rsl: Begin to dissect the rsl immediate assignment

fakebts/BTS.st

@@ -19,6 +19,8 @@
 "This is a fake base station used for injecting RSL/DTAP messages and
 simulating failure condition..."
 
+PackageLoader fileInPackage: #OsmoGSM.
+
 RSLBCCHInformation extend [
     btsDispatchOn: aBTS [
         <category: '*-BTS-Core'>
@@ -99,8 +101,20 @@ RSLRFChannelRelease extend [
             ifTrue: [self btsFreeChan: aBTS lchan: lchan]
             ifFalse: [self btsErrorChan: aBTS lchan: lchan].
     ]
+]
 
-  
+RSLImmediateAssignment extend [
+    btsDispatchOn: aBTS [
+        | gsm |
+        <category: '*-BTS-Core'>
+        self channelNumber isPchAgch
+            ifFalse: [^self error: 'Can only handle assignment on PCH/AGCH'].
+
+        "Skip the L2 Pseudo length"
+        gsm := OsmoGSM.GSM48MSG decode:
+                  (self fullL3Info readStream skip: 1; yourself).
+        gsm requestReference ra printNl.
+    ]
 ]
 
 Object subclass: BTS [

fakebts/RSLMsg.st

@@ -719,6 +719,11 @@ RSLMessageBase subclass: RSLCommonChannelManagement [
         <category: 'creation'>
         channel_number := aNumber
     ]
+
+    channelNumber [
+        <category: 'accessing'>
+        ^ channel_number
+    ]
 ]
 
 RSLCommonChannelManagement subclass: RSLChannelRequired [