Firebird .NET Data Provider reads Guids incorrectly on little-endian systems
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Key: DNET-509
URL: http://tracker.firebirdsql.org/browse/DNET-509
Project: .NET Data provider
Issue Type: Bug
Components: ADO.NET Provider
Affects Versions: 3.0.2.0
Reporter: Herman Schoenfeld
Assignee: Jiri Cincura
On a little-endian systems Guids values are not being correctly hydrated by the
Firebird ADO.NET provider.
For example, a user may insert a Guid via a query of the form
..." INSERT INTO MyTable VALUES (UUID_TO_CHAR(" + guid.ToString() + " ))"
But when that user loads the Guid back via the provider (on a little endian
system), the value is different than the correct value stored on the database
value.
The problem is that Uuid & Guid vary in storage format but not it presentation
format.The The CHAR(16) octets contain the Uuid bytes in big endian layout.
When hydrating these bytes into a Guid, the provider does not compensate for
the Guid's storage of certain parts as the native endian. The correct way to
parse the uuid into a guid is:
var rfc4122bytes = ... uuid byte array returned from
firebird ..
if (BitConverter.IsLittleEndian) {
Array.Reverse(rfc4122bytes, 0, 4);
Array.Reverse(rfc4122bytes, 4, 2);
Array.Reverse(rfc4122bytes, 6, 2);
}
var guid = new Guid(rfc4122bytes);
Suspected location of bug is in class 'DbValue' method 'GetGuid'.
As a work-around, I've written a wrapper for the FbDataReader which will
correct the invalid guid value.
public class FirebirdCorrectingReader : IDataReader {
private readonly IDataReader _decoratedReader;
public FirebirdCorrectingReader(IDataReader decoratedReader) {
_decoratedReader = decoratedReader;
}
#region IDataReader Impl
public void Dispose() {
_decoratedReader.Dispose();
}
public string GetName(int i) {
return _decoratedReader.GetName(i);
}
public string GetDataTypeName(int i) {
return _decoratedReader.GetDataTypeName(i);
}
public Type GetFieldType(int i) {
return _decoratedReader.GetFieldType(i);
}
public object GetValue(int i) {
var result = _decoratedReader.GetValue(i);
if (result is Guid) {
result = CorrectGuid((Guid)result);
}
return result;
}
public int GetValues(object[] values) {
return _decoratedReader.GetValues(values);
}
public int GetOrdinal(string name) {
return _decoratedReader.GetOrdinal(name);
}
public bool GetBoolean(int i) {
return _decoratedReader.GetBoolean(i);
}
public byte GetByte(int i) {
return _decoratedReader.GetByte(i);
}
public long GetBytes(int i, long fieldOffset, byte[] buffer,
int bufferoffset, int length) {
return _decoratedReader.GetBytes(i, fieldOffset,
buffer, bufferoffset, length);
}
public char GetChar(int i) {
return _decoratedReader.GetChar(i);
}
public long GetChars(int i, long fieldoffset, char[] buffer,
int bufferoffset, int length) {
return _decoratedReader.GetChars(i, fieldoffset,
buffer, bufferoffset, length);
}
public Guid GetGuid(int i) {
return CorrectGuid(_decoratedReader.GetGuid(i));
}
public short GetInt16(int i) {
return _decoratedReader.GetInt16(i);
}
public int GetInt32(int i) {
return _decoratedReader.GetInt32(i);
}
public long GetInt64(int i) {
return _decoratedReader.GetInt64(i);
}
public float GetFloat(int i) {
return _decoratedReader.GetFloat(i);
}
public double GetDouble(int i) {
return _decoratedReader.GetDouble(i);
}
public string GetString(int i) {
return _decoratedReader.GetString(i);
}
public decimal GetDecimal(int i) {
return _decoratedReader.GetDecimal(i);
}
public DateTime GetDateTime(int i) {
return _decoratedReader.GetDateTime(i);
}
public IDataReader GetData(int i) {
return _decoratedReader.GetData(i);
}
public bool IsDBNull(int i) {
return _decoratedReader.IsDBNull(i);
}
public int FieldCount { get { return
_decoratedReader.FieldCount; } }
object IDataRecord.this[int i] {
get { return _decoratedReader[i]; }
}
object IDataRecord.this[string name] {
get {return _decoratedReader[name]; }
}
public void Close() {
_decoratedReader.Close();
}
public DataTable GetSchemaTable() {
return _decoratedReader.GetSchemaTable();
}
public bool NextResult() {
return _decoratedReader.NextResult();
}
public bool Read() {
return _decoratedReader.Read();
}
public int Depth { get { return _decoratedReader.Depth; } }
public bool IsClosed { get { return _decoratedReader.IsClosed;
} }
public int RecordsAffected { get { return
_decoratedReader.RecordsAffected; } }
#endregion
public static Guid CorrectGuid(Guid badlyParsedGuid) {
var rfc4122bytes = badlyParsedGuid.ToByteArray();
if (BitConverter.IsLittleEndian) {
Array.Reverse(rfc4122bytes, 0, 4);
Array.Reverse(rfc4122bytes, 4, 2);
Array.Reverse(rfc4122bytes, 6, 2);
}
return new Guid(rfc4122bytes);
}
}
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