From 326914f92aeb690e5e70320a131a170f91da181f Mon Sep 17 00:00:00 2001
From: King_DuckZ <king_duckz@gmx.com>
Date: Wed, 12 Aug 2020 01:07:45 +0100
Subject: [PATCH] Add example file that's been there forever

---
 example.c | 88 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 88 insertions(+)
 create mode 100644 example.c

diff --git a/example.c b/example.c
new file mode 100644
index 0000000..ed1df19
--- /dev/null
+++ b/example.c
@@ -0,0 +1,88 @@
+//This program is demo for using pthreads with libev.
+//Try using Timeout values as large as 1.0 and as small as 0.000001
+//and notice the difference in the output
+
+//(c) 2009 debuguo
+//(c) 2013 enthusiasticgeek for stack overflow
+//Free to distribute and improve the code. Leave credits intact
+
+#include <ev.h>
+#include <stdio.h> // for puts
+#include <stdlib.h>
+#include <pthread.h>
+#include <stdbool.h>
+
+pthread_mutex_t lock;
+double timeout = 0.00001;
+ev_timer timeout_watcher;
+int timeout_count = 0;
+
+ev_async async_watcher;
+int async_count = 0;
+
+struct ev_loop* loop2;
+
+void* loop2thread(void* args)
+{
+    printf("Inside loop 2"); // Here one could initiate another timeout watcher
+    ev_loop(loop2, 0);       // similar to the main loop - call it say timeout_cb1
+    return NULL;
+}
+
+static void async_cb (EV_P_ ev_async *w, int revents)
+{
+    //puts ("async ready");
+    pthread_mutex_lock(&lock);     //Don't forget locking
+    ++async_count;
+    printf("async = %d, timeout = %d \n", async_count, timeout_count);
+    pthread_mutex_unlock(&lock);   //Don't forget unlocking
+}
+
+static void timeout_cb (EV_P_ ev_timer *w, int revents) // Timer callback function
+{
+    //puts ("timeout");
+    if (ev_async_pending(&async_watcher)==false) { //the event has not yet been processed (or even noted) by the event loop? (i.e. Is it serviced? If yes then proceed to)
+        ev_async_send(loop2, &async_watcher); //Sends/signals/activates the given ev_async watcher, that is, feeds an EV_ASYNC event on the watcher into the event loop.
+    }
+
+    pthread_mutex_lock(&lock);     //Don't forget locking
+    ++timeout_count;
+    pthread_mutex_unlock(&lock);   //Don't forget unlocking
+    w->repeat = timeout;
+    ev_timer_again(loop, &timeout_watcher); //Start the timer again.
+}
+
+int main (int argc, char** argv)
+{
+    if (argc < 2) {
+        puts("Timeout value missing.\n./demo <timeout>");
+        return -1;
+    }
+    timeout = atof(argv[1]);
+
+    struct ev_loop *loop = EV_DEFAULT;  //or ev_default_loop (0);
+
+    //Initialize pthread
+    pthread_mutex_init(&lock, NULL);
+    pthread_t thread;
+
+    // This loop sits in the pthread
+    loop2 = ev_loop_new(0);
+
+    //This block is specifically used pre-empting thread (i.e. temporary interruption and suspension of a task, without asking for its cooperation, with the intention to resume that task later.)
+    //This takes into account thread safety
+    ev_async_init(&async_watcher, async_cb);
+    ev_async_start(loop2, &async_watcher);
+    pthread_create(&thread, NULL, loop2thread, NULL);
+
+    ev_timer_init (&timeout_watcher, timeout_cb, timeout, 0.); // Non repeating timer. The timer starts repeating in the timeout callback function
+    ev_timer_start (loop, &timeout_watcher);
+
+    // now wait for events to arrive
+    ev_loop(loop, 0);
+    //Wait on threads for execution
+    pthread_join(thread, NULL);
+
+    pthread_mutex_destroy(&lock);
+    return 0;
+}