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

[Adrian Thurston]

You could put %body_read at the end of the final CRLF. It seems you're
parsing only a single request/response at once and you don't need to
separate them. That means that when the input buffer is fully consumed
you're at the end.

Adrian

Horacio Sanson wrote:
> 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
> 
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