Allow to provide user data for the filter subscribe callback

wrappers/cfuncs.go

@@ -5,10 +5,10 @@ package main
 #include "libnimbus.h"
 
 // receiveHandler gateway function
-void receiveHandler_cgo(received_message * msg)
+void receiveHandler_cgo(received_message * msg, void* udata)
 {
-	void receiveHandler(received_message*);
-	receiveHandler(msg);
+	void receiveHandler(received_message* msg, void* udata);
+	receiveHandler(msg, udata);
 }
 */
 import "C"

wrappers/libnimbus.h

@@ -45,7 +45,7 @@ typedef struct {
   uint8_t topic[4];
 } topic;
 
-typedef void (*received_msg_handler)(received_message* msg);
+typedef void (*received_msg_handler)(received_message* msg, void* udata);
 
 /** Initialize Nim and the status library */
 void NimMain();
@@ -88,7 +88,7 @@ int nimbus_get_symkey(const char* id, uint8_t* symkey);
 
 /* Subscribe to given filter */
 const char* nimbus_subscribe_filter(filter_options* filter_options,
-  received_msg_handler msg);
+  received_msg_handler msg, void* udata);
 int nimbus_unsubscribe_filter(const char* id);
 /* Post Whisper message */
 int nimbus_post(post_message* msg);

wrappers/libnimbus.nim

@@ -338,8 +338,8 @@ proc nimbus_post(message: ptr CPostMessage): bool {.exportc,foreignThreadGc.} =
                             powTarget = message.powTarget)
 
 proc nimbus_subscribe_filter(options: ptr CFilterOptions,
-    handler: proc (msg: ptr CReceivedMessage) {.gcsafe, cdecl.}):
-    cstring {.exportc, foreignThreadGc.} =
+    handler: proc (msg: ptr CReceivedMessage, udata: pointer) {.gcsafe, cdecl.},
+    udata: pointer = nil): cstring {.exportc, foreignThreadGc.} =
   ## In case of a passed handler, the received msg needs to be copied before the
   ## handler ends.
   ## TODO: provide some user context passing here else this is rather useless?
@@ -379,7 +379,7 @@ proc nimbus_subscribe_filter(options: ptr CFilterOptions,
       if msg.dst.isSome():
         cmsg.recipientPublicKey = msg.decoded.src.get()
 
-      handler(addr cmsg)
+      handler(addr cmsg, udata)
 
     result = node.subscribeFilter(filter, c_handler)
 

wrappers/wrapper_example.c

@@ -9,7 +9,7 @@
 
 void NimMain();
 
-void print_msg(received_message* msg) {
+void print_msg(received_message* msg, void* udata) {
   // Note: early null chars will terminate string early
   printf("received message %.*s\n", (int)msg->decodedLen, msg->decoded);
 }

wrappers/wrapper_whisper_example.go

@@ -11,7 +11,7 @@ import (
 #cgo LDFLAGS: -Wl,-rpath,'$ORIGIN' -L${SRCDIR}/../build -lnimbus -lm
 #include "libnimbus.h"
 
-void receiveHandler_cgo(received_message * msg); // Forward declaration.
+void receiveHandler_cgo(received_message * msg, void* udata); // Forward declaration.
 */
 import "C"
 
@@ -30,10 +30,13 @@ func poll() {
 }
 
 //export receiveHandler
-func receiveHandler(msg *C.received_message) {
+func receiveHandler(msg *C.received_message, udata unsafe.Pointer) {
 	fmt.Printf("[nim-status] received message %s\n",
 		C.GoStringN((*C.char)(msg.decoded), (C.int)(msg.decodedLen)) )
 	fmt.Printf("[nim-status] source public key %x\n", msg.source)
+	msgCount := (*int)(udata)
+	*msgCount += 1
+	fmt.Printf("[nim-status] message count %d\n", *msgCount)
 }
 
 func Start() {
@@ -51,11 +54,14 @@ func StatusListenAndPost(channel string) {
 	symKeyId := C.GoString(C.nimbus_add_symkey_from_password(C.CString(channel)))
 	asymKeyId := C.GoString(C.nimbus_new_keypair())
 
+	msgCount := 0
 	options := C.filter_options{symKeyID: C.CString(symKeyId),
 		minPow: 0.002,
 		topic: C.nimbus_string_to_topic(C.CString(channel)).topic}
-	C.nimbus_subscribe_filter(&options,
-		(C.received_msg_handler)(unsafe.Pointer(C.receiveHandler_cgo)))
+	filterId := C.GoString(C.nimbus_subscribe_filter(&options,
+		(C.received_msg_handler)(unsafe.Pointer(C.receiveHandler_cgo)),
+		unsafe.Pointer(&msgCount)))
+	fmt.Printf("[nim-status] filter subscribed, id: %s\n", filterId)
 
 	postMessage := C.post_message{symKeyID: C.CString(symKeyId),
 		sourceID: C.CString(asymKeyId),