367 lines
8.9 KiB
Rust
367 lines
8.9 KiB
Rust
// Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//! Types dealing with dynamic mutability
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use prelude::*;
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use cast;
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use util::NonCopyable;
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/*
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A dynamic, mutable location.
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Similar to a mutable option type, but friendlier.
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*/
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#[no_freeze]
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#[deriving(Clone, DeepClone, Eq)]
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#[allow(missing_doc)]
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pub struct Cell<T> {
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priv value: Option<T>
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}
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impl<T> Cell<T> {
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/// Creates a new full cell with the given value.
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pub fn new(value: T) -> Cell<T> {
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Cell { value: Some(value) }
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}
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/// Yields the value, failing if the cell is empty.
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pub fn take(&self) -> T {
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let this = unsafe { cast::transmute_mut(self) };
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if this.is_empty() {
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fail!("attempt to take an empty cell");
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}
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this.value.take_unwrap()
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}
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/// Yields the value if the cell is full, or `None` if it is empty.
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pub fn take_opt(&self) -> Option<T> {
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let this = unsafe { cast::transmute_mut(self) };
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this.value.take()
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}
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/// Returns true if the cell is empty and false if the cell is full.
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pub fn is_empty(&self) -> bool {
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self.value.is_none()
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}
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}
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#[test]
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fn test_basic() {
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let value_cell = Cell::new(~10);
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assert!(!value_cell.is_empty());
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let value = value_cell.take();
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assert!(value == ~10);
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assert!(value_cell.is_empty());
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}
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#[test]
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#[should_fail]
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fn test_take_empty() {
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let value_cell: Cell<~int> = Cell::new(~0);
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value_cell.take();
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value_cell.take();
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}
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/// A mutable memory location with dynamically checked borrow rules
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#[no_freeze]
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pub struct RefCell<T> {
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priv value: T,
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priv borrow: BorrowFlag,
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priv nc: NonCopyable
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}
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// Values [1, MAX-1] represent the number of `Ref` active
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// (will not outgrow its range since `uint` is the size of the address space)
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type BorrowFlag = uint;
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static UNUSED: BorrowFlag = 0;
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static WRITING: BorrowFlag = -1;
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impl<T> RefCell<T> {
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/// Create a new `RefCell` containing `value`
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pub fn new(value: T) -> RefCell<T> {
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RefCell {
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value: value,
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borrow: UNUSED,
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nc: NonCopyable
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}
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}
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/// Consumes the `RefCell`, returning the wrapped value.
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pub fn unwrap(self) -> T {
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assert!(self.borrow == UNUSED);
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self.value
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}
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unsafe fn as_mut<'a>(&'a self) -> &'a mut RefCell<T> {
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cast::transmute_mut(self)
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}
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/// Attempts to immutably borrow the wrapped value.
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///
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/// The borrow lasts until the returned `Ref` exits scope. Multiple
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/// immutable borrows can be taken out at the same time.
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///
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/// Returns `None` if the value is currently mutably borrowed.
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pub fn try_borrow<'a>(&'a self) -> Option<Ref<'a, T>> {
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match self.borrow {
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WRITING => None,
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_ => {
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unsafe { self.as_mut().borrow += 1; }
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Some(Ref { parent: self })
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}
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}
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}
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/// Immutably borrows the wrapped value.
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///
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/// The borrow lasts until the returned `Ref` exits scope. Multiple
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/// immutable borrows can be taken out at the same time.
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///
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/// # Failure
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///
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/// Fails if the value is currently mutably borrowed.
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pub fn borrow<'a>(&'a self) -> Ref<'a, T> {
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match self.try_borrow() {
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Some(ptr) => ptr,
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None => fail!("RefCell<T> already mutably borrowed")
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}
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}
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/// Mutably borrows the wrapped value.
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///
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/// The borrow lasts untile the returned `RefMut` exits scope. The value
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/// cannot be borrowed while this borrow is active.
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///
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/// Returns `None` if the value is currently borrowed.
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pub fn try_borrow_mut<'a>(&'a self) -> Option<RefMut<'a, T>> {
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match self.borrow {
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UNUSED => unsafe {
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let mut_self = self.as_mut();
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mut_self.borrow = WRITING;
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Some(RefMut { parent: mut_self })
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},
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_ => None
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}
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}
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/// Mutably borrows the wrapped value.
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///
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/// The borrow lasts untile the returned `RefMut` exits scope. The value
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/// cannot be borrowed while this borrow is active.
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///
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/// # Failure
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///
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/// Fails if the value is currently borrowed.
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pub fn borrow_mut<'a>(&'a self) -> RefMut<'a, T> {
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match self.try_borrow_mut() {
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Some(ptr) => ptr,
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None => fail!("RefCell<T> already borrowed")
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}
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}
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/// Immutably borrows the wrapped value and applies `blk` to it.
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///
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/// # Failure
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///
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/// Fails if the value is currently mutably borrowed.
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#[inline]
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pub fn with<U>(&self, blk: |&T| -> U) -> U {
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let ptr = self.borrow();
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blk(ptr.get())
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}
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/// Mutably borrows the wrapped value and applies `blk` to it.
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///
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/// # Failure
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///
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/// Fails if the value is currently borrowed.
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#[inline]
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pub fn with_mut<U>(&self, blk: |&mut T| -> U) -> U {
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let mut ptr = self.borrow_mut();
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blk(ptr.get())
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}
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}
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impl<T: Clone> Clone for RefCell<T> {
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fn clone(&self) -> RefCell<T> {
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let x = self.borrow();
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RefCell::new(x.get().clone())
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}
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}
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impl<T: DeepClone> DeepClone for RefCell<T> {
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fn deep_clone(&self) -> RefCell<T> {
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let x = self.borrow();
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RefCell::new(x.get().deep_clone())
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}
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}
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impl<T: Eq> Eq for RefCell<T> {
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fn eq(&self, other: &RefCell<T>) -> bool {
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let a = self.borrow();
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let b = other.borrow();
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a.get() == b.get()
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}
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}
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/// Wraps a borrowed reference to a value in a `RefCell` box.
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pub struct Ref<'box, T> {
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priv parent: &'box RefCell<T>
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}
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#[unsafe_destructor]
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impl<'box, T> Drop for Ref<'box, T> {
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fn drop(&mut self) {
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assert!(self.parent.borrow != WRITING && self.parent.borrow != UNUSED);
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unsafe { self.parent.as_mut().borrow -= 1; }
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}
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}
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impl<'box, T> Ref<'box, T> {
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/// Retrieve an immutable reference to the stored value.
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#[inline]
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pub fn get<'a>(&'a self) -> &'a T {
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&self.parent.value
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}
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}
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/// Wraps a mutable borrowed reference to a value in a `RefCell` box.
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pub struct RefMut<'box, T> {
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priv parent: &'box mut RefCell<T>
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}
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#[unsafe_destructor]
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impl<'box, T> Drop for RefMut<'box, T> {
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fn drop(&mut self) {
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assert!(self.parent.borrow == WRITING);
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self.parent.borrow = UNUSED;
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}
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}
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impl<'box, T> RefMut<'box, T> {
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/// Retrieve a mutable reference to the stored value.
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#[inline]
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pub fn get<'a>(&'a mut self) -> &'a mut T {
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&mut self.parent.value
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}
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}
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#[cfg(test)]
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mod test {
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use super::*;
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#[test]
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fn double_imm_borrow() {
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let x = RefCell::new(0);
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let _b1 = x.borrow();
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x.borrow();
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}
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#[test]
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fn no_mut_then_imm_borrow() {
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let x = RefCell::new(0);
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let _b1 = x.borrow_mut();
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assert!(x.try_borrow().is_none());
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}
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#[test]
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fn no_imm_then_borrow_mut() {
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let x = RefCell::new(0);
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let _b1 = x.borrow();
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assert!(x.try_borrow_mut().is_none());
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}
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#[test]
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fn no_double_borrow_mut() {
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let x = RefCell::new(0);
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let _b1 = x.borrow_mut();
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assert!(x.try_borrow_mut().is_none());
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}
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#[test]
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fn imm_release_borrow_mut() {
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let x = RefCell::new(0);
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{
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let _b1 = x.borrow();
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}
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x.borrow_mut();
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}
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#[test]
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fn mut_release_borrow_mut() {
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let x = RefCell::new(0);
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{
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let _b1 = x.borrow_mut();
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}
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x.borrow();
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}
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#[test]
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fn double_borrow_single_release_no_borrow_mut() {
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let x = RefCell::new(0);
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let _b1 = x.borrow();
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{
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let _b2 = x.borrow();
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}
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assert!(x.try_borrow_mut().is_none());
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}
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#[test]
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fn with_ok() {
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let x = RefCell::new(0);
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assert_eq!(1, x.with(|x| *x+1));
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}
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#[test]
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#[should_fail]
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fn mut_borrow_with() {
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let x = RefCell::new(0);
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let _b1 = x.borrow_mut();
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x.with(|x| *x+1);
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}
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#[test]
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fn borrow_with() {
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let x = RefCell::new(0);
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let _b1 = x.borrow();
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assert_eq!(1, x.with(|x| *x+1));
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}
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#[test]
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fn with_mut_ok() {
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let x = RefCell::new(0);
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x.with_mut(|x| *x += 1);
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let b = x.borrow();
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assert_eq!(1, *b.get());
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}
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#[test]
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#[should_fail]
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fn borrow_with_mut() {
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let x = RefCell::new(0);
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let _b = x.borrow();
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x.with_mut(|x| *x += 1);
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}
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#[test]
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#[should_fail]
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fn discard_doesnt_unborrow() {
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let x = RefCell::new(0);
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let _b = x.borrow();
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let _ = _b;
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let _b = x.borrow_mut();
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}
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}
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