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Append content of TMemoryStream to TFileStream

Posted on 2006-06-16
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Hi there.

I have a TFileStream and TMemoryStream.

What I want to do is

Open TMemoryStream - fill with something

Open TFileStream - write TMemoryStream to the end of TFileSream
Close TFileStream

Clear TMemoryStream

Someone got some pointers?
Thanks
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Question by:wildzero
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3 Comments
 
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Accepted Solution

by:
Russell Libby earned 1000 total points
ID: 16925338

This may sound redundant, by why use a memory stream when you are just appending data to the file stream? Anyways, here are 3 examples of peforming the operation you described (using slightly different techniques):

Regards,
Russell

var  strmMem:       TMemoryStream;
     strmFile:      TFileStream;
     szBuffer:      Array [0..127] of Char;
begin

  StrCopy(@szBuffer, 'Hello world'#13#10);

  // Example one - uses both a memory and file stream
  strmMem:=TMemoryStream.Create;
  try
     strmMem.Write(szBuffer, StrLen(@szBuffer));
     if FileExists('c:\test.txt') then
        strmFile:=TFileStream.Create('c:\test.txt', fmOpenReadWrite)
     else
        strmFile:=TFileStream.Create('c:\test.txt', fmCreate);
     try
        strmFile.Seek(0, soFromEnd);
        strmFile.CopyFrom(strmMem, 0);
     finally
        strmFile.Free;
     end;
  finally
     strmMem.Free;
  end;

  // Example two - uses just a file stream
  if FileExists('c:\test.txt') then
     strmFile:=TFileStream.Create('c:\test.txt', fmOpenReadWrite)
  else
     strmFile:=TFileStream.Create('c:\test.txt', fmCreate);
  try
     strmFile.Seek(0, soFromEnd);
     strmFile.Write(szBuffer, StrLen(szBuffer));
  finally
     strmFile.Free;
  end;

  // Example three - uses a memory stream to load file contents, modify, and then resave
  strmMem:=TMemoryStream.Create;
  try
     if FileExists('c:\test.txt') then strmMem.LoadFromFile('c:\test.txt');
     strmMem.Seek(0, soFromEnd);
     strmMem.Write(szBuffer, StrLen(szBuffer));
     strmMem.SaveToFile('c:\test.txt');
  finally
     strmFile.Free;
  end;

end;



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LVL 10

Author Comment

by:wildzero
ID: 16925468
Hi there,

Because I am downloading a file from the internet
need to put the memory buffer into a local file on each cycle

so

downlading file
 when each memory buffer is full append to file

that way if the program/computer crashed then it should still resume later without a corrupt file because if I download 1 mb file but kill the prorgram before it's complete the local file still says 1mb when only really say 200k is downloaded...

let me try ur examples
:D
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LVL 10

Author Comment

by:wildzero
ID: 16925637
excellent - thank you :)
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