callagent: Big performance improvement, cache the parser

Constructing a PetitParser is an expensive operation (Object>>becomeForward:)
we can keep the parser in the class. For the SIPTransactions we keep it as
a global, it is assumed that all SIPTransactions operate through the same
process and will not run into concurrency issues.

callagent/SIPCallAgent.st

@@ -208,7 +208,7 @@ Object subclass: SIPUserAgentBase [
 ]
 
 SIPUserAgentBase subclass: SIPUserAgent [
-    | transactions retransmit sem |
+    | dialogs transactions retransmit sem parser |
     <category: 'SIP-Callagent'>
     <comment: 'I am a user agent base'>
 
@@ -274,13 +274,18 @@ SIPUserAgentBase subclass: SIPUserAgent [
         OsmoDispatcher dispatchBlock: [self transportDataInternal: aData].
     ]
 
+    parser [
+        <category: 'parser'>
+        ^ parser ifNil: [parser := SIPParser new]
+    ]
+
     transportDataInternal: aData [
         | req data |
         <category: 'private'>
 
         [
             data := aData data copyFrom: 1 to: aData size.
-            req := SIPParser parse: data asString onError: [:e |
+            req := self parser parse: data asString onError: [:e |
                 data printNl.
                 self logError: 'Failed to parse: "%1" with %2'
                                 % {data asString. e} area: #sip.

callagent/SIPTransactions.st

@@ -31,6 +31,8 @@ Object subclass: SIPTransaction [
     SIPTransaction class >> stateTerminated [ <category: 'states'> ^ #terminated ]
     SIPTransaction class >> stateCanceled   [ <category: 'states'> ^ #canceled ]
 
+    Grammar := nil.
+
     SIPTransaction class >> createWith: aDialog on: aUA  cseq: aCseq [
         <category: 'creation'>
         ^ self new
@@ -41,6 +43,20 @@ Object subclass: SIPTransaction [
             yourself.
     ]
 
+    SIPTransaction class >> grammar [
+        <category: 'private'>
+        ^ Grammar ifNil: [Grammar := SIPGrammar new]
+    ]
+
+    SIPTransaction class >> verifyGrammar: aData [
+        <category: 'private'>
+        self grammar parse: aData onError: [:e |
+            e logException: 'Outgoing data has parsing error' area: #sip.
+            e signal
+        ]
+    ]
+
+
     initialize [
         <category: 'creation'>
         sem := RecursionLock new.
@@ -103,7 +119,7 @@ Object subclass: SIPTransaction [
         <category: 'private'>
 
         "validate the output"
-        res := SIPGrammar parse: aData.
+        self class verifyGrammar: aData.
 
         datagram := Sockets.Datagram
                                 data: aData