Abe Voelker's blog Programming stuff, mainly

OpenEdge ABL Utility: Get Program Parameters (Main Block) from R-code

6 minute read

I have recently been working on a new compiler interface and backend for my workplace. I am pretty much done with it at this point - and the adventure is worthy of it’s own blog post - however, I thought I would share a little script with the world that might be useful to others.

Basically, I wanted to table-ize as much meta information about a program as possible when it gets compiled. One piece of information I wanted is the main block parameters of a program (e.g. DEFINE INPUT PARAMETER ipcString AS CHARACTER. at the top of the program). I mean, how cool would it be to do a simple check on RUN statements to see if they will fail at compile-time (by checking existing compile snapshots of the program referenced by the RUN; assuming of course that the RUN statement can be evaluated at compile-time)?

I started by checking the OpenEdge handbook, expecting to see something useful. Nope, nothing like that in the RCODE-INFO handle section. Nope, INTERNAL-ENTRIES requires me to run the program (unrelated thought: how is this even useful, anyway?).

Hmm, guess I’ll check the XREF-XML output… okay, this isn’t good. Main block PARAMETERs do not show up as anything that allows you to identify them as a PARAMETER. They actually look identical when compared to a plain DEFINE VARIABLE statement! So that’s no good either. (Note: this is not an issue with internal procedures’ parameters)

Unwilling to give up, I ended up submitting the question to Progress Corp. directly, who informed me that I could actually analyze the object (.r) code directly in my “favorite text editor” and the PARAMETERs would be visible near the top of the binary gibberish. I tried to get them to give me an algorithmic way to pull this information out of the binary gobbledy-gook, but I was not provided with such info. They also told me that they are unable to provide me with a utility written in OpenEdge ABL to do this with, since it is an epic fail when it comes to parsing binary files (this is really amazing information, considering it is a 4GL, fourth-generation language and all!).

So, I went ahead and used Perl (the programmer’s swiss army knife) and a best guess at an algorithmic way to pull this information. Here is the script I came up with:

#!/usr/bin/perl
#-------------------------------------------------------------------------------
# File:       getRcodeParams.pl
# Purpose:    Decodes the main block parameters of compiled OpenEdge ABL r-code.
# Arguments:  [0] File system location of an r-code file to parse
# Returns:    List of parameters (newline-separated) from the main execution
#             block. The parameters are in the form:
#             [input/output type] [variable name] [datatype]
# Author(s):  Abe Voelker
# Created:    2010-09-14
# Notes:      * This code has only been tested on 10.1C Unix r-code.  It may not
#               be applicable to other environments, or all that stable even on
#               10.1C Unix due to there being no such thing as an OpenEdge ABL
#               'standard' - the parsing is done based purely upon guesswork.
#             * It appears that the datatype for temp-tables is TABLE.  Also,
#               the names of classes are converted to uppercase.
#             * Future work could easily get more signature information from the
#               r-code based on my observations.  For example, temp-table and
#               forward-defined functions have information available in the
#               section beginning shortly after this program finishes parsing...
#-------------------------------------------------------------------------------

#Validate argument
if (($#ARGV + 1) != 1) { die "You must pass in the location of the .r code to parse!"; }

#Read the entire file into memory
open FILE, $ARGV[0] or die $!;
binmode FILE;
my ($buf, $data, $n);
while (($n = read FILE, $data, 64) != 0) {
  $buf .= $data;
}
close(FILE);

#Find the magic start token
$iStart = index($buf, "\0MAIN ");
if ($iStart == -1) { die "The magic start token was not found!"; }
$iStart += 6; #We don't want the MAIN piece in our string...

#Find the magic end token
$iEnd = index($buf, "\0", $iStart);
if ($iEnd == -1) { die "The magic end token was not found!"; }

#Store the parsed param results in an array
$parmChunk = substr($buf, $iStart, ($iEnd - $iStart));
@params = split (/,/, $parmChunk);
shift(@params); shift(@params); #The top two elements are useless

#Print results to stdout
foreach $param (@params) {
    print "$param\n";
}

As noted in the script’s “notes” section, this has only been tested on OpenEdge 10.1C code compiled on Unix. Also noted are the fact that there appears to be other useful info in there, like TEMP-TABLE and FUNCTION definitions.

A future version could be created to pull this information as well. Perhaps it would be a good opportunity for me to practice some Perl (dare I imagine, maybe even some object-oriented Perl?). I made a gist of it on github so that it can be version controlled, so look for any updates on there first.

Before anyone brings it up, I did consider using Proparse (for the entire project, actually) but I considered the API a bit too unwieldy for me to pick up in the limited timeframe required for this project (I will talk more about that when I write the full adventure posting). I would really like to explore it since compilation is a topic that interests me quite a bit, but I will probably spend more time on learning Ruby and coming up with a Progress migration plan for my employer…