124 lines
2.5 KiB
Forth
Executable file
124 lines
2.5 KiB
Forth
Executable file
#!/usr/bin/env retro
|
|
|
|
# uuencode
|
|
|
|
This is an implementation of `uuencode` in Retro. This takes a
|
|
file name and renders the uuencoded data to standard output.
|
|
|
|
|
|
## Prep Work
|
|
|
|
First, determine the size of the file.
|
|
|
|
~~~
|
|
#0 script:get-argument file:R file:open
|
|
&file:size &file:close bi 'SIZE const
|
|
~~~
|
|
|
|
With this, I can create a buffer to hold the file and read it
|
|
into memory.
|
|
|
|
~~~
|
|
'Data d:create SIZE allot
|
|
&Data #0 script:get-argument file:slurp
|
|
~~~
|
|
|
|
|
|
## The Header
|
|
|
|
A uuencoded file starts with a header line of the form:
|
|
|
|
begin <mode> <file><newline>
|
|
|
|
I am hard coding the mode as 0644.
|
|
|
|
~~~
|
|
:header (-) #0 script:get-argument 'begin_0644_%s1\n s:format s:put ;
|
|
~~~
|
|
|
|
|
|
## Data Encoding
|
|
|
|
Here's how uuencoding works:
|
|
|
|
* Three characters are packed into a cell.
|
|
|
|
Cat = (C) 01000011 (a) 01100001 (t) 01110100
|
|
|
|
* This is divided into a quartet of six bit values.
|
|
|
|
Cat = 010000 110110 000101 110100
|
|
|
|
* 32 is added to each, yielding a printable character.
|
|
* At this point, "Cat" has become 0V%T.
|
|
|
|
So the basic encoding words will need to pack a cell and
|
|
then unpack it into characters.
|
|
|
|
~~~
|
|
:mask #63 and ;
|
|
:to-char #32 + ;
|
|
|
|
:decode (n-)
|
|
dup #18 shift mask to-char c:put
|
|
dup #12 shift mask to-char c:put
|
|
dup #6 shift mask to-char c:put
|
|
mask to-char c:put ;
|
|
|
|
:pack
|
|
#0 [ fetch-next ] dip + #-8 shift
|
|
[ fetch-next ] dip + #-8 shift
|
|
[ fetch-next ] dip + ;
|
|
~~~
|
|
|
|
The actual conversion is pretty easy. Output is given as
|
|
lines, starting with an encoded length followed by the
|
|
encoded data. The encoded length is just the actual value
|
|
with 32 added to it and displayed as an ASCII character.
|
|
|
|
Lines are 45 unencoded characters in length, so will start
|
|
with an `M`, except for the last one, which may be shorter.
|
|
|
|
So:a
|
|
|
|
~~~
|
|
:full-line $M c:put #15 [ pack decode ] times nl ;
|
|
:remaining-size SIZE #45 mod #32 + c:put ;
|
|
:partial-line SIZE #45 mod #3 / [ pack decode ] times ;
|
|
:final-bundle SIZE #45 mod #3 mod
|
|
#2 [ fetch-next #-16 shift swap fetch #-8 shift + decode ] case
|
|
#1 [ fetch #-16 shift decode ] case
|
|
drop ;
|
|
~~~
|
|
|
|
And then using the factors to do the conversion:
|
|
|
|
~~~
|
|
:convert
|
|
&Data
|
|
SIZE #45 / &full-line times
|
|
remaining-size partial-line final-bundle nl ;
|
|
~~~
|
|
|
|
|
|
## The Footer
|
|
|
|
A uuencoded file ends with two lines:
|
|
|
|
`
|
|
end
|
|
|
|
The backtick is used to denote a line with a length of zero
|
|
characters.
|
|
|
|
~~~
|
|
:footer $` c:put nl 'end s:put nl ;
|
|
~~~
|
|
|
|
|
|
## Run Everything
|
|
|
|
~~~
|
|
:uuencode header convert footer ;
|
|
uuencode
|
|
~~~
|