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Splitting a 2mb file into 2 * 1mb and back again

Posted on 1998-09-19
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Last Modified: 2010-04-06
Just say I had a 2mb file. Is there a way (in code, D2) to split this file into 2 seperate files then be able to join them together to make the original file again. The reason being that a file of 2mb won't go on a floppy and i'm toying with the idea to make a little app for myself that will do it. I know I could span disks with pkzip etc but would like to do it myself. Any good suggestions will receive the finished util once finished.
ps I know how to get it back into 1 file with the DOS command COPY File1 File2 /B But how to split it in the first place.
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Question by:joshordan
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5 Comments
 
LVL 2

Accepted Solution

by:
rene100 earned 800 total points
ID: 1340286
hi

here are two functions that should do the job:

procedure SplitFile(FileName,NewFile1,NewFile2: string);
var
fStream: TMemoryStream;
dStream1,dStream2: TMemoryStream;
tLength1,tLength2: longint;
begin
fStream:=TMemoryStream.create;
dStream1:=TMemoryStream.create;
dStream2:=TMemoryStream.create;
fStream.LoadFromFile(FileName);
if fStream.size mod 2 =0 then
   begin
   tLength1:=Trunc(FStream.size/2);
   tLength2:=Trunc(FStream.size/2);
   end
else
   begin;
   tLength1:=Trunc(FStream.size/2-0.5);
   tLength2:=Trunc(FStream.size/2+0.5);
   end;
dStream1.CopyFrom(fStream,tLength1);
dStream2.CopyFrom(fStream,tLength2);
dStream1.SaveToFile(NewFile1);
dStream2.SaveToFile(Newfile2);
dStream1.free;
dStream2.free;
fStream.free;
end;

procedure ConcatFiles(File1,file2,NewFileName: string);
var
fStream: TMemoryStream;
dStream1,dStream2: TMemoryStream;
begin
fStream:=TMemoryStream.create;
dStream1:=TMemoryStream.create;
dStream2:=TMemoryStream.create;
dStream1.LoadFromFile(File1);
dStream2.LoadFromFile(File2);
fStream.CopyFrom(dStream1,dStream1.size);
fStream.CopyFrom(dStream2,dStream2.size);
fStream.SaveToFile(NewFileName);
dStream1.free;
dStream2.free;
fStream.free;
end;

regards
rene
0
 
LVL 10

Expert Comment

by:viktornet
ID: 1340287
Here is how.....
-------------
var
  inFile, outFile : File;
  CopyBuffer : Pointer;
  iRecsOK, iRecsWr, iX: Integer;
  sFileName : String;
CONST
  ChunkSize : LongInt = 1024000;
begin
  GetMem(CopyBuffer, ChunkSize);
  sFileName := 'C:\windows\desktop\test';
  AssignFile(inFile, sFileName + '.ZIP');
  Reset(inFile);
  iX := 1;
  repeat
    AssignFile(outFile, sFileName + IntToStr(iX) + '.ZIP');
    Rewrite(outFile);
    inc(iX);
    BlockRead(inFile, CopyBuffer^, ChunkSize, iRecsOK);
    BlockWrite(outFile, CopyBuffer^, iRecsOK, iRecsWr);
    ClosFile(outFile);
  until (iRecsOK < Chunksize);
  CloseFile(inFile);
  FreeMem(CopyBuffer, Chunksize);
end;
------------
Regards,
Viktor Ivanov
0
 
LVL 10

Expert Comment

by:viktornet
ID: 1340288
There is a mistake...

Do you see where it says ClosFile(outFile); this is supose to be CloseFile(outFile);

Regards,
Viktor Ivanov
0
 

Author Comment

by:joshordan
ID: 1340289
Rene / Viktor,

Many thanks for guiding me.

Rene
I can see that your 2 functions have exactly the required result, but.. :) All is OK until the file changed size from 2mb, ie, it changes from 2mb to 5mb or beyond. Is there a way to make the functions a little more generic as to be able to handle any sized file??
0
 
LVL 2

Expert Comment

by:rene100
ID: 1340290
try this:

procedure TForm1.SplitFile(FileName,NewFile1,NewFile2: string);
var
fStream: TMemoryStream;
dStream1,dStream2: TMemoryStream;
tLength1,tLength2: longint;
begin
fStream:=TMemoryStream.create;
dStream1:=TMemoryStream.create;
dStream2:=TMemoryStream.create;
fStream.LoadFromFile(FileName);
if fStream.size mod 2 =0 then
   begin
   tLength1:=Trunc(FStream.size/2);
   tLength2:=Trunc(FStream.size/2);
   end
else
   begin;
   tLength1:=Trunc(FStream.size/2-0.5);
   tLength2:=Trunc(FStream.size/2+0.5);
   end;
dStream1.CopyFrom(fStream,tLength1);
dStream1.SaveToFile(NewFile1);
dStream1.free;
fStream.Position:=tLength1;
dStream2.CopyFrom(fStream,tLength2);
dStream2.SaveToFile(Newfile2);
dStream2.free;
fStream.free;
end;

procedure Tform1.ConcatFiles(File1,file2,NewFileName: string);
var
fStream: TMemoryStream;
dStream1,dStream2: TMemoryStream;
begin
fStream:=TMemoryStream.create;
dStream1:=TMemoryStream.create;
dStream2:=TMemoryStream.create;
dStream1.LoadFromFile(File1);
dStream2.LoadFromFile(File2);
fStream.CopyFrom(dStream1,dStream1.size);
fStream.Position:=dStream1.Size;
fStream.CopyFrom(dStream2,dStream2.size);
dStream1.free;
dStream2.free;
fStream.SaveToFile(NewFileName);
fStream.free;
end;
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