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extern crate proc_macro;
use proc_macro::TokenStream;
use proc_macro2::Ident;
use quote::{format_ident, quote};
use syn::parse::{Parse, ParseStream};
use syn::{parse_macro_input, punctuated::Punctuated, DeriveInput, LitInt, Path, Token, Variant};
struct NameInfo {
struct_name: Ident,
struct_base: Ident,
struct_version: u16,
}
fn rsplit_once<'a>(s: &'a str, delimiter: char) -> Option<(&'a str, &'a str)> {
let split_pos = s.rfind(delimiter)?;
let a = &s[..split_pos];
let b = &s[(split_pos + 1)..];
Some((a, b))
}
impl NameInfo {
fn from_name(ident: &Ident) -> Self {
let struct_name = ident.clone();
let struct_name_string = struct_name.to_string();
let (struct_base, struct_version) = match rsplit_once(&struct_name_string, 'V') {
Some((base, version)) => {
if base.is_empty() {
panic!("failed to parse struct name");
}
let base = Ident::new(&base, ident.span());
let version: u16 = version.parse().expect("failed to parse struct version");
(base, version)
}
None => panic!("failed to parse struct name into base+version"),
};
NameInfo {
struct_name,
struct_base,
struct_version,
}
}
}
fn versioned_name(base: &Ident, version: u16) -> Ident {
let name = format!("{}V{}", base, version);
Ident::new(&name, base.span())
}
#[proc_macro_derive(Versioned)]
pub fn derive_versioned(input: TokenStream) -> TokenStream {
let input = parse_macro_input!(input as DeriveInput);
let NameInfo {
struct_name,
struct_base,
struct_version,
} = NameInfo::from_name(&input.ident);
let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
let expanded = quote! {
#[doc(hidden)]
#[allow(
non_upper_case_globals,
unused_attributes,
unused_qualifications,
non_camel_case_types,
non_snake_case
)]
const _: () = {
#[allow(rust_2018_idioms, clippy::useless_attribute)]
extern crate aversion as _aversion;
#[automatically_derived]
impl #impl_generics _aversion::Versioned
for #struct_name #ty_generics #where_clause {
const VER: u16 = #struct_version;
type Base = #struct_base;
}
};
};
expanded.into()
}
#[proc_macro_derive(UpgradeLatest)]
pub fn derive_upgrade_latest(input: TokenStream) -> TokenStream {
let input = parse_macro_input!(input as DeriveInput);
let NameInfo {
struct_name,
struct_base,
struct_version,
} = NameInfo::from_name(&input.ident);
let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
let all_versions = (1..=struct_version)
.into_iter()
.map(|ii| (ii, versioned_name(&struct_base, ii)))
.collect::<Vec<_>>();
let read_message_arms = all_versions
.iter()
.map(|(v, n)| quote_read_message_arm(*v, n, &struct_name));
let all_hops = (1..struct_version - 1)
.into_iter()
.map(|ii| quote_from_version_hop(&struct_base, ii, struct_version))
.collect::<Vec<_>>();
let expanded = quote! {
#[doc(hidden)]
#[allow(
non_upper_case_globals,
unused_attributes,
unused_qualifications,
non_camel_case_types,
non_snake_case
)]
const _: () = {
#[allow(rust_2018_idioms, clippy::useless_attribute)]
extern crate aversion as _aversion;
#[automatically_derived]
impl #impl_generics _aversion::group::UpgradeLatest
for #struct_name #ty_generics #where_clause {
fn upgrade_latest<Src>(src: &mut Src, header: Src::Header) -> ::std::result::Result<Self, Src::Error>
where
Src: _aversion::group::DataSource,
{
use _aversion::group::GroupHeader;
let ver = header.msg_ver();
match ver {
#(#read_message_arms)*
_ => Err(src.unknown_version::<#struct_base>(ver)),
}
}
}
#(#all_hops)*
};
};
expanded.into()
}
fn quote_read_message_arm(
version: u16,
versioned_name: &Ident,
target_name: &Ident,
) -> proc_macro2::TokenStream {
quote! {
#version => {
let msg = src.read_message::<#versioned_name>(&header)?;
let upgraded = <#target_name as _aversion::FromVersion::<#versioned_name>>::from_version(msg);
Ok(upgraded)
}
}
}
fn quote_from_version_hop(base: &Ident, lo: u16, hi: u16) -> proc_macro2::TokenStream {
assert!(hi > lo);
if hi - lo < 2 {
return quote! {};
}
fn tmp_ident(x: u16) -> Ident {
format_ident!("v{}", x)
}
let upgrade_chain = (lo..hi)
.into_iter()
.map(|ii| {
let jj = ii + 1;
let tmp_ii = tmp_ident(ii);
let tmp_jj = tmp_ident(jj);
let ident_jj = versioned_name(base, jj);
quote! {
let #tmp_jj = #ident_jj::from_version(#tmp_ii);
}
})
.collect::<Vec<_>>();
let lo_ident = versioned_name(base, lo);
let hi_ident = versioned_name(base, hi);
let lo_tmp = tmp_ident(lo);
let hi_tmp = tmp_ident(hi);
quote! {
impl FromVersion<#lo_ident> for #hi_ident {
fn from_version(#lo_tmp: #lo_ident) -> Self {
#(#upgrade_chain)*
#hi_tmp
}
}
}
}
#[proc_macro_derive(GroupDeserialize)]
pub fn derive_group_deserialize(input: TokenStream) -> TokenStream {
let input = parse_macro_input!(input as DeriveInput);
let enum_name = &input.ident;
let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
let source_struct = input.data;
let variants = if let syn::Data::Enum(syn::DataEnum { variants, .. }) = source_struct {
variants
} else {
panic!("couldn't find enum variants");
};
let match_arms = variants
.iter()
.map(|v| {
let gv = GroupVariant::from_enum_variant(v);
gv.to_match_arm(enum_name)
})
.collect::<Vec<_>>();
let expanded = quote! {
#[doc(hidden)]
#[allow(
non_upper_case_globals,
unused_attributes,
unused_qualifications,
non_camel_case_types,
non_snake_case
)]
const _: () = {
#[allow(rust_2018_idioms, clippy::useless_attribute)]
extern crate aversion as _aversion;
#[automatically_derived]
impl #impl_generics _aversion::GroupDeserialize
for #enum_name #ty_generics #where_clause {
fn read_message<Src>(src: &mut Src) -> ::std::result::Result<Self, Src::Error>
where
Src: _aversion::group::DataSource,
{
use _aversion::{MessageId, group::{GroupHeader, UpgradeLatest}};
let header = src.read_header()?;
match header.msg_id() {
#(#match_arms)*
_ => {
Err(src.unknown_message(header.msg_id()))
}
}
}
}
};
};
expanded.into()
}
#[derive(Debug)]
struct GroupVariant {
name: Ident,
target: Path,
}
impl GroupVariant {
fn from_enum_variant(variant: &Variant) -> GroupVariant {
let name = variant.ident.clone();
let mut target_path: Option<Path> = None;
if let syn::Fields::Unnamed(syn::FieldsUnnamed {
unnamed: variant_fields,
..
}) = &variant.fields
{
if variant_fields.len() != 1 {
panic!("enum must contain exactly 1 field");
}
let field = variant_fields.first().unwrap();
if let syn::Type::Path(syn::TypePath { path, .. }) = &field.ty {
target_path = Some(path.clone());
}
}
let target = target_path
.unwrap_or_else(|| panic!("failed to extract enum target path for {}", name));
GroupVariant { name, target }
}
fn to_match_arm(&self, enum_name: &Ident) -> proc_macro2::TokenStream {
let enum_variant = &self.name;
let struct_name = &self.target;
quote! {
#struct_name::MSG_ID => {
let msg = #struct_name::upgrade_latest(src, header)?;
Ok(#enum_name::#enum_variant(msg))
}
}
}
}
#[proc_macro]
pub fn assign_message_ids(tokens: TokenStream) -> TokenStream {
let id_list = parse_macro_input!(tokens as MessageIdList);
let id_impls = id_list.to_impl();
let expanded = quote! {
#[doc(hidden)]
#[allow(
non_upper_case_globals,
unused_attributes,
unused_qualifications,
non_camel_case_types,
non_snake_case
)]
const _: () = {
#[allow(rust_2018_idioms, clippy::useless_attribute)]
extern crate aversion as _aversion;
#id_impls
};
};
expanded.into()
}
#[derive(Debug, Default)]
struct MessageIdList {
list: Vec<MessageIdValue>,
}
#[derive(Debug)]
struct MessageIdValue {
name: Path,
msg_id: LitInt,
}
impl Parse for MessageIdValue {
fn parse(input: ParseStream) -> syn::parse::Result<Self> {
let name: Path = input.parse()?;
input.parse::<Token![:]>()?;
let msg_id: LitInt = input.parse()?;
Ok(MessageIdValue { name, msg_id })
}
}
impl Parse for MessageIdList {
fn parse(input: ParseStream) -> syn::parse::Result<Self> {
type IdList = Punctuated<MessageIdValue, Token![,]>;
let id_list = IdList::parse_terminated(input)?;
Ok(MessageIdList {
list: id_list.into_iter().collect(),
})
}
}
impl MessageIdList {
fn to_impl(&self) -> proc_macro2::TokenStream {
let mut tokens = proc_macro2::TokenStream::new();
for id_val in &self.list {
tokens.extend(id_val.to_impl())
}
tokens
}
}
impl MessageIdValue {
fn to_impl(&self) -> proc_macro2::TokenStream {
let name = &self.name;
let msg_id = &self.msg_id;
quote! {
#[automatically_derived]
impl _aversion::MessageId for #name {
const MSG_ID: u16 = #msg_id;
}
}
}
}