Club Amiga de Montreal - CAM/CAM_CD_1.iso/files/613b.lha/VIF/vif.e.doc.pp/vif.e.doc

Text File | 1992-03-07 | 7.6 KB | 236 lines

VIF.

 _V_ery _I_ntelligent _F_ilter

 C1990 Pagani Massimiliano


0 DISTRIBUTION RULES
  You can freely copy this program and give a copy to anyone, only if you
don't charge and if you give all files relative to VIF.
  You are allowed to put VIF and its files on a BBS or in public domain and
share ware collections (as Fred Fish one).
  It's forbidden modifing the files vif.e.doc, vif.c without my written
consense.
  Again, the diffusion of this program will have to be free gifting.
  The Author is not responsible of data damages/losses deriving from using
correctly, or not, the VIF program.

  OK I think that's enough, let's go...

0.1 Files
Distributions files are:

    VIF        - the executable (13364 bytes)
    VIF.c        - the source code (10819 bytes)
    VIF.doc        - italian version of this doc (9801 bytes).
    VIF.e.doc    - this English doc (7794 bytes).

If you can't find all these files, you can contact me to get the last
version (my address is at the end of this file)



1 WHAT DOES VIF DO?
VIF is a filter. It takes an input text file and outputs another text file.
During this operation VIF removes all useless characters. (We'll se in a
while what are useless chars).
This program has come out from the need of archiving, in an organic way, a
great number of documents. Before I wrote VIF, I had to use a text editor
to do the same job with a great amount of patience.
You can run VIF only from CLI. To use VIF you have to know at least
something of AmigaDOS.



2 WHICH CHARACTERS ARE REMOVED BY VIF?

2.1 Spaces -> tabs
A tab char allows to gain from 1 to 7 chars. Example:

T-------T-------T-------T-------T-------T-------T-------T-------T
__some_characters__________________other_characters.

In the first line i've pointed out the tabulations (one every 8
characters). In the second line an example of text where '_' represents the
space character.
After VIF processing the second line became:

T-------T-------T-------T-------T-------T-------T-------T-------T
__some_characters<T>    <T>    ___other_characters.

Where <T> shows a tab char. You can see that the spacing between words is
the same as before, but now you use 13 character less.


2.2 Spaces and tabs before the end of line.
Invisible characters (spaces and tabs) just before the end of a line are
useless since you can't see them and they don't contribute to any spacing,
then they will be removed without fear.


2.3 Newlines before the end of file.
Like spaces and tabs of the point 2.2 lines at the end of file are of no
use to anyone.
VIF is quite intelligent (!) in this cases: if there are some empty lines
and one of these contains only spaces and tabs, this will be considered
empty and will be removed.


2.4 Spaces covered by tabs
Here is an example:

T-------T-------T-------T-------T-------T-------T-------T-------T
__<T>    some characters

The first two spaces are useless since they are "covered" by the tab that
follows them.


2.5 ^M e ^Z
Messy Dossy computers use memory hungry conventions about text files - to
end a line they use two characters, one to return carriage at the beginning
of line (carriage return) and one to move down to the next line (line
feed).  Amiga (and many other computers) does the same with only one
character.  In few words at the end of the line you can find ^J^M, but only
^J is needed.
Another useless character is ^Z which, again in messy dossy systems, marks
the end of the file.


2.6 Optionally escape sequences.
Optionally you can remove escape sequences, i.e. characters sequences which
begin with ^[ (escape), then [ (or character 0x9B instead of these two),
followed by other chars.
These special codes are used to change color, graphic rendering (bold,
underline, italic), cursor position and for other operations.
If you print the ascii file with a "type" command you'll see these changes
correctly, but if you use an editor or a "more"-like command, it's easy
you'll see garbage.



3. USAGE
As I pointed out before, VIF works ONLY from CLI, this means no friendly
user interface. May be one day, for a future release...
There are some ways to invoke VIF. To get some help from VIF itself
it is sufficent to type:

1> vif ?


3.1 Options
In every way you use VIF, you can specify some options as follows:

1> vif -<letters>

Currently supported options are:
-e    Keep escape sequences
-q    Quiet mode: no writings.
-p    Every 16 lines read, vif print a '#'.
These options can be combined together simply specifing more than a letter
after the '-'.  [For example to keep escape sequences and to show that
something is going on, you have to use:

1> vif -ep

N.B.
1> vif -e -p
Doesn't work (at present, may be one day...)]


3.2 From stdin to stdout.
This is the first and the simplest way of working of VIF. It takes its
standard input, and put the filtered result in the standard output.
This system is usefull when using pipes and redirections.
To invoke VIF for this case you have to specify:

1> vif

Eventually followed by some options. Option -q is automatically activated,
while option -p is disabled.


3.3 From a file to another one
Syntax is:

  vif [-epq] source_file destination_file

destination_file will be created. If there is another file named like
destination_file is, it will be deleted.


3.4 From a file to itself.
The result of the filtering is put in a temporary file, at the end of the
operation, this file is copied onto the original one.
Syntax is:

  vif [-epq] file

Temporary file is named t:viftemp%d. Where %d is for an integer number.
Of course you need device t: assigned otherwise you will get the request
to insert volume T in any drive.
VIF checks if this file exists, if the check result is positive VIF
increments the number until it finds a non-existant file.
I think that's important to notice that VIF doesn't work directly on the
file, indeed you can always recover data if an error should occour.


3.5 Warning
Pay attention when you invoke VIF on a source code. In fact VIF doesn't
know anything about language syntax. Say you have the line:

T-------T-------T-------T-------T-------T-------T-------T

  printf("hello boy!\n");

VIF will translate the space between `hello' and `boy' with a tab char,
because `boy' is on a tab boundary. When you compile the source and run the
executable, you will get:

hello    boy

Three space instead of one


4 SOON ON THESE SCREENS
I have some ideas on VIF evolution. Actually I have other programs to write,
but if VIF gives me some satisfaction I will go on and implement the
following options:
- Paragraphs formatting with or without fill.
- Accented vowels substitutions: e' -> è (useless for english people, sorry).
- User interface for batch operations.
- Comments and useless spaces removal from C source code.
- paging.


5 SOME ENDING NOTES
To realize VIF I've used all good programming rules learned at school and
on the work field, indeed I think that there shouldn't be ANY problem. I've
tested VIF on 6 Mbytes of docs in multitasking (i.e. while doing other
things on the computer) and I got no problems.
Always you can recover data integrally (but when you use VIF from stdin to
stdout).
Actually VIF is NOT a pure program, it means that you can't load VIF as
resident and use it from more than one process. If I'll get enough request
to make VIF pure, I'll search the docs on pure programs and I'll turn it
pure.

If you use VIF and you think that is a good useful program and you want to
contribute to software developement ($$), or you have discovered an
interesting way to get a GURU with VIF, or you have any suggestions, my
address follows:

    Pagani Massimiliano
    via Mazzini 40
    21052 Busto Arsizio (VA)
    ITALY

For the previous last things you can contact me with e-mail at:

    [e-mail]

    [The address is equal to 131.175.6.2]

Thanx and enjoy.