Re: ASCII to ASCII compression.

On Fri, 7 Jun 2024 10:03:46 +0100
Malcolm McLean <malcolm.arthur.mclean@gmail.com> wrote:

On 07/06/2024 05:47, Mikko wrote:

On 2024-06-06 16:25:37 +0000, Malcolm McLean said:
 

Not strictly a C programming question, but smart people will see
the relavance to the topicality, which is portability.
>
Is there a compresiion algorthim which converts human language
ASCII text to compressed ASCII, preferably only "isgraph"
characters?
>
So "Mary had a little lamb, its fleece was white as snow".
>
Would become
>
QWE£$543GtT£$"||x|VVBB? 

 
There are compression algorithms that can be adapted to any possible
size of input and output character sets, including that both are
ASCII and that the output character set is a subset of the input
set.
 
Restricting the input set to ASCII may be too strong. Files that
should be ASCII files sometimes contain non-ascii bytes. The output
should be restricted to the 94 visible characters but the
decompressor should accept at least full ASCII and skip the invalid
characters as insignificant.
That permits addition of line brakes and perhaps other spaces that
could be useful for example when the file is printed for debugging.
 

That's exactly the idea. The system is robust to white space. You can
add spaces to your heart's content, and they arec just skipped.

Robustness to white spaces necessarily weakens robustness to bit flips.
Not that your set of requirements made much sense to start with...