From 8f7947d682d4b21be2d76dae2770efe7bf5d9cc7 Mon Sep 17 00:00:00 2001
From: Robert Sesek <rsesek@google.com>
Date: Fri, 20 Mar 2015 13:06:03 -0400
Subject: [PATCH] Describe FSEvent flag information.

---
 fseventw.c | 49 ++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 48 insertions(+), 1 deletion(-)

diff --git a/fseventw.c b/fseventw.c
index 7f8ea3e..e7a33a4 100644
--- a/fseventw.c
+++ b/fseventw.c
@@ -16,6 +16,46 @@
 #include <dispatch/dispatch.h>
 #include <stdio.h>
 
+typedef char FlagDescription[8];
+
+void LogControlFlagInfo(dispatch_queue_t log_queue,
+                        FSEventStreamEventFlags flags) {
+  if (flags & kFSEventStreamEventFlagUserDropped) {
+    dispatch_async(log_queue, ^{
+        printf("User-side buffer dropped event\n");
+    });
+  } else if (flags & kFSEventStreamEventFlagKernelDropped) {
+    dispatch_async(log_queue, ^{
+        printf("Kernel-side buffer dropped event\n");
+    });
+  } else if (flags & kFSEventStreamEventFlagEventIdsWrapped) {
+    dispatch_async(log_queue, ^{
+        printf("Event IDs have wrapped\n");
+    });
+  }
+}
+
+void DescribeFlags(FSEventStreamEventFlags flags, FlagDescription description) {
+  memset(description, '-', sizeof(FlagDescription));
+  description[sizeof(FlagDescription) - 1] = '\0';
+
+  if (flags & kFSEventStreamEventFlagItemCreated)
+    description[0] = 'C';
+  else if (flags & kFSEventStreamEventFlagItemModified)
+    description[1] = 'M';
+  else if (flags & kFSEventStreamEventFlagItemRemoved)
+    description[2] = 'R';
+  else if (flags & kFSEventStreamEventFlagItemRenamed)
+    description[3] = 'N';
+  else if (flags & (kFSEventStreamEventFlagItemInodeMetaMod |
+                    kFSEventStreamEventFlagItemFinderInfoMod))
+    description[4] = 'M';
+  else if (flags & kFSEventStreamEventFlagItemChangeOwner)
+    description[5] = 'O';
+  else if (flags & kFSEventStreamEventFlagItemXattrMod)
+    description[6] = 'X';
+}
+
 void EventStreamCallback(ConstFSEventStreamRef event_stream,
                          void* callback_info,
                          size_t num_events,
@@ -29,16 +69,23 @@ void EventStreamCallback(ConstFSEventStreamRef event_stream,
     const FSEventStreamEventFlags flags = event_flags[i];
     const FSEventStreamEventId ids = event_ids[i];
 
+    LogControlFlagInfo(log_queue, flags);
+
     char* path = strdup(event_paths[i]);
 
     dispatch_async(log_queue, ^{
-        printf("event %llx %x at %s\n", ids, flags, path);
+        FlagDescription flag_description;
+        DescribeFlags(flags, flag_description);
+        printf("event %llx %s at %s\n", ids, flag_description, path);
         free(path);
     });
   }
 }
 
 int main() {
+  // All logging should happen on a serial queue, so that stdout is not
+  // interleaved, as it could be when handling FSEvents on the concurrent
+  // event queue.
   dispatch_queue_t log_queue = dispatch_queue_create("com.google.fseventw.logq", DISPATCH_QUEUE_SERIAL);
   dispatch_queue_t event_queue = dispatch_queue_create("com.google.fseventw.eventq", DISPATCH_QUEUE_CONCURRENT);
 
-- 
2.43.5