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//! Types and code for describing our type-based dispatch system.
use std::collections::{BTreeMap, BTreeSet};
use serde::Serialize;
use crate::{method::method_info_by_typeid, MethodInfo_, NoUpdates};
/// A table describing, for a single RPC method,
/// which types it expects and returns, and which objects it applies to.
///
/// This is, for now, a serialize-only type; it does nothing else.
/// See [`RpcDispatchInformation`] for caveats about type names.
#[derive(Serialize, Debug, Clone)]
struct MethodDescription {
/// The type representing an invocation of this method.
/// Its fields are the method's parameters.
method_type: String,
/// The type that this method returns on successful completion.
output_type: String,
/// The type (if any) that this method delivers as an incremental status update.
update_type: Option<String>,
/// A list of the types of Objects that this method can be applied to.
applies_to_object_types: BTreeSet<String>,
}
/// A table describing the the set of RPC methods available,
/// which types they expect and return, and which objects they apply to.
/// All "type names" in this object refer to a Rust type in Arti.
/// These Rust types are mainly useful for finding the relevant types
/// in the generated Arti documentation.
/// They are not guaranteed to be stable across Arti versions:
/// for example, we might rename a type, or put it in a different module or crate.
/// They are not guaranteed to be stable across Rust versions:
/// see the caveats in [`std::any::type_name`].
pub struct RpcDispatchInformation {
/// A map from RPC method name (such as "arti:foo") to a description of that method.
methods: BTreeMap<String, MethodDescription>,
/// A map from an object type to a list of the types that object can delegate to.
delegations: BTreeMap<String, BTreeSet<String>>,
impl super::DispatchTable {
/// Return a description for all of the RPC methods available,
/// Currently, the resulting object is good for nothing but serialization.
pub fn dispatch_information(&self) -> RpcDispatchInformation {
let mut methods = BTreeMap::new();
for invoker_ent in self.map.values() {
let Some(method_info) = method_info_by_typeid(invoker_ent.invoker.method_type()) else {
continue; // This isn't an RpcMethod.
};
let rpc_method_name = method_info.method_name.to_owned();
let (object_type_name, method_type_name) =
invoker_ent.invoker.object_and_method_type_names();
let description = methods
.entry(rpc_method_name)
.or_insert_with(|| MethodDescription::new(method_type_name, method_info));
description.push_object_type(object_type_name);
let mut delegations = BTreeMap::new();
for note in inventory::iter::<DelegationNote>() {
let set = delegations
.entry((note.from_type_name)().to_string())
.or_insert_with(BTreeSet::new);
set.insert((note.to_type_name)().to_string());
RpcDispatchInformation {
methods,
delegations,
impl MethodDescription {
/// Construct a new `MethodDescription`.
fn new(method_type_name: &str, info: &MethodInfo_) -> Self {
let method_type_name = method_type_name.to_owned();
let output_type_name = (info.output_name)().to_owned();
let update_type_name = {
let name = (info.update_name)();
if name == std::any::type_name::<NoUpdates>() {
None
} else {
Some(name.to_owned())
MethodDescription {
method_type: method_type_name,
output_type: output_type_name,
update_type: update_type_name,
applies_to_object_types: Default::default(),
/// Add `object_type_name` to the list of object types this method applies to.
fn push_object_type(&mut self, object_type_name: &str) {
self.applies_to_object_types
.insert(object_type_name.to_owned());
/// Helper to implement RpcDispatchInformation.
#[derive(Debug)]
#[doc(hidden)]
#[allow(clippy::exhaustive_structs)]
pub struct DelegationNote {
/// Name of the type we're delegating from.
/// (We use a fn() here since std::any::type_name isn't yet const.)
pub from_type_name: fn() -> &'static str,
/// Name of the type we're delegating to.
pub to_type_name: fn() -> &'static str,
inventory::collect!(DelegationNote);
/// Helper: Declare that `$from_type` (which must implement `Object`)
/// can delegate to `$to_type` (which also must implement `Object`).
/// This declaration is used only to help implement `RpcDispatchInformation`.
#[macro_export]
macro_rules! register_delegation_note {
{ $from_type:ty, $to_type:ty } => {
$crate::inventory::submit!{$crate::DelegationNote {
from_type_name: std::any::type_name::<$from_type>,
to_type_name: std::any::type_name::<$to_type>,
}}