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      1 package org.bouncycastle.asn1.x509;
      2 
      3 import org.bouncycastle.asn1.ASN1InputStream;
      4 import org.bouncycastle.asn1.DERObject;
      5 import org.bouncycastle.asn1.DERObjectIdentifier;
      6 import org.bouncycastle.asn1.DERPrintableString;
      7 import org.bouncycastle.util.Strings;
      8 
      9 import java.io.IOException;
     10 
     11 /**
     12  * It turns out that the number of standard ways the fields in a DN should be
     13  * encoded into their ASN.1 counterparts is rapidly approaching the
     14  * number of machines on the internet. By default the X509Name class
     15  * will produce UTF8Strings in line with the current recommendations (RFC 3280).
     16  * <p>
     17  * An example of an encoder look like below:
     18  * <pre>
     19  * public class X509DirEntryConverter
     20  *     extends X509NameEntryConverter
     21  * {
     22  *     public DERObject getConvertedValue(
     23  *         DERObjectIdentifier  oid,
     24  *         String               value)
     25  *     {
     26  *         if (str.length() != 0 && str.charAt(0) == '#')
     27  *         {
     28  *             return convertHexEncoded(str, 1);
     29  *         }
     30  *         if (oid.equals(EmailAddress))
     31  *         {
     32  *             return new DERIA5String(str);
     33  *         }
     34  *         else if (canBePrintable(str))
     35  *         {
     36  *             return new DERPrintableString(str);
     37  *         }
     38  *         else if (canBeUTF8(str))
     39  *         {
     40  *             return new DERUTF8String(str);
     41  *         }
     42  *         else
     43  *         {
     44  *             return new DERBMPString(str);
     45  *         }
     46  *     }
     47  * }
     48  */
     49 public abstract class X509NameEntryConverter
     50 {
     51     /**
     52      * Convert an inline encoded hex string rendition of an ASN.1
     53      * object back into its corresponding ASN.1 object.
     54      *
     55      * @param str the hex encoded object
     56      * @param off the index at which the encoding starts
     57      * @return the decoded object
     58      */
     59     protected DERObject convertHexEncoded(
     60         String  str,
     61         int     off)
     62         throws IOException
     63     {
     64         str = Strings.toLowerCase(str);
     65         byte[] data = new byte[(str.length() - off) / 2];
     66         for (int index = 0; index != data.length; index++)
     67         {
     68             char left = str.charAt((index * 2) + off);
     69             char right = str.charAt((index * 2) + off + 1);
     70 
     71             if (left < 'a')
     72             {
     73                 data[index] = (byte)((left - '0') << 4);
     74             }
     75             else
     76             {
     77                 data[index] = (byte)((left - 'a' + 10) << 4);
     78             }
     79             if (right < 'a')
     80             {
     81                 data[index] |= (byte)(right - '0');
     82             }
     83             else
     84             {
     85                 data[index] |= (byte)(right - 'a' + 10);
     86             }
     87         }
     88 
     89         ASN1InputStream aIn = new ASN1InputStream(data);
     90 
     91         return aIn.readObject();
     92     }
     93 
     94     /**
     95      * return true if the passed in String can be represented without
     96      * loss as a PrintableString, false otherwise.
     97      */
     98     protected boolean canBePrintable(
     99         String  str)
    100     {
    101         return DERPrintableString.isPrintableString(str);
    102     }
    103 
    104     /**
    105      * Convert the passed in String value into the appropriate ASN.1
    106      * encoded object.
    107      *
    108      * @param oid the oid associated with the value in the DN.
    109      * @param value the value of the particular DN component.
    110      * @return the ASN.1 equivalent for the value.
    111      */
    112     public abstract DERObject getConvertedValue(DERObjectIdentifier oid, String value);
    113 }
    114