From 141d00795c9615578cfe2ced79e77a67ae5fb591 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jefferson=20Gonz=C3=A1lez?= <jgmdev@gmail.com>
Date: Tue, 27 Dec 2022 23:07:12 -0400
Subject: [PATCH] dirmonitor: use pipes on fsevents (#1274)

As suggested by Guldoman this change introduces the usage
of pipes to allow blocking the get changes call until any
file system changes are received, which now properly reduces
the cpu usage on idle to 0%.

This change better fixes #1237
---
 src/api/dirmonitor/fsevents.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/src/api/dirmonitor/fsevents.c b/src/api/dirmonitor/fsevents.c
index 2b32219c..47812f49 100644
--- a/src/api/dirmonitor/fsevents.c
+++ b/src/api/dirmonitor/fsevents.c
@@ -6,6 +6,7 @@ struct dirmonitor_internal {
   char** changes;
   size_t count;
   FSEventStreamRef stream;
+  int fds[2];
 };
 
 CFRunLoopRef main_run_loop;
@@ -39,6 +40,9 @@ static void stop_monitor_stream(struct dirmonitor_internal* monitor) {
     monitor->stream = NULL;
 
     SDL_LockMutex(monitor->lock);
+    write(monitor->fds[1], "", 1);
+    close(monitor->fds[0]);
+    close(monitor->fds[1]);
     if (monitor->count > 0) {
       for (size_t i = 0; i<monitor->count; i++) {
         free(monitor->changes[i]);
@@ -92,6 +96,9 @@ static void stream_callback(
     strcpy(monitor->changes[idx], path_list[pidx]);
   }
   monitor->count = total;
+
+  if (total > 0)
+    write(monitor->fds[1], "", 1);
   SDL_UnlockMutex(monitor->lock);
 }
 
@@ -101,16 +108,14 @@ int get_changes_dirmonitor(
   char* buffer,
   int buffer_size
 ) {
-  FSEventStreamFlushSync(monitor->stream);
+  char response[1];
+  read(monitor->fds[0], response, 1);
 
   size_t results = 0;
   SDL_LockMutex(monitor->lock);
   results = monitor->count;
   SDL_UnlockMutex(monitor->lock);
 
-  if (monitor->count <= 0)
-    SDL_Delay(100);
-
   return results;
 }
 
@@ -141,6 +146,7 @@ int add_dirmonitor(struct dirmonitor_internal* monitor, const char* path) {
   stop_monitor_stream(monitor);
 
   monitor->lock = SDL_CreateMutex();
+  pipe(monitor->fds);
 
   FSEventStreamContext context = {
     .info = monitor,
@@ -160,7 +166,7 @@ int add_dirmonitor(struct dirmonitor_internal* monitor, const char* path) {
     &context,
     CFArrayCreate(NULL, (const void **)&paths, 1, NULL),
     kFSEventStreamEventIdSinceNow,
-    10000,
+    0,
     kFSEventStreamCreateFlagNone
       | kFSEventStreamCreateFlagWatchRoot
       | kFSEventStreamCreateFlagFileEvents