Example #1
0
        /// <summary>
        /// Reads a record specified by index. This method requires the stream to be able to seek to position.
        /// If you are using a http stream, or a stream that can not stream, use ReadNext() methods to read in all records.
        /// </summary>
        /// <param name="index">Zero based index.</param>
        /// <returns>Null if record can not be read, otherwise returns a new record.</returns>
        public DbfRecord Read(long index)
        {
            //create a new record and fill it.
            DbfRecord orec = new DbfRecord(_header);

            return(Read(index, orec) ? orec : null);
        }
Example #2
0
        /// <summary>
        /// Tries to read a record and returns a new record object or null if nothing was read.
        /// </summary>
        /// <returns></returns>
        public DbfRecord ReadNext()
        {
            //create a new record and fill it.
            DbfRecord orec = new DbfRecord(_header);

            return(ReadNext(orec) ? orec : null);
        }
Example #3
0
        public void Write(DbfRecord orec, bool bClearRecordAfterWrite)
        {
            Write(orec);

            if (bClearRecordAfterWrite)
            {
                orec.Clear();
            }
        }
Example #4
0
        /// <summary>
        /// Update a record. RecordIndex (zero based index) must be more than -1, otherwise an exception is thrown.
        /// You can also use Write method which updates a record if it has RecordIndex or adds a new one if RecordIndex == -1.
        /// RecordIndex is set automatically when you call any Read() methods on this class.
        /// </summary>
        /// <param name="orec"></param>
        public void Update(DbfRecord orec)
        {
            //if header was never written, write it first, then output the record
            if (!_headerWritten)
            {
                WriteHeader();
            }


            //Check if record has an index
            if (orec.RecordIndex < 0)
            {
                throw new Exception("RecordIndex is not set, unable to update record. Set RecordIndex or call Write() method to add a new record to file.");
            }


            //Check if this record matches record size specified by header and number of columns.
            //Client can pass a record from another DBF that is incompatible with this one and that would corrupt the file.
            if (orec.Header != _header && (orec.Header.ColumnCount != _header.ColumnCount || orec.Header.RecordLength != _header.RecordLength))
            {
                throw new Exception("Record parameter does not have the same size and number of columns as the " +
                                    "header specifies. Writing this record would corrupt the DBF file. " +
                                    "This is a programming error, have you mixed up DBF file objects?");
            }

            //DBF file writer can be null if stream is not writable to...
            if (_dbfFileWriter == null)
            {
                throw new Exception("Write stream is null. Either you have opened a stream that can not be " +
                                    "writen to (a read-only stream) or you have not opened a stream at all.");
            }


            //move to the specified record, note that an exception will be thrown if stream is not seekable!
            //This is ok, since we provide a function to check whether the stream is seekable.
            long nSeekToPosition = (long)_header.HeaderLength + (long)((long)orec.RecordIndex * (long)_header.RecordLength);

            //check whether we can seek to this position. Subtract 1 from file length (there is a terminating character 1A at the end of the file)
            //so if we hit end of file, there are no more records, so return false;
            if (_dbfFile.Length < nSeekToPosition)
            {
                throw new Exception("Invalid record position. Unable to save record.");
            }

            //move to record start
            _dbfFile.Seek(nSeekToPosition, SeekOrigin.Begin);

            //write
            orec.Write(_dbfFile);
        }
Example #5
0
        /// <summary>
        /// Reads a record specified by index into oFillRecord object. You can use this method
        /// to read in and process records without creating and discarding record objects.
        /// Note that you should check that your stream is not forward-only! If you have a forward only stream, use ReadNext() functions.
        /// </summary>
        /// <param name="index">Zero based record index.</param>
        /// <param name="oFillRecord">Record object to fill, must have same size and number of fields as thid DBF file header!</param>
        /// <remarks>
        /// <returns>True if read a record was read, otherwise false. If you read end of file false will be returned and oFillRecord will NOT be modified!</returns>
        /// The parameter record (oFillRecord) must match record size specified by the header and number of columns as well.
        /// It does not have to come from the same header, but it must match the structure. We are not going as far as to check size of each field.
        /// The idea is to be flexible but safe. It's a fine balance, these two are almost always at odds.
        /// </remarks>
        public bool Read(long index, DbfRecord oFillRecord)
        {
            //check if we can fill this record with data. it must match record size specified by header and number of columns.
            //we are not checking whether it comes from another DBF file or not, we just need the same structure. Allow flexibility but be safe.
            if (oFillRecord.Header != _header && (oFillRecord.Header.ColumnCount != _header.ColumnCount || oFillRecord.Header.RecordLength != _header.RecordLength))
            {
                throw new Exception("Record parameter does not have the same size and number of columns as the " +
                                    "header specifies, so we are unable to read a record into oFillRecord. " +
                                    "This is a programming error, have you mixed up DBF file objects?");
            }

            //DBF file reader can be null if stream is not readable...
            if (_dbfFileReader == null)
            {
                throw new Exception("ReadStream is null, either you have opened a stream that can not be " +
                                    "read from (a write-only stream) or you have not opened a stream at all.");
            }


            //move to the specified record, note that an exception will be thrown is stream is not seekable!
            //This is ok, since we provide a function to check whether the stream is seekable.
            long nSeekToPosition = _header.HeaderLength + (index * _header.RecordLength);

            //check whether requested record exists. Subtract 1 from file length (there is a terminating character 1A at the end of the file)
            //so if we hit end of file, there are no more records, so return false;
            if (index < 0 || _dbfFile.Length - 1 <= nSeekToPosition)
            {
                return(false);
            }

            //move to record and read
            _dbfFile.Seek(nSeekToPosition, SeekOrigin.Begin);

            //read the record
            bool bRead = oFillRecord.Read(_dbfFile);

            if (bRead)
            {
                oFillRecord.RecordIndex = index;
            }

            return(bRead);
        }
Example #6
0
        /// <summary>
        /// Write a record to file. If RecordIndex is present, record will be updated, otherwise a new record will be written.
        /// Header will be output first if this is the first record being writen to file.
        /// This method does not require stream seek capability to add a new record.
        /// </summary>
        /// <param name="orec"></param>
        public void Write(DbfRecord orec)
        {
            //if header was never written, write it first, then output the record
            if (!_headerWritten)
            {
                WriteHeader();
            }

            //if this is a new record (RecordIndex should be -1 in that case)
            if (orec.RecordIndex < 0)
            {
                if (_dbfFileWriter.BaseStream.CanSeek)
                {
                    //calculate number of records in file. do not rely on header's RecordCount property since client can change that value.
                    //also note that some DBF files do not have ending 0x1A byte, so we subtract 1 and round off
                    //instead of just cast since cast would just drop decimals.
                    int nNumRecords = (int)Math.Round(((double)(_dbfFile.Length - _header.HeaderLength - 1) / _header.RecordLength));
                    if (nNumRecords < 0)
                    {
                        nNumRecords = 0;
                    }

                    orec.RecordIndex = nNumRecords;
                    Update(orec);
                    _header.RecordCount++;
                }
                else
                {
                    //we can not position this stream, just write out the new record.
                    orec.Write(_dbfFile);
                    _header.RecordCount++;
                }
            }
            else
            {
                Update(orec);
            }
        }
Example #7
0
        /// <summary>
        /// Read next record and fill data into parameter oFillRecord. Returns true if a record was read, otherwise false.
        /// </summary>
        /// <param name="oFillRecord"></param>
        /// <returns></returns>
        public bool ReadNext(DbfRecord oFillRecord)
        {
            //check if we can fill this record with data. it must match record size specified by header and number of columns.
            //we are not checking whether it comes from another DBF file or not, we just need the same structure. Allow flexibility but be safe.
            if (oFillRecord.Header != _header && (oFillRecord.Header.ColumnCount != _header.ColumnCount || oFillRecord.Header.RecordLength != _header.RecordLength))
            {
                throw new Exception("Record parameter does not have the same size and number of columns as the " +
                                    "header specifies, so we are unable to read a record into oFillRecord. " +
                                    "This is a programming error, have you mixed up DBF file objects?");
            }

            //DBF file reader can be null if stream is not readable...
            if (_dbfFileReader == null)
            {
                throw new Exception("Read stream is null, either you have opened a stream that can not be " +
                                    "read from (a write-only stream) or you have not opened a stream at all.");
            }

            //read next record...
            bool bRead = oFillRecord.Read(_dbfFile);

            if (bRead)
            {
                if (_isForwardOnly)
                {
                    //zero based index! set before incrementing count.
                    oFillRecord.RecordIndex = _recordsReadCount;
                    _recordsReadCount++;
                }
                else
                {
                    oFillRecord.RecordIndex = ((int)((_dbfFile.Position - _header.HeaderLength) / _header.RecordLength)) - 1;
                }
            }

            return(bRead);
        }