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use std::any::Any; use std::boxed::Box; use std::marker::Send; use super::super::SpanReference; /// Tracer implementation's context details. /// /// An OpenTracing `SpanContext` is an abstraction that holds: /// /// * Baggage items: key-value pairs that are propagated though the trace. /// * Tracer specific details: such as the trace and span ids, flags, and other /// information that are needed by the concrete tracer (Zipkin, Jaeger, ...). /// /// OpenTracingRust splits this abstraction into two: /// /// * The `SpanContext` structure: holding all the common data. /// * The `ImplContext` trait: holding implementation details. /// /// Implementations of `ImplContext` are only used by implementations of the /// `TracerInterface` and are carried around by the `SpanContext`. /// They contain span and trace identifiers and `Tracer` specific metadata. /// /// # Examples /// /// ``` /// extern crate opentracingrust; /// /// use std::any::Any; /// use opentracingrust::ImplContext; /// use opentracingrust::SpanContext; /// use opentracingrust::SpanReference; /// /// /// pub struct SomeTracerContext { /// span_id: u64, /// trace_id: u64, /// } /// /// impl ImplContext for SomeTracerContext { /// fn impl_context(&self) -> &Any { /// self /// } /// /// fn clone(&self) -> Box<ImplContext> { /// Box::new(SomeTracerContext { /// span_id: self.span_id, /// trace_id: self.trace_id, /// }) /// } /// /// fn reference_span(&mut self, reference: &SpanReference) { /// match *reference { /// SpanReference::ChildOf(ref parent) | /// SpanReference::FollowsFrom(ref parent) => { /// let context = parent.impl_context::<SomeTracerContext>().unwrap(); /// self.trace_id = context.trace_id; /// } /// } /// } /// } /// /// fn main() { /// // ... snip ... /// /// let span_context = SpanContext::new(SomeTracerContext { /// span_id: 21, /// trace_id: 42, /// }); /// /// // ... snip ... /// } /// ``` pub trait ImplContext : Send { /// Allow runtime downcasting with the `Any` interface. /// /// `SpanContext`s store implementations `ImplContext`s using `Box`es. /// This method is used by the `SpanContext::impl_context` generic method /// to downcast the boxed `ImplContext` using the `std::any::Any` interface. fn impl_context(&self) -> &Any; /// Clones an `ImplContext` trait object into a new `ImplContext` trait object. fn clone(&self) -> Box<ImplContext>; /// Allows the `ImplContext` to add references. /// /// When a reference is added to a `SpanContext` this method will be called /// so that the tracer's `ImplContext` can update its internal references. fn reference_span(&mut self, reference: &SpanReference); } /// Utility structure to create `ImplContext`s. /// /// Generic structure that creates a wrapper around structures to make them /// compatible with `ImplContext` trait objects. /// /// The wrapped structure requires the following traits to be implemented: /// /// * `Any` /// * `Clone` /// * `Send` /// * `SpanReferenceAware` /// /// # Examples /// /// ``` /// extern crate opentracingrust; /// /// use opentracingrust::ImplContext; /// use opentracingrust::ImplContextBox; /// use opentracingrust::SpanReference; /// use opentracingrust::SpanReferenceAware; /// /// #[derive(Clone)] /// struct Context { /// // ... snip ... /// } /// /// impl SpanReferenceAware for Context { /// fn reference_span(&mut self, reference: &SpanReference) { /// // ... snip ... /// } /// } /// /// fn main() { /// let context: Box<ImplContext> = Box::new(ImplContextBox::new(Context{})); /// // ... snip ... /// } /// ``` pub struct ImplContextBox<T: Any + Clone + Send + SpanReferenceAware> { inner: T } impl<T: Any + Clone + Send + SpanReferenceAware> ImplContextBox<T> { /// Wrap a compatible value into a `ImplContextBox`. pub fn new(inner: T) -> ImplContextBox<T> { ImplContextBox { inner } } } impl<T: Any + Clone + Send + SpanReferenceAware> ImplContext for ImplContextBox<T> { fn impl_context(&self) -> &Any { &self.inner } fn clone(&self) -> Box<ImplContext> { Box::new(ImplContextBox { inner: self.inner.clone() }) } fn reference_span(&mut self, reference: &SpanReference) { self.inner.reference_span(reference); } } /// Trait for structures that want to be wrapped in `ImplContextBox`s. /// /// See `ImplContext` for more information. pub trait SpanReferenceAware { /// See `ImplContext::reference_span` fn reference_span(&mut self, reference: &SpanReference); } #[cfg(test)] mod tests { use super::super::super::SpanReference; use super::ImplContext; use super::ImplContextBox; use super::SpanReferenceAware; #[derive(Debug, Clone)] struct TestContext { pub id: String } impl SpanReferenceAware for TestContext { fn reference_span(&mut self, _: &SpanReference) {} } #[test] fn clone_context() { let clone = { let context = ImplContextBox::new(TestContext { id: "ABC".to_owned() }); context.clone() }; let inner = clone.impl_context(); if let Some(inner) = inner.downcast_ref::<TestContext>() { assert_eq!(inner.id, "ABC"); } else { panic!("Failed to downcast inner context"); } } #[test] fn unwrap_context() { let context = ImplContextBox::new(TestContext { id: "ABC".to_owned() }); let inner = context.impl_context(); if let Some(inner) = inner.downcast_ref::<TestContext>() { assert_eq!(inner.id, "ABC"); } else { panic!("Failed to downcast inner context"); } } }