What's the best way to implement a string buffer in Rust?

Question

Say I want to do lots of small additions to a string in a row, what's the best way to do this? Is there a data type that's best for this?

It is not too clear what you are asking for. A buffer can be used in many ways. Maybe a parallel with languages having Interned Strings such as Java or C# since those introduced the `StringBuffer` idea would make it clearer. — Matthieu M., Dec 09 '14 at 13:02

score 41 · Accepted Answer · edited Dec 09 '14 at 07:21

41

Use the String native type, it's designed to be mutable and grow easily.

let mut s = String::new();
s.push_str("GET / HTTP/1.0\r\n");
s.push_str("User-Agent: foobar\r\n"); // Etc etc

edited Dec 09 '14 at 07:21

Chris Morgan

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answered Dec 09 '14 at 06:47

Kevin Burke

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score 5 · Answer 2 · answered Jan 23 '21 at 12:40

Say I want to do lots of small additions to a string in a row [...]

If "additions" are not &str you can use the target String as a Writer to push string representations of other data types:

fn main() {
    let mut target_string = String::new();
    use std::fmt::Write;
    write!(target_string, "an integer: {}\n", 42).unwrap();
    writeln!(target_string, "a boolean: {}", true).unwrap();

    assert_eq!("an integer: 42\na boolean: true\n", target_string);
}

The Write trait is required by the macro write!. Anything which implements write can be written to with the macro write!. To use Write methods, it must first be brought into scope. The Write trait is brought into scope with use std::fmt::Write;.

Documentation:

write!(..): https://doc.rust-lang.org/core/macro.write.html
writeln!(..): https://doc.rust-lang.org/core/macro.writeln.html

The Resource used to write this answer: Rust String concatenation

What's the best way to implement a string buffer in Rust?

2 Answers2