[ragel-users] Small help with RTSP + SDP parser

[Horacio Sanson]

Here is part of my parser that deals with RTSP response body part. As
you can see the message_body is delimited by CRLF that is a simle
("\n"? "\r") expression.
My problem is when the response has a SDP message as part of the
response body. This is because SDP fields are also delimited with CRLF
(see example at the end). In this case the body_read action is called
for each SDP field instead of only once at the end of the body. In
consequence I get several calls to memcpy when in fact I only expect
one at the end of the message body (i.e. 27 times in the example
below).

The end result is still correct, the SDP is completely copied inside
the msg->body buffer, but calling memcpy per SDP field is undesired
for performance reasons. What rule/tip/trick/hack can I use to make
the body_read action be executed only once at the end of the RTSP
message body??

thanks
Horacio

################################################################################
#        Ragel rules
################################################################################

action body_test  { body_offset++ < msg->body_len }
action body_start { body_start = fpc; body_offset = 0 }
action body_end   {body_end = fpc;}
action body_read {
    tmpbuf_len = body_end - body_start;
    memcpy(msg->body, body_start, tmpbuf_len);
}

message_body = any+ >body_start @body_end when body_test %body_read;

Response = (                            # Section 7
     Status_Line
     (
         general_header                 # Section 5
         | response_header              # Section 6.2
         | entity_header                # Section 8.1
         | CSeq                        # Section 12.17
         | Session                       # Section 12.37
         | Transport                     # Section 12.39
         | darwin_header                 # Darwin SS proprietary
     )*
     CRLF
     message_body?                       # Section 4.3
     CRLF %{ msg->finished = 1; SUJMSG("RTSP Finish\n"); }
 );

main := (Request | Response);


################################################################################
# Example RTSP response:
################################################################################
RTSP/1.0 200 OK
Server: DSS/5.5.5 (Build/489.16; Platform/Linux; Release/Darwin;
state/beta; )
Cseq: 411
Last-Modified: Thu, 16 Oct 2008 00:21:52 GMT
Cache-Control: must-revalidate
Content-length: 741
Date: Thu, 23 Oct 2008 02:30:28 GMT
Expires: Thu, 23 Oct 2008 02:30:28 GMT
Content-Type: application/sdp
x-Accept-Retransmit: our-retransmit
x-Accept-Dynamic-Rate: 1
Content-Base: rtsp://www.fake.com:554/BBB.mp4/

v=0
o=StreamingServer 3433717827 1224116512000 IN IP4 218.45.218.150
s=/BBB.mp4
u=http:///
e=admin@
c=IN IP4 0.0.0.0
b=AS:500
t=0 0
a=control:*
a=x-copyright: MP4/3GP File hinted with GPAC 0.4.4 (C)2000-2005 -
http://gpac.sourceforge.net
a=range:npt=0- 596.45800
m=video 0 RTP/AVP 96
b=AS:400
a=rtpmap:96 H264/90000
a=control:trackID=65536
a=fmtp:96 profile-level-id=42C01E; packetization-mode=1;
sprop-parameter-sets=Z0LAHppzgUBf8sIAAAMAAgAAAwBhHixc8A==,aM4yyA==
a=framesize:96 640-360
m=audio 0 RTP/AVP 97
b=AS:100
a=rtpmap:97 mpeg4-generic/48000/2
a=control:trackID=65537
a=fmtp:97 profile-level-id=41; config=1190; streamType=5;
mode=AAC-hbr; objectType=64; sizeLength=13; indexLength=3;
indexDeltaLength=3