Introduce a new base module

Cargo.toml

@@ -1,3 +1,7 @@
+[workspace]
+resolver = "2"
+members = [".", "./macros"]
+
 [package]
 name = "domain"
 version = "0.10.3"
@@ -16,11 +20,9 @@ readme = "README.md"
 keywords = ["DNS", "domain"]
 license = "BSD-3-Clause"
 
-[lib]
-name = "domain"
-path = "src/lib.rs"
-
 [dependencies]
+domain-macros  = { path = "./macros", version = "0.10.3" }
+
 arbitrary      = { version = "1.4.1", optional = true, features = ["derive"] }
 octseq         = { version = "0.5.2", default-features = false }
 time           = { version = "0.3.1", default-features = false }
@@ -48,6 +50,12 @@ tokio-stream   = { version = "0.1.1", optional = true }
 tracing        = { version = "0.1.40", optional = true }
 tracing-subscriber = { version = "0.3.18", optional = true, features = ["env-filter"] }
 
+# 'zerocopy' provides simple derives for converting types to and from byte
+# representations, along with network-endian integer primitives.  These are
+# used to define simple elements of DNS messages and their serialization.
+zerocopy = "0.8.5"
+zerocopy-derive = "0.8.5"
+
 [features]
 default     = ["std", "rand"]
 

macros/Cargo.toml

@@ -0,0 +1,28 @@
+[package]
+name = "domain-macros"
+
+# Copied from 'domain'.
+version = "0.10.3"
+rust-version = "1.68.2"
+edition = "2021"
+
+authors = ["NLnet Labs <[email protected]>"]
+description = "Procedural macros for the `domain` crate."
+documentation = "https://docs.rs/domain-macros"
+homepage = "https://github.com/nlnetlabs/domain/"
+repository = "https://github.com/nlnetlabs/domain/"
+keywords = ["DNS", "domain"]
+license = "BSD-3-Clause"
+
+[lib]
+proc-macro = true
+
+[dependencies.proc-macro2]
+version = "1.0"
+
+[dependencies.syn]
+version = "2.0"
+features = ["visit"]
+
+[dependencies.quote]
+version = "1.0"

macros/src/data.rs

@@ -0,0 +1,159 @@
+//! Working with structs, enums, and unions.
+
+use std::ops::Deref;
+
+use proc_macro2::TokenStream;
+use quote::{quote, ToTokens};
+use syn::{spanned::Spanned, *};
+
+//----------- Struct ---------------------------------------------------------
+
+/// A defined 'struct'.
+pub struct Struct {
+    /// The identifier for this 'struct'.
+    ident: Ident,
+
+    /// The fields in this 'struct'.
+    fields: Fields,
+}
+
+impl Struct {
+    /// Construct a [`Struct`] for a 'Self'.
+    pub fn new_as_self(fields: &Fields) -> Self {
+        Self {
+            ident: <Token![Self]>::default().into(),
+            fields: fields.clone(),
+        }
+    }
+
+    /// Whether this 'struct' has no fields.
+    pub fn is_empty(&self) -> bool {
+        self.fields.is_empty()
+    }
+
+    /// The number of fields in this 'struct'.
+    pub fn num_fields(&self) -> usize {
+        self.fields.len()
+    }
+
+    /// The fields of this 'struct'.
+    pub fn fields(&self) -> impl Iterator<Item = &Field> + '_ {
+        self.fields.iter()
+    }
+
+    /// The sized fields of this 'struct'.
+    pub fn sized_fields(&self) -> impl Iterator<Item = &Field> + '_ {
+        self.fields().take(self.num_fields() - 1)
+    }
+
+    /// The unsized field of this 'struct'.
+    pub fn unsized_field(&self) -> Option<&Field> {
+        self.fields.iter().next_back()
+    }
+
+    /// The names of the fields of this 'struct'.
+    pub fn members(&self) -> impl Iterator<Item = Member> + '_ {
+        self.fields
+            .iter()
+            .enumerate()
+            .map(|(i, f)| make_member(i, f))
+    }
+
+    /// The names of the sized fields of this 'struct'.
+    pub fn sized_members(&self) -> impl Iterator<Item = Member> + '_ {
+        self.members().take(self.num_fields() - 1)
+    }
+
+    /// The name of the last field of this 'struct'.
+    pub fn unsized_member(&self) -> Option<Member> {
+        self.fields
+            .iter()
+            .next_back()
+            .map(|f| make_member(self.num_fields() - 1, f))
+    }
+
+    /// Construct a builder for this 'struct'.
+    pub fn builder<F: Fn(Member) -> Ident>(
+        &self,
+        f: F,
+    ) -> StructBuilder<'_, F> {
+        StructBuilder {
+            target: self,
+            var_fn: f,
+        }
+    }
+}
+
+/// Construct a [`Member`] from a field and index.
+fn make_member(index: usize, field: &Field) -> Member {
+    match &field.ident {
+        Some(ident) => Member::Named(ident.clone()),
+        None => Member::Unnamed(Index {
+            index: index as u32,
+            span: field.ty.span(),
+        }),
+    }
+}
+
+//----------- StructBuilder --------------------------------------------------
+
+/// A means of constructing a 'struct'.
+pub struct StructBuilder<'a, F: Fn(Member) -> Ident> {
+    /// The 'struct' being constructed.
+    target: &'a Struct,
+
+    /// A map from field names to constructing variables.
+    var_fn: F,
+}
+
+impl<F: Fn(Member) -> Ident> StructBuilder<'_, F> {
+    /// The initializing variables for this 'struct'.
+    pub fn init_vars(&self) -> impl Iterator<Item = Ident> + '_ {
+        self.members().map(&self.var_fn)
+    }
+
+    /// The names of the sized fields of this 'struct'.
+    pub fn sized_init_vars(&self) -> impl Iterator<Item = Ident> + '_ {
+        self.sized_members().map(&self.var_fn)
+    }
+
+    /// The name of the last field of this 'struct'.
+    pub fn unsized_init_var(&self) -> Option<Ident> {
+        self.unsized_member().map(&self.var_fn)
+    }
+}
+
+impl<F: Fn(Member) -> Ident> Deref for StructBuilder<'_, F> {
+    type Target = Struct;
+
+    fn deref(&self) -> &Self::Target {
+        self.target
+    }
+}
+
+impl<F: Fn(Member) -> Ident> ToTokens for StructBuilder<'_, F> {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        let ident = &self.ident;
+        match self.fields {
+            Fields::Named(_) => {
+                let members = self.members();
+                let init_vars = self.init_vars();
+                quote! {
+                    #ident { #(#members: #init_vars),* }
+                }
+            }
+
+            Fields::Unnamed(_) => {
+                let init_vars = self.init_vars();
+                quote! {
+                    #ident ( #(#init_vars),* )
+                }
+            }
+
+            Fields::Unit => {
+                quote! { #ident }
+            }
+        }
+        .to_tokens(tokens);
+    }
+}