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//! This provides a high-level binding to `emacs-module`, Emacs's support for dynamic modules. //! //! Code for a minimal module looks like this: //! //! ```no_run //! use emacs::{defun, Env, Result, Value}; //! //! emacs::plugin_is_GPL_compatible!(); //! //! #[emacs::module(name = "greeting")] //! fn init(_: &Env) -> Result<()> { Ok(()) } //! //! #[defun] //! fn say_hello(env: &Env, name: String) -> Result<Value<'_>> { //! env.message(&format!("Hello, {}!", name)) //! } //! ``` //! //! ```emacs-lisp //! (require 'greeting) //! (greeting-say-hello "Emacs") //! ``` //! //! See [User Guide] and [examples]. //! //! [User Guide]: https://ubolonton.github.io/emacs-module-rs/ //! [Examples]: https://github.com/ubolonton/emacs-rs-examples/ use std::cell::{RefCell, Ref, RefMut}; use std::ffi::CString; #[doc(inline)] pub use emacs_macros::{defun, module}; use raw::*; #[doc(no_inline)] pub use failure::{Error, ResultExt}; #[doc(inline)] pub use self::error::{ErrorKind, Result}; #[macro_use] mod macros; mod convert; #[doc(hidden)] pub mod error; #[doc(hidden)] pub mod func; #[doc(hidden)] pub mod globals; // This exposes some raw types for module to use (e.g. in `emacs_module_init`) without having to // declare the raw `emacs_module` as a dependency. #[doc(hidden)] pub mod raw { pub use emacs_module::{emacs_env, emacs_runtime, emacs_value}; } // External dependencies that are mostly used by macros instead of user code. #[doc(hidden)] pub mod deps { pub use libc; pub use ctor; pub use lazy_static; } /// Main point of interaction with the Lisp runtime. #[derive(Debug)] pub struct Env { pub(crate) raw: *mut emacs_env, /// Raw values "rooted" during the lifetime of this `Env`. pub(crate) protected: RefCell<Vec<emacs_value>>, } /// Like [`Env`], but is available only in exported functions. This has additional methods to handle /// arguments passed from Lisp code. /// /// [`Env`]: struct.Env.html #[doc(hidden)] #[derive(Debug)] pub struct CallEnv { env: Env, nargs: usize, args: *mut emacs_value, } /// A type that represents Lisp values. /// Values of this type can be copied around, but are lifetime-bound to the [`Env`] they come from. /// /// They are also "proxy values" that are only useful when converted to Rust values, or used as /// arguments when calling back into the Lisp runtime. /// /// [`Env`]: struct.Env.html #[derive(Debug, Clone, Copy)] pub struct Value<'e> { pub(crate) raw: emacs_value, pub env: &'e Env, } // XXX: More accurate would be `CloneFromLisp` or `Decode`, but ... /// Converting Lisp [`Value`] into a Rust type. /// /// # Implementation /// /// The lifetime parameter is put on the trait itself, instead of the method. This allows it to be /// implemented for [`Value`] itself. /// /// [`Value`]: struct.Value.html pub trait FromLisp<'e>: Sized { fn from_lisp(value: Value<'e>) -> Result<Self>; } // XXX: More accurate would be `CloneToLisp`, `Encode`, but ... /// Converting a Rust type into Lisp [`Value`]. /// /// # Implementation /// /// The lifetime parameter is put on the trait itself, instead of the method. This allows the impl /// for [`Value`] to simply return the input, instead of having to create a new [`Value`]. /// /// [`Value`]: struct.Value.html pub trait IntoLisp<'e> { // TODO: Consider putting the lifetime parameter on the method. Look at rustler, maybe use its // env lifetime invariance trick. fn into_lisp(self, env: &'e Env) -> Result<Value<'e>>; } /// Allowing a type to be exposed to Lisp, where its values appear as opaque objects, or "embedded /// user pointers" (printed as `#<user-ptr ...>`). /// /// When a (boxed) value of this type is transferred to Lisp, the GC becomes its owner. Afterwards, /// module code can only access it through immutable references. pub trait Transfer: Sized { /// Finalizes a value. This is called by the GC when it discards a value of this type. Module /// code that needs custom destructor logic should implement [`Drop`], instead of overriding /// this. /// /// This function also serves as a form of runtime type tag. unsafe extern "C" fn finalizer(ptr: *mut libc::c_void) { #[cfg(build = "debug")] println!("Finalizing {} {:#?}", Self::type_name(), ptr); Box::from_raw(ptr as *mut Self); } // TODO: This should be derived automatically. Use `typename` crate or something. /// Returns the name of this type. This is used to report runtime type error, when a function /// expects this type, but some Lisp code passes a different type of "user pointer". fn type_name() -> &'static str; // TODO: Consider using a wrapper struct to carry the type info, to enable better runtime // reporting of type error (and to enable something like `rs-module/type-of`). } /// Public APIs. impl Env { #[doc(hidden)] pub unsafe fn new(raw: *mut emacs_env) -> Self { let protected = RefCell::new(vec![]); Self { raw, protected } } #[doc(hidden)] pub unsafe fn from_runtime(runtime: *mut emacs_runtime) -> Self { let get_env = (*runtime).get_environment.expect("Cannot get Emacs environment"); let raw = get_env(runtime); Self::new(raw) } #[doc(hidden)] pub fn raw(&self) -> *mut emacs_env { self.raw } pub fn intern(&self, name: &str) -> Result<Value<'_>> { raw_call_value!(self, intern, CString::new(name)?.as_ptr()) } // TODO: Return an enum? pub fn type_of(&self, value: Value<'_>) -> Result<Value<'_>> { raw_call_value!(self, type_of, value.raw) } // TODO: Add a convenient macro? pub fn call(&self, name: &str, args: &[Value<'_>]) -> Result<Value<'_>> { let symbol = self.intern(name)?; // XXX Hmm let mut args: Vec<emacs_value> = args.iter().map(|v| v.raw).collect(); raw_call_value!(self, funcall, symbol.raw, args.len() as libc::ptrdiff_t, args.as_mut_ptr()) } // TODO: Add a method to Value instead. pub fn is_not_nil(&self, value: Value<'_>) -> bool { raw_call_no_exit!(self, is_not_nil, value.raw) } // TODO: Implement Eq for Value instead. pub fn eq(&self, a: Value<'_>, b: Value<'_>) -> bool { raw_call_no_exit!(self, eq, a.raw, b.raw) } pub fn list(&self, args: &[Value<'_>]) -> Result<Value<'_>> { self.call("list", args) } pub fn provide(&self, name: &str) -> Result<Value<'_>> { let name = self.intern(name)?; call_lisp!(self, "provide", name) } pub fn message(&self, text: &str) -> Result<Value<'_>> { let text = text.into_lisp(self)?; call_lisp!(self, "message", text) } } // TODO: Add tests to make sure the protected values are not leaked. impl Drop for Env { fn drop(&mut self) { #[cfg(build = "debug")] println!("Unrooting {} values protected by {:?}", self.protected.borrow().len(), self); for raw in self.protected.borrow().iter() { raw_call_no_exit!(self, free_global_ref, *raw); } } } impl<'e> Value<'e> { /// Constructs a new `Value`. Module code should not call this directly. It is public only for /// some internal macros to use. /// /// # Safety /// /// The raw value must come from the given [`Env`]. /// /// [`Env`]: struct.Env.html #[doc(hidden)] pub unsafe fn new(raw: emacs_value, env: &'e Env) -> Self { Self { raw, env } } /// Constructs a new `Value` and "roots" its underlying raw value (GC-managed) during the /// lifetime of the given [`Env`]. Module code should not call this directly. It is public only /// for some internal macros to use. /// /// # Safety /// /// The raw value must still be alive. This function is needed to protect new values returned /// from Emacs runtime, due to [this issue](https://github.com/ubolonton/emacs-module-rs/issues/2). /// /// [`Env`]: struct.Env.html #[allow(unused_unsafe)] #[doc(hidden)] pub unsafe fn new_protected(raw: emacs_value, env: &'e Env) -> Self { env.protected.borrow_mut().push(raw_call_no_exit!(env, make_global_ref, raw)); Self::new(raw, env) } /// Converts this value into a Rust value of the given type. #[inline] pub fn into_rust<T: FromLisp<'e>>(self) -> Result<T> { FromLisp::from_lisp(self) } #[inline] pub fn into_ref<T>(self) -> Result<Ref<'e, T>> { let container: &RefCell<T> = self.into_rust()?; Ok(container.try_borrow()?) } #[inline] pub fn into_ref_mut<T>(self) -> Result<RefMut<'e, T>> { let container: &RefCell<T> = self.into_rust()?; Ok(container.try_borrow_mut()?) } // TODO: Rename this to `borrow_mut`? Also, remove FromLisp implementation for &T. On the other // hand, `Value` is similar to `Rc`, so `get_mut` may make sense. /// Returns a mutable reference to the underlying Rust data wrapped by this value. /// /// # Safety /// /// There are several ways this can go wrong: /// /// - Lisp code can pass the same object through 2 different values in an argument list. /// - Rust code earlier in the call chain may have copied this value. /// - Rust code later in the call chain may receive a copy of this value. /// /// In general, it is better to wrap Rust data in `RefCell`, `Mutex`, or `RwLock` guards, before /// moving them to Lisp, and then only access them through these guards (which can be obtained /// back through [`into_rust`]). This method is for squeezing out the last bit of performance in /// very rare situations. /// /// [`into_rust`]: #method.into_rust pub unsafe fn get_mut<T: Transfer>(&mut self) -> Result<&mut T> { self.env.get_raw_pointer(self.raw).map(|r| &mut *r) } }