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//! Defines "provider" traits and implementations for different types of I/O operations. //! //! The purpose of this is mainly for dependency injection: by having your code depend on a //! generic provider, it can be tested by giving it a virtual, inspectable implementation of that //! provider. In production, the "real" implementation can be used. //! //! Each type of provider exists in its own submodule and can be used independently. However, //! this module also contains the all-encompassing `IoProvider` trait which provides access to //! all of them. If you have a lot of I/O dependencies, it might be easier to create and pass //! around one `&mut IoProvider` rather than several different providers. //! //! # Examples //! //! ``` //! extern crate io_providers; //! //! use std::io::Write; //! use std::path::Path; //! use io_providers::{IoProvider, LocalIoProvider, VirtualIoProvider}; //! use io_providers::env::Provider as EnvProvider; //! use io_providers::stream::Provider as StreamProvider; //! //! /// Gets the current working directory and prints it to stdout. //! fn do_work<P: IoProvider>(io: &mut P) { //! let cur_dir = io.env().current_dir().unwrap(); //! let stdout = io.stream().output(); //! writeln!(stdout, "The current directory is: {}", cur_dir.to_str().unwrap()).unwrap(); //! } //! //! fn main() { //! test_do_work_prints_current_dir(); //! //! // Use a local I/O provider here to get real interaction with the system //! let mut io = LocalIoProvider::new(); //! do_work(&mut io); //! } //! //! fn test_do_work_prints_current_dir() { //! // Use a virtual I/O provider here so we can verify how it was used //! let mut virtual_io = VirtualIoProvider::new(); //! virtual_io.env().set_current_dir(Path::new("/foo/bar")).unwrap(); //! //! do_work(&mut virtual_io); //! //! assert_eq!( //! "The current directory is: /foo/bar\n", //! ::std::str::from_utf8(virtual_io.stream().read_output()).unwrap()); //! } //! ``` pub mod env; pub mod stream; /// Provides access to an environment provider and a stream provider. /// /// See `env::Provider` and `stream::Provider` for more information. pub trait IoProvider { // The type of the environment provider. type E: env::Provider; // The type of the stream provider. type S: stream::Provider; /// Gets the `env::Provider`. fn env<'a>(&'a mut self) -> &'a mut Self::E; /// Gets the `stream::Provider`. fn stream<'a>(&'a mut self) -> &'a mut Self::S; } /// "Real" implementer of `IoProvider`, using standard streams and the local environment. /// /// See `env::Local` and `stream::Std` for more information. pub struct LocalIoProvider { env: env::Local, stream: stream::Std, } impl LocalIoProvider { /// Creates a new `LocalIoProvider`. pub fn new() -> LocalIoProvider { LocalIoProvider { env: env::Local, stream: stream::Std::new(), } } } impl IoProvider for LocalIoProvider { type E = env::Local; type S = stream::Std; fn env<'a>(&'a mut self) -> &'a mut env::Local { &mut self.env } fn stream<'a>(&'a mut self) -> &'a mut stream::Std { &mut self.stream } } /// Virtual implementer of `IoProvider`, using in-memory data which can be inspected. /// /// See `env::Virtual` and `stream::Virtual` for more information. pub struct VirtualIoProvider { env: env::Virtual, stream: stream::Virtual, } impl VirtualIoProvider { /// Creates a new `VirtualIoProvider`. pub fn new() -> VirtualIoProvider { VirtualIoProvider { env: env::Virtual::new(), stream: stream::Virtual::new(), } } } impl IoProvider for VirtualIoProvider { type E = env::Virtual; type S = stream::Virtual; fn env<'a>(&'a mut self) -> &'a mut env::Virtual { &mut self.env } fn stream<'a>(&'a mut self) -> &'a mut stream::Virtual { &mut self.stream } }