72 lines
2.3 KiB
Rust
72 lines
2.3 KiB
Rust
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// Copyright 2014 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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use std::container::Container;
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use std::iter::FromIterator;
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use std::slice;
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// Note: Once Dynamically Sized Types (DST) lands, this should be
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// replaced with something like `enum Owned<'a, Sized? U>{ Owned(~U),
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// Borrowed(&'a U) }`; and then `U` could be instantiated with `[T]`
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// or `str`, etc.
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/// MaybeOwnedVector<'a,T> abstracts over `Vec<T>` and `&'a [T]`.
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///
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/// Some clients will have a pre-allocated vector ready to hand off in
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/// a slice; others will want to create the set on the fly and hand
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/// off ownership.
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#[deriving(Eq)]
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pub enum MaybeOwnedVector<'a,T> {
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Growable(Vec<T>),
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Borrowed(&'a [T]),
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}
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impl<'a,T> MaybeOwnedVector<'a,T> {
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pub fn iter(&'a self) -> slice::Items<'a,T> {
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match self {
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&Growable(ref v) => v.iter(),
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&Borrowed(ref v) => v.iter(),
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}
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}
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}
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impl<'a,T> Container for MaybeOwnedVector<'a,T> {
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fn len(&self) -> uint {
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match self {
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&Growable(ref v) => v.len(),
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&Borrowed(ref v) => v.len(),
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}
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}
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}
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// The `Vector` trait is provided in the prelude and is implemented on
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// both `&'a [T]` and `Vec<T>`, so it makes sense to try to support it
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// seamlessly. The other vector related traits from the prelude do
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// not appear to be implemented on both `&'a [T]` and `Vec<T>`. (It
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// is possible that this is an oversight in some cases.)
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//
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// In any case, with `Vector` in place, the client can just use
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// `as_slice` if they prefer that over `match`.
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impl<'b,T> slice::Vector<T> for MaybeOwnedVector<'b,T> {
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fn as_slice<'a>(&'a self) -> &'a [T] {
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match self {
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&Growable(ref v) => v.as_slice(),
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&Borrowed(ref v) => v.as_slice(),
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}
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}
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}
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impl<'a,T> FromIterator<T> for MaybeOwnedVector<'a,T> {
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fn from_iter<I:Iterator<T>>(iterator: I) -> MaybeOwnedVector<T> {
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Growable(FromIterator::from_iter(iterator))
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}
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}
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