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From: wct@po.CWRU.Edu (William C. Thompson)
Newsgroups: comp.lang.pascal
Subject: Re: Saving dynamic structures to disk & recalling revisited....
Message-ID: <1991Apr22.134725.27033@usenet.ins.cwru.edu>
Date: 22 Apr 91 13:47:25 GMT
References: <1991Apr22.085440.15582@usenet.ins.cwru.edu>
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Reply-To: wct@po.CWRU.Edu (William C. Thompson)
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In a previous article, wct@po.CWRU.Edu (William C. Thompson) says:

I managed to fix my own problem...  Here is the solution, though.

>type
>  buffer=array[1..64000] of byte;
>
>procedure saveimage(x1,y1,x2,y2:word; fn:string; var size:word);
>{ This procedure captures an image from the screen and writes
>  it to the specified file and returns the size.  There is no error
>  checking as to how much memory is available.  The size of an image
>  is the number of pixels divided by two plus 6 (VGA mode) }
>var
>  f: file of byte;
      ^^^^^^^^^^^^   Change this to just plain FILE

>  p: ^buffer;
>  i: word;
>begin
>  size:=imagesize(x1,y1,x2,y2);
>  getmem(p,size);                 { allocate space }
>  getimage(x1,y1,x2,y2,p^);       { capture the image from screen }
>  assign(f,fn);

>  rewrite(f);
>  for i:=1 to size do write(f,p^[i]);  { write image to disk }

Replace these lines with 

rewrite(f,1)    { tells compiler file's object size is 1 }
blockwrite(f,p^,size,dummy)

>  freemem(p,size);                { return memory }
>  close(f);
>end;
>
>procedure recallimage(x1,y1:word; fn: string; size:word; wput:byte);
>{ This procedure reads in an image from the specified file
>  and puts the image on the screen }
>var
>  f: file of byte;           
      ^^^^^^^^^^^^    Same here...
>  p: ^buffer;
>  i: word;
>begin
>  getmem(p,size);                { allocate space }
>  assign(f,fn);                  { prepare file }

>  reset(f);
>  for i:=1 to size do read(f,p^[i]);        { read in the image }

Replace these two lines by 
reset(f,1);
blockread(f,p^,size,dummy)

>  close(f);
>  putimage(x1,y1,p^,wput);       { put image on screen }
>  freemem(p,size);               { return memory }
>end;

>The only drawback at all is that the part where I read from and 
>write to a file is slow.  I tried BlockWrite and BlockRead,
>but those made my files WAY too big.  The file sizes didn't
>match the number of bytes I told it to write.  Here is the code
>I used ---
>
>BlockRead(f,p^,size,n)      &     BlockWrite(f,p^,size,n)

I think the main problem was that I didn't tell the compiler
how big the file's objects were.  Once I made that change,
everything fell into place.
-- 
Ticking away, the moments that make up a dull day.   | William C. Thompson
You fritter and waste the hours in an offhand way.   | Michelson 620D (wct)
Kicking around on a piece of ground in your hometown,| a.k.a. Master of Time,
waiting for someone or something to show you the way.| Space, and Dimension