From: James Gessling [jgessling@yahoo.com]
Sent: Tuesday, July 23, 2002 10:31 AM
To: Info-VAX@Mvb.Saic.Com
Subject: How to create a shareable image from an object library (long)

I had occasion to do this, so thought I'd share.  The
object library is libcurl available from
http://curl.haxx.se/libcurl/ This library allows you
to write programs to do various things that a web
browser would do.  We use it for programmicaly communicating
to web servers with HTTP post and get, but it can do a lot more.

The provided build script makes a libcurl.olb which provides the
curl_ routines that are called from the application.
I could have linked each application against this library, but
since the plan was to have several processes running the
application at the same time, it made sense to use a shareable
image to reduce memory usage.

The trick to making the shareable image is to create an option
file with all the entry points.  This is pretty easy.

First list all the entry points in the object library.

$ library/list=libcurl.opt/names libcurl.olb

In libcurl.opt, you will see a header and then lines like:

Module BASE64

CURL_BASE64_DECODE
CURL_BASE64_ENCODE

Module CONNECT

CURL_CONNECTHOST
CURL_NONBLOCK

There's more than this, but this will do for an example. In your
favorite editor, remove all the blank lines and those lines starting
with "Module", this now looks like:

CURL_BASE64_DECODE
CURL_BASE64_ENCODE
CURL_CONNECTHOST
CURL_NONBLOCK

To make these into procedure entries for the symbol_vector,
use a learn sequence to make them look like:

CURL_BASE64_DECODE=PROCEDURE, -
CURL_BASE64_ENCODE=PROCEDURE, -
CURL_CONNECTHOST=PROCEDURE, -
CURL_NONBLOCK=PROCEDURE, -

This library was built from C code using /names=uppercase (the
default).  I like to provide upper and lower case entry points,
especially if a shareable is to be used from different languages.
So I added an lower case alias to each entry, like this:

CURL_BASE64_DECODE=PROCEDURE, -
curl_base64_decode/CURL_BASE64_DECODE=PROCEDURE, -
CURL_BASE64_ENCODE=PROCEDURE, -
curl_base64_encode/CURL_BASE64_ENCODE=PROCEDURE, -
CURL_CONNECTHOST=PROCEDURE, -
curl_connecthost/CURL_CONNECTHOST=PROCEDURE, -
CURL_NONBLOCK=PROCEDURE, -
curl_nonblock/CURL_NONBLOCK=PROCEDURE, -

(good time to learn how to do learn sequences in EVE)
Add the top and bottom sections to make it a real options file,
note removal of last comma.

case_sensitive=YES
GSMATCH=LEQUAL,1,1000
SYMBOL_VECTOR=( -
CURL_BASE64_DECODE=PROCEDURE, -
curl_base64_decode/CURL_BASE64_DECODE=PROCEDURE, -
CURL_BASE64_ENCODE=PROCEDURE, -
curl_base64_encode/CURL_BASE64_ENCODE=PROCEDURE, -
CURL_CONNECTHOST=PROCEDURE, -
curl_connecthost/CURL_CONNECTHOST=PROCEDURE, -
CURL_NONBLOCK=PROCEDURE, -
curl_nonblock/CURL_NONBLOCK=PROCEDURE -
)
case_sensitive=NO

Now create your shareable like this:

$ link/share=libcurl.exe libcurl.olb/lib, -
        libcurl.opt/option, -
        [--.OPENSSL-0_9_6D.AXP.EXE.SSL]libssl/lib ,-
        [--.OPENSSL-0_9_6D.AXP.EXE.CRYPTO]libcrypto/lib

Needed those other two libraries to support SSL.

To link an application using this shareable.

$ define libcurl disk:[dir]libcurl.exe
$ link /exe=app.exe app.obj,sys$input/opt
          libcurl/share

At runtime be sure the definition of libcurl points to
the shareable library so the image activator can find it.
As a side benefit linking against the shareable versus the
object library is significantly faster, this can make a
real difference in large projects.

Regards,  Jim