C# TdsParserStateObject.TryReadByte方法代码示例

        internal bool TryProcessAltMetaData(int cColumns, TdsParserStateObject stateObj, out _SqlMetaDataSet metaData) {
            Debug.Assert(cColumns > 0, "should have at least 1 column in altMetaData!");

            metaData = null;
            _SqlMetaDataSet altMetaDataSet = new _SqlMetaDataSet(cColumns, null);
            int[] indexMap = new int[cColumns];

            if (!stateObj.TryReadUInt16(out altMetaDataSet.id)) {
                return false;
            }

            byte byCols;
            if (!stateObj.TryReadByte(out byCols)) {
                return false;
            }

            while (byCols > 0) {
                if (!stateObj.TrySkipBytes(2)) { // ignore ColNum ...
                    return false;
                }
                byCols--;
            }

            // pass 1, read the meta data off the wire
            for (int i = 0; i < cColumns; i++) {
                // internal meta data class
                _SqlMetaData col = altMetaDataSet[i];

                if (!stateObj.TryReadByte(out col.op)) {
                    return false;
                }
                if (!stateObj.TryReadUInt16(out col.operand)) {
                    return false;
                }

                // TCE is not applicable to AltMetadata.
                if (!TryCommonProcessMetaData(stateObj, col, null, fColMD: false, columnEncryptionSetting: SqlCommandColumnEncryptionSetting.Disabled)) {
                    return false;
                }

                if (ADP.IsEmpty(col.column)) {
                    // create column name from op
                    switch (col.op) {
                        case TdsEnums.AOPAVG:
                            col.column = "avg";
                            break;

                        case TdsEnums.AOPCNT:
                            col.column = "cnt";
                            break;

                        case TdsEnums.AOPCNTB:
                            col.column = "cntb";
                            break;

                        case TdsEnums.AOPMAX:
                            col.column = "max";
                            break;

                        case TdsEnums.AOPMIN:
                            col.column = "min";
                            break;

                        case TdsEnums.AOPSUM:
                            col.column = "sum";
                            break;

                        case TdsEnums.AOPANY:
                            col.column = "any";
                            break;

                        case TdsEnums.AOPNOOP:
                            col.column = "noop";
                            break;

                        case TdsEnums.AOPSTDEV:
                            col.column = "stdev";
                            break;

                        case TdsEnums.AOPSTDEVP:
                            col.column = "stdevp";
                            break;

                        case TdsEnums.AOPVAR:
                            col.column = "var";
                            break;

                        case TdsEnums.AOPVARP:
                            col.column = "varp";
                            break;
                    }
                }
                indexMap[i] = i;
            }

            altMetaDataSet.indexMap = indexMap;
            altMetaDataSet.visibleColumns = cColumns;

            metaData = altMetaDataSet;
            return true;
//.........这里部分代码省略.........

        //
        // Read in a SQLVariant
        //
        // SQLVariant looks like:
        // struct
        // {
        //      BYTE TypeTag
        //      BYTE cbPropBytes
        //      BYTE[] Properties
        //      BYTE[] DataVal
        // }
        internal bool TryReadSqlVariant(SqlBuffer value, int lenTotal, TdsParserStateObject stateObj)
        {
            // get the SQLVariant type
            byte type;
            if (!stateObj.TryReadByte(out type))
            {
                return false;
            }
            ushort lenMax = 0; // maximum lenData of value inside variant

            // read cbPropBytes
            byte cbPropsActual;
            if (!stateObj.TryReadByte(out cbPropsActual))
            {
                return false;
            }
            MetaType mt = MetaType.GetSqlDataType(type, 0 /*no user datatype*/, 0 /* no lenData, non-nullable type */);
            byte cbPropsExpected = mt.PropBytes;

            int lenConsumed = TdsEnums.SQLVARIANT_SIZE + cbPropsActual; // type, count of propBytes, and actual propBytes
            int lenData = lenTotal - lenConsumed; // length of actual data

            // read known properties and skip unknown properties
            Debug.Assert(cbPropsActual >= cbPropsExpected, "cbPropsActual is less that cbPropsExpected!");

            //
            // now read the value
            //
            switch (type)
            {
                case TdsEnums.SQLBIT:
                case TdsEnums.SQLINT1:
                case TdsEnums.SQLINT2:
                case TdsEnums.SQLINT4:
                case TdsEnums.SQLINT8:
                case TdsEnums.SQLFLT4:
                case TdsEnums.SQLFLT8:
                case TdsEnums.SQLMONEY:
                case TdsEnums.SQLMONEY4:
                case TdsEnums.SQLDATETIME:
                case TdsEnums.SQLDATETIM4:
                case TdsEnums.SQLUNIQUEID:
                    if (!TryReadSqlValueInternal(value, type, lenData, stateObj))
                    {
                        return false;
                    }
                    break;

                case TdsEnums.SQLDECIMALN:
                case TdsEnums.SQLNUMERICN:
                    {
                        Debug.Assert(cbPropsExpected == 2, "SqlVariant: invalid PropBytes for decimal/numeric type!");

                        byte precision;
                        if (!stateObj.TryReadByte(out precision))
                        {
                            return false;
                        }
                        byte scale;
                        if (!stateObj.TryReadByte(out scale))
                        {
                            return false;
                        }

                        // skip over unknown properties
                        if (cbPropsActual > cbPropsExpected)
                        {
                            if (!stateObj.TrySkipBytes(cbPropsActual - cbPropsExpected))
                            {
                                return false;
                            }
                        }

                        if (!TryReadSqlDecimal(value, TdsEnums.MAX_NUMERIC_LEN, precision, scale, stateObj))
                        {
                            return false;
                        }
                        break;
                    }

                case TdsEnums.SQLBIGBINARY:
                case TdsEnums.SQLBIGVARBINARY:
                    //Debug.Assert(TdsEnums.VARNULL == lenData, "SqlVariant: data length for Binary indicates null?");
                    Debug.Assert(cbPropsExpected == 2, "SqlVariant: invalid PropBytes for binary type!");

                    if (!stateObj.TryReadUInt16(out lenMax))
                    {
                        return false;
                    }
//.........这里部分代码省略.........

        //
        // returns the token length of the token or tds type
        // Returns -1 for partially length prefixed (plp) types for metadata info.
        // DOES NOT handle plp data streams correctly!!!
        // Plp data streams length information should be obtained from GetDataLength
        //
        internal bool TryGetTokenLength(byte token, TdsParserStateObject stateObj, out int tokenLength)
        {
            Debug.Assert(token != 0, "0 length token!");

            switch (token)
            { // rules about SQLLenMask no longer apply to new tokens (as of 7.4)
                case TdsEnums.SQLFEATUREEXTACK:
                    tokenLength = -1;
                    return true;
                case TdsEnums.SQLSESSIONSTATE:
                    return stateObj.TryReadInt32(out tokenLength);
            }

            {
                if (token == TdsEnums.SQLUDT)
                { // special case for UDTs
                    tokenLength = -1; // Should we return -1 or not call GetTokenLength for UDTs?
                    return true;
                }
                else if (token == TdsEnums.SQLRETURNVALUE)
                {
                    tokenLength = -1; // In Yukon, the RETURNVALUE token stream no longer has length
                    return true;
                }
                else if (token == TdsEnums.SQLXMLTYPE)
                {
                    ushort value;
                    if (!stateObj.TryReadUInt16(out value))
                    {
                        tokenLength = 0;
                        return false;
                    }
                    tokenLength = (int)value;
                    Debug.Assert(tokenLength == TdsEnums.SQL_USHORTVARMAXLEN, "Invalid token stream for xml datatype");
                    return true;
                }
            }

            switch (token & TdsEnums.SQLLenMask)
            {
                case TdsEnums.SQLFixedLen:
                    tokenLength = ((0x01 << ((token & 0x0c) >> 2))) & 0xff;
                    return true;
                case TdsEnums.SQLZeroLen:
                    tokenLength = 0;
                    return true;
                case TdsEnums.SQLVarLen:
                case TdsEnums.SQLVarCnt:
                    if (0 != (token & 0x80))
                    {
                        ushort value;
                        if (!stateObj.TryReadUInt16(out value))
                        {
                            tokenLength = 0;
                            return false;
                        }
                        tokenLength = value;
                        return true;
                    }
                    else if (0 == (token & 0x0c))
                    {
                        if (!stateObj.TryReadInt32(out tokenLength))
                        {
                            return false;
                        }
                        return true;
                    }
                    else
                    {
                        byte value;
                        if (!stateObj.TryReadByte(out value))
                        {
                            tokenLength = 0;
                            return false;
                        }
                        tokenLength = value;
                        return true;
                    }
                default:
                    Debug.Assert(false, "Unknown token length!");
                    tokenLength = 0;
                    return true;
            }
        }

        private bool TryProcessColumnHeaderNoNBC(SqlMetaDataPriv col, TdsParserStateObject stateObj, out bool isNull, out ulong length)
        {
            if (col.metaType.IsLong && !col.metaType.IsPlp)
            {
                //
                // we don't care about TextPtrs, simply go after the data after it
                //
                byte textPtrLen;
                if (!stateObj.TryReadByte(out textPtrLen))
                {
                    isNull = false;
                    length = 0;
                    return false;
                }

                if (0 != textPtrLen)
                {
                    // read past text pointer
                    if (!stateObj.TrySkipBytes(textPtrLen))
                    {
                        isNull = false;
                        length = 0;
                        return false;
                    }

                    // read past timestamp
                    if (!stateObj.TrySkipBytes(TdsEnums.TEXT_TIME_STAMP_LEN))
                    {
                        isNull = false;
                        length = 0;
                        return false;
                    }

                    isNull = false;
                    return TryGetDataLength(col, stateObj, out length);
                }
                else
                {
                    isNull = true;
                    length = 0;
                    return true;
                }
            }
            else
            {
                // non-blob columns
                ulong longlen;
                if (!TryGetDataLength(col, stateObj, out longlen))
                {
                    isNull = false;
                    length = 0;
                    return false;
                }
                isNull = IsNull(col.metaType, longlen);
                length = (isNull ? 0 : longlen);
                return true;
            }
        }

        /// <summary>
        /// This method skips bytes of a single column value from the media. It supports NBCROW and handles all types of values, including PLP and long
        /// </summary>
        internal bool TrySkipValue(SqlMetaDataPriv md, int columnOrdinal, TdsParserStateObject stateObj)
        {
            if (stateObj.IsNullCompressionBitSet(columnOrdinal))
            {
                return true;
            }

            if (md.metaType.IsPlp)
            {
                ulong ignored;
                if (!TrySkipPlpValue(UInt64.MaxValue, stateObj, out ignored))
                {
                    return false;
                }
            }
            else if (md.metaType.IsLong)
            {
                Debug.Assert(!md.metaType.IsPlp, "Plp types must be handled using SkipPlpValue");

                byte textPtrLen;
                if (!stateObj.TryReadByte(out textPtrLen))
                {
                    return false;
                }

                if (0 != textPtrLen)
                {
                    if (!stateObj.TrySkipBytes(textPtrLen + TdsEnums.TEXT_TIME_STAMP_LEN))
                    {
                        return false;
                    }

                    int length;
                    if (!TryGetTokenLength(md.tdsType, stateObj, out length))
                    {
                        return false;
                    }
                    if (!stateObj.TrySkipBytes(length))
                    {
                        return false;
                    }
                }
            }
            else
            {
                int length;
                if (!TryGetTokenLength(md.tdsType, stateObj, out length))
                {
                    return false;
                }

                // if false, no value to skip - it's null
                if (!IsNull(md.metaType, (ulong)length))
                {
                    if (!stateObj.TrySkipBytes(length))
                    {
                        return false;
                    }
                }
            }

            return true;
        }

        internal bool TryProcessAltMetaData(int cColumns, TdsParserStateObject stateObj, out _SqlMetaDataSet metaData)
        {
            Debug.Assert(cColumns > 0, "should have at least 1 column in altMetaData!");

            metaData = null;

            _SqlMetaDataSet altMetaDataSet = new _SqlMetaDataSet(cColumns);
            int[] indexMap = new int[cColumns];

            if (!stateObj.TryReadUInt16(out altMetaDataSet.id))
            {
                return false;
            }

            byte byCols;
            if (!stateObj.TryReadByte(out byCols))
            {
                return false;
            }

            while (byCols > 0)
            {
                if (!stateObj.TrySkipBytes(2))
                { // ignore ColNum ...
                    return false;
                }
                byCols--;
            }

            // pass 1, read the meta data off the wire
            for (int i = 0; i < cColumns; i++)
            {
                // internal meta data class
                _SqlMetaData col = altMetaDataSet[i];

                byte op;
                if (!stateObj.TryReadByte(out op))
                {
                    return false;
                }
                ushort operand;
                if (!stateObj.TryReadUInt16(out operand))
                {
                    return false;
                }

                if (!TryCommonProcessMetaData(stateObj, col))
                {
                    return false;
                }

                indexMap[i] = i;
            }

            altMetaDataSet.indexMap = indexMap;
            altMetaDataSet.visibleColumns = cColumns;

            metaData = altMetaDataSet;
            return true;
        }

        private bool TryProcessOneTable(TdsParserStateObject stateObj, ref int length, out MultiPartTableName multiPartTableName)
        {
            ushort tableLen;
            MultiPartTableName mpt;
            string value;

            multiPartTableName = default(MultiPartTableName);

            mpt = new MultiPartTableName();
            byte nParts;

            // Find out how many parts in the TDS stream
            if (!stateObj.TryReadByte(out nParts))
            {
                return false;
            }
            length--;
            if (nParts == 4)
            {
                if (!stateObj.TryReadUInt16(out tableLen))
                {
                    return false;
                }
                length -= 2;
                if (!stateObj.TryReadString(tableLen, out value))
                {
                    return false;
                }
                mpt.ServerName = value;
                nParts--;
                length -= (tableLen * 2); // wide bytes
            }
            if (nParts == 3)
            {
                if (!stateObj.TryReadUInt16(out tableLen))
                {
                    return false;
                }
                length -= 2;
                if (!stateObj.TryReadString(tableLen, out value))
                {
                    return false;
                }
                mpt.CatalogName = value;
                length -= (tableLen * 2); // wide bytes
                nParts--;
            }
            if (nParts == 2)
            {
                if (!stateObj.TryReadUInt16(out tableLen))
                {
                    return false;
                }
                length -= 2;
                if (!stateObj.TryReadString(tableLen, out value))
                {
                    return false;
                }
                mpt.SchemaName = value;
                length -= (tableLen * 2); // wide bytes
                nParts--;
            }
            if (nParts == 1)
            {
                if (!stateObj.TryReadUInt16(out tableLen))
                {
                    return false;
                }
                length -= 2;
                if (!stateObj.TryReadString(tableLen, out value))
                {
                    return false;
                }
                mpt.TableName = value;
                length -= (tableLen * 2); // wide bytes
                nParts--;
            }
            Debug.Assert(nParts == 0, "ProcessTableName:Unidentified parts in the table name token stream!");

            multiPartTableName = mpt;
            return true;
        }

        internal bool TryProcessError(byte token, TdsParserStateObject stateObj, out SqlError error)
        {
            ushort shortLen;
            byte byteLen;
            int number;
            byte state;
            byte errorClass;

            error = null;

            if (!stateObj.TryReadInt32(out number))
            {
                return false;
            }
            if (!stateObj.TryReadByte(out state))
            {
                return false;
            }
            if (!stateObj.TryReadByte(out errorClass))
            {
                return false;
            }

            Debug.Assert(((errorClass >= TdsEnums.MIN_ERROR_CLASS) && token == TdsEnums.SQLERROR) ||
                          ((errorClass < TdsEnums.MIN_ERROR_CLASS) && token == TdsEnums.SQLINFO), "class and token don't match!");

            if (!stateObj.TryReadUInt16(out shortLen))
            {
                return false;
            }
            string message;
            if (!stateObj.TryReadString(shortLen, out message))
            {
                return false;
            }

            if (!stateObj.TryReadByte(out byteLen))
            {
                return false;
            }

            string server;

            // If the server field is not received use the locally cached value.
            if (byteLen == 0)
            {
                server = _server;
            }
            else
            {
                if (!stateObj.TryReadString(byteLen, out server))
                {
                    return false;
                }
            }

            if (!stateObj.TryReadByte(out byteLen))
            {
                return false;
            }
            string procedure;
            if (!stateObj.TryReadString(byteLen, out procedure))
            {
                return false;
            }

            int line;
            if (_isYukon)
            {
                if (!stateObj.TryReadInt32(out line))
                {
                    return false;
                }
            }
            else
            {
                ushort shortLine;
                if (!stateObj.TryReadUInt16(out shortLine))
                {
                    return false;
                }
                line = shortLine;
                // If we haven't yet completed processing login token stream yet, we may be talking to a Yukon server
                // In that case we still have to read another 2 bytes
                if (_state == TdsParserState.OpenNotLoggedIn)
                {
                    // Login incomplete
                    byte b;
                    if (!stateObj.TryPeekByte(out b))
                    {
                        return false;
                    }
                    if (b == 0)
                    {
                        // This is an invalid token value
                        ushort value;
                        if (!stateObj.TryReadUInt16(out value))
                        {
                            return false;
                        }
//.........这里部分代码省略.........

        // Main parse loop for the top-level tds tokens, calls back into the I*Handler interfaces
        internal bool TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, out bool dataReady)
        {
            Debug.Assert((SniContext.Undefined != stateObj.SniContext) &&       // SniContext must not be Undefined
                ((stateObj._attentionSent) || ((SniContext.Snix_Execute != stateObj.SniContext) && (SniContext.Snix_SendRows != stateObj.SniContext))),  // SniContext should not be Execute or SendRows unless attention was sent (and, therefore, we are looking for an ACK)
                        String.Format("Unexpected SniContext on call to TryRun; SniContext={0}", stateObj.SniContext));

            if (TdsParserState.Broken == State || TdsParserState.Closed == State)
            {
                dataReady = true;
                return true; // Just in case this is called in a loop, expecting data to be returned.
            }

            dataReady = false;

            do
            {
                // If there is data ready, but we didn't exit the loop, then something is wrong
                Debug.Assert(!dataReady, "dataReady not expected - did we forget to skip the row?");

                if (stateObj._internalTimeout)
                {
                    runBehavior = RunBehavior.Attention;
                }

                if (TdsParserState.Broken == State || TdsParserState.Closed == State)
                    break; // jump out of the loop if the state is already broken or closed.

                if (!stateObj._accumulateInfoEvents && (stateObj._pendingInfoEvents != null))
                {
                    if (RunBehavior.Clean != (RunBehavior.Clean & runBehavior))
                    {
                        SqlConnection connection = null;
                        if (_connHandler != null)
                            connection = _connHandler.Connection; // SqlInternalConnection holds the user connection object as a weak ref
                        // We are omitting checks for error.Class in the code below (see processing of INFO) since we know (and assert) that error class
                        // error.Class < TdsEnums.MIN_ERROR_CLASS for info message. 
                        // Also we know that TdsEnums.MIN_ERROR_CLASS<TdsEnums.MAX_USER_CORRECTABLE_ERROR_CLASS
                        if ((connection != null) && connection.FireInfoMessageEventOnUserErrors)
                        {
                            foreach (SqlError error in stateObj._pendingInfoEvents)
                                FireInfoMessageEvent(connection, stateObj, error);
                        }
                        else
                            foreach (SqlError error in stateObj._pendingInfoEvents)
                                stateObj.AddWarning(error);
                    }
                    stateObj._pendingInfoEvents = null;
                }

                byte token;
                if (!stateObj.TryReadByte(out token))
                {
                    return false;
                }

                if (!IsValidTdsToken(token))
                {
                    Debug.Assert(false, String.Format((IFormatProvider)null, "unexpected token; token = {0,-2:X2}", token));
                    _state = TdsParserState.Broken;
                    _connHandler.BreakConnection();
                    throw SQL.ParsingError();
                }

                int tokenLength;
                if (!TryGetTokenLength(token, stateObj, out tokenLength))
                {
                    return false;
                }

                switch (token)
                {
                    case TdsEnums.SQLERROR:
                    case TdsEnums.SQLINFO:
                        {
                            if (token == TdsEnums.SQLERROR)
                            {
                                stateObj._errorTokenReceived = true; // Keep track of the fact error token was received - for Done processing.
                            }

                            SqlError error;
                            if (!TryProcessError(token, stateObj, out error))
                            {
                                return false;
                            }

                            if (token == TdsEnums.SQLINFO && stateObj._accumulateInfoEvents)
                            {
                                Debug.Assert(error.Class < TdsEnums.MIN_ERROR_CLASS, "INFO with class > TdsEnums.MIN_ERROR_CLASS");

                                if (stateObj._pendingInfoEvents == null)
                                    stateObj._pendingInfoEvents = new List<SqlError>();
                                stateObj._pendingInfoEvents.Add(error);
                                stateObj._syncOverAsync = true;
                                break;
                            }

                            if (RunBehavior.Clean != (RunBehavior.Clean & runBehavior))
                            {
                                // If FireInfoMessageEventOnUserErrors is true, we have to fire event without waiting.
//.........这里部分代码省略.........

        // augments current metadata with table and key information
        private bool TryProcessColInfo(_SqlMetaDataSet columns, SqlDataReader reader, TdsParserStateObject stateObj, out _SqlMetaDataSet metaData) {
            Debug.Assert(columns != null && columns.Length > 0, "no metadata available!");

            metaData = null;

            for (int i = 0; i < columns.Length; i++) {
                _SqlMetaData col = columns[i];

                byte ignored;
                if (!stateObj.TryReadByte(out ignored)) { // colnum, ignore
                    return false;
                }
                if (!stateObj.TryReadByte(out col.tableNum)) {
                    return false;
                }

                // interpret status
                byte status;
                if (!stateObj.TryReadByte(out status)) {
                    return false;
                }

                col.isDifferentName = (TdsEnums.SQLDifferentName == (status & TdsEnums.SQLDifferentName));
                col.isExpression = (TdsEnums.SQLExpression == (status & TdsEnums.SQLExpression));
                col.isKey = (TdsEnums.SQLKey == (status & TdsEnums.SQLKey));
                col.isHidden = (TdsEnums.SQLHidden == (status & TdsEnums.SQLHidden));

                // read off the base table name if it is different than the select list column name
                if (col.isDifferentName) {
                    byte len;
                    if (!stateObj.TryReadByte(out len)) {
                        return false;
                    }
                    if (!stateObj.TryReadString(len, out col.baseColumn)) {
                        return false;
                    }
                }

                // Fixup column name - only if result of a table - that is if it was not the result of
                // an expression.
                if ((reader.TableNames != null) && (col.tableNum > 0)) {
                    Debug.Assert(reader.TableNames.Length >= col.tableNum, "invalid tableNames array!");
                    col.multiPartTableName = reader.TableNames[col.tableNum - 1];
                }

                // MDAC 60109: expressions are readonly
                if (col.isExpression) {
                    col.updatability = 0;
                }
            }

            // set the metadata so that the stream knows some metadata info has changed
            metaData = columns;
            return true;
        }

         private bool TryProcessUDTMetaData(SqlMetaDataPriv metaData, TdsParserStateObject stateObj) {

            ushort shortLength;
            byte byteLength;

            if (!stateObj.TryReadUInt16(out shortLength)) { // max byte size
                return false;
            }
            metaData.length = shortLength;

            // database name
            if (!stateObj.TryReadByte(out byteLength)) {
                return false;
            }
            if (byteLength != 0) {
                if (!stateObj.TryReadString(byteLength, out metaData.udtDatabaseName)) {
                    return false;
                }
            }

            // schema name
            if (!stateObj.TryReadByte(out byteLength)) {
                return false;
            }
            if (byteLength != 0) {
                if (!stateObj.TryReadString(byteLength, out metaData.udtSchemaName)) {
                    return false;
                }
            }

            // type name
            if (!stateObj.TryReadByte(out byteLength)) {
                return false;
            }
            if (byteLength != 0) {
                if (!stateObj.TryReadString(byteLength, out metaData.udtTypeName)) {
                    return false;
                }
            }

            if (!stateObj.TryReadUInt16(out shortLength)) {
                return false;
            }
            if (shortLength != 0) {
                if (!stateObj.TryReadString(shortLength, out metaData.udtAssemblyQualifiedName)) {
                    return false;
                }
            }

            return true;
        }       

        private bool TryCommonProcessMetaData(TdsParserStateObject stateObj, _SqlMetaData col, SqlTceCipherInfoTable? cipherTable, bool fColMD, SqlCommandColumnEncryptionSetting columnEncryptionSetting) {
            byte byteLen;
            UInt32 userType;

            // read user type - 4 bytes Yukon, 2 backwards
            if (IsYukonOrNewer) {
                if (!stateObj.TryReadUInt32(out userType)) {
                    return false;
                }
            }
            else {
                ushort userTypeShort;
                if (!stateObj.TryReadUInt16(out userTypeShort)) {
                    return false;
                }
                userType = userTypeShort;
            }

            // read flags and set appropriate flags in structure
            byte flags;
            if (!stateObj.TryReadByte(out flags)) {
                return false;
            }

            col.updatability = (byte)((flags & TdsEnums.Updatability) >> 2);
            col.isNullable = (TdsEnums.Nullable == (flags & TdsEnums.Nullable));
            col.isIdentity = (TdsEnums.Identity == (flags & TdsEnums.Identity));

            // read second byte of column metadata flags
            if (!stateObj.TryReadByte(out flags)) {
                return false;
            }
            
            col.isColumnSet = (TdsEnums.IsColumnSet == (flags & TdsEnums.IsColumnSet));
            if (fColMD && _serverSupportsColumnEncryption) {
                col.isEncrypted = (TdsEnums.IsEncrypted == (flags & TdsEnums.IsEncrypted));
            }

            // Read TypeInfo
            if (!TryProcessTypeInfo (stateObj, col, userType)) {
                return false;
            }

            // Read tablename if present
            if (col.metaType.IsLong && !col.metaType.IsPlp) {
                if (_isYukon) {
                    int  unusedLen = 0xFFFF;      //We ignore this value
                    if (!TryProcessOneTable(stateObj, ref unusedLen, out col.multiPartTableName)) {
                        return false;
                    }
                } else {
                    ushort shortLen;
                    if (!stateObj.TryReadUInt16(out shortLen)) {
                        return false;
                    }
                    string tableName;
                    if (!stateObj.TryReadString(shortLen, out tableName)) {
                        return false;
                    }
                    // with Sql2000 this is returned as an unquoted mix of catalog.owner.table
                    // all of which may contain "." and unable to parse correctly from the string alone
                    // example "select * from pubs..[A.B.C.D.E]" AND only when * will contain a image/text/ntext column
                    // by delay parsing from execute to SqlDataReader.GetSchemaTable to enable more scenarios
                    col.multiPartTableName = new MultiPartTableName(tableName);
                }
            }

            // Read the TCE column cryptoinfo
            if (fColMD && _serverSupportsColumnEncryption && col.isEncrypted) {
                // If the column is encrypted, we should have a valid cipherTable
                if (cipherTable.HasValue && !TryProcessTceCryptoMetadata (stateObj, col, cipherTable.Value, columnEncryptionSetting, isReturnValue: false)) {
                    return false;
                }
            }

            // Read the column name 
            if (!stateObj.TryReadByte(out byteLen)) {
                return false;
            }
            if (!stateObj.TryReadString(byteLen, out col.column)) {
                return false;
            }

            // We get too many DONE COUNTs from the server, causing too meany StatementCompleted event firings.
            // We only need to fire this event when we actually have a meta data stream with 0 or more rows.
            stateObj._receivedColMetaData = true;
            return true;
        }

        private bool TryProcessTypeInfo (TdsParserStateObject stateObj, SqlMetaDataPriv col, UInt32 userType) {
            byte byteLen;
            byte tdsType;
            if (!stateObj.TryReadByte(out tdsType)) {
                return false;
            }

            if (tdsType == TdsEnums.SQLXMLTYPE)
                col.length = TdsEnums.SQL_USHORTVARMAXLEN;  //Use the same length as other plp datatypes
            else if (IsVarTimeTds(tdsType))
                col.length = 0;  // placeholder until we read the scale, just make sure it's not SQL_USHORTVARMAXLEN
            else if (tdsType == TdsEnums.SQLDATE) {
                col.length = 3;
            }
            else {
                if (!TryGetTokenLength(tdsType, stateObj, out col.length)) {
                    return false;
                }
            }

            col.metaType = MetaType.GetSqlDataType(tdsType, userType, col.length);
            col.type = col.metaType.SqlDbType;

            // If sphinx, do not change to nullable type
            if (_isShiloh)
                col.tdsType = (col.isNullable ? col.metaType.NullableType : col.metaType.TDSType);
            else
                col.tdsType = tdsType;

            if (_isYukon) {
                if (TdsEnums.SQLUDT == tdsType) {
                    if (!TryProcessUDTMetaData((SqlMetaDataPriv) col, stateObj)) {
                        return false;
                    }
                }

                if (col.length == TdsEnums.SQL_USHORTVARMAXLEN) {
                    Debug.Assert(tdsType == TdsEnums.SQLXMLTYPE ||
                                 tdsType == TdsEnums.SQLBIGVARCHAR ||
                                 tdsType == TdsEnums.SQLBIGVARBINARY ||
                                 tdsType == TdsEnums.SQLNVARCHAR ||
                                 tdsType == TdsEnums.SQLUDT,
                                 "Invalid streaming datatype");
                    col.metaType = MetaType.GetMaxMetaTypeFromMetaType(col.metaType);
                    Debug.Assert(col.metaType.IsLong, "Max datatype not IsLong");
                    col.length = Int32.MaxValue;
                    if (tdsType == TdsEnums.SQLXMLTYPE) {
                        byte schemapresent;
                        if (!stateObj.TryReadByte(out schemapresent)) {
                            return false;
                        }

                        if ((schemapresent & 1) != 0) {
                            if (!stateObj.TryReadByte(out byteLen)) {
                                return false;
                            }
                            if (byteLen != 0) {
                                if (!stateObj.TryReadString(byteLen, out col.xmlSchemaCollectionDatabase)) {
                                    return false;
                                }
                            }

                            if (!stateObj.TryReadByte(out byteLen)) {
                                return false;
                            }
                            if (byteLen != 0) {
                                if (!stateObj.TryReadString(byteLen, out col.xmlSchemaCollectionOwningSchema)) {
                                    return false;
                                }
                            }

                            short shortLen;
                            if (!stateObj.TryReadInt16(out shortLen)) {
                                return false;
                            }
                            if (byteLen != 0) {
                                if (!stateObj.TryReadString(shortLen, out col.xmlSchemaCollectionName)) {
                                    return false;
                                }
                            }
                        }
                    }
                }
            }

            if (col.type == SqlDbType.Decimal) {
                if (!stateObj.TryReadByte(out col.precision)) {
                    return false;
                }
                if (!stateObj.TryReadByte(out col.scale)) {
                    return false;
                }
            }

            if (col.metaType.IsVarTime) {
                if (!stateObj.TryReadByte(out col.scale)) {
                    return false;
                }

                Debug.Assert(0 <= col.scale && col.scale <= 7);
//.........这里部分代码省略.........

        /// <summary>
        /// <para> Parses the TDS message to read single CIPHER_INFO entry.</para>
        /// </summary>
        internal bool TryReadCipherInfoEntry (TdsParserStateObject stateObj, out SqlTceCipherInfoEntry entry) {
            byte cekValueCount = 0;
            entry = new SqlTceCipherInfoEntry(ordinal: 0);

            // Read the DB ID
            int dbId;
            if (!stateObj.TryReadInt32(out dbId)) {
                return false;
            }

            // Read the keyID
            int keyId;
            if (!stateObj.TryReadInt32(out keyId)) {
                return false;
            }

            // Read the key version
            int keyVersion;
            if (!stateObj.TryReadInt32(out keyVersion)) {
                return false;
            }

            // Read the key MD Version
            byte[] keyMDVersion = new byte[8];
            if (!stateObj.TryReadByteArray(keyMDVersion, 0, 8)) {
                return false;
            }

            // Read the value count
            if (!stateObj.TryReadByte (out cekValueCount)) {
                return false;
            }

            for (int i = 0; i < cekValueCount; i++) {
                // Read individual CEK values
                byte[] encryptedCek;
                string keyPath;
                string keyStoreName;
                byte algorithmLength;
                string algorithmName;
                ushort shortValue;
                byte byteValue;
                int length;

                // Read the length of encrypted CEK 
                if (!stateObj.TryReadUInt16 (out shortValue)) {
                    return false; 
                }

                length = shortValue;
                encryptedCek = new byte[length];

                // Read the actual encrypted CEK
                if (!stateObj.TryReadByteArray (encryptedCek, 0, length)) {
                    return false;
                }

                // Read the length of key store name
                if (!stateObj.TryReadByte (out byteValue)) {
                    return false;
                }

                length = byteValue;

                // And read the key store name now
                if (!stateObj.TryReadString(length, out keyStoreName)) {
                    return false;
                }

                // Read the length of key Path
                if (!stateObj.TryReadUInt16 (out shortValue)) {
                    return false;
                }

                length = shortValue;

                // Read the key path string
                if (!stateObj.TryReadString(length, out keyPath)) {
                    return false;
                }

                // Read the length of the string carrying the encryption algo
                if (!stateObj.TryReadByte(out algorithmLength)) {
                    return false;
                }

                length = (int)algorithmLength;

                // Read the string carrying the encryption algo  (eg. RSA_PKCS_OAEP)
                if (!stateObj.TryReadString(length, out algorithmName)) {
                    return false;
                }

                // Add this encrypted CEK blob to our list of encrypted values for the CEK
                entry.Add(encryptedCek, 
                    databaseId: dbId, 
                    cekId: keyId, 
//.........这里部分代码省略.........

        internal bool TryProcessReturnValue(int length, TdsParserStateObject stateObj, out SqlReturnValue returnValue)
        {
            returnValue = null;
            SqlReturnValue rec = new SqlReturnValue();
            rec.length = length;        // In Yukon this length is -1
            ushort parameterIndex;
            if (!stateObj.TryReadUInt16(out parameterIndex))
            {
                return false;
            }
            byte len;
            if (!stateObj.TryReadByte(out len))
            { // Length of parameter name
                return false;
            }

            if (len > 0)
            {
                if (!stateObj.TryReadString(len, out rec.parameter))
                {
                    return false;
                }
            }

            // read status and ignore
            byte ignored;
            if (!stateObj.TryReadByte(out ignored))
            {
                return false;
            }

            UInt32 userType;

            // read user type - 4 bytes Yukon, 2 backwards
            if (!stateObj.TryReadUInt32(out userType))
            {
                return false;
            }

            // read off the flags
            ushort ignoredFlags;
            if (!stateObj.TryReadUInt16(out ignoredFlags))
            {
                return false;
            }

            // read the type
            byte tdsType;
            if (!stateObj.TryReadByte(out tdsType))
            {
                return false;
            }

            // read the MaxLen
            // For xml datatpyes, there is no tokenLength
            int tdsLen;

            if (tdsType == TdsEnums.SQLXMLTYPE)
            {
                tdsLen = TdsEnums.SQL_USHORTVARMAXLEN;
            }
            else if (IsVarTimeTds(tdsType))
                tdsLen = 0;  // placeholder until we read the scale, just make sure it's not SQL_USHORTVARMAXLEN
            else if (tdsType == TdsEnums.SQLDATE)
            {
                tdsLen = 3;
            }
            else
            {
                if (!TryGetTokenLength(tdsType, stateObj, out tdsLen))
                {
                    return false;
                }
            }

            rec.metaType = MetaType.GetSqlDataType(tdsType, userType, tdsLen);
            rec.type = rec.metaType.SqlDbType;

            // always use the nullable type for parameters if Shiloh or later
            // Sphinx sometimes sends fixed length return values
            rec.tdsType = rec.metaType.NullableType;
            rec.isNullable = true;
            if (tdsLen == TdsEnums.SQL_USHORTVARMAXLEN)
            {
                rec.metaType = MetaType.GetMaxMetaTypeFromMetaType(rec.metaType);
            }

            if (rec.type == SqlDbType.Decimal)
            {
                if (!stateObj.TryReadByte(out rec.precision))
                {
                    return false;
                }
                if (!stateObj.TryReadByte(out rec.scale))
                {
                    return false;
                }
            }

            if (rec.metaType.IsVarTime)
//.........这里部分代码省略.........