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ANSI I/O extensiond documentation
$Id: AIO-Extension.txt,v 1.4 2005/04/02 10:14:23 antirez Exp $
Overview
~~~~~~~~
The AIO (ANSI I/O) extension implements an I/O interface for Jim using only
ANSI-C capabilities. The goal of the extension is to make Jim able to
work with files in environments where the only assumption that can be
done is that there is an ANSI-C compiler, or where the binary size matters
(the AIO extension is very small compared to size that the real Tcl-alike
channels implementation will have).
Goals
~~~~~
The AIO extension was developed in order to be able to experiment with
two ideas.
The first is the idea to build a replacement for autoconf/automake
using the fact that Jim is small and ANSI-C, so the build process may
build Jim with the assumption of an ANSI-C compiler, and a Jim script will
check what exists in the system and will generate the Makefile and config.h.
Autconf/make is such a crap that it's worth to experiment with this idea...
The second idea is to create a micro starkit runtime, using a very small
implementation of zlib called muzcat, and AIO.
Usage
~~~~~
The AIO extension exports an Object Based interface for files. In order
to open a file use:
set f [aio.open filename]
this will open the file in read-only. It's possible to specify the mode:
set f [aio.open filename w+]
The [aio.open] command returns a file handle, that is a command name that
can be used to perform operations on the file. A real example:
Welcome to Jim version 0, Copyright (c) 2005 Salvatore Sanfilippo
0 jim> package require aio
1.0
0 jim> set f [aio.open /etc/passwd]
aio.handle0
0 jim> $f gets line
30
0 jim> puts $line
root:x:0:0:root:/root:/bin/zsh
The "methods" of an AIO file object are an exact copy of the usual
Tcl commands for file I/O. In order to have the full list of
the methods currenty supported, pass a bad method as argument,
like in the example (but don't trust the example, the extension is
in active development so probably there will be more functionality when
you are reading this document):
0 jim> $f helpme
Runtime error, file "?", line 1:
bad AIO method "helpme": must be close, seek, tell, gets, puts, or flush
In order to close the file, use the 'close' method that will have as side effect
to close the file and that the command associated with the file will be removed.
Standard files
~~~~~~~~~~~~~~
The AIO library is able to return handles about the standard C channels
stdin, stdout and stderr. In order to do so just use:
set f [aio.open standard input]
Valid standard file names are "input", "output", "error".
For standard files, the close method will just remove the command associated
with the handle, without to really close the file.
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