I can read and write BLOB field into my databases with ZeOS.
Unfortunatelly if I use mysql-4.1/mysql-5 protocol on a MySQL server (4.1/5), I can not get back the same content of the BLOB field as it was saved. The following procedures were tested and used with the following protocols: firebird, postgresql, ado (MSSQL).
Can anybody help?
Code: Select all
// (De-)Compress functions
procedure CompressStream(aSource,aTarget:TStream);
var
compStream:TCompressionStream;
begin
compStream:=TCompressionStream.Create(clFastest,aTarget);
try
aSource.Position:=0;
compStream.CopyFrom(aSource,aSource.Size);
compStream.CompressionRate;
finally
compStream.Free;
end;
end;
procedure DecompressStream(aSorce,aTarget:TStream);
var
decompStream:TDecompressionStream;
nRead:integer;
Buffer:array[0..1023] of Char;
Count:integer;
begin
decompStream:=TDecompressionStream.Create(aSorce);
try
if aSorce.Size > 0 then begin
decompStream.Position:=0;
Count:=1024;
repeat
try
nRead:=decompStream.Read(Buffer,Count);
except
on E:Exception do begin
raise Exception.Create('Decompression error when write ir to stream!');
end;
end;
try
aTarget.WriteBuffer(Buffer,nRead);
except
on E:Exception do begin
raise Exception.Create('Decompression error when write ir to stream!');
end;
end;
until nRead=0;
end;
finally
decompStream.Free;
end;
end;
procedure ReadBlobField(ImageField:TBlobField;Image:TImage;DeCompress:boolean);
var
memoStream:TMemoryStream;
compStream:TMemoryStream;
begin
if ImageField.IsNull then begin
memoStream:=TMemoryStream.Create;
Image.AutoSize:=true;
Image.Picture.Bitmap.LoadFromStream(memoStream);
Image.AutoSize:=false;
exit;
end;
memoStream:=TMemoryStream.Create;
if DeCompress then compStream:=TMemoryStream.Create else compStream:=nil;
try
// blob kiolvasása
(* DbExpress
bstream:=TSQLBlobStream.Create(ImageField,bmReadWrite);
bstream.ReadBlobData;
bstream.Position:=0;
try
if DeCompress then begin
compStream.LoadFromStream(bstream);
compStream.Position:=0;
DecompressStream(compStream,memoStream);
end else begin
memoStream.LoadFromStream(bstream);
end;
except
on E:Exception do begin
ShowPSError('Blob field reading error: '+#10+E.Message);
memoStream.Size:=0;
if DeCompress then compStream.Size:=0;
end;
end;
bstream.Free;
*)
try
if DeCompress then begin
ImageField.SaveToStream(compStream);
compStream.Position:=0;
DecompressStream(compStream,memoStream);
end else begin
ImageField.SaveToStream(memoStream);
end;
except
on E:Exception do begin
ShowPSError('Blob field reading error: '+#10+E.Message);
memoStream.Size:=0;
if DeCompress then compStream.Size:=0;
end;
end;
try
Image.AutoSize:=true;
memoStream.Position:=0;
Image.Picture.Bitmap.FreePixmap;
Image.Picture.Bitmap.FreeImage;
if memoStream.Size>0 then begin
memoStream.Position:=0;
Image.Picture.Bitmap.LoadFromStream(memoStream);
end;
Image.AutoSize:=false;
except
on E:Exception do ShowPSError('Image creating error: '+#10+E.Message);
end;
finally
memoStream.Free;
if DeCompress then compStream.Free;
end;
end;
procedure WriteBlobParam(ImageParam:TParam;Image:TImage;Compress:boolean);
var
memoStream:TMemoryStream;
compStream:TMemoryStream;
begin
memoStream:=TMemoryStream.Create;
if Compress then compStream:=TMemoryStream.Create else compStream:=nil;
try
Image.Picture.Bitmap.SaveToStream(memoStream);
if memoStream.Size=0 then begin
if AnsiContainsText(DM.conDB.Protocol,'mssql') or
(AnsiContainsText(DM.conDB.Database, 'SQLOLEDB')) then begin
ImageParam.Value:=0
end else begin
ImageParam.Value:=Null;
// ImageParam.LoadFromStream(memoStream,ImageParam.DataType);
end;
end else begin
// memoStream.Size;
memoStream.Position:=0;
if Compress then begin
CompressStream(memoStream,compStream);
compStream.Position:=0;
ImageParam.LoadFromStream(compStream,ImageParam.DataType);
end else begin
memoStream.Position:=0;
ImageParam.LoadFromStream(memoStream,ImageParam.DataType);
end;
memoStream.Position:=0;
end;
finally
memoStream.Free;
if Compress then compStream.Free
end;
end;
