Symbian: How to write HBufC* to file

Question

Hi,

I am trying to read data from a file into an HBufC8 variable and then write the same data into another file. Here is my testcode; the inner loop of the read repeats 4 times to read 5000 chars in each iteration. However, when I try to write the data back into a file, the file "testfile.txt" is empty. Will play a little bit more around with it but help would be appreciated as always ;) Thanks

  HBufC8* iFileBuffer = HBufC8::NewL(20000); 
     TPtr8 ptr(iFileBuffer->Des());

  fp.Seek(ESeekStart,pos);

     Err = fp.Read(ptr);

  while(!Err && ptr.Length()>0)
  {
  Err = fp.Read(ptr);
  Printf(_L("Data read: %d \n\n"), ptr.Length());   
  } 

  fp.Create(iFileServer,_L("C:\\testfile.txt"), EFileWrite);

     fp.Seek(ESeekEnd,pos);   

  fp.Write(*iFileBuffer);
  fp.Close();

  delete(iFileBuffer);

Answer 1

The first thing I did when playing around with Symbian was to ditch their insane IO classes and use normal C IO:

for instance, this writes a png file from a symbian memorybuffer

 #include <stdio.h>
 #include <string.h>

 fp = fopen("c:\\data\\others\\pngfile.png","wb");
 if(fp)
 {
      fwrite((char*)httpInputBufDesc->Ptr(), httpInputBufDesc->Length(), 1, fp);
      fclose(fp);
      fflush(fp);
 }
 else
 {
      LOG("Failed to write to disk\n");
 }

as a bonus this is 3 times more portable, if you ever decide to write for a different platform (which might not be very far fetched since Symbian seems to loose more and more developers and even aid from Nokia)

Answer 2

You're reading max. 20000 bytes of input file twice. The first read is likely to have read in the entire file. In that case the second read returns 0 bytes which you are writing out to the second file.

Also you probably don't want to use the same RFile handle for both files. It's also a good habit to Close the files when done, though the files get automagically closed also when you close your file server session.