OpenEuphoria

Re: Compression idea

• Posted by Grape_ Vine_ <g__vine at HOTMAIL.COM> Jan 24, 2001
• 517 views

It does help, Give's me a idea of what work,
Even if not as well as planed. I am working
on fixing the length of the dictionary word
to 6 or 8 bytes, it take's 3-5 bytes to
index into the dictionary, So even if its
not great its a start for better search's

Grape

>From: Lewis Townsend <keroltarr at HOTMAIL.COM>
>Reply-To: Euphoria Programming for MS-DOS <EUPHORIA at LISTSERV.MUOHIO.EDU>
>To: EUPHORIA at LISTSERV.MUOHIO.EDU
>Subject: Re: Compression idea
>Date: Tue, 23 Jan 2001 16:36:19 -0600
>
>Hello Grape_,
>
>>The problem is just how to decide what is a sting of data that belongs in
>>the dictionary.
>
>I started writing a compression library based on a "similar"
>idea at one time. However, when I got it finished, it didn't
>provide very good compression. Don't be discouraged by my lack
>of success since your idea is significantly different that my
>word "similar" above is a debatable. The similarity however
>was that it DID search for repeated strings so that they
>could be replaced by something shorter. I don't have the
>file available at this computer but I think the search code
>was something like this:
>
>sequence source -- is the source string
>constant slen = length( source )
>integer len -- length of current segment
>sequence s -- current segment
>
>for len = 2 to floor( slen/2 ) do -- slen/2 is maximum seg length
>  for pos = 1 to slen-len do -- try every segment in the source
>    s = source[pos..pos+len] -- extract segment
>    if match( s, source[pos+len..slen] ) -- is there any more of it?
>      --this is a repeated string
>    end if
>  end for
>end for
>
>I hope this is somehow helpful as it is completely un-tested.
>
>later,
>Lewis Townsend
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