Fix no_std. (#248)

Fixes various issues preventing building in a no-std environment.

Cargo.toml

@@ -17,11 +17,11 @@ name = "domain"
 path = "src/lib.rs"
 
 [dependencies]
-octseq         = "0.3"
-time           = "0.3.1"
+octseq         = { version = "0.3.2", default-features = false }
+time           = { version = "0.3.1", default-features = false }
 
 rand           = { version = "0.8", optional = true }
-bytes          = { version = "1.0", optional = true }
+bytes          = { version = "1.0", optional = true, default-features = false }
 chrono         = { version = "0.4.6", optional = true, default-features = false }
 futures-util   = { version = "0.3", optional = true }
 heapless       = { version = "0.7", optional = true }
@@ -46,7 +46,7 @@ resolv-sync = ["resolv", "tokio/rt"]
 serde       = ["dep:serde", "octseq/serde"]
 sign        = ["std"]
 smallvec    = ["dep:smallvec", "octseq/smallvec"]
-std         = []
+std         = ["bytes?/std", "octseq/std", "time/std"]
 tsig        = ["bytes", "ring", "smallvec"]
 validate    = ["std", "ring"]
 zonefile    = ["bytes", "std"]

src/base/wire.rs

@@ -46,6 +46,9 @@ impl Composer for bytes::BytesMut {}
 #[cfg(feature = "smallvec")]
 impl<A: smallvec::Array<Item = u8>> Composer for smallvec::SmallVec<A> {}
 
+#[cfg(feature = "heapless")]
+impl<const N: usize> Composer for heapless::Vec<u8, N> {}
+
 impl<T: Composer> Composer for &mut T {
     fn append_compressed_dname<N: ToDname + ?Sized>(
         &mut self,