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From: fir <fir@grunge.pl>
Newsgroups: comp.lang.c
Subject: Re: simple compression mathod to code itself?
Date: Sat, 06 Apr 2024 13:53:14 +0200
Organization: i2pn2 (i2pn.org)
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David LaRue wrote:
> fir <fir@grunge.pl> wrote in news:uupflr$5t1n$1@i2pn2.org:
>
>> i not code at all in recent years
>> (recently i coded half of my compuler with a plan to write second half
>> but its to ambitious to lazy coding mood i got recently)
>> but recently i started this slamm coding modd and found
>> ite pleasurable
>>
>> searching for lazy side things i could code in such mood
>> i thought maybe i wopuld like to have compression routine
>> but i would like to write it myself sortla like i use quicksort
>> or so but i also want to write it myself
>>
>> so is there maybe some method i could use i mean some simple
>> routine that compresses and uncompresses an array of bytes but
>> maybe something a bit more complex than RLE (rune length encoding)
>> - only thing i know from this domain
>>
>
> Hello fir,
>
> A method a bit more complex that you might try builds a table of all bytes
> as you scan them from the input.  The compressed output is a reference to
> the table you just built (wnhem repeated byte strings are found, otherwise
> feed the input to the compressed image so that the expansion method can
> build the sme dynamic table the encoder built.  The table generally has a
> limit on the number of entries (usually a good size) and allows the table
> of bytes to dynamically change as new patterns are read from the input.
>
> This is a well known and documented compression/expansion algorithm.  PKZIP
> and other engines use this as one of their compression methodz.  Look for
> the description of that if you need more details to figure out what you
> need to write.
>
> Expansion is the reverse.  Read the source (now the compressed image) and
> build the compression table from the bytes.  As encoded references to the
> compression table are read from the compressed image output the source byte
> sequences.  The output should be the same as what your encoder originally
> read.
>
> A good check on the final code is to compare the original input with the
> eventual output and make sure they agree exactly.
>
> Have fun,
>
> David
>
this could be good but i dont quite understood that .. but eventually 
could be good...

i thinged something abut that if rle search for repetitions of 1
byte then maybe after that search for repetitions of 2 bytes, then 3 
bytes, 4 bytes and so on.. then do some "report" how many found and then 
find a way to encode that

  need to think a bit becouse if rle only stores repetitions that are 
one after another then this method should store  repetitions that have
various distances among them


i also do nto want to spend a much time on this 1-2 days eventually