/// <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 (!mHeaderWritten)
{
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 != mHeader && (orec.Header.ColumnCount != mHeader.ColumnCount || orec.Header.RecordLength != mHeader.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 (mDbfFileWriter == 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)mHeader.HeaderLength + (long)((long)orec.RecordIndex * (long)mHeader.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 (mDbfFile.Length < nSeekToPosition)
{
throw new Exception("Invalid record position. Unable to save record.");
}
//move to record start
mDbfFile.Seek(nSeekToPosition, SeekOrigin.Begin);
//write
orec.Write(mDbfFile);
}
/// <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 (!mHeaderWritten)
{
WriteHeader();
}
//if this is a new record (RecordIndex should be -1 in that case)
if (orec.RecordIndex < 0)
{
if (mDbfFileWriter.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)(mDbfFile.Length - mHeader.HeaderLength - 1) / mHeader.RecordLength));
if (nNumRecords < 0)
{
nNumRecords = 0;
}
orec.RecordIndex = nNumRecords;
Update(orec);
mHeader.RecordCount++;
}
else
{
//we can not position this stream, just write out the new record.
orec.Write(mDbfFile);
mHeader.RecordCount++;
}
}
else
{
Update(orec);
}
}