- a few additional MIB tree management methods added to MibViewController

  to better address ordered nature of MIB tree nodes (namely, getFirst*,
  getLast* family of methods)
- rfc1902.ObjectIdentity() now accepts 'last' keyword parameter to
  position on last (otherwise, first) object in given MIB module.

3 files changed, 39 insertions, 9 deletions

diff --git a/CHANGES b/CHANGES
index a14a4cb..0fcf308 100644
--- a/CHANGES
+++ b/CHANGES
@@ -101,6 +101,9 @@ Revision 4.2.6
   than using them instead of its default core MIBs.
 - Removed RowStatus default value as it may collide with possible subclass
   constraints.
+- A few additional MIB tree management methods added to MibViewController
+  to better address ordered nature of MIB tree nodes (namely, getFirst*,
+  getLast* family of methods).
 - Fix to authoritative engine side snmpEngineID discovery procedure: 
   respond with notInTimeWindows rather then with unsupportedSecurityLevel
   at time synchronization phase.
diff --git a/pysnmp/smi/rfc1902.py b/pysnmp/smi/rfc1902.py
index 75fa7b9..8e5f905 100644
--- a/pysnmp/smi/rfc1902.py
+++ b/pysnmp/smi/rfc1902.py
@@ -21,8 +21,9 @@ from pysnmp import debug
 class ObjectIdentity:
     stDirty, stClean = 1, 2
         
-    def __init__(self, *args):
+    def __init__(self, *args, **kwargs):
         self.__args = args
+        self.__kwargs = kwargs
         self.__mibSourcesToAdd = self.__modNamesToLoad = None
         self.__asn1SourcesToAdd = None
         self.__state  = self.stDirty
@@ -179,7 +180,10 @@ class ObjectIdentity:
                 self.__symName = self.__args[1]
             else:
                 mibViewController.mibBuilder.loadModules(self.__modName)
-                oid, _, _ = mibViewController.getFirstNodeName(self.__modName)
+                if self.__kwargs.get('last'):
+                    oid,_,_ = mibViewController.getLastNodeName(self.__modName)
+                else:
+                    oid,_,_ = mibViewController.getFirstNodeName(self.__modName)
                 _, self.__symName, _ = mibViewController.getNodeLocation(oid)
 
             mibNode, = mibViewController.mibBuilder.importSymbols(
diff --git a/pysnmp/smi/view.py b/pysnmp/smi/view.py
index f7f6118..61ea964 100644
--- a/pysnmp/smi/view.py
+++ b/pysnmp/smi/view.py
@@ -142,13 +142,19 @@ class MibViewController:
 
     # Module management
     
-    def getFirstModuleName(self):
+    def getOrderedModuleName(self, index):
         self.indexMib()
         modNames = self.__mibSymbolsIdx.keys()
         if modNames:
-            return modNames[0]
+            return modNames[index]
         raise error.SmiError('No modules loaded at %s' % self)
 
+    def getFirstModuleName(self):
+        return self.getOrderedModuleName(0)
+
+    def getLastModuleName(self):
+        return self.getOrderedModuleName(-1)
+
     def getNextModuleName(self, modName):
         self.indexMib()
         try:
@@ -234,7 +240,7 @@ class MibViewController:
                     oid + suffix + nodeName[1:], modName
                     )
         
-    def getFirstNodeName(self, modName=''):
+    def getOrderedNodeName(self, index, modName=''):
         self.indexMib()
         if modName in self.__mibSymbolsIdx:
             mibMod = self.__mibSymbolsIdx[modName]
@@ -245,10 +251,21 @@ class MibViewController:
         if not mibMod['oidToLabelIdx']:
             raise error.NoSuchObjectError(
                 str='No variables at MIB module %s at %s' % (modName, self)
-                )
-        oid, label = mibMod['oidToLabelIdx'].items()[0]
+            )
+        try:
+            oid, label = mibMod['oidToLabelIdx'].items()[index]
+        except KeyError:
+            raise error.NoSuchObjectError(
+                str='No symbol at position %s in MIB module %s at %s' % (index, modName, self)
+            )
         return oid, label, ()
+
+    def getFirstNodeName(self, modName=''):
+        return self.getOrderedNodeName(0, modName)
         
+    def getLastNodeName(self, modName=''):
+        return self.getOrderedNodeName(-1, modName)
+
     def getNextNodeName(self, nodeName, modName=''):
         oid, label, suffix = self.getNodeName(nodeName, modName)
         try:
@@ -291,7 +308,7 @@ class MibViewController:
                 )
         return m, typeName
         
-    def getFirstTypeName(self, modName=''):
+    def getOrderedTypeName(self, index, modName=''):
         self.indexMib()
         if modName in self.__mibSymbolsIdx:
             mibMod = self.__mibSymbolsIdx[modName]
@@ -303,9 +320,15 @@ class MibViewController:
             raise error.NoSuchObjectError(
                 str='No types at MIB module %s at %s' % (modName, self)
                 )
-        t = mibMod['typeToModIdx'].keys()[0]
+        t = mibMod['typeToModIdx'].keys()[index]
         return mibMod['typeToModIdx'][t], t
         
+    def getFirstTypeName(self, modName=''):
+        return self.getOrderedTypeName(0, modName)
+
+    def getLastTypeName(self, modName=''):
+        return self.getOrderedTypeName(-1, modName)
+        
     def getNextType(self, typeName, modName=''):
         m, t = self.getTypeName(typeName, modName)
         try: