added some SNMP app-specific types and cleaned up some BER-encoding problems

with integers.

Author: blackhedd

lib/net/ber.rb

@@ -364,31 +364,14 @@ class Fixnum
   # to_ber
   #
   def to_ber
-    # originally used pack("w") which is WRONG.
-    #i = [self].pack('w')
-
-    # PLEASE optimize this code path. It's awfully ugly and probably slow.
-    # It also doesn't understand negative numbers yet.
-    raise Net::BER::BerError.new( "range error in fixnum" ) unless self >= 0
-    z = [self].pack("N")
-    zlen = if self < 0x80
-	1
-    elsif self < 0x8000
-	2
-    elsif self < 0x800000
-	3
-    else
-	4
-    end
-    [2, zlen].pack("CC") + z[0-zlen,zlen]
+    "\002" + to_ber_internal
   end
 
   #
   # to_ber_enumerated
   #
   def to_ber_enumerated
-    i = [self].pack('w')
-    [10, i.length].pack("CC") + i
+    "\012" + to_ber_internal
   end
 
   #
@@ -403,6 +386,34 @@ def to_ber_length_encoding
     end
   end
 
+  # Generate a BER-encoding for an application-defined INTEGER.
+  # Example: SNMP's Counter, Gauge, and TimeTick types.
+  #
+  def to_ber_application tag
+      [0x40 + tag].pack("C") + to_ber_internal
+  end
+
+  #--
+  # Called internally to BER-encode the length and content bytes of a Fixnum.
+  # The caller will prepend the tag byte.
+  def to_ber_internal
+    # PLEASE optimize this code path. It's awfully ugly and probably slow.
+    # It also doesn't understand negative numbers yet.
+    raise Net::BER::BerError.new( "range error in fixnum" ) unless self >= 0
+    z = [self].pack("N")
+    zlen = if self < 0x80
+	1
+    elsif self < 0x8000
+	2
+    elsif self < 0x800000
+	3
+    else
+	4
+    end
+    [zlen].pack("C") + z[0-zlen,zlen]
+  end
+  private :to_ber_internal
+
 end # class Fixnum
 
 
@@ -416,6 +427,12 @@ def to_ber
     # Ruby represents Bignums as two's-complement numbers so we may actually be
     # good as far as representing negatives goes.
     # I'm sure this implementation can be improved performance-wise if necessary.
+    # Ruby's Bignum#size returns the number of bytes in the internal representation
+    # of the number, but it can and will include leading zero bytes on at least
+    # some implementations. Evidently Ruby stores these as sets of quadbytes.
+    # It's not illegal in BER to encode all of the leading zeroes but let's strip
+    # them out anyway.
+    #
     sz = self.size
     out = "\000" * sz
     (sz*8).times {|bit|
@@ -424,7 +441,11 @@ def to_ber
 	end
     }
 
-    [2, sz].pack("CC") + out.reverse
+    while out.length > 1 and out[-1] == 0
+	out.slice!(-1,1)
+    end
+
+    [2, out.length].pack("CC") + out.reverse
   end
 
 end

lib/net/snmp.rb

@@ -36,6 +36,9 @@ class SNMP
 	AsnSyntax = BER.compile_syntax({
 	    :application => {
 		:primitive => {
+		    1 => :integer,	# Counter32, (RFC1155 sec 6)
+		    2 => :integer,	# Gauge32, (RFC1155 sec 6)
+		    3 => :integer	# TimeTicks32, (RFC1155 sec 6)
 		},
 		:constructed => {
 		}
@@ -51,6 +54,42 @@ class SNMP
 	    }
 	})
 
+	# SNMP 32-bit counter.
+	# Defined in RFC1155 (Structure of Mangement Information), section 6.
+	# A 32-bit counter is an ASN.1 application [1] implicit unsigned integer
+	# with a range from 0 to 2^^32 - 1.
+	class Counter32
+	    def initialize value
+		@value = value
+	    end
+	    def to_ber
+		@value.to_ber_application(1)
+	    end
+	end
+
+	# SNMP 32-bit gauge.
+	# Defined in RFC1155 (Structure of Mangement Information), section 6.
+	# A 32-bit counter is an ASN.1 application [2] implicit unsigned integer.
+	class Gauge32
+	    def initialize value
+		@value = value
+	    end
+	    def to_ber
+		@value.to_ber_application(2)
+	    end
+	end
+
+	# SNMP 32-bit timer-ticks.
+	# Defined in RFC1155 (Structure of Mangement Information), section 6.
+	# A 32-bit counter is an ASN.1 application [3] implicit unsigned integer.
+	class TimerTicks32
+	    def initialize value
+		@value = value
+	    end
+	    def to_ber
+		@value.to_ber_application(3)
+	    end
+	end
     end
 
     class SnmpPdu

tests/testber.rb

@@ -18,9 +18,9 @@ def setup
   # 5000000000 is a Bignum, which hits different code.
   def test_ber_integers
     assert_equal( "\002\001\005", 5.to_ber )
-    assert_equal( "\002\002\203t", 500.to_ber )
-    assert_equal( "\002\003\203\206P", 50000.to_ber )
-    assert_equal( "\002\005\222\320\227\344\000", 5000000000.to_ber )
+    assert_equal( "\002\002\001\364", 500.to_ber )
+    assert_equal( "\002\003\0\303P", 50000.to_ber )
+    assert_equal( "\002\005\001*\005\362\000", 5000000000.to_ber )
   end
 
   def test_ber_bignums

tests/testsnmp.rb

@@ -113,6 +113,15 @@ def test_make_bad_response
       # Not specifying variables doesn't create an error. (Maybe it should?)
   end
 
+  def test_snmp_integers
+      c32 = Net::SNMP::Counter32.new(100)
+      assert_equal( "A\001d", c32.to_ber )
+      g32 = Net::SNMP::Gauge32.new(100)
+      assert_equal( "B\001d", g32.to_ber )
+      t32 = Net::SNMP::TimerTicks32.new(100)
+      assert_equal( "C\001d", t32.to_ber )
+  end
+
 end