Oct 02

The Knuth-Morris-Pratt Pattern Matching Algorithm can be used to search a byte array.


public class KPM {
    /**
     * Search the data byte array for the first occurrence 
     * of the byte array pattern.
     */
    public static int indexOf(byte[] data, byte[] pattern) {
        int[] failure = computeFailure(pattern);

        int j = 0;

        for (int i = 0; i < data.length; i++) {
            while (j > 0 && pattern[j] != data[i]) {
                j = failure[j - 1];
            }
            if (pattern[j] == data[i]) { 
                j++; 
            }
            if (j == pattern.length) {
                return i - pattern.length + 1;
            }
        }
        return -1;
    }

    /**
     * Computes the failure function using a boot-strapping process,
     * where the pattern is matched against itself.
     */
    private int[] computeFailure(byte[] pattern) {
        int[] failure = new int[pattern.length];

        int j = 0;
        for (int i = 1; i < pattern.length; i++) {
            while (j>0 && pattern[j] != pattern[i]) {
                j = failure[j - 1];
            }
            if (pattern[j] == pattern[i]) {
                j++;
            }
            failure[i] = j;
        }

        return failure;
    }
}

written by objects \\ tags: , , , ,

Mar 27

To use anonymous access for an LDAP search or query set the value of Context.SECURITY_AUTHENTICATION to “none” in the environment used to create the initial context.

Hashtable env = new Hashtable();
env.put(Context.INITIAL_CONTEXT_FACTORY, 
    "com.sun.jndi.ldap.LdapCtxFactory");
env.put(Context.PROVIDER_URL, providerUrl);

// Use 'none' for anonymous access
env.put(Context.SECURITY_AUTHENTICATION, "none");

// Create the initial context
DirContext ctx = new InitialDirContext(env);

written by objects \\ tags: , , ,