Expand description
§Cap’n Web Core Protocol
Core implementation of the Cap’n Web protocol, providing capability-based RPC with promise pipelining.
§Features
- Capability-based security: Unforgeable object references with fine-grained access control
- Promise pipelining: Chain dependent calls without waiting for intermediate results
- IL expression evaluation: Execute complex operations with the Intermediate Language
- Wire protocol compliance: Full compatibility with the official TypeScript implementation
§Quick Start
use capnweb_core::{CapId, RpcTarget, RpcError, Value};
use async_trait::async_trait;
use serde_json::json;
#[derive(Debug)]
struct Calculator;
#[async_trait]
impl RpcTarget for Calculator {
async fn call(&self, method: &str, args: Vec<Value>) -> Result<Value, RpcError> {
match method {
"add" => {
// Note: Value is from capnweb_core, not serde_json
// In a real implementation, you'd need to convert between types
Ok(Value::String("result".to_string()))
}
_ => Err(RpcError::not_found("method not found")),
}
}
async fn get_property(&self, _property: &str) -> Result<Value, RpcError> {
Err(RpcError::not_found("property access not implemented"))
}
}§Protocol Concepts
§Capabilities
Capabilities are unforgeable references to remote objects. They provide secure, fine-grained access control without ambient authority.
§Promise Pipelining
Calls can be chained on promises before they resolve, reducing round-trips:
ⓘ
let user = client.call(cap, "getUser", vec![user_id]);
let profile = client.pipeline(&user, vec!["profile"], "load", vec![]);§IL (Intermediate Language)
The IL allows expressing complex operations that execute on the server:
ⓘ
let expr = ILExpression::if_expr(
ILExpression::var(0),
ILExpression::literal(json!("authenticated")),
ILExpression::literal(json!("anonymous"))
);Re-exports§
pub use codec::decode_message;pub use codec::encode_message;pub use error::ErrorCode;pub use error::RpcError;pub use ids::CallId;pub use ids::CapId;pub use ids::PromiseId;pub use il::Op;pub use il::Plan;pub use il::Source;pub use il_executor::ILExecutor;pub use il_extended::ILContext;pub use il_extended::ILError;pub use il_extended::ILExpression;pub use il_extended::ILOperation;pub use il_extended::ILPlan;pub use msg::Message;pub use msg::Outcome;pub use msg::Target;pub use promise::ArgValue;pub use promise::ExtendedTarget;pub use promise::PendingPromise;pub use promise::PromiseDependencyGraph;pub use promise_map::MapOperation;pub use promise_map::PipelinedCall;pub use promise_map::PromiseMapExecutor;pub use protocol::capability_registry::CapabilityRegistry;pub use protocol::capability_registry::RegistrableCapability;pub use protocol::ids::ExportId;pub use protocol::ids::ImportId;pub use protocol::tables::ExportTable;pub use protocol::tables::ImportTable;pub use protocol::tables::Value;pub use protocol::wire::parse_wire_batch;pub use protocol::wire::serialize_wire_batch;pub use protocol::wire::PropertyKey;pub use protocol::wire::WireExpression;pub use protocol::wire::WireMessage;pub use protocol::expression::Expression;pub use protocol::message::Message as LegacyMessage;