mono/mcs/class/System.Data/System.Data.Odbc/OdbcDataReader.cs

//
// System.Data.Odbc.OdbcDataReader
//
// Author:
//   Brian Ritchie ([email protected]) 
//   Daniel Morgan <[email protected]>
//   Sureshkumar T <[email protected]> (2004)
//
// Copyright (C) Brian Ritchie, 2002
// Copyright (C) Daniel Morgan, 2002
//

//
// Copyright (C) 2004 Novell, Inc (http://www.novell.com)
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
// 
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//

using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Data.Common;
#if NET_2_0
using System.Data.ProviderBase;
#endif // NET_2_0
using System.Text;

namespace System.Data.Odbc
{
#if NET_2_0
        public sealed class OdbcDataReader : DbDataReaderBase
#else
	public sealed class OdbcDataReader : MarshalByRefObject, IDataReader, IDisposable, IDataRecord, IEnumerable
#endif
	{
		#region Fields
		
		private OdbcCommand command;
		private bool open;
		private int currentRow;
		private OdbcColumn[] cols;
		private IntPtr hstmt;
#if ONLY_1_1
		private CommandBehavior behavior;
#endif // ONLY_1_1

		#endregion

		#region Constructors

		internal OdbcDataReader (OdbcCommand command, CommandBehavior behavior)
#if NET_2_0
                        : base (behavior)
#endif // NET_2_0
		{
			this.command = command;
#if ONLY_1_1
			this.CommandBehavior=behavior;
#endif // ONLY_1_1
			open = true;
			currentRow = -1;
			hstmt=command.hStmt;
			// Init columns array;
			short colcount=0;
			libodbc.SQLNumResultCols(hstmt, ref colcount);
			cols=new OdbcColumn[colcount];
			GetSchemaTable ();
		}

		#endregion

		#region Properties

#if ONLY_1_1
                private CommandBehavior CommandBehavior 
                {
                        get { return behavior; }
                        set { value = behavior; }
                }
#endif // ONLY_1_1
                
#if NET_2_0
                [MonoTODO]
                public override int VisibleFieldCount
                {
                        get { throw new NotImplementedException (); }
                }

                [MonoTODO]
                protected override bool IsValidRow 
                {
                        get { throw new NotImplementedException (); }
                }

#endif // NET_2_0
		public
#if NET_2_0
                override
#endif // NET_2_0
                int Depth {
			get {
				return 0; // no nested selects supported
			}
		}

		public
#if NET_2_0
                override
#endif // NET_2_0
                int FieldCount {
			get {
				return cols.Length;
			}
		}

		public
#if NET_2_0
                override
#endif // NET_2_0
                bool IsClosed {
			get {
				return !open;
			}
		}

		public
#if NET_2_0
                override
#endif // NET_2_0
                object this[string name] {
			get {
				int pos;

				if (currentRow == -1)
					throw new InvalidOperationException ();

				pos = ColIndex(name);
				
				if (pos == -1)
					throw new IndexOutOfRangeException ();

				return this[pos];
			}
		}

		public
#if NET_2_0
                override
#endif // NET_2_0
                object this[int index] {
			get {
				return (object) GetValue (index);
			}
		}

                [MonoTODO]
		public
#if NET_2_0
                override
#endif // NET_2_0
                int RecordsAffected {
			get {
				return -1;
			}
		}

		[MonoTODO]
		public
#if NET_2_0
                override
#endif // NET_2_0
                bool HasRows {
			get { throw new NotImplementedException(); }
		}

		#endregion

		#region Methods
		
		private int ColIndex(string colname)
		{
			int i=0;
			foreach (OdbcColumn col in cols)
			{
				if (col != null && col.ColumnName==colname)
					return i;
				i++;
			}
			return -1;
		}

		// Dynamically load column descriptions as needed.
		private OdbcColumn GetColumn(int ordinal)
		{
			if (cols[ordinal]==null)
			{
				short bufsize=255;
				byte[] colname_buffer=new byte[bufsize];
				string colname;
				short colname_size=0;
				uint ColSize=0;
				short DecDigits=0, Nullable=0, dt=0;
				OdbcReturn ret=libodbc.SQLDescribeCol(hstmt, Convert.ToUInt16(ordinal+1), 
					colname_buffer, bufsize, ref colname_size, ref dt, ref ColSize, 
					ref DecDigits, ref Nullable);
				if ((ret!=OdbcReturn.Success) && (ret!=OdbcReturn.SuccessWithInfo)) 
					throw new OdbcException(new OdbcError("SQLDescribeCol",OdbcHandleType.Stmt,hstmt));
				colname=System.Text.Encoding.Default.GetString(colname_buffer);
				colname=colname.Replace((char) 0,' ').Trim();
				OdbcColumn c=new OdbcColumn(colname, (SQL_TYPE) dt);
				c.AllowDBNull=(Nullable!=0);
				c.Digits=DecDigits;
				if (c.IsStringType)
					c.MaxLength=(int)ColSize;
				cols[ordinal]=c;
			}
			return cols[ordinal];
		}

		public
#if NET_2_0
                override
#endif // NET_2_0
                void Close ()
		{
			// FIXME : have to implement output parameter binding
			OdbcReturn ret = libodbc.SQLFreeStmt (hstmt, libodbc.SQLFreeStmtOptions.Close);
			if ((ret!=OdbcReturn.Success) && (ret!=OdbcReturn.SuccessWithInfo)) 
				throw new OdbcException(new OdbcError("SQLCloseCursor",OdbcHandleType.Stmt,hstmt));
	
			open = false;
			currentRow = -1;

			ret = libodbc.SQLFreeHandle( (ushort) OdbcHandleType.Stmt, hstmt);
			if ((ret!=OdbcReturn.Success) && (ret!=OdbcReturn.SuccessWithInfo)) 
				throw new OdbcException(new OdbcError("SQLFreeHandle",OdbcHandleType.Stmt,hstmt));

                        if ((this.CommandBehavior & CommandBehavior.CloseConnection)==CommandBehavior.CloseConnection)
				this.command.Connection.Close();
		}

		~OdbcDataReader ()
		{
			if (open)
				Close ();
		}

		public 
#if NET_2_0
		override
#endif // NET_2_0
		bool GetBoolean (int ordinal)
		{
			return (bool) GetValue(ordinal);
		}

		public 
#if NET_2_0
		override
#endif // NET_2_0
		byte GetByte (int ordinal)
		{
			return (byte) Convert.ToByte(GetValue(ordinal));
		}

		public 
#if NET_2_0
		override
#endif // NET_2_0
		long GetBytes (int ordinal, long dataIndex, byte[] buffer, int bufferIndex, int length)
		{
                        OdbcReturn ret = OdbcReturn.Error;
                        bool copyBuffer = false;
                        int returnVal = 0, outsize = 0;
                        byte [] tbuff = new byte [length+1];

                        length = buffer == null ? 0 : length;
                        ret=libodbc.SQLGetData (hstmt, (ushort) (ordinal+1), SQL_C_TYPE.BINARY, tbuff, length, 
                                        ref outsize);

                        if (ret == OdbcReturn.NoData)
                                return 0;

                        if ( (ret != OdbcReturn.Success) && (ret != OdbcReturn.SuccessWithInfo)) 
                                throw new OdbcException (new OdbcError ("SQLGetData", OdbcHandleType.Stmt, hstmt));

			OdbcError odbcErr = null;
			if ( (ret == OdbcReturn.SuccessWithInfo))
				odbcErr = new OdbcError ("SQLGetData", OdbcHandleType.Stmt, hstmt);

                        if (buffer == null)
                                return outsize; //if buffer is null,return length of the field
                        
                        if (ret == OdbcReturn.SuccessWithInfo) {
                                if (outsize == (int) OdbcLengthIndicator.NoTotal)
                                        copyBuffer = true;
                                else if (outsize == (int) OdbcLengthIndicator.NullData) {
                                        copyBuffer = false;
                                        returnVal = -1;
                                } else {
                                        string sqlstate = odbcErr.SQLState;
                                        //SQLState: String Data, Right truncated
                                        if (sqlstate != libodbc.SQLSTATE_RIGHT_TRUNC) 
                                                throw new OdbcException ( odbcErr);
                                        copyBuffer = true;
                                }
                        } else {
                                copyBuffer = outsize == -1 ? false : true;
                                returnVal = outsize;
                        }

                        if (copyBuffer) {
                                int i = 0;
                                while (tbuff [i] != libodbc.C_NULL) {
                                        buffer [bufferIndex + i] = tbuff [i];
                                        i++;
                                }
                                returnVal = i;
                        }
                        return returnVal;
		}
		
		[MonoTODO]
		public 
#if NET_2_0
		override
#endif // NET_2_0
		char GetChar (int ordinal)
		{
			throw new NotImplementedException ();
		}

		[MonoTODO]
		public 
#if NET_2_0
		override
#endif // NET_2_0
		long GetChars (int ordinal, long dataIndex, char[] buffer, int bufferIndex, int length)
		{
			throw new NotImplementedException ();
		}

		[MonoTODO]
		[EditorBrowsableAttribute (EditorBrowsableState.Never)]
		public 
#if NET_2_0
		new
#endif // NET_2_0
		IDataReader GetData (int ordinal)
		{
			throw new NotImplementedException ();
		}

		public 
#if NET_2_0
		override
#endif // NET_2_0
		string GetDataTypeName (int index)
		{
			return GetColumn(index).OdbcType.ToString();
		}

		public DateTime GetDate(int ordinal) {
			return GetDateTime(ordinal);
		}

		public 
#if NET_2_0
		override
#endif // NET_2_0
		DateTime GetDateTime (int ordinal)
		{
			return (DateTime) GetValue(ordinal);
		}

		[MonoTODO]
		public 
#if NET_2_0
		override
#endif // NET_2_0
		decimal GetDecimal (int ordinal)
		{
			throw new NotImplementedException ();
		}

		public 
#if NET_2_0
		override
#endif // NET_2_0
		double GetDouble (int ordinal)
		{
			return (double) GetValue(ordinal);
		}

		public 
#if NET_2_0
		override
#endif // NET_2_0
		Type GetFieldType (int index)
		{
			return GetColumn(index).DataType;
		}

		public 
#if NET_2_0
		override
#endif // NET_2_0
		float GetFloat (int ordinal)
		{
			return (float) GetValue(ordinal);
		}

		[MonoTODO]
		public 
#if NET_2_0
		override
#endif // NET_2_0
		Guid GetGuid (int ordinal)
		{
			throw new NotImplementedException ();
		}

		public 
#if NET_2_0
		override
#endif // NET_2_0
		short GetInt16 (int ordinal)
		{
			return (short) GetValue(ordinal);
		}

		public 
#if NET_2_0
		override
#endif // NET_2_0
		int GetInt32 (int ordinal)
		{
			return (int) GetValue(ordinal);
		}

		public 
#if NET_2_0
		override
#endif // NET_2_0
		long GetInt64 (int ordinal)
		{
			return (long) GetValue(ordinal);
		}

		public 
#if NET_2_0
		override
#endif // NET_2_0
		string GetName (int index)
		{
			return GetColumn(index).ColumnName;
		}

		public 
#if NET_2_0
		override
#endif // NET_2_0
		int GetOrdinal (string name)
		{
			int i=ColIndex(name);

			if (i==-1)
				throw new IndexOutOfRangeException ();
			else
				return i;
		}

		[MonoTODO]
		public
#if NET_2_0
                override
#endif // NET_2_0
                DataTable GetSchemaTable() 
		{	

			DataTable dataTableSchema = null;
			// Only Results from SQL SELECT Queries 
			// get a DataTable for schema of the result
			// otherwise, DataTable is null reference
			if(cols.Length > 0) 
			{
                                string [] keys = GetPrimaryKeys ();
				
				dataTableSchema = new DataTable ();
				
				dataTableSchema.Columns.Add ("ColumnName", typeof (string));
				dataTableSchema.Columns.Add ("ColumnOrdinal", typeof (int));
				dataTableSchema.Columns.Add ("ColumnSize", typeof (int));
				dataTableSchema.Columns.Add ("NumericPrecision", typeof (int));
				dataTableSchema.Columns.Add ("NumericScale", typeof (int));
				dataTableSchema.Columns.Add ("IsUnique", typeof (bool));
				dataTableSchema.Columns.Add ("IsKey", typeof (bool));
				DataColumn dc = dataTableSchema.Columns["IsKey"];
				dc.AllowDBNull = true; // IsKey can have a DBNull
				dataTableSchema.Columns.Add ("BaseCatalogName", typeof (string));
				dataTableSchema.Columns.Add ("BaseColumnName", typeof (string));
				dataTableSchema.Columns.Add ("BaseSchemaName", typeof (string));
				dataTableSchema.Columns.Add ("BaseTableName", typeof (string));
				dataTableSchema.Columns.Add ("DataType", typeof(Type));
				dataTableSchema.Columns.Add ("AllowDBNull", typeof (bool));
				dataTableSchema.Columns.Add ("ProviderType", typeof (int));
				dataTableSchema.Columns.Add ("IsAliased", typeof (bool));
				dataTableSchema.Columns.Add ("IsExpression", typeof (bool));
				dataTableSchema.Columns.Add ("IsIdentity", typeof (bool));
				dataTableSchema.Columns.Add ("IsAutoIncrement", typeof (bool));
				dataTableSchema.Columns.Add ("IsRowVersion", typeof (bool));
				dataTableSchema.Columns.Add ("IsHidden", typeof (bool));
				dataTableSchema.Columns.Add ("IsLong", typeof (bool));
				dataTableSchema.Columns.Add ("IsReadOnly", typeof (bool));

				DataRow schemaRow;
								
				for (int i = 0; i < cols.Length; i += 1 ) 
				{
					OdbcColumn col=GetColumn(i);

					schemaRow = dataTableSchema.NewRow ();
					dataTableSchema.Rows.Add (schemaRow);
										
					schemaRow["ColumnName"] = col.ColumnName;
					schemaRow["ColumnOrdinal"] = i + 1;
					
					schemaRow["ColumnSize"] = col.MaxLength;
					schemaRow["NumericPrecision"] = 0;
					schemaRow["NumericScale"] = 0;
					// TODO: need to get KeyInfo

					schemaRow["IsUnique"] = false;
					schemaRow["IsKey"] = DBNull.Value;
                                       
                                        for (int j=0; j < keys.Length; j++) {
                                                if (keys [j] == col.ColumnName) {
                                                        schemaRow ["IsUnique"] = true;
                                                        schemaRow ["IsKey"] = true;
                                                }
                                        }

					schemaRow["BaseCatalogName"] = "";				
					schemaRow["BaseColumnName"] = col.ColumnName;
					schemaRow["BaseSchemaName"] = "";
					schemaRow["BaseTableName"] = "";
					schemaRow["DataType"] = col.DataType;

					schemaRow["AllowDBNull"] = col.AllowDBNull;
					
					schemaRow["ProviderType"] = (int) col.OdbcType;
					// TODO: all of these
					schemaRow["IsAliased"] = false;
					schemaRow["IsExpression"] = false;
					schemaRow["IsIdentity"] = false;
					schemaRow["IsAutoIncrement"] = false;
					schemaRow["IsRowVersion"] = false;
					schemaRow["IsHidden"] = false;
					schemaRow["IsLong"] = false;
					schemaRow["IsReadOnly"] = false;
					
					// FIXME: according to Brian, 
					// this does not work on MS .NET
					// however, we need it for Mono 
					// for now
					schemaRow.AcceptChanges();
					
				}
                                dataTableSchema.AcceptChanges();
			}
                        return dataTableSchema;
		}

		public 
#if NET_2_0
		override
#endif // NET_2_0
		string GetString (int ordinal)
		{
			return (string) GetValue(ordinal);
		}

		[MonoTODO]
		public TimeSpan GetTime (int ordinal)
		{
			throw new NotImplementedException ();
		}

		public 
#if NET_2_0
		override
#endif // NET_2_0
		object GetValue (int ordinal)
		{
			if (currentRow == -1)
				throw new IndexOutOfRangeException ();

			if (ordinal>cols.Length-1 || ordinal<0)
				throw new IndexOutOfRangeException ();

			OdbcReturn ret;
			int outsize=0, bufsize;
			byte[] buffer;
			OdbcColumn col=GetColumn(ordinal);
			object DataValue=null;
			ushort ColIndex=Convert.ToUInt16(ordinal+1);

			// Check cached values
			if (col.Value==null)
			{
                                // odbc help file
				// mk:@MSITStore:C:\program%20files\Microsoft%20Data%20Access%20SDK\Docs\odbc.chm::/htm/odbcc_data_types.htm
				switch (col.OdbcType)
				{
					case OdbcType.Decimal:
						bufsize=50;
						buffer=new byte[bufsize];  // According to sqlext.h, use SQL_CHAR for decima. 
                                                // 2005 03 10 : this now works with unixodbc with numeric c type.
						ret=libodbc.SQLGetData(hstmt, ColIndex, col.SqlCType, buffer, bufsize, ref outsize);
						byte[] temp = new byte[outsize];
                                                for (int i=0;i<outsize;i++)
                                                        temp[i]=buffer[i];

						if (outsize!=-1)
							DataValue=Decimal.Parse(System.Text.Encoding.Default.GetString(temp));
						break;
					case OdbcType.TinyInt:
						short short_data=0;
						ret=libodbc.SQLGetData(hstmt, ColIndex, col.SqlCType, ref short_data, 0, ref outsize);
						DataValue=System.Convert.ToByte(short_data);
						break;
					case OdbcType.Int:
						int int_data=0;
						ret=libodbc.SQLGetData(hstmt, ColIndex, col.SqlCType, ref int_data, 0, ref outsize);
						DataValue=int_data;
						break;

					case OdbcType.SmallInt:
                                                short sint_data=0;
                                                ret=libodbc.SQLGetData(hstmt, ColIndex, col.SqlCType, ref sint_data, 0, ref outsize);
                                                DataValue=sint_data;
                                                break;

					case OdbcType.BigInt:
						long long_data=0;
						ret=libodbc.SQLGetData(hstmt, ColIndex, col.SqlCType, ref long_data, 0, ref outsize);
						DataValue=long_data;
						break;
					case OdbcType.NVarChar:
						bufsize=col.MaxLength*2+1; // Unicode is double byte
						buffer=new byte[bufsize];
						ret=libodbc.SQLGetData(hstmt, ColIndex, col.SqlCType, buffer, bufsize, ref outsize);
						if (outsize!=-1)
							DataValue=System.Text.Encoding.Unicode.GetString(buffer,0,outsize);
						break;
					case OdbcType.VarChar:
						bufsize=col.MaxLength+1;
						buffer=new byte[bufsize];  // According to sqlext.h, use SQL_CHAR for both char and varchar
						ret=libodbc.SQLGetData(hstmt, ColIndex, col.SqlCType, buffer, bufsize, ref outsize);
						if (outsize!=-1)
							DataValue=System.Text.Encoding.Default.GetString(buffer,0,outsize);
						break;
					case OdbcType.Real:
						float float_data=0;
						ret=libodbc.SQLGetData(hstmt, ColIndex, col.SqlCType, ref float_data, 0, ref outsize);
						DataValue=float_data;
						break;
                                        case OdbcType.Double:
						double double_data=0;
						ret=libodbc.SQLGetData(hstmt, ColIndex, col.SqlCType, ref double_data, 0, ref outsize);
						DataValue=double_data;
						break;
					case OdbcType.Timestamp:
					case OdbcType.DateTime:
					case OdbcType.Date:
					case OdbcType.Time:
						OdbcTimestamp ts_data=new OdbcTimestamp();
                                                ret=libodbc.SQLGetData(hstmt, ColIndex, col.SqlCType, ref ts_data, 0, ref outsize);
                                                if (outsize!=-1) // This means SQL_NULL_DATA 
							DataValue=new DateTime(ts_data.year,ts_data.month,ts_data.day,ts_data.hour,
								ts_data.minute,ts_data.second,Convert.ToInt32(ts_data.fraction));
						break;
                                        case OdbcType.Binary :
                                        case OdbcType.Image :
                                                bufsize = col.MaxLength + 1;
                                                buffer = new byte [bufsize];
                                                long read = GetBytes (ordinal, 0, buffer, 0, bufsize);
                                                ret = OdbcReturn.Success;
                                                DataValue = buffer;
                                                break;
					default:
						bufsize=255;
						buffer=new byte[bufsize];
						ret=libodbc.SQLGetData(hstmt, ColIndex, SQL_C_TYPE.CHAR, buffer, bufsize, ref outsize);
						DataValue=System.Text.Encoding.Default.GetString(buffer);
						break;
				}

				if ((ret!=OdbcReturn.Success) && (ret!=OdbcReturn.SuccessWithInfo)) 
					throw new OdbcException(new OdbcError("SQLGetData",OdbcHandleType.Stmt,hstmt));

				if (outsize==-1) // This means SQL_NULL_DATA 
					col.Value=DBNull.Value;
				else
					col.Value=DataValue;
			}
			return col.Value;
		}
		
		public 
#if NET_2_0
		override
#endif // NET_2_0
		int GetValues (object[] values)
		{
			int numValues = 0;

			// copy values
			for (int i = 0; i < values.Length; i++) {
				if (i < FieldCount) {
					values[i] = GetValue(i);
				}
				else {
					values[i] = null;
				}
			}

			// get number of object instances in array
			if (values.Length < FieldCount)
				numValues = values.Length;
			else if (values.Length == FieldCount)
				numValues = FieldCount;
			else
				numValues = FieldCount;

			return numValues;
		}

#if ONLY_1_1

                [MonoTODO]
		IDataReader IDataRecord.GetData (int ordinal)
		{
			throw new NotImplementedException ();
		}

		[MonoTODO]
		void IDisposable.Dispose ()
		{
		}

                IEnumerator IEnumerable.GetEnumerator ()
		{
			return new DbEnumerator (this);
		}
#endif // ONLY_1_1

		public
#if NET_2_0
                override
#endif // NET_2_0
                bool IsDBNull (int ordinal)
		{
			return (GetValue(ordinal) is DBNull);
		}

		/// <remarks>
		/// 	Move to the next result set.
		/// </remarks>
		public
#if NET_2_0
                override
#endif // NET_2_0
                bool NextResult ()
		{
			OdbcReturn ret = OdbcReturn.Success;
			ret = libodbc.SQLMoreResults (hstmt);
			if (ret == OdbcReturn.Success) {
				short colcount = 0;
				libodbc.SQLNumResultCols (hstmt, ref colcount);
				cols = new OdbcColumn [colcount];
				GetSchemaTable ();
			}	
			return (ret==OdbcReturn.Success);
		}

		/// <remarks>
		///	Load the next row in the current result set.
		/// </remarks>
		public bool NextRow ()
		{
			OdbcReturn ret=libodbc.SQLFetch (hstmt);
			if (ret != OdbcReturn.Success)
				currentRow = -1;
			else
				currentRow++;

			// Clear cached values from last record
			foreach (OdbcColumn col in cols)
			{
				if (col != null)
					col.Value = null;
			}
			return (ret == OdbcReturn.Success);
		}


                private int GetColumnAttribute (int column, FieldIdentifier fieldId)
                {
                        OdbcReturn ret = OdbcReturn.Error;
                        byte [] buffer = new byte [255];
                        int outsize = 0;
                        int val = 0;
                        ret = libodbc.SQLColAttribute (hstmt, column, fieldId, 
                                                       buffer, buffer.Length, 
                                                       ref outsize, ref val);
                        if (ret != OdbcReturn.Success && ret != OdbcReturn.SuccessWithInfo)
                                throw new OdbcException (new OdbcError ("SQLColAttribute",
                                                                        OdbcHandleType.Stmt,
                                                                        hstmt)
                                                         );
                        return val;
                        
                }

                private string GetColumnAttributeStr (int column, FieldIdentifier fieldId)
                {
                        OdbcReturn ret = OdbcReturn.Error;
                        byte [] buffer = new byte [255];
                        int outsize = 0;
                        int val = 0;
                        ret = libodbc.SQLColAttribute (hstmt, column, fieldId, 
                                                       buffer, buffer.Length, 
                                                       ref outsize, ref val);
                        if (ret != OdbcReturn.Success && ret != OdbcReturn.SuccessWithInfo)
                                throw new OdbcException (new OdbcError ("SQLColAttribute",
                                                                        OdbcHandleType.Stmt,
                                                                        hstmt)
                                                         );
                        string value = Encoding.Default.GetString (buffer);
                        return value;
                }

                private string [] GetPrimaryKeys ()
                {
                        if (cols.Length <= 0)
                                return new string [0];

                        string [] keys = new string [cols.Length];
                        IntPtr handle = IntPtr.Zero;
                        OdbcReturn ret = OdbcReturn.Error;                  
                        try {
                                ret=libodbc.SQLAllocHandle(OdbcHandleType.Stmt, 
                                                           command.Connection.hDbc, ref handle);
				if ((ret!=OdbcReturn.Success) && (ret!=OdbcReturn.SuccessWithInfo)) 
					throw new OdbcException(new OdbcError("SQLAllocHandle",
                                                                              OdbcHandleType.Dbc,
                                                                              command.Connection.hDbc));

                                string tableName   = GetColumnAttributeStr (1, FieldIdentifier.TableName);
                                string schemaName  = GetColumnAttributeStr (1, FieldIdentifier.SchemaName);
                                string catalogName = GetColumnAttributeStr (1, FieldIdentifier.CatelogName);
                                ret = libodbc.SQLPrimaryKeys (handle, catalogName, -3,  
                                                              schemaName, -3, 
                                                              tableName, -3);
                                if (ret != OdbcReturn.Success && ret != OdbcReturn.SuccessWithInfo)
                                        throw new OdbcException (new OdbcError ("SQLPrimaryKeys", OdbcHandleType.Stmt, handle));
                        
                                int length = 0;
                                byte [] primaryKey = new byte [255];
                        
                                ret = libodbc.SQLBindCol (handle, 4, SQL_C_TYPE.CHAR, primaryKey, primaryKey.Length, ref length);
                                if (ret != OdbcReturn.Success && ret != OdbcReturn.SuccessWithInfo)
                                        throw new OdbcException (new OdbcError ("SQLBindCol", OdbcHandleType.Stmt, handle));
                        
                                int i = 0;                              
                                while (true) {
                                        ret = libodbc.SQLFetch (handle);
                                        if (ret != OdbcReturn.Success && ret != OdbcReturn.SuccessWithInfo)
                                                break;
                                        string pkey = Encoding.Default.GetString (primaryKey);
                                        keys [i++] = pkey;
                                }
                        } catch (OdbcException){
                                // FIXME: Try using SQLStatistics
                        } finally {
                                if (handle != IntPtr.Zero) {
                                        ret = libodbc.SQLFreeStmt (handle, libodbc.SQLFreeStmtOptions.Close);
                                        if ((ret!=OdbcReturn.Success) && (ret!=OdbcReturn.SuccessWithInfo)) 
                                                throw new OdbcException(new OdbcError("SQLFreeStmt",OdbcHandleType.Stmt,handle));
                                        
                                        ret = libodbc.SQLFreeHandle( (ushort) OdbcHandleType.Stmt, handle);
                                                if ((ret!=OdbcReturn.Success) && (ret!=OdbcReturn.SuccessWithInfo)) 
                                                        throw new OdbcException(new OdbcError("SQLFreeHandle",OdbcHandleType.Stmt,handle));
                                }                             
                                        
                        }
                        
                        return keys;
                }

		public
#if NET_2_0
                override
#endif // NET_2_0
                bool Read ()
		{
			return NextRow ();
		}

#if NET_2_0
                [MonoTODO]
		public override object GetProviderSpecificValue (int i)
                {
                       throw new NotImplementedException ();
                }
                
                [MonoTODO]
		public override int GetProviderSpecificValues (object[] values)
                {
                       throw new NotImplementedException ();
                }

                [MonoTODO]
		public override Type GetFieldProviderSpecificType (int i)
                {
                       throw new NotImplementedException ();
                }
                
#endif // NET_2_0


		#endregion
	}
}