Solved

Split a binary file by searching for string

Posted on 1997-09-04
4
184 Views
Last Modified: 2010-04-04
I have a data file (binary) within which are contained
further data files. i.e.

GRIB.........(unknown number of chars)......GRIB.........
(unknown number of chars)......GRIB.........
(unknown number of chars)......GRIB.........
(unknown number of chars)......GRIB.........
(unknown number of chars)......
etc. etc.
GRIB.........
(unknown number of chars)......EOF

What I want to be able to do, is to read the datafile,
search for the first occurance of the string GRIB then
write GRIB and all the next characters out to file number
one, until GRIB occurs again. At this point, I will write
GRIB and all the characters out to file number two, until
GRIB occurs again of EOF. i.e. I want to split the
datafile into smaller files using the string GRIB as the
cutting point..

Anybody have a code segment (function) to do this ?
0
Comment
Question by:iwatkins
  • 4
4 Comments
 
LVL 8

Accepted Solution

by:
ZifNab earned 100 total points
ID: 1343661
Hi itwatkins,

Maybe this helps, haven't tested it, so you have to test it yourself. Question, you constantly speak about chars. Is the file a char file? If so, you have to change to code a little bit.

How to call the function :

NewPos := SearchTextNext({File},{Start position},{Str})

{Start Position} = Position in file from where function has to start searching for {Str}

The value in NewPos gives the position of the first byte after {Str}

Type ByteFile : File of Byte;

function SearchTextNext(f:ByteFile;Pos:Integer;Str:ShortString):Integer
var J, OldPos : integer;
    Found : Boolean;
    I : Byte;
begin
 Found := False;
 J := 1;
 Seek(f,Pos);
 OldPos := FilePos(f);
 while not(EOF(f)) and Found then begin
  Read(f,I);
  if (Char(I) = Str[J]) and (OldPos=FilePos(f)-SizeOf(I)) then J := J+1
   else J := 1;
  OldPos := FilePos(f);
  if J = Length(Str)+1 then
   begin
    Found = True;
    Result := FilePos(f);
   end;
 end;
end;

Hope this is what you want.
Have fun,
c.u. ZifNab;
0
 
LVL 8

Expert Comment

by:ZifNab
ID: 1343662
Hi iwatkins,

Use function like this :

Euhm, better take backup of your data file!

Haven't tested this.

var OldFile, NewFile   : ByteFile;
    BeginPos, EndPos,I : Integer;
    chars              : Byte;

begin
  {$I-}
  AssignFile(OldFile, {FileName});
  FileMode := 0;  ( Set file access to read only }
  Reset(OldFile);
  {$I+}
  if IORESULT <> 0 then .... {Error}
   else begin
    BeginPos := SearchNextFile(OldFile,FilePos(OldFile),'GRIB');
    while not EOF(OldFile) do begin
     EndPos  := SearchNextFile(OldFile,FilePos(OldFile),'GRIB');
     Seek(OldFile, BeginPos);
  {Make newfile ready, change filename!! Not done in this demo!}
     {$I-} AssignFile(NewFile, {FileName})
           Rewrite(NewFile);
           for i := BeginPos To EndPos do begin
            read(OldFile,Chars);
            write(NewFile,Chars);
           end;
           CloseFile(NewFile);
     {$I+}
     if IORESULT <> 0 then ..... {OOOPS, ERROR}
     Seek(OldFile, EndPos);
    end;  
   end;
  {$I-}
  CloseFile(OldFile);
  {$I+}
end;

that's how you call it in your program. If this is what you needed and you need some answer, please be quick to ask them because I'm going on holiday soon.

Have fun,
In the sun,
c.u. ZifNab;
0
 
LVL 8

Expert Comment

by:ZifNab
ID: 1343663
And offcourse,
a fault!

changes :

EndPos := SearchNextFile(OldFile,BeginPos,'GRIB');

if IORESULT <> 0 then ..... {OOOPS, ERROR}
Seek(OldFile, EndPos);
BeginPos := EndPos;

Have fun,
c.u. ZifNab;

0
 
LVL 8

Expert Comment

by:ZifNab
ID: 1343664
So it worked! Great!

Have fun,
c.u. ZifNab;


0

Featured Post

NAS Cloud Backup Strategies

This article explains backup scenarios when using network storage. We review the so-called “3-2-1 strategy” and summarize the methods you can use to send NAS data to the cloud

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Introduction The parallel port is a very commonly known port, it was widely used to connect a printer to the PC, if you look at the back of your computer, for those who don't have newer computers, there will be a port with 25 pins and a small print…
In my programming career I have only very rarely run into situations where operator overloading would be of any use in my work.  Normally those situations involved math with either overly large numbers (hundreds of thousands of digits or accuracy re…
Along with being a a promotional video for my three-day Annielytics Dashboard Seminor, this Micro Tutorial is an intro to Google Analytics API data.
A short tutorial showing how to set up an email signature in Outlook on the Web (previously known as OWA). For free email signatures designs, visit https://www.mail-signatures.com/articles/signature-templates/?sts=6651 If you want to manage em…

803 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question