refactor!: clippy and idiomatic Rust compliance

- Add clippy and Rust idiom lint attributes
- Refactor code for clippy::pedantic and idiomatic style
- Replace unwrap() with infallible constructors where possible
- Improve error handling and documentation
- Use assert! instead of panic! for invariants
- Prefer From over Into for conversions
- Update examples and tests for new API
- Remove unused imports and code
- Add Default implementation for Responder

Author: roderickvd

examples/register.rs

@@ -3,13 +3,8 @@ pub fn main() {
     builder.parse_filters("libmdns=debug");
     builder.init();
 
-    let responder = libmdns::Responder::new().unwrap();
-    let _svc = responder.register(
-        "_http._tcp".to_owned(),
-        "libmdns Web Server".to_owned(),
-        80,
-        &["path=/"],
-    );
+    let responder = libmdns::Responder::new();
+    let _svc = responder.register("_http._tcp", "libmdns Web Server", 80, &["path=/"]);
 
     loop {
         ::std::thread::sleep(::std::time::Duration::from_secs(10));

examples/register_with_ip_list.rs

@@ -10,12 +10,7 @@ pub fn main() {
     ];
 
     let responder = libmdns::Responder::new_with_ip_list(vec).unwrap();
-    let _svc = responder.register(
-        "_http._tcp".to_owned(),
-        "libmdns Web Server".to_owned(),
-        80,
-        &["path=/"],
-    );
+    let _svc = responder.register("_http._tcp", "libmdns Web Server", 80, &["path=/"]);
 
     loop {
         ::std::thread::sleep(::std::time::Duration::from_secs(10));

src/dns_parser/builder.rs

@@ -41,7 +41,7 @@ impl Builder<Questions> {
     pub fn new_query(id: u16, recursion: bool) -> Builder<Questions> {
         let mut buf = Vec::with_capacity(512);
         let head = Header {
-            id: id,
+            id,
             query: true,
             opcode: Opcode::StandardQuery,
             authoritative: false,
@@ -57,7 +57,7 @@ impl Builder<Questions> {
         buf.extend([0u8; 12].iter());
         head.write(&mut buf[..12]);
         Builder {
-            buf: buf,
+            buf,
             max_size: Some(512),
             _state: PhantomData,
         }
@@ -66,10 +66,10 @@ impl Builder<Questions> {
     pub fn new_response(id: u16, recursion: bool, authoritative: bool) -> Builder<Questions> {
         let mut buf = Vec::with_capacity(512);
         let head = Header {
-            id: id,
+            id,
             query: false,
             opcode: Opcode::StandardQuery,
-            authoritative: authoritative,
+            authoritative,
             truncated: false,
             recursion_desired: recursion,
             recursion_available: false,
@@ -82,15 +82,15 @@ impl Builder<Questions> {
         buf.extend([0u8; 12].iter());
         head.write(&mut buf[..12]);
         Builder {
-            buf: buf,
+            buf,
             max_size: Some(512),
             _state: PhantomData,
         }
     }
 }
 
 impl<T> Builder<T> {
-    fn write_rr(&mut self, name: &Name, cls: QueryClass, ttl: u32, data: &RRData) {
+    fn write_rr(&mut self, name: &Name<'_>, cls: QueryClass, ttl: u32, data: &RRData<'_>) {
         name.write_to(&mut self.buf).unwrap();
         self.buf.write_u16::<BigEndian>(data.typ() as u16).unwrap();
         self.buf.write_u16::<BigEndian>(cls as u16).unwrap();
@@ -103,6 +103,12 @@ impl<T> Builder<T> {
         data.write_to(&mut self.buf).unwrap();
         let data_size = self.buf.len() - data_offset;
 
+        assert!(
+            (data_offset <= 65535),
+            "{} is too long to write to a RR record",
+            data_offset
+        );
+        #[allow(clippy::cast_possible_truncation)]
         BigEndian::write_u16(
             &mut self.buf[size_offset..size_offset + 2],
             data_size as u16,
@@ -166,7 +172,7 @@ impl<T: MoveTo<Questions>> Builder<T> {
     #[allow(dead_code)]
     pub fn add_question(
         self,
-        qname: &Name,
+        qname: &Name<'_>,
         qtype: QueryType,
         qclass: QueryClass,
     ) -> Builder<Questions> {
@@ -183,10 +189,10 @@ impl<T: MoveTo<Questions>> Builder<T> {
 impl<T: MoveTo<Answers>> Builder<T> {
     pub fn add_answer(
         self,
-        name: &Name,
+        name: &Name<'_>,
         cls: QueryClass,
         ttl: u32,
-        data: &RRData,
+        data: &RRData<'_>,
     ) -> Builder<Answers> {
         let mut builder = self.move_to::<Answers>();
 
@@ -201,10 +207,10 @@ impl<T: MoveTo<Nameservers>> Builder<T> {
     #[allow(dead_code)]
     pub fn add_nameserver(
         self,
-        name: &Name,
+        name: &Name<'_>,
         cls: QueryClass,
         ttl: u32,
-        data: &RRData,
+        data: &RRData<'_>,
     ) -> Builder<Nameservers> {
         let mut builder = self.move_to::<Nameservers>();
 
@@ -219,10 +225,10 @@ impl Builder<Additional> {
     #[allow(dead_code)]
     pub fn add_additional(
         self,
-        name: &Name,
+        name: &Name<'_>,
         cls: QueryClass,
         ttl: u32,
-        data: &RRData,
+        data: &RRData<'_>,
     ) -> Builder<Additional> {
         let mut builder = self.move_to::<Additional>();
 
@@ -243,7 +249,7 @@ mod test {
     #[test]
     fn build_query() {
         let mut bld = Builder::new_query(1573, true);
-        let name = Name::from_str("example.com").unwrap();
+        let name = Name::from_str("example.com");
         bld = bld.add_question(&name, QT::A, QC::IN);
         let result = b"\x06%\x01\x00\x00\x01\x00\x00\x00\x00\x00\x00\
                       \x07example\x03com\x00\x00\x01\x00\x01";
@@ -253,7 +259,7 @@ mod test {
     #[test]
     fn build_srv_query() {
         let mut bld = Builder::new_query(23513, true);
-        let name = Name::from_str("_xmpp-server._tcp.gmail.com").unwrap();
+        let name = Name::from_str("_xmpp-server._tcp.gmail.com");
         bld = bld.add_question(&name, QT::SRV, QC::IN);
         let result = b"[\xd9\x01\x00\x00\x01\x00\x00\x00\x00\x00\x00\
             \x0c_xmpp-server\x04_tcp\x05gmail\x03com\x00\x00!\x00\x01";

src/dns_parser/enums.rs

@@ -4,6 +4,7 @@ use super::Error;
 ///
 /// All "EXPERIMENTAL" markers here are from the RFC
 #[derive(Debug, PartialEq, Eq, Clone, Copy, Hash)]
+#[allow(clippy::upper_case_acronyms)]
 pub enum Type {
     /// a host addresss
     A = 1,
@@ -55,6 +56,7 @@ pub enum Type {
 ///
 /// All "EXPERIMENTAL" markers here are from the RFC
 #[derive(Debug, PartialEq, Eq, Clone, Copy, Hash)]
+#[allow(clippy::upper_case_acronyms)]
 pub enum QueryType {
     /// a host addresss
     A = 1,
@@ -153,7 +155,7 @@ pub enum ResponseCode {
 
 impl From<u16> for Opcode {
     fn from(code: u16) -> Opcode {
-        use self::Opcode::*;
+        use self::Opcode::{InverseQuery, Reserved, ServerStatusRequest, StandardQuery};
         match code {
             0 => StandardQuery,
             1 => InverseQuery,
@@ -162,10 +164,10 @@ impl From<u16> for Opcode {
         }
     }
 }
-impl Into<u16> for Opcode {
-    fn into(self) -> u16 {
-        use self::Opcode::*;
-        match self {
+impl From<Opcode> for u16 {
+    fn from(val: Opcode) -> Self {
+        use self::Opcode::{InverseQuery, Reserved, ServerStatusRequest, StandardQuery};
+        match val {
             StandardQuery => 0,
             InverseQuery => 1,
             ServerStatusRequest => 2,
@@ -176,7 +178,9 @@ impl Into<u16> for Opcode {
 
 impl From<u8> for ResponseCode {
     fn from(code: u8) -> ResponseCode {
-        use self::ResponseCode::*;
+        use self::ResponseCode::{
+            FormatError, NameError, NoError, NotImplemented, Refused, Reserved, ServerFailure,
+        };
         match code {
             0 => NoError,
             1 => FormatError,
@@ -189,10 +193,12 @@ impl From<u8> for ResponseCode {
         }
     }
 }
-impl Into<u8> for ResponseCode {
-    fn into(self) -> u8 {
-        use self::ResponseCode::*;
-        match self {
+impl From<ResponseCode> for u8 {
+    fn from(val: ResponseCode) -> Self {
+        use self::ResponseCode::{
+            FormatError, NameError, NoError, NotImplemented, Refused, Reserved, ServerFailure,
+        };
+        match val {
             NoError => 0,
             FormatError => 1,
             ServerFailure => 2,
@@ -206,7 +212,10 @@ impl Into<u8> for ResponseCode {
 
 impl QueryType {
     pub fn parse(code: u16) -> Result<QueryType, Error> {
-        use self::QueryType::*;
+        use self::QueryType::{
+            All, A, AAAA, AXFR, CNAME, HINFO, MAILA, MAILB, MB, MF, MG, MINFO, MR, MX, NS, NULL,
+            PTR, SOA, SRV, TXT, WKS,
+        };
         match code {
             1 => Ok(A),
             2 => Ok(NS),
@@ -236,7 +245,7 @@ impl QueryType {
 
 impl QueryClass {
     pub fn parse(code: u16) -> Result<QueryClass, Error> {
-        use self::QueryClass::*;
+        use self::QueryClass::{Any, CH, CS, HS, IN};
         match code {
             1 => Ok(IN),
             2 => Ok(CS),
@@ -250,7 +259,10 @@ impl QueryClass {
 
 impl Type {
     pub fn parse(code: u16) -> Result<Type, Error> {
-        use self::Type::*;
+        use self::Type::{
+            A, AAAA, CNAME, DNSKEY, DS, HINFO, MB, MF, MG, MINFO, MR, MX, NS, NSEC, NULL, OPT, PTR,
+            RRSIG, SOA, SRV, TXT, WKS,
+        };
         match code {
             1 => Ok(A),
             2 => Ok(NS),
@@ -281,7 +293,7 @@ impl Type {
 
 impl Class {
     pub fn parse(code: u16) -> Result<Class, Error> {
-        use self::Class::*;
+        use self::Class::{CH, CS, HS, IN};
         match code {
             1 => Ok(IN),
             2 => Ok(CS),

src/dns_parser/error.rs

@@ -26,4 +26,6 @@ pub enum Error {
     LabelIsNotAscii,
     #[error("parser is in the wrong state")]
     WrongState,
+    #[error("label length exceeds maximum allowed size")]
+    LabelTooLong,
 }

src/dns_parser/header.rs

@@ -15,6 +15,7 @@ mod flag {
 
 /// Represents parsed header of the packet
 #[derive(Debug, PartialEq, Eq, Clone, Copy)]
+#[allow(clippy::struct_excessive_bools)]
 pub struct Header {
     pub id: u16,
     pub query: bool,
@@ -61,12 +62,10 @@ impl Header {
     ///
     /// When buffer size is not exactly 12 bytes
     pub fn write(&self, data: &mut [u8]) {
-        if data.len() != 12 {
-            panic!("Header size is exactly 12 bytes");
-        }
+        assert_eq!(data.len(), 12, "Header size is exactly 12 bytes");
         let mut flags = 0u16;
-        flags |= Into::<u16>::into(self.opcode) << flag::OPCODE_MASK.trailing_zeros();
-        flags |= Into::<u8>::into(self.response_code) as u16;
+        flags |= u16::from(self.opcode) << flag::OPCODE_MASK.trailing_zeros();
+        flags |= u16::from(u8::from(self.response_code));
         if !self.query {
             flags |= flag::QUERY;
         }

src/dns_parser/mod.rs

@@ -12,4 +12,4 @@ pub use self::header::Header;
 mod rrdata;
 pub use self::rrdata::RRData;
 mod builder;
-pub use self::builder::{Answers, Builder, Questions};
+pub use self::builder::{Answers, Builder};