Crate bos[−][src]
Expand description
This crate provides flexible
Borrowed, Owned or Shared (B.O.S.) smart pointers.
They are like std’s Cow
but with additonal Arc
and Rc
variants.
Unlike std’s Cow
,
they can also be used with types
that don’t implement Clone
or ToOwned
.
The bos
smart pointers allow you to:
- share data efficiently
- decide ownership at runtime
- avoid cloning the data until it becomes necessary
“A” stands for “atomic”
For example Abos
implements Send
and Sync
but does not have a Rc
variant.
Bos
does not implement Send
or Sync
but does have a Rc
variant.
AbosStr
and BosStr
types
Abos
and Bos
are often used with str
or similar types.
Feel free to have a look at our handy type aliases below.
features
Enable additional features or optional dependencies
by adding the following to your Cargo.toml
,
replacing “x.y” with the version you want.
[dependencies]
bos = { version = "x.y", features = ["serde", "lifetime"] }
Examples
use std::sync::Arc;
use bos::AbosStr;
// No need to allocate memory for a &'static str
let title = AbosStr::Borrowed("Dune");
// The author's name shouldn't be too long.
// So we can just store it in a normal String.
let author = AbosStr::Owned(read_file("dune/author.txt"));
// A whole book is really long.
// And we want to share this string with multiple threads.
// So it would be efficient to store in an Arc,
// since cloning the Arc does not clone the String data inside of it.
let book_text = AbosStr::Arc(Arc::new(read_file("dune/book.txt")));
// We can store a &str, String and Arc<String> inside the same Vec
// because we are using the AbosStr enum.
let book_infos: Vec<AbosStr> = vec![title, author, book_text];
fn read_file(path: &str) -> String {
// ...
}
This example shows how to use Abos
in a struct
using the lifetime
and serde
crates.
use assert_matches::assert_matches;
use bos::AbosStr;
use lifetime::{IntoStatic, ToBorrowed};
use serde::{Deserialize, Deserializer};
use std::sync::Arc;
#[derive(IntoStatic, ToBorrowed, Deserialize)]
struct Header<'a> {
name: AbosStr<'a>,
#[serde(deserialize_with = "arc_string_if_long")]
value: AbosStr<'a>,
}
fn arc_string_if_long<'b, 'de, D>(d: D) -> Result<AbosStr<'b>, D::Error>
where
D: Deserializer<'de>,
{
let s: String = Deserialize::deserialize(d)?;
Ok(if s.len() < 10 { // 10 is way too small. Try something like 1000 in your code.
AbosStr::Owned(s)
} else {
AbosStr::Arc(Arc::new(s))
})
}
// Let's pretend this JSON String came over the network.
let header_json =
String::from(r#"{ "name":"content", "value":"text/html; charset=UTF-8" }"#);
let content: Header<'static> = serde_json::from_str(&header_json)?;
let mut content_type: Header<'_> = content.to_borrowed();
content_type.name += "-type"; // creates a new String
// content header has not moved
assert_eq!(content.name, "content");
assert_eq!(content_type.name, "content-type");
assert_matches!(&content_type.value, AbosStr::BorrowedArc(arc) if Arc::strong_count(arc) == 1);
let static_content_type: Header<'static> = content_type.into_static();
assert_eq!(static_content_type.value, "text/html; charset=UTF-8");
assert_matches!(&static_content_type.value, AbosStr::Arc(arc) if Arc::strong_count(arc) == 2);
Enums
Type Definitions
Atomic Borrowed, Owned or Shared heap allocating smart pointer.
Atomic Borrowed, Owned or Shared str
smart pointer.
Atomic Borrowed, Owned or Shared smart pointer for types implementing the ToOwned
(T.O.) trait.
Atomic Borrowed, Owned or Shared Vec
smart pointer.
Borrowed, Owned or Shared heap allocating smart pointer.
Borrowed, Owned or Shared str
smart pointer.
Borrowed, Owned or Shared smart pointer for types implementing the ToOwned
(T.O.) trait.
Borrowed, Owned or Shared Vec
smart pointer.