ugh, forgot to put in header...

codes/codes-callback.h

+/*
+ * Copyright (C) 2015 University of Chicago.
+ * See COPYRIGHT notice in top-level directory.
+ *
+*/
+
+#ifndef CODES_CALLBACK_H
+#define CODES_CALLBACK_H
+
+#include <assert.h>
+#include "codes/lp-msg.h"
+
+/* This header defines the following conventions for callback-based event
+ * processing (i.e., RPC-like event flow where the callee sends a "return
+ * event" to the caller)
+ *
+ * callers:
+ * - give the caller event size (for sanity checking)
+ * - use the msg_header convention (lp-msg.h)
+ * - specify an integer tag to identify which call the callee return event
+ *   corresponds to, in the case of multiple pending callbacks
+ * - specify an offset to the return structure, which is defined by the callees
+ *
+ * callees:
+ * - use the resulting set of offsets to write and issue the callback
+ *
+ * The recommended calling convention for these types of event flows is:
+ * void event_func(<params...>, int tag, struct codes_cb_info const * cb);
+ */
+
+struct codes_cb_info {
+    int event_size;
+    int header_offset;
+    int tag_offset;
+    int cb_ret_offset;
+};
+
+/* helper struct for callees - wrap up the typical inputs */
+struct codes_cb_params {
+    struct codes_cb_info info;
+    msg_header h;
+    int tag;
+};
+
+/* function-like sugar for initializing a codes_cb_info */
+#define INIT_CODES_CB_INFO(_cb_info_ptr, _event_type, _header_field, _tag_field, _cb_ret_field) \
+    do { \
+        (_cb_info_ptr)->event_size    = sizeof(_event_type); \
+        (_cb_info_ptr)->header_offset = offsetof(_event_type, _header_field); \
+        (_cb_info_ptr)->tag_offset    = offsetof(_event_type, _tag_field); \
+        (_cb_info_ptr)->cb_ret_offset = offsetof(_event_type, _cb_ret_field); \
+    } while (0)
+
+#define SANITY_CHECK_CB(_cb_info_ptr, _ret_type) \
+    do { \
+        int _total_size = sizeof(_ret_type) + sizeof(int) + sizeof(msg_header);\
+        int _esize = (_cb_info_ptr)->event_size; \
+        assert(_esize >= _total_size); \
+        assert(_esize >= (_cb_info_ptr)->header_offset + sizeof(msg_header)); \
+        assert(_esize >= (_cb_info_ptr)->tag_offset + sizeof(int)); \
+        assert(_esize >= (_cb_info_ptr)->cb_ret_offset + sizeof(_ret_type)); \
+    } while (0)
+
+#endif /* end of include guard: CODES_CALLBACK_H */
+
+/*
+ * Local variables:
+ *  c-indent-level: 4
+ *  c-basic-offset: 4
+ *  indent-tabs-mode: nil
+ * End:
+ *
+ * vim: ft=c ts=8 sts=4 sw=4 expandtab
+ */