If this user should also be programmer you can create a new role copying from %Developer
and then remove the DB's that you want him to lock out like this  just for NS = USER


.

Thanks for the pointer!
Good to see that someone got the time to productize the idea of Custom Index Type
With this development the win could have been even more dramatic.

My benchmark was done in  March2011,  so Caché version must have been 2010 .  
2013.1 was my last version @ISC  just rolling out.
At that time bitmaps helped only with rather relaxed precision.

For an engineer this sounds like a quite challenging exercise to rewrite a PGP lib in COS.
 

But it seems more promising to wrap the existing (and hopefully well tested) code and consume it from Caché using one of the existing Gateways:

- Callout Gateway http://docs.intersystems.com/latest/csp/docbook/DocBook.UI.Page.cls?KEY=...

- ActiveX Gateway  http://docs.intersystems.com/latest/csp/docbook/DocBook.UI.Page.cls?KEY=...

- or just  connect
over TCP/IP http://docs.intersystems.com/latest/csp/docbook/DocBook.UI.Page.cls?KEY=...
or UDP http://docs.intersystems.com/latest/csp/docbook/DocBook.UI.Page.cls?KEY=...
or a Pipe  http://docs.intersystems.com/latest/csp/docbook/DocBook.UI.Page.cls?KEY=...

I bet the community has even more ideas to reuse the existing code

indeed this is surprising.

but is this really:   do content.ReadLine(,,isEOL)

it should be a pass by reference to receive something back do content.ReadLine(,,.isEOL) 
with the <dot> in front of the variable 

You still have the option to create your own %ZLANGC00.int 
and make you own ZZEXIT to avoid the risky HALT

It's a miracle to me how HALT could survive from PDP-7 sn#103 at MGH and nobody touched it.

                           

to me this looks like your content had an extra $C(13,10) at the end.
It could help to  have the full content at hands. 
eg:
before  content.OutputToDevice()
set ck=content.Read()
set ^ck($i(^ck))=ck
do content.Rewind()

I expect  zwrite ^ck will show more than 3  lines
That would indicate that the source of trouble is on the input side. 
Some closing action ?   

 

if you change wnl() ...
to
wnl()  quit
you just disable it to see if it plays a role at all    

I don't see a call for  wnl()   
but ancient coding practices  would suggest its:  writenewline just that
and that's what it does without any other content.
though the remark is rater direct if interpreting feedback := line

// Should be smart as well: routines ending with write ! will create an empty feedback!