/// <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);
}
/// <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);
}