[AOLSERVER] OT: Embedding Tcl Interp into existing C application
Hello, Sorry for the OT, but I thought this would be the best list to contact about this. There is an existing app that is multi-threaded, that I wanted to added the ability to execute Tcl code from this app. This reminded me very much of how aolserver works, so I was going to start digging into the aolserver code to see how it is done. However, before I start, I was wondering if any kind souls out there have any helpful tips...maybe an overview on how aolserver does this, where to start looking in the code, and any general threading tips. thanks, --brett -- AOLserver - http://www.aolserver.com/ To Remove yourself from this list, simply send an email to [EMAIL PROTECTED] with the body of SIGNOFF AOLSERVER in the email message. You can leave the Subject: field of your email blank.
Re: [AOLSERVER] OT: Embedding Tcl Interp into existing C application
On 2004.08.27, Brett Schwarz [EMAIL PROTECTED] wrote: However, before I start, I was wondering if any kind souls out there have any helpful tips...maybe an overview on how aolserver does this, where to start looking in the code, and any general threading tips. How you go about embedding the Tcl interpreter will depend on what it'll be used for and how. Can you elaborate on some details about your requirements? -- Dossy -- Dossy Shiobara mail: [EMAIL PROTECTED] Panoptic Computer Network web: http://www.panoptic.com/ He realized the fastest way to change is to laugh at your own folly -- then you can let go and quickly move on. (p. 70) -- AOLserver - http://www.aolserver.com/ To Remove yourself from this list, simply send an email to [EMAIL PROTECTED] with the body of SIGNOFF AOLSERVER in the email message. You can leave the Subject: field of your email blank.
Re: [AOLSERVER] OT: Embedding Tcl Interp into existing C application
--- Dossy Shiobara [EMAIL PROTECTED] wrote: On 2004.08.27, Brett Schwarz [EMAIL PROTECTED] wrote: However, before I start, I was wondering if any kind souls out there have any helpful tips...maybe an overview on how aolserver does this, where to start looking in the code, and any general threading tips. How you go about embedding the Tcl interpreter will depend on what it'll be used for and how. Can you elaborate on some details about your requirements? Sure, I didn't elaborate before, because I was trying to keep the OT noise down. Anyways, there is an open source PBX system (asterisk) that has an programming interface that is very similar to CGI (in fact it is called AGI). Right now, it forks off a process everytime an AGI is called (just like CGI). I would like to change that so that Tcl scripts are loaded in ahead of time, and are executed in process (no forking). Pretty much how aolserver runs tcl procs and tcl pages. More info for asterisk can be gotten here: www.asterisk.org, and I actually wrote an article about it that you can get an overview about here: http://linuxjournal.com/article.php?sid=6769 which gives an example of an AGI. Hope that helps... thanks for your time, --brett -- AOLserver - http://www.aolserver.com/ To Remove yourself from this list, simply send an email to [EMAIL PROTECTED] with the body of SIGNOFF AOLSERVER in the email message. You can leave the Subject: field of your email blank.
Re: [AOLSERVER] OT: Embedding Tcl Interp into existing C application
On Fri, Aug 27, 2004 at 11:11:59AM -0700, Brett Schwarz wrote: Sure, I didn't elaborate before, because I was trying to keep the OT noise down. Actually, I think this sort of discussion, while not PRECISELY on topic for the AOLserver list, is more than close enough for discsussion. In fact, I'd like to encourage it. Your question is basically one example of, I know that AOLserver does X really well, I'd like to understand how, so that I can do something similar to X with a different program.. I think those sorts of engineering design questions are likely to teach many of us something useful. Anyways, there is an open source PBX system (asterisk) that has an programming interface that is very similar to CGI (in fact it is called AGI). Right now, it forks off a process everytime an AGI is called (just like CGI). I would like to change that so that Tcl scripts are loaded in ahead of time, and are executed in process (no forking). Pretty much how aolserver runs tcl procs and tcl pages. You might also consider something like FastCGI. Maybe that approach would be easier to integrate into the Asterisk codebase than AOLserver's in-process interpreter approach, I dunno. Now, I've never done it, but my understanding is that anytime you want to combine Tcl and C, your first thing to decide is which language is in charge? In AOLserver the C code is in charge, and that's the way Ousterhout originally envisioned embedding Tcl. The other way, more popular lately, is to make Tcl in charge, and embed all your C functionality into tclsh as new Tcl commands. I imagine that depending on how the Asterisk code is organized, one or both of those approaches should be feasible. But of course, unless the whole codebase is already organized as a library for easy embedding into other code, the AOLserver style C is in charge way sounds more likely. http://linuxjournal.com/article.php?sid=6769 which http://www.asterisk.org/ -- Andrew Piskorski [EMAIL PROTECTED] http://www.piskorski.com/ -- AOLserver - http://www.aolserver.com/ To Remove yourself from this list, simply send an email to [EMAIL PROTECTED] with the body of SIGNOFF AOLSERVER in the email message. You can leave the Subject: field of your email blank.
Re: [AOLSERVER] OT: Embedding Tcl Interp into existing C application
On 2004.08.27, Brett Schwarz [EMAIL PROTECTED] wrote: Anyways, there is an open source PBX system (asterisk) that has an programming interface that is very similar to CGI (in fact it is called AGI). Right now, it forks off a process everytime an AGI is called (just like CGI). I would like to change that so that Tcl scripts are loaded in ahead of time, and are executed in process (no forking). Pretty much how aolserver runs tcl procs and tcl pages. You specifically asked about embedding Tcl in a multithreaded application. Is Asterix multi-threaded? If it is, and they fork and exec a new process for each AGI invocation, that's interesting ... The simplest thing to do is to start by not pre-loading all the scripts ahead of time (since there's still no multi-threaded Tcl_CloneInterp() function, loading them ahead of time may not benefit you much). I'd start by simply creating a new Tcl interp. and evaluate a script, instead of fork/exec of an external program. This also keeps a lof of the headaches of multi-threaded programming out of your hair. Expose the Asterix API to Tcl by creating Tcl commands from C. Once you've got that working, then just tune for performance as real measurements dictate. A good page to learn how to start embedding Tcl in your C app. can be found on the Tcl'ers Wiki: How to embed Tcl in C applications http://wiki.tcl.tk/2074 -- Dossy -- Dossy Shiobara mail: [EMAIL PROTECTED] Panoptic Computer Network web: http://www.panoptic.com/ He realized the fastest way to change is to laugh at your own folly -- then you can let go and quickly move on. (p. 70) -- AOLserver - http://www.aolserver.com/ To Remove yourself from this list, simply send an email to [EMAIL PROTECTED] with the body of SIGNOFF AOLSERVER in the email message. You can leave the Subject: field of your email blank.
Re: [AOLSERVER] OT: Embedding Tcl Interp into existing C application
--- Andrew Piskorski [EMAIL PROTECTED] wrote: On Fri, Aug 27, 2004 at 11:11:59AM -0700, Brett Schwarz wrote: Sure, I didn't elaborate before, because I was trying to keep the OT noise down. Actually, I think this sort of discussion, while not PRECISELY on topic for the AOLserver list, is more than close enough for discsussion. In fact, I'd like to encourage it. Your question is basically one example of, I know that AOLserver does X really well, I'd like to understand how, so that I can do something similar to X with a different program.. I think those sorts of engineering design questions are likely to teach many of us something useful. Anyways, there is an open source PBX system (asterisk) that has an programming interface that is very similar to CGI (in fact it is called AGI). Right now, it forks off a process everytime an AGI is called (just like CGI). I would like to change that so that Tcl scripts are loaded in ahead of time, and are executed in process (no forking). Pretty much how aolserver runs tcl procs and tcl pages. You might also consider something like FastCGI. Maybe that approach would be easier to integrate into the Asterisk codebase than AOLserver's in-process interpreter approach, I dunno. I thought, in essense, aolserver is FastCGI. What are the differences? Now, I've never done it, but my understanding is that anytime you want to combine Tcl and C, your first thing to decide is which language is in charge? In AOLserver the C code is in charge, and that's the way Ousterhout originally envisioned embedding Tcl. The other way, more popular lately, is to make Tcl in charge, and embed all your C functionality into tclsh as new Tcl commands. I imagine that depending on how the Asterisk code is organized, one or both of those approaches should be feasible. But of course, unless the whole codebase is already organized as a library for easy embedding into other code, the AOLserver style C is in charge way sounds more likely. By default, C is in charge, since this is an existing C app. -- AOLserver - http://www.aolserver.com/ To Remove yourself from this list, simply send an email to [EMAIL PROTECTED] with the body of SIGNOFF AOLSERVER in the email message. You can leave the Subject: field of your email blank.
Re: [AOLSERVER] OT: Embedding Tcl Interp into existing C application
--- Dossy Shiobara [EMAIL PROTECTED] wrote: On 2004.08.27, Brett Schwarz [EMAIL PROTECTED] wrote: Anyways, there is an open source PBX system (asterisk) that has an programming interface that is very similar to CGI (in fact it is called AGI). Right now, it forks off a process everytime an AGI is called (just like CGI). I would like to change that so that Tcl scripts are loaded in ahead of time, and are executed in process (no forking). Pretty much how aolserver runs tcl procs and tcl pages. You specifically asked about embedding Tcl in a multithreaded application. Is Asterix multi-threaded? If it is, and they fork and exec a new process for each AGI invocation, that's interesting ... yes, it is multi-threaded. They fork, because it is an external program. Just think of CGI. The simplest thing to do is to start by not pre-loading all the scripts ahead of time (since there's still no multi-threaded Tcl_CloneInterp() function, loading them ahead of time may not benefit you much). I'd But, what is the impact of loaded them ahead of time? I thought that's was aolserver does (i.e. the tcl procs). I realize that there is some performance problems with cloning an interp, but isn't this done at startup time, where I don't necessarily care about timing? Or am I way off base here? start by simply creating a new Tcl interp. and evaluate a script, instead of fork/exec of an external program. This also keeps a lof of the headaches of multi-threaded programming out of your hair. Expose the Asterix API to Tcl by creating Tcl commands from C. Here's one of the deals that I am clueless about mult-threaded programming. This is how I would think it would happen. The main thread would read that it is a Tcl app, and so it needs to send that to the Tcl_Interp. I would imagine that the Tcl_Interp would be in anther thread. So, I am assuming that there is communication between the threads. Is this similar to how aolserver does it? If so, where would I begin to look to see how data is passed back and forth? Once you've got that working, then just tune for performance as real measurements dictate. A good page to learn how to start embedding Tcl in your C app. can be found on the Tcl'ers Wiki: How to embed Tcl in C applications http://wiki.tcl.tk/2074 I am familiar with embedding Tcl in C, I am just unsure how its works in a mult-threaded environment...especially how data is passed back and forth between the main C thread, and the thread that has Tcl embedded. thanks for the info...I am learning ;) --brett -- AOLserver - http://www.aolserver.com/ To Remove yourself from this list, simply send an email to [EMAIL PROTECTED] with the body of SIGNOFF AOLSERVER in the email message. You can leave the Subject: field of your email blank.
