fsmonitor: implement an internal fsmonitor backend for macOS using FS…

…Events

Signed-off-by: Kevin Willford <Kevin.Willford@microsoft.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

compat/fsmonitor/macos.c

@@ -0,0 +1,133 @@
+/*
+ * Let Apple's headers declare `isalnum()` first, before
+ * Git's headers override it via a constant
+ */
+#include <string.h>
+#include <CoreFoundation/CoreFoundation.h>
+#include <CoreServices/CoreServices.h>
+
+#include "cache.h"
+#include "fsmonitor.h"
+
+static struct strbuf watch_dir = STRBUF_INIT;
+static FSEventStreamRef stream;
+
+static void fsevent_callback(ConstFSEventStreamRef streamRef,
+			     void *ctx,
+			     size_t num_of_events,
+			     void * event_paths,
+			     const FSEventStreamEventFlags event_flags[],
+			     const FSEventStreamEventId event_ids[])
+{
+	int i;
+	struct stat st;
+	char **paths = (char **)event_paths;
+	struct fsmonitor_queue_item dummy, *queue = &dummy;
+	uint64_t time = getnanotime();
+	struct fsmonitor_daemon_state *state = ctx;
+
+	/* Ensure strictly increasing timestamps */
+	pthread_mutex_lock(&state->queue_update_lock);
+	if (time <= state->latest_update)
+		time = state->latest_update + 1;
+	pthread_mutex_unlock(&state->queue_update_lock);
+
+	for (i = 0; i < num_of_events; i++) {
+		int special;
+		const char *path = paths[i] + watch_dir.len;
+		size_t len = strlen(path);
+
+		if (*path == '/') {
+			path++;
+			len--;
+		}
+
+		special = fsmonitor_special_path(state, path, len,
+						 (event_flags[i] & (kFSEventStreamEventFlagRootChanged | kFSEventStreamEventFlagItemRemoved)) &&
+						 lstat(paths[i], &st));
+
+		if ((event_flags[i] & kFSEventStreamEventFlagKernelDropped) ||
+		    (event_flags[i] & kFSEventStreamEventFlagUserDropped)) {
+			trace2_data_string("fsmonitor", the_repository, "message", "Dropped event");
+			fsmonitor_queue_path(state, &queue, "/", 1, time);
+		}
+
+		if (!special && fsmonitor_queue_path(state, &queue,
+						     path, len, time) < 0) {
+			state->error_code = -1;
+			error("could not queue '%s'; exiting",
+			      path);
+			fsmonitor_listen_stop(state);
+			return;
+		} else if (special == FSMONITOR_DAEMON_QUIT) {
+			trace2_data_string("fsmonitor", the_repository, "message", ".git directory being removed so quitting.");
+			exit(0);
+
+		} else if (special < 0) {
+			fsmonitor_listen_stop(state);
+			return;
+		}
+	}
+
+	/* Only update the queue if it changed */
+	if (queue != &dummy) {
+		pthread_mutex_lock(&state->queue_update_lock);
+		if (state->first)
+			state->first->previous = dummy.previous;
+		dummy.previous->next = state->first;
+		state->first = queue;
+		state->latest_update = time;
+		pthread_mutex_unlock(&state->queue_update_lock);
+	}
+}
+
+struct fsmonitor_daemon_state *fsmonitor_listen(struct fsmonitor_daemon_state *state)
+{
+	FSEventStreamCreateFlags flags = kFSEventStreamCreateFlagNoDefer |
+		kFSEventStreamCreateFlagWatchRoot |
+		kFSEventStreamCreateFlagFileEvents;
+	CFStringRef watch_path;
+	CFArrayRef paths_to_watch;
+	FSEventStreamContext ctx = {
+		0,
+		state,
+		NULL,
+		NULL,
+		NULL
+	};
+
+	trace2_region_enter("fsmonitor", "fsevents", the_repository);
+	strbuf_addstr(&watch_dir, get_git_work_tree());
+	trace2_printf("Start watching: '%s' for fsevents", watch_dir.buf);
+
+	watch_path = CFStringCreateWithCString(NULL, watch_dir.buf, kCFStringEncodingUTF8);
+	paths_to_watch = CFArrayCreate(NULL, (const void **)&watch_path, 1, NULL);
+	stream = FSEventStreamCreate(NULL, fsevent_callback, &ctx, paths_to_watch,
+				     kFSEventStreamEventIdSinceNow, 0.1, flags);
+	if (stream == NULL)
+		die("Unable to create FSEventStream.");
+
+	FSEventStreamScheduleWithRunLoop(stream, CFRunLoopGetCurrent(), kCFRunLoopDefaultMode);
+	if (!FSEventStreamStart(stream))
+		die("Failed to start the FSEventStream");
+
+	pthread_mutex_lock(&state->initial_mutex);
+	state->latest_update = getnanotime();
+	state->initialized = 1;
+	pthread_cond_signal(&state->initial_cond);
+	pthread_mutex_unlock(&state->initial_mutex);
+
+	CFRunLoopRun();
+
+	trace2_region_leave("fsmonitor", "fsevents", the_repository);
+	return state;
+}
+
+int fsmonitor_listen_stop(struct fsmonitor_daemon_state *state)
+{
+	CFRunLoopStop(CFRunLoopGetCurrent());
+	FSEventStreamStop(stream);
+	FSEventStreamInvalidate(stream);
+	FSEventStreamRelease(stream);
+	return 0;
+}

config.mak.uname

@@ -144,6 +144,8 @@ ifeq ($(uname_S),Darwin)
 			MSGFMT = /usr/local/opt/gettext/bin/msgfmt
 		endif
 	endif
+	FSMONITOR_DAEMON_BACKEND = macos
+	BASIC_LDFLAGS += -framework CoreServices
 endif
 ifeq ($(uname_S),SunOS)
 	NEEDS_SOCKET = YesPlease