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Newsgroups: comp.databases.berkeley-db
Date: Mon, 4 Mar 2013 10:03:54 -0800 (PST)
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Subject: Help: Read Berkeley Key,Value using C#
From: ggkraemer@gmail.com
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Xref: csiph.com comp.databases.berkeley-db:17

I'm new to C#.  
I have installed Berkeley 5.3.21 using the distribution msi.

Can someone please tell me how to correct my C# program to decode a recNo Berkeley database.  I can do it using C++; but I'm having problems understanding how to retrieve/decode the key,value pairs using C#.

TIA
Garry

-------------------- Code -------------------------
//
//define Btree false
//

// Berkeley database is a recNo database with key,value pair defined as:
//    key - unsigned int (1-4095)
//    value - structure _bdbcomponentrecord (same as class defined below)
//


using System;
using System.IO;
using System.Collections.Generic;
using System.Collections;
using System.Diagnostics;
using System.Text;
using System.Runtime.Serialization.Formatters.Binary;
using BerkeleyDB;
using System.Runtime.InteropServices;

namespace AccessingBerkeley
{
    
    //
    // Replaces struct _bdbcomponentrecord
    //
     public class _bdbcomponentrecord
    {
        public int maintenanceaction;
        public int componentstate;
        public uint componentcode;
        public int componenttype;
        public string componentname = new string(new char[51]);
        public byte rsvd; // Alignment
        public int enginetype;

//        public static string CopyFrom(DatabaseEntry dbt)
//        {
//            System.Text.ASCIIEncoding decode = new ASCIIEncoding();
//            return decode.GetString(dbt.Data);
//        }
    }
   
    class Program
    {
        static void Main(string[] args)
        {
#if Btree
            BTreeDatabase btreeDB;
            BTreeDatabaseConfig btreeConfig;            
#else
            RecnoDatabase recnoDB;
            RecnoDatabaseConfig recnoConfig;  
#endif

            Cursor dbc;
            DatabaseEntry key;
            DatabaseEntry data;
            string buff, dbFileName, keyString, keyStr;
            int keyVal;
            int compNo;
            int recNo;

            _bdbcomponentrecord rec = new _bdbcomponentrecord();

            try
            {
                String pwd = Environment.CurrentDirectory;
                pwd = Path.Combine(pwd, "..");
                pwd = Path.Combine(pwd, "..");
                if (IntPtr.Size == 4)
                    pwd = Path.Combine(pwd, "Win32");
                else
                    pwd = Path.Combine(pwd, "x64");
#if DEBUG
                pwd = Path.Combine(pwd, "Debug");
#else
                pwd = Path.Combine(pwd, "Release");
#endif
                pwd += ";" + Environment.GetEnvironmentVariable("PATH");
                Environment.SetEnvironmentVariable("PATH", pwd);
            }
            catch (Exception e)
            {
                Console.WriteLine(
                    "Unable to set the PATH environment variable.");
                Console.WriteLine(e.Message);
                return;
            }

            try
            {
#if Btree
                dbFileName = @"C:\BDB\componen.bdb";
#else
                dbFileName = @"C:\BDB\componen.bdb";
#endif
                if (args.Length > 0)
                {
                    dbFileName = args[0];
                }
            }
            catch
            {
                usage();
                return;
            }

#if false
            if (File.Exists(dbFileName))
            {
                while (true)
                {
                    Console.Write
                        ("{0} already exists.  Delete it? (y/n) ", dbFileName);
                    buff = Console.ReadLine().ToLower();
                    if (buff == "y" || buff == "n")
                        break;
                }

                if (buff == "y")
                {
                    try
                    {
                        File.Delete(dbFileName);
                    }
                    catch
                    {
                        Console.WriteLine("Unable to delete {0}.", dbFileName);
                        return;
                    }
                }
            }
            
#endif
#if Btree
            btreeConfig = new BTreeDatabaseConfig();
            btreeConfig.Duplicates = DuplicatesPolicy.SORTED;
            btreeConfig.ErrorPrefix = "excs_access";
            btreeConfig.Creation = CreatePolicy.IF_NEEDED;
            btreeConfig.CacheSize = new CacheInfo(0, 64 * 1024, 1);
            btreeConfig.PageSize = 8 * 1024;
#else
            recnoConfig = new RecnoDatabaseConfig();
            recnoConfig.ErrorPrefix = "excs_access";
            recnoConfig.Creation = CreatePolicy.IF_NEEDED;
            recnoConfig.CacheSize = new CacheInfo(0, 32 * 1024, 1);
            recnoConfig.PageSize = 1024;
#endif

            try
            {
#if Btree
                btreeDB = BTreeDatabase.Open(dbFileName, btreeConfig);
#else
                recnoDB = RecnoDatabase.Open(dbFileName, recnoConfig);
#endif
            }
            catch (Exception e)
            {
                Console.WriteLine("Error opening {0}.", dbFileName);
                Console.WriteLine(e.Message);
                Console.Write("\nPress any key to exit >");
                Console.ReadKey(true);
                return;
            }

            key = new DatabaseEntry();
            data = new DatabaseEntry();

#if false
            while (true)
            {
                Console.Write("key [blank line to quit] > ");
                keyString = Console.ReadLine();
                if (keyString == "")
                    break;

                keyVal = Convert.ToInt32(keyString);
                keyStr = Convert.ToString(keyVal);

                dbtFromString(key, keyStr);
                dbtFromString(data, reverse(keyString));

                try
                {
#if Btree
                    btreeDB.Put(key, data);
#else					
                    recnoDB.PutNoOverwrite(key, data);
#endif
					}
                catch
                {
                    return;
                }

            }
            
#endif

#if Btree
            using (dbc = btreeDB.Cursor())
            {

                Console.WriteLine("All key : data pairs:");
                foreach (KeyValuePair<DatabaseEntry, DatabaseEntry> p in dbc) {
                        Console.WriteLine("{0}::{1}",
                        strFromDBT(p.Key), strFromDBT(p.Value));
                }
                }
            }
#else
            using (dbc = recnoDB.Cursor())
            {

                Console.WriteLine("All key : data pairs:");
                foreach (KeyValuePair<DatabaseEntry, DatabaseEntry> p in dbc)
                {
                    //bdbcomponentrecvar.CopyFrom(p.Value); 
                    compNo = Convert.ToInt32(p.Key);
                    Console.WriteLine("{0}", compNo);
                }
            }
#endif
            Console.Write("Press any key to exit >");
            Console.ReadKey(true);
#if Btree
            btreeDB.Close();
#else
            recnoDB.Close();
#endif
        }


        #region Utilities
        public static void usage()
        {
            Console.WriteLine(
                "Usage: excs_access [database]");
        }

        static void dbtFromString(DatabaseEntry dbt, string s)
        {
            dbt.Data = System.Text.Encoding.ASCII.GetBytes(s);
        }

        public static string strFromDBT(DatabaseEntry dbt)
        {

            System.Text.ASCIIEncoding decode =
                new ASCIIEncoding();
            return decode.GetString(dbt.Data);
        }

        public static string reverse(string s)
        {
            StringBuilder tmp = new StringBuilder(s.Length);
            for (int i = s.Length - 1; i >= 0; i--)
                tmp.Append(s[i]);
            return tmp.ToString();
        }
        #endregion Utilities

    }
}
-------------------- End Code -------------------------