Hi. I'm looking for an open-source, thread-safe, simple to use lib for using hash tables in my C app. libcmph seems to be what I'm looking for, but was hoping for feed back on a few questions:

1. Are libcmph functions thread-safe? The README file didn't explicitly say so...

2. Is any one else a little confused about the licensing? README says LGPL, COPYING says MPL, website says dual-license. So does that mean you just use whichever one you want?

3. I'm open to better suggestions for a hashing table library. Ideals are: simple to use, open source, thread-safe, and must be in Debian Lenny repository. :]

I never used it myself, but the Glib library may be what you're looking for. It is used by many (all?) Gnome and GTK apps, so widely available and already loaded in RAM on quite a few systems. And clearly licensed by the LGPL.

I'm not sure if it is thread safe though. But I suppose that will be documented.

For coding against Glib, you will probably also want to install the "libglib2.0-dev" and "libglib2.0-doc" packages on your own system.

Glib is huge, obtuse, difficult to use, heavily abstracted, over-designed, and slow.

The site for the project is cmph.sourceforge.net

It's a wonderfully simple and functional tool.

Hi -

Without getting into the merits of cmph, let me emphasize that Hko is absolutely correct.

GLib can be an excellent solution for many different problems (including, perhaps, this one). And since GLib is so widely used, the base runtime is already likely to be loaded on most desktops, making the overhead essentially "zero" for any new app that wants to use Glib.

IMHO .. PSM

I'm going to come to CoderMan's defense here. We don't know what the software in question is meant to perform, where it is meant to be run, or what constraints it has. Suggesting to use a different library doesn't seem to answer the question, merely blow past it. Further, if he's not using this software on a machine that even has glib installed (such as a university server, or home file-serving machine) then he'll have to install glib, and all of glib's dependancies.

CoderMan:
Simply grep the source for things which are known to be posix-compliant thread-safe keywords. IE:

REENTRANT
pthread_mutex
_r(

the list goes on. If all else fails, you can really familiarize yourself with it and RTFS. If that still doesn't give any indication that it is threadsafe, you should assume that it isn't and use posix locks before and after your calls to the library.

-Aaron

If there are special requirements or circumstances, the OP should have mentioned that IMHO. As you said: we don't know...

I don't agree in this case. Please re-read the OP's point (3).

That is very true of course. But the dependencies for glib are not that much: on ubuntu: libc6, libpcre3, libselinux1. And I guess you could get rid of selinux if you compile it yourself.

Also, I now noted that, CMPH does perfect hashes only. This means it is not not very suited to do not-so-dynamic hash tables, i.e. very good for "read often, but write/modify sparsely". The reason is perfect hashes need to be recalculated every time the hash-tables is modified. But for reading it is much more efficient than non-perfect hashes. CMPH is more specialized for a lot of look-ups on the hash table, containing a lot of entries. Glib's hash table is more general purpose.