sc/condition

Condition

Overview

• Condition wrapper.
• Provides passing data between signal and wait threads.
• Normally, if no thread waits on a condition, signal is missed. This
  implementation differs as it will keep a result variable when 'signal' is
  called. Signal will mark the condition 'done', so when another thread calls
  wait(), it won't be blocked, it will return immediately with the user
  provided data.
• Conditions can be problematic if you are looking for performance. E.g :
  • Thread A calls wait()
  • Thread B locks the mutex and calls signal() and just before it calls
    mutex unlock(), Thread A wakes up and sees mutex is still locked so it goes
    back to sleep.
  • So, this implementation provides 'async wait()' semantics, 'wait
    thread2 can call wait() later, even after signal thread completes its job.

Usage

#include "sc_cond.h"

#include <stdio.h>

int main()
{
    struct sc_cond cond;

    sc_cond_init(&cond);
    sc_cond_signal(&cond, "test"); // Call this on thread-1
    char* p = sc_cond_wait(&cond); // Call this on another thread.

    printf("%s \n", p);

    return 0;
}