dd13a80344
This does not actually add anything that wasn't there, but is merely an optimization for the given cases, which would have incurred additional heap allocation for adding empty strings, and improving the ergonomics of `Cow` with strings.
66 lines
2.2 KiB
Rust
66 lines
2.2 KiB
Rust
// Copyright 2012-2013-2014 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::borrow::Cow;
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// check that Cow<'a, str> implements addition
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#[test]
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fn check_cow_add() {
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borrowed1 = Cow::Borrowed("Hello, ");
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borrowed2 = Cow::Borrowed("World!");
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borrow_empty = Cow::Borrowed("");
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owned1 = Cow::Owned("Hi, ".into());
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owned2 = Cow::Owned("Rustaceans!".into());
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owned_empty = Cow::Owned("".into());
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assert_eq!("Hello, World!", borrowed1 + borrowed2);
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assert_eq!("Hello, Rustaceans!", borrowed1 + owned2);
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assert_eq!("Hello, World!", owned1 + borrowed2);
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assert_eq!("Hello, Rustaceans!", owned1 + owned2);
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if let Cow::Owned(_) = borrowed1 + borrow_empty {
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panic!("Adding empty strings to a borrow should note allocate");
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}
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if let Cow::Owned(_) = borrow_empty + borrowed1 {
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panic!("Adding empty strings to a borrow should note allocate");
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}
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if let Cow::Owned(_) = borrowed1 + owned_empty {
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panic!("Adding empty strings to a borrow should note allocate");
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}
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if let Cow::Owned(_) = owned_empty + borrowed1 {
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panic!("Adding empty strings to a borrow should note allocate");
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}
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}
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fn check_cow_add_assign() {
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borrowed1 = Cow::Borrowed("Hello, ");
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borrowed2 = Cow::Borrowed("World!");
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borrow_empty = Cow::Borrowed("");
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owned1 = Cow::Owned("Hi, ".into());
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owned2 = Cow::Owned("Rustaceans!".into());
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owned_empty = Cow::Owned("".into());
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let borrowed1clone = borrowed1.clone();
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borrowed1clone += borrow_empty;
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assert_eq!((&borrowed1clone).as_ptr(), (&borrowed1).as_ptr());
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borrowed1clone += owned_empty;
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assert_eq!((&borrowed1clone).as_ptr(), (&borrowed1).as_ptr());
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owned1 += borrowed2;
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borrowed1 += owned2;
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assert_eq!("Hello, World!", owned1);
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assert_eq!("Hello, Rustaceans!", borrowed1);
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}
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