core: parser - helper functions to test msg context id

- use (msg id, pid) to identify the message context id
- to be used for matching the message context when caching values are
  stored per it
- reported by Klaus Darilion for $TV(...)

parser/msg_parser.c

@@ -871,3 +871,29 @@ hdr_field_t* next_sibling_hdr_by_name(hdr_field_t *hf)
 	}
 	return NULL;
 }
+
+/**
+ * set msg context id
+ * - return: -1 on error; 0 - on set
+ */
+int msg_ctx_id_set(sip_msg_t *msg, msg_ctx_id_t *mid)
+{
+	if(msg==NULL || mid==NULL)
+		return -1;
+	mid->msgid = msg->id;
+	mid->pid = msg->pid;
+	return 0;
+}
+
+/**
+ * check msg context id
+ * - return: -1 on error; 0 - on no match; 1 - on match
+ */
+int msg_ctx_id_match(sip_msg_t *msg, msg_ctx_id_t *mid)
+{
+	if(msg==NULL || mid==NULL)
+		return -1;
+	if(msg->id != mid->msgid || msg->pid!=mid->pid)
+		return 0;
+	return 1;
+}

parser/msg_parser.h

@@ -461,5 +461,25 @@ void reset_path_vector(struct sip_msg* msg);
 /** reset a previously forced send socket. */
 #define reset_force_socket(msg) set_force_socket(msg, 0)
 
+/**
+ * struct to identify a msg context
+ * - the pair of pid and message-id
+ */
+typedef struct msg_ctx_id {
+	int pid;
+	int msgid;
+} msg_ctx_id_t;
+
+/**
+ * set msg context id
+ * - return: -1 on error; 0 - on set 
+ */
+int msg_ctx_id_set(sip_msg_t *msg, msg_ctx_id_t *mid);
+
+/**
+ * check msg context id
+ * - return: -1 on error; 0 - on no match; 1 - on match
+ */
+int msg_ctx_id_match(sip_msg_t *msg, msg_ctx_id_t *mid);
 
 #endif