source: main/trunk/greenstone2/common-src/src/jdbmedit/JdbmAPI.java@ 21402

/**********************************************************************
 *
 * JdbmAPI.java -- 
 * A component of the Greenstone digital library software
 * from the New Zealand Digital Library Project at the 
 * University of Waikato, New Zealand.
 *
 * Copyright (C) 2010  The New Zealand Digital Library Project
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program 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 for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 **********************************************************************/

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;

import java.util.Properties;
import java.util.ArrayList;

import jdbm.RecordManager;
import jdbm.RecordManagerFactory;
import jdbm.helper.FastIterator;
import jdbm.htree.HTree;



public class JdbmAPI
{
    static String TNAME = "greenstone";

    RecordManager  recman_;
    HTree          hashtable_;

    public JdbmAPI(String db_filename,boolean must_exist)
    throws IOException
    {
        // create or open a record manager
        Properties props = new Properties();
        recman_ = RecordManagerFactory.createRecordManager(db_filename, props);

        // load existing table (if exists) otherwise create new one
        long recid = recman_.getNamedObject(TNAME);

    if (recid != 0) {
        System.err.println("# Loading existing database table '" + TNAME +"' ...");
        hashtable_ = HTree.load(recman_, recid);
    }
    else {

        if (must_exist) {
        recman_.close();
        System.err.println("Database table '" + TNAME +"' does not exist.");
        throw new IOException();
        }
        else {
        System.err.println("# No database table '" + TNAME +"' to set.  Creating new one");
        hashtable_ = HTree.createInstance(recman_);
        recman_.setNamedObject(TNAME, hashtable_.getRecid());
        }
    }
    }

    public JdbmAPI(String db_filename)
    throws IOException
    {
    // default is that database does not have to exist
    this(db_filename,false);
    }
    
    public void append(String key, String val)
    throws IOException
    {           
    String orig_val = (String)hashtable_.get(key);           
    String new_val = orig_val + val;

    hashtable_.put(key,new_val);
    recman_.commit();
    }

    public void set(String key, String val)
    throws IOException
           
    {
    hashtable_.put(key,val);
    recman_.commit();
    }

    public void delete(String key)
    throws IOException
    {
    hashtable_.remove(key);
    recman_.commit();
    }
    

    public String get(String key)
        throws IOException
    {
    FastIterator   iter;
    String         val;

    val = (String) hashtable_.get(key);
        
        recman_.commit();
    return val;
    }


    public ArrayList get_keys()
        throws IOException
    {
    ArrayList keys = new ArrayList();

    FastIterator iter = hashtable_.keys();
        String next_key = (String) iter.next();

        while (next_key != null) {
        keys.add(next_key);
            next_key = (String) iter.next();
        }
        
        recman_.commit();
    return keys;
    }

    public void close()
        throws IOException
    {
    recman_.close();
    System.err.println("# Done");
    }


    public static void skip_eol(BufferedReader brin)
        throws IOException
    {
    int c = brin.read();
    if (c == '\r') {
        // Assume Windows style EOL
        // consume another character
        c = brin.read();
    }
    if (c != '\n') {
        System.err.println("JdbmAPI: Warning, expected end-of-line character, but encountered '" + (char)c + "' ord(" + c + ")");
    }
    }

    public static void print_usage()
    {
    System.err.println("");
    System.err.println("Usage: java JdbmAPI database-name");
    System.err.println("");
    System.err.println("  - The JDBM commands to perform are then taken from standard-in");
    System.err.println("  - Commands (with operands) are:");
    System.err.println("      Keys");
    System.err.println("      Get\\n<key>");
    System.err.println("      Set\\n<key>\\n<vallen>\\n<val>");
    System.err.println("      Append\\n<key>\\n<vallen>\\n<val>");
    System.err.println("      Delete\\n<key>");
    System.err.println("");
    System.err.println("  - Operands are given on separate lines.");
    System.err.println("  - In the case of <val> it is preceeded by its length.");
    System.err.println("");
    System.err.println("  - For example the following would set the key 'HASH0143' to 'testing':");
    System.err.println("      Set");
    System.err.println("      HASH0143");
    System.err.println("      7");
    System.err.println("      testing");
    System.err.println("");
    System.exit(-1);
    }

    public static void main(String[] args)
    {
    int argc = args.length;

    // sanity check
    if (argc != 1) {
        print_usage();
    }

    try {
        String dbname = args[0];
        JdbmAPI jdbm_api = new JdbmAPI(dbname);

        InputStreamReader isr=new InputStreamReader(System.in);
        BufferedReader brin = new BufferedReader(isr);

        boolean encountered_error = false;

        String cmd = brin.readLine();
        while (cmd != null) {
        if (cmd.equals("Keys")) {
            ArrayList keys = jdbm_api.get_keys();

            int keys_len = keys.size();
            System.out.println(keys_len);

            for (int i=0; i<keys_len; i++) {
            String key = (String) keys.get(i);
            System.out.println(key);
            }
        }
        else if ((cmd.equals("Get")) || (cmd.equals("Delete"))) {
            String key = brin.readLine();
            if (key != null) {
            
            if (cmd.equals("Get")) {
                String val = jdbm_api.get(key);
                System.out.println(val.length());
                System.out.println(val);
            }
            else {
                jdbm_api.delete(key);
            }

            }
            else {
            System.err.println("JdbmAPI: Command '" + cmd + "'ended prematurely");
            encountered_error = true;
            break;
            }

        }
        else if ((cmd.equals("Set")) || (cmd.equals("Append"))) {
            String key = brin.readLine();

            String vallen_str = brin.readLine();
            if (vallen_str==null) {
            System.err.println("JdbmAPI: Command '" + cmd + "'ended prematurely");
            encountered_error = true;
            break;
            }
            int vallen = Integer.parseInt(vallen_str);
            char[] valbuffer = new char[vallen];
            brin.read(valbuffer,0,vallen);
            skip_eol(brin);
            
            if (valbuffer.length==0) {
            System.err.println("JdbmAPI: Command '" + cmd + "'ended prematurely");
            encountered_error = true;
            break;
            }

            String val = new String(valbuffer);

            if (cmd.equals("Set")) {
            jdbm_api.set(key,val);
            }
            else {
            jdbm_api.append(key,val);
            }
        }
        else {
            System.err.println("JdbmAPI: Unrecognised command '" + cmd + "'");
            encountered_error = true;
        }

        // read in next command (may be null, signifying eof)
        cmd = brin.readLine();      
        }

        jdbm_api.close();

        if (encountered_error) {
        System.exit(-1);
        }
    }

    catch (IOException e) {
        e.printStackTrace();
    }
    
    }

}