public DbaseWriter(string filename)
{
_dbaseFileStream = File.Open(filename, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.Read);
_dbaseWriter = new BinaryWriter(_dbaseFileStream, Encoding.ASCII);
_dbaseReader = new BinaryReader(_dbaseFileStream);
if (_dbaseFileStream.Length > 0)
{
_header = DbaseHeader.ParseDbfHeader(_dbaseReader);
_schema = DbaseSchema.GetFeatureTableForFields(_header.Columns);
}
}
internal static DbaseHeader ParseDbfHeader(BinaryReader reader)
{
DbaseHeader header = new DbaseHeader();
if (reader.ReadByte() != DbaseConstants.DbfVersionCode)
{
throw new NotSupportedException("Unsupported DBF Type");
}
header.LastUpdate = new DateTime((int)reader.ReadByte() + 1900, (int)reader.ReadByte(), (int)reader.ReadByte()); //Read the last update date
header.RecordCount = reader.ReadUInt32(); // read number of records.
short storedHeaderLength = reader.ReadInt16(); // read length of header structure.
short storedRecordLength = reader.ReadInt16(); // read length of a record
reader.BaseStream.Seek(DbaseConstants.EncodingOffset, SeekOrigin.Begin); //Seek to encoding flag
header.LanguageDriver = reader.ReadByte(); //Read and parse Language driver
reader.BaseStream.Seek(DbaseConstants.ColumnDescriptionOffset, SeekOrigin.Begin); //Move past the reserved bytes
int numberOfColumns = (storedHeaderLength - DbaseConstants.ColumnDescriptionOffset) / DbaseConstants.ColumnDescriptionLength; // calculate the number of DataColumns in the header
DbaseField[] columns = new DbaseField[numberOfColumns];
for (int i = 0; i < columns.Length; i++)
{
columns[i] = new DbaseField();
columns[i].ColumnName = System.Text.Encoding.UTF7.GetString((reader.ReadBytes(11))).Replace("\0", "").Trim();
char fieldtype = reader.ReadChar();
columns[i].Address = reader.ReadInt32();
short fieldLength = reader.ReadByte();
if (fieldtype == 'N' || fieldtype == 'F')
{
columns[i].Decimals = reader.ReadByte();
}
else
{
fieldLength += (short)((short)reader.ReadByte() << 8);
}
columns[i].Length = fieldLength;
switch (fieldtype)
{
case 'L':
columns[i].DataType = typeof(bool);
break;
case 'C':
columns[i].DataType = typeof(string);
break;
case 'D':
columns[i].DataType = typeof(DateTime);
break;
case 'N':
//If the number doesn't have any decimals, make the type an integer, if possible
if (columns[i].Decimals == 0)
{
if (columns[i].Length <= 4)
{
columns[i].DataType = typeof(Int16);
}
else if (columns[i].Length <= 9)
{
columns[i].DataType = typeof(Int32);
}
else if (columns[i].Length <= 18)
{
columns[i].DataType = typeof(Int64);
}
else
{
columns[i].DataType = typeof(double);
}
}
else
{
columns[i].DataType = typeof(double);
}
break;
case 'F':
columns[i].DataType = typeof(float);
break;
case 'B':
columns[i].DataType = typeof(byte[]);
break;
default:
throw new NotSupportedException("Invalid or unknown DBase field type '" + fieldtype +
"' in column '" + columns[i].ColumnName + "'");
}
// Move stream to next field record
reader.BaseStream.Seek(DbaseConstants.BytesFromEndOfDecimalInFieldRecord, SeekOrigin.Current);
}
header.Columns = columns;
if (storedHeaderLength != header.HeaderLength)
{
throw new Exception("Recorded header length doesn't equal computed header length");
}
if (storedRecordLength != header.RecordLength)
{
throw new Exception("Recorded record length doesn't equal computed record length");
}
return(header);
}
