C-THREAD:
A limited implementation of threads using call/cc
This is a quick and dirty guile library that allows programs to manually switch between saved program states. Using this library strongly resembles using threads (with semaphores and manual scheduling), but the implementation does not invoke the os at all. Everything is implemented using call/cc on a single OS thread.
Here's how to use it:
- First, add some cthreads to a global thread queue.
- Then, invoke a context switch to pass control to the next cthread in line.
That's pretty much all this library does.
API Reference:
First thing's first:
(use-modules (cthread))To add a new thread to the global thread queue, use add-cthread.
[procedure]
add-cthread *proc* . *args*
Register a new cthread to the front of the calling process's global cthread queue. The cthread has a starting point of *proc*, which will be called with the argument list *args*.
If, while *proc*'s cthread is executing, *proc* returns, then the cthread will execute (remove-cthread).
This procedure returns immediately. It's return value is unspecified.
Once you've registered some cthreads, you can invoke a context switch with next-cthread to pass control to them.
[procedure]
next-cthread
Save the calling cthread's execution state to the back of the process's global cthread queue, then pop a cthread from the event queue and pass control to it. The return value of this procedure is unspecified.
You can unregister the calling thread and have it ceace execution with remove-cthread.
[procedure]
remove-cthread
Pass control to the next cthread popped from the cthread queue, but do not save the execution state of the calling cthread. The calling cthread is lost.
If the cthread queue is empty, terminate the calling process.
This procedure does not return.
Finally, you can check the size of the queue with num-cthreads.
[procedure]
num-cthreads => n
n := a positive integer
Return the number of cthreads currently in the cthread queue.