)
        : evenStringLength(publicKey.getW().getCoordinates().getX().getValue().toBigInt().toString(16)));
    publicKeyPoint.appendChild(factoryDoc.createTextNode("\n            "));
    publicKeyPoint.appendChild(publicKeyX);

    Element publicKeyY = factoryDoc.createElementNS(ecdsaNS, ecdsaNSP + ":Y");
    publicKeyY.setAttributeNS(xsiNS, xsiNSP + ":type", fieldElemTypeString);
    publicKeyY.setAttributeNS(null, "Value",
      (fieldId == Field.PRIME_FIELD)
        ? publicKey.getW().getCoordinates().getY().getValue().toBigInt().toString(10)
        : evenStringLength(publicKey.getW().getCoordinates().getY().getValue().toBigInt().toString(16)));
    publicKeyPoint.appendChild(factoryDoc.createTextNode("\n            "));
    publicKeyPoint.appendChild(publicKeyY);
    publicKeyPoint.appendChild(factoryDoc.createTextNode("\n          "));

    eCDSAKeyValue.appendChild(factoryDoc.createTextNode("\n          "));
    eCDSAKeyValue.appendChild(publicKeyPoint);
    eCDSAKeyValue.appendChild(factoryDoc.createTextNode("\n        "));

    return eCDSAKeyValue;
  }
  */
  /* ---------------------------------------------------------------------------------------------------- */

  private static String getECDSANSPrefix(Element element)
  {
     // FIXXME: Review this function (GK, 11.06.2002) - should return a list of strings, since more than
     // one NS prefix can be bound to the ECDSA namespace

     HashMap inScopeNSAttrs = getInScopeNSAttrs(element);
     Iterator inScopeNSAttrsIt = inScopeNSAttrs.keySet().iterator();
     while (inScopeNSAttrsIt.hasNext())
     {
       Attr currentAttr = (Attr)inScopeNSAttrs.get(inScopeNSAttrsIt.next());
       if (ECDSAConstants.NAMESPACE_ECDSAKEYVALUE_.equals(currentAttr.getValue()))
       {
         return ("xmlns".equals(currentAttr.getNodeName())) ? "" : currentAttr.getNodeName().substring(6);
       }
     }
     return null;
  }

  /* ---------------------------------------------------------------------------------------------------- */

  // Converts an octet string representation into an int array as needed for the IAIK ECC library
  // String: rightmost byte is least significant byte
  // IntArray: rightmost byte is LEAST significant byte
  private static int[] octetString2IntArray(String octetString)
  {
    int byteCount = octetString.length()/2;
    int[] intArray = new int[byteCount/4 + ((byteCount % 4 != 0) ? 1 : 0)];
    for (int i = 0; i < byteCount; i++)
    {
      int oSStartPos = octetString.length() - (i + 1) * 2;
      int currentByte = Integer.parseInt(octetString.substring(oSStartPos, oSStartPos + 2), 16);
      intArray[i/4] += (currentByte & 0xFF) << ((i % 4) * 8);
    }
    return intArray;
  }

  /* ---------------------------------------------------------------------------------------------------- */

  // Converts an octet string representation into a byte array as needed for the IAIK ECC library
  // String: rightmost byte is least significant byte
  // ByteArray: rightmost byte is MOST significant byte
  private static byte[] octetString2ByteArray(String octetString)
  {
    int byteCount = octetString.length()/2;
    byte[] byteArray = new byte[byteCount];
    for (int i = 0; i < byteCount; i++)
    {
      int oSStartPos = octetString.length() - (i + 1) * 2;
      byteArray[byteCount - i - 1] = (byte) Integer.parseInt(octetString.substring(
        oSStartPos, oSStartPos + 2), 16);
    }
    return byteArray;
  }

  /* ---------------------------------------------------------------------------------------------------- */

  private static String evenStringLength(String hexString)
  {
    return (hexString.length() % 2 != 0) ? "0" + hexString : hexString;
  }

  /* ---------------------------------------------------------------------------------------------------- */

  private static Element getChildElement(Element parent, String namespace, String localName,
    int instance)
  {
    NodeList namedElements = parent.getElementsByTagNameNS(namespace, localName);
    if (namedElements.getLength() < instance) return null;
    return (Element)namedElements.item(instance - 1);
  }

  /* ---------------------------------------------------------------------------------------------------- */

  private static String getChildElementText(Element parent, String namespace, String localName,
    int instance)
  {
    Element child = getChildElement(parent, namespace, localName, instance);
    if (child == null) return null;
    NodeList childNodes = child.getChildNodes();
    int nodeCount = 0;
    while (nodeCount < childNodes.getLength())
    {
      Node currentNode = childNodes.item(nodeCount);
      if (currentNode.getNodeType() == Node.TEXT_NODE) return currentNode.getNodeValue();
      nodeCount++;
    }
    return null;
  }

  /* ---------------------------------------------------------------------------------------------------- */

  public static HashMap getInScopeNSAttrs(Element element)
  {
    // Get all ancestors of element
    Vector ancestors = new Vector();
    ancestors.add(element);
    Node currentAncestor = element;
    while ((currentAncestor = currentAncestor.getParentNode()) != null &&
           currentAncestor.getNodeType() == Node.ELEMENT_NODE)
    {
      ancestors.add(currentAncestor);
    }

    // Scan all ancestors for NS attributes
    HashMap inScopeNSAttrs = new HashMap();
    for (int i = ancestors.size() - 1; i >= 0; i--)
    {
      Element currentAncestorElem = (Element)ancestors.get(i);
      NamedNodeMap attrs = currentAncestorElem.getAttributes();
      for (int j = 0; j < attrs.getLength(); j++)
      {
        Attr currentAttr = (Attr)attrs.item(j);
        String currentAttrName = currentAttr.getNodeName();
        if ("xmlns".equals(currentAttrName) || currentAttrName.startsWith("xmlns:"))
        {
          inScopeNSAttrs.put(currentAttrName, currentAttr);
        }
      }
    }

    // Check if default NS attribute is in list; if value is empty remove it from list
    Attr defaultNSAttr = (Attr)inScopeNSAttrs.get("xmlns");
    if (defaultNSAttr != null && "".equals(defaultNSAttr.getValue())) inScopeNSAttrs.remove("xmlns");

    return inScopeNSAttrs;
  }
}