watcher-c: for better ffi, support a ptr-based event callback api

watcher-c/include/wtr/watcher-c.h

@@ -57,8 +57,12 @@ struct wtr_watcher_event {
     events and will return nothing. */
 typedef void (* wtr_watcher_callback)(struct wtr_watcher_event event, void* context);
 
+typedef void (* wtr_watcher_eventref_callback)(struct wtr_watcher_event* event, void* context);
+
 void* wtr_watcher_open(char const* const path, wtr_watcher_callback callback, void* context);
 
+void* wtr_watcher_open_eventref_stream(char const* const path, wtr_watcher_eventref_callback callback, void* context);
+
 bool wtr_watcher_close(void* watcher);
 
 #ifdef __cplusplus

watcher-c/src/test-watcher-c.c

@@ -4,7 +4,7 @@
 #include <unistd.h>
 #include <poll.h>
 
-void callback(struct wtr_watcher_event event, void* data)
+void callback(struct wtr_watcher_event* event, void* data)
 {
   int* count = (int*)data;
   *count += 1;
@@ -27,11 +27,11 @@ void callback(struct wtr_watcher_event event, void* data)
     "associated path name: %s\n",
 #endif
     *count,
-    event.path_name,
-    event.effect_type,
-    event.path_type,
-    event.effect_time,
-    event.associated_path_name ? event.associated_path_name : "");
+    event->path_name,
+    event->effect_type,
+    event->path_type,
+    event->effect_time,
+    event->associated_path_name ? event->associated_path_name : "");
 }
 
 void do_poll_read_loop(int read_fd)
@@ -84,7 +84,7 @@ int main(int argc, char** argv)
   }
   if (argc == 3) strncpy(path, argv[2], sizeof(path) - 1);
   int count = 0;
-  void* watcher = wtr_watcher_open(path, callback, &count);
+  void* watcher = wtr_watcher_open_eventref_stream(path, callback, &count);
   if (! watcher) return 1;
   getchar();
   if (! wtr_watcher_close(watcher)) return 1;

watcher-c/src/watcher-c.cpp

@@ -33,17 +33,13 @@ static int utf16_to_utf8(wchar_t const* utf16_buf, char* utf8_buf, int utf8_buf_
 }
 #endif
 
-void* wtr_watcher_open(
-  char const* const path,
-  wtr_watcher_callback callback,
-  void* context)
+#ifndef _WIN32
+inline int make_ev_view(wtr::watcher::event const& ev_owned, wtr_watcher_event& ev_view)
+#else
+inline int make_ev_view(wtr::watcher::event const& ev_owned, wtr_watcher_event& ev_view, char* path_name, char* associated_path_name)
+#endif
 {
-  auto wrapped_callback = [callback, context](wtr::watcher::event ev_owned)
-  {
-    wtr_watcher_event ev_view = {};
 #ifdef _WIN32
-    char path_name[PATH_BUF_LEN] = {0};
-    char associated_path_name[PATH_BUF_LEN] = {0};
     int wp = utf16_to_utf8(ev_owned.path_name.c_str(), path_name, PATH_BUF_LEN);
     if (wp <= 0) return;
     ev_view.path_name = path_name;
@@ -61,11 +57,49 @@ void* wtr_watcher_open(
     ev_view.effect_type = (int8_t)ev_owned.effect_type;
     ev_view.path_type = (int8_t)ev_owned.path_type;
     ev_view.effect_time = ev_owned.effect_time;
+    return 0;
+}
+
+void* wtr_watcher_open(
+  char const* const path,
+  wtr_watcher_callback callback,
+  void* context)
+{
+  auto wrapped_callback = [callback, context](wtr::watcher::event ev_owned)
+  {
+    wtr_watcher_event ev_view = {};
+#ifdef _WIN32
+    char path_name[PATH_BUF_LEN] = {0};
+    char associated_path_name[PATH_BUF_LEN] = {0};
+    if (make_ev_view(ev_owned, ev_view, path_name, associated_path_name)) return;
+#else
+    if (make_ev_view(ev_owned, ev_view)) return;
+#endif
     callback(ev_view, context);
   };
   return (void*)new wtr::watcher::watch(path, wrapped_callback);
 }
 
+void* wtr_watcher_open_eventref_stream(
+  char const* const path,
+  wtr_watcher_eventref_callback callback,
+  void* context)
+{
+  auto wrapped_callback = [callback, context](wtr::watcher::event ev_owned)
+  {
+    wtr_watcher_event ev_view = {};
+#ifdef _WIN32
+    char path_name[PATH_BUF_LEN] = {0};
+    char associated_path_name[PATH_BUF_LEN] = {0};
+    if (make_ev_view(ev_owned, ev_view, path_name, associated_path_name)) return;
+#else
+    if (make_ev_view(ev_owned, ev_view)) return;
+#endif
+    callback(&ev_view, context);
+  };
+  return (void*)new wtr::watcher::watch(path, wrapped_callback);
+}
+
 bool wtr_watcher_close(void* watcher)
 {
   if (! watcher) return false;