source: main/branches/stable_gs3/greenstone3/src/java/org/greenstone/gsdl3/util/GDBMWrapper.java@ 21914

/*
 *    GDBMWrapper.java
 *    Copyright (C) 2008 New Zealand Digital Library, http://www.nzdl.org
 *
 *    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.
 */
package org.greenstone.gsdl3.util;

import au.com.pharos.gdbm.GdbmFile;
import au.com.pharos.packing.*;
import au.com.pharos.gdbm.GdbmException;

import org.apache.log4j.Logger;

import java.io.UnsupportedEncodingException;
import java.io.File;

/** java wrapper class for gdbm - uses Java-GDBM written by Martin Pool
 * replaces gdbmclass in the old version
 */

public class GDBMWrapper 
  implements FlatDatabaseWrapper {

  static Logger logger = Logger.getLogger(org.greenstone.gsdl3.util.GDBMWrapper.class.getName());
  
  /* GdbmFile modes:
     READER - read access, many readers may share the database
     WRITER - read/write access, exclusive access
     WRCREAT - read/write access, create db if doesn't exist
     NEWDB - read/write access, db should be replaced if exists
  */
    
    
    protected GdbmFile db_=null;
    
  /** open the database filename, with mode mode - uses the constants
      above, eg GdbmFile.WRITER */
  public boolean openDatabase(String filename, int mode) {
    // need to convert mode to GdbmFile mode
    if (mode == READ) { 
      mode = GdbmFile.READER;
    } else if (mode == WRITE) {
      mode = GdbmFile.WRITER;
    }   else {
      logger.error ("invalid mode, "+mode+ ", opening db for reading only");
      mode = GdbmFile.READER;
    }
    try {
    if (db_!=null) {
        db_.close();
    }

    // The java version of the C++ code in common-src/src/lib/gdbmclass.cpp
    if(mode == GdbmFile.READER) {
      // Looking to read in the database
      // we now use gdb extension. Check for ldb/bdb in case of legacy collection
      // if not (first time) then generate using txt2db
        if (!new File(filename).exists()) {
          logger.warn("Database file " + filename + " does not exist. Looking for ldb/bdb version");
          int extension = filename.lastIndexOf('.');
          String filename_head = filename.substring(0, extension);
          filename = filename_head + ".ldb";
          if (!new File(filename).exists()) {
        filename = filename_head + ".bdb";
        
        if (!new File(filename).exists()) {
        logger.warn("ldb/bdb version of database file " + filename + " does not exist. Looking for txtgz version of db file.");
        // put the filename back to gdb
        filename = filename_head + ".gdb";
        // need to generate architecture native GDBM file using txt2db
        
        // replace sought after gdbm filename ext with ".txt.gz"
        
        String txtgzFilename = filename_head + ".txt.gz";
        if(new File(txtgzFilename).exists()) {          
            // Test to make sure Perl is on the path
            // On Linux, the output of the test goes to STDOUT so redirect it to STDERR
            String cmdTest = "perl -v 2>&1";            
            //String cmdTest = "echo %PATH%";
            int returnValue = Processing.runProcess(cmdTest);
            if (returnValue != 0) {
            logger.error("Tried to find Perl. Return exit value of running " 
                     + cmdTest + ": " +  returnValue + ", (expected this to be 0)");
            logger.error("Check that Perl is set in your PATH environment variable.");
            //log.error("At present, PATH=" + System.getenv("PATH"));
            }
            
            String cmd = "perl -S txtgz-to-gdbm.pl \"" + txtgzFilename + "\" \"" + filename + "\"";
            returnValue = Processing.runProcess(cmd);
            // For some reason, launching this command with gsdl_system() still returns 1
            // even when it returns 0 when run from the command-line. We can check whether
            // we succeeded by looking at whether the output database file was created.
            if (returnValue != 0) {
            logger.warn("Warning, non-zero return value on running command \"" + cmd + "\": " + returnValue);
            if (!new File(filename).exists()) {
                logger.error("Tried to run command \"" + cmd + "\", but it failed");
            }
            }           
        }
        }
          }
          
        }
    }

    db_ = new GdbmFile(filename, mode);
    } catch ( GdbmException e) { // the database wasn't opened or created
    logger.error("couldn't open database "+filename);
    return false;
    } 
    db_.setKeyPacking(new StringPacking());
    db_.setValuePacking(new StringPacking());
    return true;
  }
  
  /** close the database associated with this wrapper */
  public void closeDatabase() {
    try {
      if (db_ != null) {
       db_.close();
       db_ = null;
        if(System.getProperty("os.name").startsWith("Windows")) {
            //Hack: force Windows to let go of the gdb file
            System.gc();
        }
      }
    } catch (GdbmException e) {
      // should never get here - close never actually throws an exception
      logger.error("error on close()");
    }
  }

  public String getValue(String key) {
    if (db_==null) {
      return null;
    }
    String s_info;
    try {
    try {
        // The key is UTF8: do db lookup using the UTF8 version of key
        s_info = (String)db_.fetch(key.getBytes("UTF-8"));
    } catch(UnsupportedEncodingException e) {
        logger.warn("utf8 key for " + key 
             + " unrecognised. Retrying with default encoding.");
        // retry db lookup using default encoding of key instead of UTF8
        s_info = (String)db_.fetch(key);
    }
    } catch (GdbmException e) {
      logger.error("couldn't get record");
      return null;
    }
    if (s_info==null) {
      // record not present
      logger.error("key "+key+" not present in db");
      return null;
    }
    return s_info;
  }

  /** sets the key value as info 
   * TODO - not implemented yet */
  public boolean setValue (String key, String value) {
    if (db_==null) {
      return false;
    }
    return false;
  }
  /** deletes the entry for key 
   * TODO - not implemented yet */
  public boolean deleteKey(String key) {
    if (db_==null) {
      return false;
    }
    return false;
  }

    /** returns a string of key-value entries that
     *  can be printed for debugging purposes. */
    public String displayAllEntries() {
    StringBuffer output = new StringBuffer();
    try{
        java.util.Enumeration e = db_.keys();
        while(e.hasMoreElements()) {
        Object key = e.nextElement();
        Object value = db_.fetch(key);

        output.append("key href: ");
        output.append((String)key);
        output.append("\tvalue ID: ");
        output.append((String)value);
        output.append("\n");
        //logger.warn("key: " + key + "\tvalue: " + value);

        String urlkey = java.net.URLEncoder.encode((String)key, "UTF8");
        output.append("URL encoded key: " + urlkey);
        //logger.warn("URL encoded key: " + urlkey);
        }
    } catch(UnsupportedEncodingException e) {
        logger.warn("Trouble converting key to UTF-8.");
    } catch(Exception e) {
        logger.warn("Exception encountered when trying to displayAllEntries():" + e);
    }
    return output.toString();
    }
}