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Randel Bjorkquist · Guest

Hi all,

I've got my BLOB to load into the SQL Server just peachy, but I can't get
them back out. What I'm trying to do is store the BLOB file in the
database, along with its's file name (in a separate field of course). Then
extract the BLOB from the database, save it to a file, and use
ShellExecute() to open. Currently, I'm only trying to get this to work with
the Bitmap files.

Here is what I'm doing:
1 - I'm get the dataset,
2 - using the "CreateBlobStream()" method of the TDataSet
3 - NEED A WAY TO SAVE TO A PHYSICAL FILE
4 - use ShellExecute() to open.

Here is my code:
void __fastcall Tfrm_Main::OpenBlob(TObject *Sender)
{
AnsiString TestFile = "C:\Temp\Test.bmp";
TDataSet* Data = dm_Picture->ds_Picture->DataSet;

TBlobField* Picture = new TBlobField(Data);
TBlobStream* PicStream = new TBlobStream(Picture, bmRead);
:
//TRY TO SAVE TO FILE HERE,
//USE THE FILE NAME "TestFile"
:
delete Picture;
delete PicStream;

ShellExecute(NULL, "open", TestFile.c_str(), NULL, "C:\", SW_SHOW);
}//end of "Tfrm_Main::OpenBlob" method

Thanks for any help,

Randel Bjorkquist

Randel Bjorkquist · Guest

Hey all,

I got something to work, but I don't like it. Is this correct? Is there a
better way of doing this? I tried to base if off the "CreateBlobStream"
example.

//--------------------------------------------------------------------------
-
void __fastcall Tfrm_Main::SpeedButton1Click(TObject *Sender)
{
AnsiString TestFileName = "C:\Temp\";

TDataSet* Data = dm_Picture->ds_Picture->DataSet;

TestFileName += Data->FieldByName("FileName")->AsString;

TFileStream* FileStream = new TFileStream(TestFileName, fmCreate);
TBlobStream* PicStream =
dynamic_cast<TBlobStream*>(Data->CreateBlobStream(Data->FieldByName("Picture
"), bmRead));

FileStream->CopyFrom(PicStream, PicStream->Size);
FileStream->Write(FileStream,PicStream->Size);

delete PicStream;
delete FileStream;

ShellExecute(NULL, "open", TestFileName.c_str(), NULL, "C:\", SW_SHOW);
}

Again, any help is desired.

Randel Bjorkquist

"Randel Bjorkquist" <rbjorkquist (AT) coilcraft (DOT) com> wrote

Randel Bjorkquist · Guest

Found a mistake, here is the corrected code:

//--------------------------------------------------------------------------
-
void __fastcall Tfrm_Main::SpeedButton1Click(TObject *Sender)
{
AnsiString TestFileName = "C:\Temp\";

TDataSet* Data = dm_Picture->ds_Picture->DataSet;
TestFileName += Data->FieldByName("FileName")->AsString;

TBlobStream* PicStream;
TFileStream* FileStream;

try{
FileStream = new TFileStream(TestFileName, fmCreate);
PicStream =
dynamic_cast<TBlobStream*>(Data->CreateBlobStream(Data->FieldByName("Picture
"), bmRead));

if(PicStream != NULL){
FileStream->CopyFrom(PicStream, 0);
}//end of "if(PicStream != NULL)"
}//end "try-block"
__finally{
delete PicStream;
delete FileStream;
}//end of "__finally"

ShellExecute(NULL, "open", TestFileName.c_str(), NULL, "C:\", SW_SHOW);
}

"Randel Bjorkquist" <rbjorkquist (AT) coilcraft (DOT) com> wrote

Arnie Mauer · Guest

Randel Bjorkquist · Guest

Hey Arnie,

I guess with I just didn't understand how the TFileStream and TBlobStream
worked. When I first read the about them, I misinterpreted what it was
saying. It just didn't seem right to me, but it worked. I have been able
to get code to work, but was absolutely wrong, if you can understand. So I
just wanted to make sure I understood and or was doing it right. Also,
having to delete both pointers, when I only use the "new" keyword once,
really through me.

So if you have any comments or sugguestions, I'll be more then happy to read
them.

I really do thank you for your reply,

Randel Bjorkquist

The code in your reply is an older example of what I finally got working,
below is the most current.
//--------------------------------------------------------------------------
void __fastcall Tfrm_Main::SpeedButton1Click(TObject *Sender)
{
AnsiString TestFileName = "C:\Temp\";

TDataSet* Data = dm_Picture->ds_Picture->DataSet;
TestFileName += Data->FieldByName("FileName")->AsString;

TBlobStream* PicStream;
TFileStream* FileStream;

try{
FileStream = new TFileStream(TestFileName, fmCreate);
PicStream =
dynamic_cast<TBlobStream*>(Data->CreateBlobStream(Data->FieldByName("Picture
"), bmRead));

if(PicStream != NULL){
FileStream->CopyFrom(PicStream, 0);
}//end of "if(PicStream != NULL)"
}//end "try-block"
__finally{
delete PicStream;
delete FileStream;
}//end of "__finally"

ShellExecute(NULL, "open", TestFileName.c_str(), NULL, "C:\", SW_SHOW);
}

"Arnie Mauer" <xxx (AT) nowhere (DOT) net> wrote

Arnie Mauer · Guest

"Randel Bjorkquist" <rbjorkquist (AT) coilcraft (DOT) com> wrote

Crimson Rider · Guest

I am also trying to retrieve a BLOB field from my database, but I am having the
problem that I can't seem to read any BLOB's greater then 32769 bytes, ie 32k
from it.

If I connect to my MySQL database from Mascon or the like I can see that there
is a picture of about 60k in the datafield, however I only seem to be able to
get the first 32k of it. What am I doing wrong ?

This is the code I use.

TMemoryStream * ptrLoadStream;
TJPEGImage * ptrJPEG = new TJPEGImage();

ptrLoadStream = new TMemoryStream();
ptrJPEG->Assign( DataMod->qImage );

ptrJPEG->SaveToFile("somefile.jpg");

Where qImage is the TBlobField that of the query that retrieves the image from
the databse in the first place.

Any help would be welcome.

Regards
Crimson