msg-format: make it possible for a format plugin to specify a factory for LogProto

Some format plugins (notably the upcoming pacct) will possibly need a
custom LogProto instance when reading binary file formats. This
patch adds a construct_proto() virtual function to the MsgFormatHandler
class for exactly this purpose.

NOTE: this callback only works for file sources as of now, but may change in
the future.

Author: bazsi

src/affile/affile.c

@@ -155,20 +155,22 @@ affile_sd_construct_proto(AFFileSourceDriver *self, LogTransport *transport)
 {
   guint flags;
   LogProto *proto;
-
-  flags = ((self->reader_options.follow_freq > 0)
-           ? LPBS_IGNORE_EOF
-           : LPBS_NOMREAD);
-
-  if (self->flags & AFFILE_PIPE)
-    {
-      if (self->reader_options.padding)
-        proto = log_proto_record_server_new(transport, self->reader_options.padding, flags);
-      else
-        proto = log_proto_text_server_new(transport, self->reader_options.msg_size, flags);
-    }
+  MsgFormatHandler *handler;
+
+  flags =
+    ((self->reader_options.follow_freq > 0)
+     ? LPBS_IGNORE_EOF
+     : LPBS_NOMREAD) |
+    ((self->flags & AFFILE_PIPE) ? 0 : LPBS_POS_TRACKING);
+
+  handler = self->reader_options.parse_options.format_handler;
+  if ((handler && handler->construct_proto))
+    proto = self->reader_options.parse_options.format_handler->construct_proto(&self->reader_options.parse_options, transport, flags);
+  else if (self->reader_options.padding)
+    proto = log_proto_record_server_new(transport, self->reader_options.padding, flags);
   else
-    proto = log_proto_text_server_new(transport, self->reader_options.msg_size, LPBS_POS_TRACKING | flags);
+    proto = log_proto_text_server_new(transport, self->reader_options.msg_size, flags);
+
   return proto;
 }
 
@@ -206,7 +208,6 @@ affile_sd_notify(LogPipe *s, LogPipe *sender, gint notify_code, gpointer user_da
             log_reader_set_follow_filename(self->reader, self->filename->str);
             log_reader_set_immediate_check(self->reader);
 
-
             log_pipe_append(self->reader, s);
             if (!log_pipe_init(self->reader, cfg))
               {

src/msg-format.h

@@ -3,6 +3,7 @@
 
 #include "syslog-ng.h"
 #include "timeutils.h"
+#include "logproto.h"
 
 #include <regex.h>
 
@@ -41,6 +42,7 @@ typedef struct _MsgFormatOptions
 
 struct _MsgFormatHandler
 {
+  LogProto *(*construct_proto)(MsgFormatOptions *options, LogTransport *transport, guint flags);
   void (*parse)(MsgFormatOptions *options, const guchar *data, gsize length, LogMessage *msg);
 };