New subject: FlateDecode

10 May 2004


      Frank Heckenbach wrote:
...
I suggest to link to the existing C libraries (libz and/or libpng). I 
don't generally recommend translating standard libraries to Pascal. 
The C libraries are tested by more people and (usually) maintained, 
and writing a Pascal interface is much easier than translating the 
whole library (especially if only a small part of the library 
interface is actually needed, like in many cases I know).
In principle, yes. However, the problem that I find is that many of the 
existing C libraries contain mainly low level stuff (at least, to me). 
Eike's zlib unit is an excellent interface to the C library, but I find 
that I am struggling to use it to decompress a compressed file, or to 
create one.
What I personally find helpful are high level functions, built on top 
of the interface units, so that, for example, I can "BlockRead" from a 
file to a buffer, pass that buffer to a high level (de)compression 
routine, retrieve the processed data in another buffer, and 
"BlockWrite" that to a file, or do whatever with it. PasZlib provides 
this kind of facility, which is why I decided to use it. But of course, 
it won't compile under GPC.
Perhaps Eike could provide some high level functions if he has the 
time?
e.g.,
1. zlib_compress (inbuf, outbuf : pointer; insize, outsize : cardinal; 
Var result : cardinal);
2. zlib_decompress (inbuf, outbuf : pointer; insize, outsize : 
cardinal; Var result : cardinal);
Then one can do something like;
while not eof (infile) 
do begin
   blockread (infile, infbuf^, sizeof (infbuf^), bRead);
   zlib_compress (infbuf, outbuf, bRead, sizeof (outbuf^), compsize);
   blockwrite (outfile, outbuf^, compsize, bWritten);
end;
Or perhaps I am just underestimating how difficult it would be to write 
such high level functions ...
Best regards, The Chief
--------
Prof. Abimbola A. Olowofoyeku (The African Chief) 
web:  http://www.bigfoot.com/~african_chief/

Re: FlateDecode