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use ::{ NifEnv, NifTerm }; use ::wrapper::nif_interface::{ self, NIF_ENV, NIF_TERM }; use ::types::pid::NifPid; use std::ptr; use std::sync::{Arc, Weak}; impl<'a> NifEnv<'a> { /// Send a message to a process. /// /// The Erlang VM imposes some odd restrictions on sending messages. /// You can send messages in either of these situations: /// /// * The current thread is managed by the Erlang VM, and `self` is the /// environment of the calling process (that is, the environment that /// Rustler passed in to your NIF); *or* /// /// * The current thread is *not* managed by the Erlang VM. /// /// # Panics /// /// Panics if the above rules are broken (by trying to send a message from /// an `OwnedEnv` on a thread that's managed by the Erlang VM). /// pub fn send(self, pid: &NifPid, message: NifTerm<'a>) { let thread_type = nif_interface::enif_thread_type(); let env = if thread_type == nif_interface::ERL_NIF_THR_UNDEFINED { ptr::null_mut() } else if thread_type == nif_interface::ERL_NIF_THR_NORMAL_SCHEDULER || thread_type == nif_interface::ERL_NIF_THR_DIRTY_CPU_SCHEDULER || thread_type == nif_interface::ERL_NIF_THR_DIRTY_IO_SCHEDULER { // Panic if `self` is not the environment of the calling process. self.pid(); self.as_c_arg() } else { panic!("NifEnv::send(): unrecognized calling thread type"); }; // Send the message. unsafe { nif_interface::enif_send(env, pid.as_c_arg(), ptr::null_mut(), message.as_c_arg()); } } /// Decodes binary data to a term. /// /// Follows the erlang /// [External Term Format](http://erlang.org/doc/apps/erts/erl_ext_dist.html). pub fn binary_to_term(self, data: &[u8]) -> Option<(NifTerm<'a>, usize)> { unsafe { ::wrapper::env::binary_to_term(self.as_c_arg(), data, true) .map(|(term, size)| (NifTerm::new(self, term), size)) } } /// Like `binary_to_term`, but can only be called on valid /// and trusted data. pub unsafe fn binary_to_term_trusted(self, data: &[u8]) -> Option<(NifTerm<'a>, usize)> { ::wrapper::env::binary_to_term(self.as_c_arg(), data, false) .map(|(term, size)| (NifTerm::new(self, term), size)) } } /// A process-independent environment, a place where Erlang terms can be created outside of a NIF /// call. /// /// Rust code can use an owned environment to build a message and send it to an /// Erlang process. /// /// use rustler::env::OwnedEnv; /// use rustler::types::pid::NifPid; /// use rustler::NifEncoder; /// /// fn send_string_to_pid(data: &str, pid: &NifPid) { /// let mut msg_env = OwnedEnv::new(); /// msg_env.send_and_clear(pid, |env| data.encode(env)); /// } /// /// There's no way to run Erlang code in an `OwnedEnv`. It's not a process. It's just a workspace /// for building terms. pub struct OwnedEnv { env: Arc<NIF_ENV> } unsafe impl Send for OwnedEnv {} impl OwnedEnv { /// Allocates a new process-independent environment. pub fn new() -> OwnedEnv { OwnedEnv { env: Arc::new(unsafe { nif_interface::enif_alloc_env() }) } } /// Run some code in this environment. pub fn run<F, R>(&self, closure: F) -> R where F: for<'a> FnOnce(NifEnv<'a>) -> R { let env_lifetime = (); let env = unsafe { NifEnv::new(&env_lifetime, *self.env) }; closure(env) } /// Send a message from a Rust thread to an Erlang process. /// /// The environment is cleared as though by calling the `.clear()` method. /// To avoid that, use `env.send(pid, term)` instead. /// /// # Panics /// /// Panics if called from a thread that is managed by the Erlang VM. You /// can only use this method on a thread that was created by other /// means. (This curious restriction is imposed by the Erlang VM.) /// pub fn send_and_clear<F>(&mut self, recipient: &NifPid, closure: F) where F: for<'a> FnOnce(NifEnv<'a>) -> NifTerm<'a> { if nif_interface::enif_thread_type() != nif_interface::ERL_NIF_THR_UNDEFINED { panic!("send_and_clear: current thread is managed"); } let message = self.run(|env| closure(env).as_c_arg()); let c_env = *self.env; self.env = Arc::new(c_env); // invalidate SavedTerms unsafe { nif_interface::enif_send(ptr::null_mut(), recipient.as_c_arg(), c_env, message); } } /// Free all terms in this environment and clear it for reuse. /// /// This invalidates `SavedTerm`s that were saved in this environment; /// if you later try to `.load()` one, you'll get a panic. /// /// Unless you call this method after a call to `run()`, all terms created within the /// environment hang around in memory until the `OwnedEnv` is dropped: garbage collection does /// not continually happen as needed in a NIF environment. pub fn clear(&mut self) { let c_env = *self.env; self.env = Arc::new(c_env); unsafe { nif_interface::enif_clear_env(c_env); } } /// Save a term for use in a later call to `.run()` or `.send()`. /// /// For your safety, Rust doesn't let you save `NifTerm` values from one `.run()` call to a /// later `.run()` call. If you try, it'll complain about lifetimes. /// /// `.save()` offers a way to do this. For example, maybe you'd like to copy a term from the /// caller into an `OwnedEnv`, then use that term on another thread. /// /// # use rustler::{ NifEnv, NifTerm }; /// use rustler::env::OwnedEnv; /// use std::thread; /// /// fn thread_example<'a>(env: NifEnv<'a>, term: NifTerm<'a>) { /// // Copy `term` into a new OwnedEnv, for use on another thread. /// let mut thread_env = OwnedEnv::new(); /// let saved_term = thread_env.save(term); /// /// thread::spawn(move || { /// // Now run some code on the thread, using the saved term. /// thread_env.run(|env| { /// let term = saved_term.load(env); /// //... do stuff with term ... /// }); /// }); /// } /// /// **Note: There is no way to save terms across `OwnedEnv::send()` or `clear()`.** /// If you try, the `.load()` call will panic. pub fn save<'a>(&self, term: NifTerm<'a>) -> SavedTerm { SavedTerm { term: self.run(|env| term.in_env(env).as_c_arg()), env_generation: Arc::downgrade(&self.env), } } } impl Drop for OwnedEnv { fn drop(&mut self) { unsafe { nif_interface::enif_free_env(*self.env); } } } /// A term that was created in an `OwnedEnv` and saved for later use. /// /// These are created by calling `OwnedEnv::save()`. See that method's documentation for an /// example. #[derive(Clone)] pub struct SavedTerm { env_generation: Weak<NIF_ENV>, term: NIF_TERM, } unsafe impl Send for SavedTerm {} impl SavedTerm { /// Load this saved term back into its environment. /// /// # Panics /// /// `env` must be the `NifEnv` of a `.run()` or `.send()` call on the /// `OwnedEnv` where this term was saved, and the `OwnedEnv` must not have /// been cleared or dropped since then. Otherwise this method will panic. pub fn load<'a>(&self, env: NifEnv<'a>) -> NifTerm<'a> { // Check that the saved term is still valid. match self.env_generation.upgrade() { None => panic!("term is from a cleared or dropped OwnedEnv"), Some(ref env_arc) if **env_arc == env.as_c_arg() => unsafe { NifTerm::new(env, self.term) }, _ => panic!("can't load SavedTerm into a different environment"), } } }