110 lines
3.6 KiB
Rust
110 lines
3.6 KiB
Rust
// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
|
|
// file at the top-level directory of this distribution and at
|
|
// http://rust-lang.org/COPYRIGHT.
|
|
//
|
|
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
|
|
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
|
|
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
|
|
// option. This file may not be copied, modified, or distributed
|
|
// except according to those terms.
|
|
|
|
//! The Finally trait provides a method, `finally` on
|
|
//! stack closures that emulates Java-style try/finally blocks.
|
|
//!
|
|
//! Using the `finally` method is sometimes convenient, but the type rules
|
|
//! prohibit any shared, mutable state between the "try" case and the
|
|
//! "finally" case. For advanced cases, the `try_finally` function can
|
|
//! also be used. See that function for more details.
|
|
//!
|
|
//! # Examples
|
|
//!
|
|
//! ```
|
|
//! # #![feature(unboxed_closures)]
|
|
//!
|
|
//! use std::finally::Finally;
|
|
//!
|
|
//! (|| {
|
|
//! // ...
|
|
//! }).finally(|| {
|
|
//! // this code is always run
|
|
//! })
|
|
//! ```
|
|
|
|
#![unstable(feature = "core")]
|
|
#![deprecated(since = "1.0.0",
|
|
reason = "It is unclear if this module is more robust than implementing \
|
|
Drop on a custom type, and this module is being removed with no \
|
|
replacement. Use a custom Drop implementation to regain existing \
|
|
functionality.")]
|
|
#![allow(deprecated)]
|
|
|
|
use ops::{Drop, FnMut, FnOnce};
|
|
|
|
/// A trait for executing a destructor unconditionally after a block of code,
|
|
/// regardless of whether the blocked fails.
|
|
pub trait Finally<T> {
|
|
/// Executes this object, unconditionally running `dtor` after this block of
|
|
/// code has run.
|
|
fn finally<F>(&mut self, dtor: F) -> T where F: FnMut();
|
|
}
|
|
|
|
impl<T, F> Finally<T> for F where F: FnMut() -> T {
|
|
fn finally<G>(&mut self, mut dtor: G) -> T where G: FnMut() {
|
|
try_finally(&mut (), self, |_, f| (*f)(), |_| dtor())
|
|
}
|
|
}
|
|
|
|
/// The most general form of the `finally` functions. The function
|
|
/// `try_fn` will be invoked first; whether or not it panics, the
|
|
/// function `finally_fn` will be invoked next. The two parameters
|
|
/// `mutate` and `drop` are used to thread state through the two
|
|
/// closures. `mutate` is used for any shared, mutable state that both
|
|
/// closures require access to; `drop` is used for any state that the
|
|
/// `try_fn` requires ownership of.
|
|
///
|
|
/// **WARNING:** While shared, mutable state between the try and finally
|
|
/// function is often necessary, one must be very careful; the `try`
|
|
/// function could have panicked at any point, so the values of the shared
|
|
/// state may be inconsistent.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// use std::finally::try_finally;
|
|
///
|
|
/// struct State<'a> { buffer: &'a mut [u8], len: usize }
|
|
/// # let mut buf = [];
|
|
/// let mut state = State { buffer: &mut buf, len: 0 };
|
|
/// try_finally(
|
|
/// &mut state, (),
|
|
/// |state, ()| {
|
|
/// // use state.buffer, state.len
|
|
/// },
|
|
/// |state| {
|
|
/// // use state.buffer, state.len to cleanup
|
|
/// })
|
|
/// ```
|
|
pub fn try_finally<T, U, R, F, G>(mutate: &mut T, drop: U, try_fn: F, finally_fn: G) -> R where
|
|
F: FnOnce(&mut T, U) -> R,
|
|
G: FnMut(&mut T),
|
|
{
|
|
let f = Finallyalizer {
|
|
mutate: mutate,
|
|
dtor: finally_fn,
|
|
};
|
|
try_fn(&mut *f.mutate, drop)
|
|
}
|
|
|
|
struct Finallyalizer<'a, A:'a, F> where F: FnMut(&mut A) {
|
|
mutate: &'a mut A,
|
|
dtor: F,
|
|
}
|
|
|
|
#[unsafe_destructor]
|
|
impl<'a, A, F> Drop for Finallyalizer<'a, A, F> where F: FnMut(&mut A) {
|
|
#[inline]
|
|
fn drop(&mut self) {
|
|
(self.dtor)(self.mutate);
|
|
}
|
|
}
|