Fix case of tagged empty variable in Get request and add test

src/snmp.rs

@@ -284,6 +284,7 @@ fn parse_objectsyntax<'a>(i:&'a[u8]) -> IResult<&'a[u8],ObjectSyntax> {
                     _ => Err(Err::Error(error_position!(i, ErrorKind::Custom(DER_TAG_ERROR)))),
                 }
             } else {
+                        if hdr.len == 0 { return Ok((rem, ObjectSyntax::Empty)); }
                         map_res!(
                             rem,
                             apply!(der_read_element_content_as, hdr.tag, hdr.len as usize),

tests/v2c.rs

@@ -0,0 +1,54 @@
+#[macro_use] extern crate pretty_assertions;
+extern crate der_parser;
+extern crate snmp_parser;
+extern crate nom;
+
+use nom::IResult;
+use snmp_parser::*;
+use der_parser::oid::Oid;
+
+static SNMPV2_GET: &'static [u8] = include_bytes!("../assets/snmpv2c-get-response.bin");
+
+#[test]
+fn test_snmp_v2_get() {
+    let empty = &b""[..];
+    let bytes = SNMPV2_GET;
+    let expected = Ok((empty,SnmpMessage{
+        version: 1,
+        community: String::from("public"),
+        pdu:SnmpPdu::Generic(
+            SnmpGenericPdu{
+                pdu_type: PduType::Response,
+                req_id:97083662,
+                err:ErrorStatus(0),
+                err_index:0,
+                var:vec![
+                    SnmpVariable{
+                        oid: Oid::from(&[1, 3, 6, 1, 2, 1, 25, 1, 1, 0]),
+                        val: ObjectSyntax::Ticks(970069)
+                    },
+                    SnmpVariable{
+                        oid: Oid::from(&[1, 3, 6, 1, 2, 1, 25, 1, 5, 0]),
+                        val: ObjectSyntax::Gauge(3)
+                    },
+                    SnmpVariable{
+                        oid: Oid::from(&[1, 3, 6, 1, 2, 1, 25, 1, 5, 1]),
+                        val: ObjectSyntax::Empty
+                    }
+                ],
+            }),
+    }));
+    let res = parse_snmp_v1(&bytes);
+    match &res {
+        &Ok((_,ref r)) => {
+            // debug!("r: {:?}",r);
+            eprintln!("SNMP: v={}, c={:?}, pdu_type={:?}",r.version,r.community,r.pdu_type());
+            // debug!("PDU: type={}, {:?}", pdu_type, pdu_res);
+            for ref v in r.vars_iter() {
+                eprintln!("v: {:?}",v);
+            }
+        },
+        _ => (),
+    };
+    assert_eq!(res, expected);
+}